diff -Nru bzip2-1.0.1/AUTHORS bzip2-1.0.1.new/AUTHORS --- bzip2-1.0.1/AUTHORS Thu Jan 1 01:00:00 1970 +++ bzip2-1.0.1.new/AUTHORS Sat Jun 24 20:13:05 2000 @@ -0,0 +1 @@ +Julian Seward diff -Nru bzip2-1.0.1/CHANGES bzip2-1.0.1.new/CHANGES --- bzip2-1.0.1/CHANGES Sat Jun 24 20:13:27 2000 +++ bzip2-1.0.1.new/CHANGES Thu Jan 1 01:00:00 1970 @@ -1,167 +0,0 @@ - - -0.9.0 -~~~~~ -First version. - - -0.9.0a -~~~~~~ -Removed 'ranlib' from Makefile, since most modern Unix-es -don't need it, or even know about it. - - -0.9.0b -~~~~~~ -Fixed a problem with error reporting in bzip2.c. This does not effect -the library in any way. Problem is: versions 0.9.0 and 0.9.0a (of the -program proper) compress and decompress correctly, but give misleading -error messages (internal panics) when an I/O error occurs, instead of -reporting the problem correctly. This shouldn't give any data loss -(as far as I can see), but is confusing. - -Made the inline declarations disappear for non-GCC compilers. - - -0.9.0c -~~~~~~ -Fixed some problems in the library pertaining to some boundary cases. -This makes the library behave more correctly in those situations. The -fixes apply only to features (calls and parameters) not used by -bzip2.c, so the non-fixedness of them in previous versions has no -effect on reliability of bzip2.c. - -In bzlib.c: - * made zero-length BZ_FLUSH work correctly in bzCompress(). - * fixed bzWrite/bzRead to ignore zero-length requests. - * fixed bzread to correctly handle read requests after EOF. - * wrong parameter order in call to bzDecompressInit in - bzBuffToBuffDecompress. Fixed. - -In compress.c: - * changed setting of nGroups in sendMTFValues() so as to - do a bit better on small files. This _does_ effect - bzip2.c. - - -0.9.5a -~~~~~~ -Major change: add a fallback sorting algorithm (blocksort.c) -to give reasonable behaviour even for very repetitive inputs. -Nuked --repetitive-best and --repetitive-fast since they are -no longer useful. - -Minor changes: mostly a whole bunch of small changes/ -bugfixes in the driver (bzip2.c). Changes pertaining to the -user interface are: - - allow decompression of symlink'd files to stdout - decompress/test files even without .bz2 extension - give more accurate error messages for I/O errors - when compressing/decompressing to stdout, don't catch control-C - read flags from BZIP2 and BZIP environment variables - decline to break hard links to a file unless forced with -f - allow -c flag even with no filenames - preserve file ownerships as far as possible - make -s -1 give the expected block size (100k) - add a flag -q --quiet to suppress nonessential warnings - stop decoding flags after --, so files beginning in - can be handled - resolved inconsistent naming: bzcat or bz2cat ? - bzip2 --help now returns 0 - -Programming-level changes are: - - fixed syntax error in GET_LL4 for Borland C++ 5.02 - let bzBuffToBuffDecompress return BZ_DATA_ERROR{_MAGIC} - fix overshoot of mode-string end in bzopen_or_bzdopen - wrapped bzlib.h in #ifdef __cplusplus ... extern "C" { ... } - close file handles under all error conditions - added minor mods so it compiles with DJGPP out of the box - fixed Makefile so it doesn't give problems with BSD make - fix uninitialised memory reads in dlltest.c - -0.9.5b -~~~~~~ -Open stdin/stdout in binary mode for DJGPP. - -0.9.5c -~~~~~~ -Changed BZ_N_OVERSHOOT to be ... + 2 instead of ... + 1. The + 1 -version could cause the sorted order to be wrong in some extremely -obscure cases. Also changed setting of quadrant in blocksort.c. - -0.9.5d -~~~~~~ -The only functional change is to make bzlibVersion() in the library -return the correct string. This has no effect whatsoever on the -functioning of the bzip2 program or library. Added a couple of casts -so the library compiles without warnings at level 3 in MS Visual -Studio 6.0. Included a Y2K statement in the file Y2K_INFO. All other -changes are minor documentation changes. - -1.0 -~~~ -Several minor bugfixes and enhancements: - -* Large file support. The library uses 64-bit counters to - count the volume of data passing through it. bzip2.c - is now compiled with -D_FILE_OFFSET_BITS=64 to get large - file support from the C library. -v correctly prints out - file sizes greater than 4 gigabytes. All these changes have - been made without assuming a 64-bit platform or a C compiler - which supports 64-bit ints, so, except for the C library - aspect, they are fully portable. - -* Decompression robustness. The library/program should be - robust to any corruption of compressed data, detecting and - handling _all_ corruption, instead of merely relying on - the CRCs. What this means is that the program should - never crash, given corrupted data, and the library should - always return BZ_DATA_ERROR. - -* Fixed an obscure race-condition bug only ever observed on - Solaris, in which, if you were very unlucky and issued - control-C at exactly the wrong time, both input and output - files would be deleted. - -* Don't run out of file handles on test/decompression when - large numbers of files have invalid magic numbers. - -* Avoid library namespace pollution. Prefix all exported - symbols with BZ2_. - -* Minor sorting enhancements from my DCC2000 paper. - -* Advance the version number to 1.0, so as to counteract the - (false-in-this-case) impression some people have that programs - with version numbers less than 1.0 are in someway, experimental, - pre-release versions. - -* Create an initial Makefile-libbz2_so to build a shared library. - Yes, I know I should really use libtool et al ... - -* Make the program exit with 2 instead of 0 when decompression - fails due to a bad magic number (ie, an invalid bzip2 header). - Also exit with 1 (as the manual claims :-) whenever a diagnostic - message would have been printed AND the corresponding operation - is aborted, for example - bzip2: Output file xx already exists. - When a diagnostic message is printed but the operation is not - aborted, for example - bzip2: Can't guess original name for wurble -- using wurble.out - then the exit value 0 is returned, unless some other problem is - also detected. - - I think it corresponds more closely to what the manual claims now. - - -1.0.1 -~~~~~ -* Modified dlltest.c so it uses the new BZ2_ naming scheme. -* Modified makefile-msc to fix minor build probs on Win2k. -* Updated README.COMPILATION.PROBLEMS. - -There are no functionality changes or bug fixes relative to version -1.0.0. This is just a documentation update + a fix for minor Win32 -build problems. For almost everyone, upgrading from 1.0.0 to 1.0.1 is -utterly pointless. Don't bother. diff -Nru bzip2-1.0.1/COPYING bzip2-1.0.1.new/COPYING --- bzip2-1.0.1/COPYING Thu Jan 1 01:00:00 1970 +++ bzip2-1.0.1.new/COPYING Sat Jun 24 20:13:05 2000 @@ -0,0 +1,39 @@ + +This program, "bzip2" and associated library "libbzip2", are +copyright (C) 1996-2000 Julian R Seward. All rights reserved. + +Redistribution and use in source and binary forms, with or without +modification, are permitted provided that the following conditions +are met: + +1. Redistributions of source code must retain the above copyright + notice, this list of conditions and the following disclaimer. + +2. The origin of this software must not be misrepresented; you must + not claim that you wrote the original software. If you use this + software in a product, an acknowledgment in the product + documentation would be appreciated but is not required. + +3. Altered source versions must be plainly marked as such, and must + not be misrepresented as being the original software. + +4. The name of the author may not be used to endorse or promote + products derived from this software without specific prior written + permission. + +THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS +OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED +WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY +DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE +GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS +INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, +WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING +NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS +SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + +Julian Seward, Cambridge, UK. +jseward@acm.org +bzip2/libbzip2 version 1.0 of 21 March 2000 + diff -Nru bzip2-1.0.1/ChangeLog bzip2-1.0.1.new/ChangeLog --- bzip2-1.0.1/ChangeLog Thu Jan 1 01:00:00 1970 +++ bzip2-1.0.1.new/ChangeLog Sat Jun 24 20:13:05 2000 @@ -0,0 +1 @@ + diff -Nru bzip2-1.0.1/INSTALL bzip2-1.0.1.new/INSTALL --- bzip2-1.0.1/INSTALL Thu Jan 1 01:00:00 1970 +++ bzip2-1.0.1.new/INSTALL Sat Jun 24 20:13:06 2000 @@ -0,0 +1,182 @@ +Basic Installation +================== + + These are generic installation instructions. + + The `configure' shell script attempts to guess correct values for +various system-dependent variables used during compilation. It uses +those values to create a `Makefile' in each directory of the package. +It may also create one or more `.h' files containing system-dependent +definitions. Finally, it creates a shell script `config.status' that +you can run in the future to recreate the current configuration, a file +`config.cache' that saves the results of its tests to speed up +reconfiguring, and a file `config.log' containing compiler output +(useful mainly for debugging `configure'). + + If you need to do unusual things to compile the package, please try +to figure out how `configure' could check whether to do them, and mail +diffs or instructions to the address given in the `README' so they can +be considered for the next release. If at some point `config.cache' +contains results you don't want to keep, you may remove or edit it. + + The file `configure.in' is used to create `configure' by a program +called `autoconf'. You only need `configure.in' if you want to change +it or regenerate `configure' using a newer version of `autoconf'. + +The simplest way to compile this package is: + + 1. `cd' to the directory containing the package's source code and type + `./configure' to configure the package for your system. If you're + using `csh' on an old version of System V, you might need to type + `sh ./configure' instead to prevent `csh' from trying to execute + `configure' itself. + + Running `configure' takes awhile. While running, it prints some + messages telling which features it is checking for. + + 2. Type `make' to compile the package. + + 3. Optionally, type `make check' to run any self-tests that come with + the package. + + 4. Type `make install' to install the programs and any data files and + documentation. + + 5. You can remove the program binaries and object files from the + source code directory by typing `make clean'. To also remove the + files that `configure' created (so you can compile the package for + a different kind of computer), type `make distclean'. There is + also a `make maintainer-clean' target, but that is intended mainly + for the package's developers. If you use it, you may have to get + all sorts of other programs in order to regenerate files that came + with the distribution. + +Compilers and Options +===================== + + Some systems require unusual options for compilation or linking that +the `configure' script does not know about. You can give `configure' +initial values for variables by setting them in the environment. Using +a Bourne-compatible shell, you can do that on the command line like +this: + CC=c89 CFLAGS=-O2 LIBS=-lposix ./configure + +Or on systems that have the `env' program, you can do it like this: + env CPPFLAGS=-I/usr/local/include LDFLAGS=-s ./configure + +Compiling For Multiple Architectures +==================================== + + You can compile the package for more than one kind of computer at the +same time, by placing the object files for each architecture in their +own directory. To do this, you must use a version of `make' that +supports the `VPATH' variable, such as GNU `make'. `cd' to the +directory where you want the object files and executables to go and run +the `configure' script. `configure' automatically checks for the +source code in the directory that `configure' is in and in `..'. + + If you have to use a `make' that does not supports the `VPATH' +variable, you have to compile the package for one architecture at a time +in the source code directory. After you have installed the package for +one architecture, use `make distclean' before reconfiguring for another +architecture. + +Installation Names +================== + + By default, `make install' will install the package's files in +`/usr/local/bin', `/usr/local/man', etc. You can specify an +installation prefix other than `/usr/local' by giving `configure' the +option `--prefix=PATH'. + + You can specify separate installation prefixes for +architecture-specific files and architecture-independent files. If you +give `configure' the option `--exec-prefix=PATH', the package will use +PATH as the prefix for installing programs and libraries. +Documentation and other data files will still use the regular prefix. + + In addition, if you use an unusual directory layout you can give +options like `--bindir=PATH' to specify different values for particular +kinds of files. Run `configure --help' for a list of the directories +you can set and what kinds of files go in them. + + If the package supports it, you can cause programs to be installed +with an extra prefix or suffix on their names by giving `configure' the +option `--program-prefix=PREFIX' or `--program-suffix=SUFFIX'. + +Optional Features +================= + + Some packages pay attention to `--enable-FEATURE' options to +`configure', where FEATURE indicates an optional part of the package. +They may also pay attention to `--with-PACKAGE' options, where PACKAGE +is something like `gnu-as' or `x' (for the X Window System). The +`README' should mention any `--enable-' and `--with-' options that the +package recognizes. + + For packages that use the X Window System, `configure' can usually +find the X include and library files automatically, but if it doesn't, +you can use the `configure' options `--x-includes=DIR' and +`--x-libraries=DIR' to specify their locations. + +Specifying the System Type +========================== + + There may be some features `configure' can not figure out +automatically, but needs to determine by the type of host the package +will run on. Usually `configure' can figure that out, but if it prints +a message saying it can not guess the host type, give it the +`--host=TYPE' option. TYPE can either be a short name for the system +type, such as `sun4', or a canonical name with three fields: + CPU-COMPANY-SYSTEM + +See the file `config.sub' for the possible values of each field. If +`config.sub' isn't included in this package, then this package doesn't +need to know the host type. + + If you are building compiler tools for cross-compiling, you can also +use the `--target=TYPE' option to select the type of system they will +produce code for and the `--build=TYPE' option to select the type of +system on which you are compiling the package. + +Sharing Defaults +================ + + If you want to set default values for `configure' scripts to share, +you can create a site shell script called `config.site' that gives +default values for variables like `CC', `cache_file', and `prefix'. +`configure' looks for `PREFIX/share/config.site' if it exists, then +`PREFIX/etc/config.site' if it exists. Or, you can set the +`CONFIG_SITE' environment variable to the location of the site script. +A warning: not all `configure' scripts look for a site script. + +Operation Controls +================== + + `configure' recognizes the following options to control how it +operates. + +`--cache-file=FILE' + Use and save the results of the tests in FILE instead of + `./config.cache'. Set FILE to `/dev/null' to disable caching, for + debugging `configure'. + +`--help' + Print a summary of the options to `configure', and exit. + +`--quiet' +`--silent' +`-q' + Do not print messages saying which checks are being made. To + suppress all normal output, redirect it to `/dev/null' (any error + messages will still be shown). + +`--srcdir=DIR' + Look for the package's source code in directory DIR. Usually + `configure' can determine that directory automatically. + +`--version' + Print the version of Autoconf used to generate the `configure' + script, and exit. + +`configure' also accepts some other, not widely useful, options. diff -Nru bzip2-1.0.1/LICENSE bzip2-1.0.1.new/LICENSE --- bzip2-1.0.1/LICENSE Sat Jun 24 20:13:27 2000 +++ bzip2-1.0.1.new/LICENSE Thu Jan 1 01:00:00 1970 @@ -1,39 +0,0 @@ - -This program, "bzip2" and associated library "libbzip2", are -copyright (C) 1996-2000 Julian R Seward. All rights reserved. - -Redistribution and use in source and binary forms, with or without -modification, are permitted provided that the following conditions -are met: - -1. Redistributions of source code must retain the above copyright - notice, this list of conditions and the following disclaimer. - -2. The origin of this software must not be misrepresented; you must - not claim that you wrote the original software. If you use this - software in a product, an acknowledgment in the product - documentation would be appreciated but is not required. - -3. Altered source versions must be plainly marked as such, and must - not be misrepresented as being the original software. - -4. The name of the author may not be used to endorse or promote - products derived from this software without specific prior written - permission. - -THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS -OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED -WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE -ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY -DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL -DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE -GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS -INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, -WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING -NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS -SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. - -Julian Seward, Cambridge, UK. -jseward@acm.org -bzip2/libbzip2 version 1.0 of 21 March 2000 - diff -Nru bzip2-1.0.1/Makefile-libbz2_so bzip2-1.0.1.new/Makefile-libbz2_so --- bzip2-1.0.1/Makefile-libbz2_so Sat Jun 24 20:13:27 2000 +++ bzip2-1.0.1.new/Makefile-libbz2_so Thu Jan 1 01:00:00 1970 @@ -1,43 +0,0 @@ - -# This Makefile builds a shared version of the library, -# libbz2.so.1.0.1, with soname libbz2.so.1.0, -# at least on x86-Linux (RedHat 5.2), -# with gcc-2.7.2.3. Please see the README file for some -# important info about building the library like this. - -SHELL=/bin/sh -CC=gcc -BIGFILES=-D_FILE_OFFSET_BITS=64 -CFLAGS=-fpic -fPIC -Wall -Winline -O2 -fomit-frame-pointer -fno-strength-reduce $(BIGFILES) - -OBJS= blocksort.o \ - huffman.o \ - crctable.o \ - randtable.o \ - compress.o \ - decompress.o \ - bzlib.o - -all: $(OBJS) - $(CC) -shared -Wl,-soname -Wl,libbz2.so.1.0 -o libbz2.so.1.0.1 $(OBJS) - $(CC) $(CFLAGS) -o bzip2-shared bzip2.c libbz2.so.1.0.1 - rm -f libbz2.so.1.0 - ln -s libbz2.so.1.0.1 libbz2.so.1.0 - -clean: - rm -f $(OBJS) bzip2.o libbz2.so.1.0.1 libbz2.so.1.0 bzip2-shared - -blocksort.o: blocksort.c - $(CC) $(CFLAGS) -c blocksort.c -huffman.o: huffman.c - $(CC) $(CFLAGS) -c huffman.c -crctable.o: crctable.c - $(CC) $(CFLAGS) -c crctable.c -randtable.o: randtable.c - $(CC) $(CFLAGS) -c randtable.c -compress.o: compress.c - $(CC) $(CFLAGS) -c compress.c -decompress.o: decompress.c - $(CC) $(CFLAGS) -c decompress.c -bzlib.o: bzlib.c - $(CC) $(CFLAGS) -c bzlib.c diff -Nru bzip2-1.0.1/Makefile.am bzip2-1.0.1.new/Makefile.am --- bzip2-1.0.1/Makefile.am Thu Jan 1 01:00:00 1970 +++ bzip2-1.0.1.new/Makefile.am Sat Jun 24 20:17:47 2000 @@ -0,0 +1,31 @@ +SUBDIRS = doc + +bin_PROGRAMS = bzip2 bzip2recover +bzip2_SOURCES = bzip2.c + +bzip2_LDADD = libbz2.la +bzip2recover_SOURCES = bzip2recover.c +lib_LTLIBRARIES = libbz2.la +libbz2_la_SOURCES = \ + blocksort.c \ + huffman.c \ + crctable.c \ + randtable.c \ + compress.c \ + decompress.c \ + bzlib.c \ + bzlib.h \ + bzlib_private.h + +libbz2_la_LDFLAGS = -version-info 1:0:0 +include_HEADERS = bzlib.h bzlib_private.h + +bzip2SCRIPTS = bzless + +EXTRA_DIST = README README.COMPILATION.PROBLEMS \ + Y2K_INFO libbz2.def libbz2.dsp \ + sample1.bz2 sample1.ref sample2.bz2 sample2.ref sample3.bz2 sample3.ref + +install-exec-hook: + $(LN_S) -f bzip2 $(DESTDIR)$(bindir)/bunzip2 + $(LN_S) -f bzip2 $(DESTDIR)$(bindir)/bzcat diff -Nru bzip2-1.0.1/NEWS bzip2-1.0.1.new/NEWS --- bzip2-1.0.1/NEWS Thu Jan 1 01:00:00 1970 +++ bzip2-1.0.1.new/NEWS Sat Jun 24 20:13:06 2000 @@ -0,0 +1,12 @@ + + +1.0.1 +~~~~~ +* Modified dlltest.c so it uses the new BZ2_ naming scheme. +* Modified makefile-msc to fix minor build probs on Win2k. +* Updated README.COMPILATION.PROBLEMS. + +There are no functionality changes or bug fixes relative to version +1.0.0. This is just a documentation update + a fix for minor Win32 +build problems. For almost everyone, upgrading from 1.0.0 to 1.0.1 is +utterly pointless. Don't bother. diff -Nru bzip2-1.0.1/acinclude.m4 bzip2-1.0.1.new/acinclude.m4 --- bzip2-1.0.1/acinclude.m4 Thu Jan 1 01:00:00 1970 +++ bzip2-1.0.1.new/acinclude.m4 Sat Jun 24 20:13:06 2000 @@ -0,0 +1,129 @@ +#serial 7 + +dnl By default, many hosts won't let programs access large files; +dnl one must use special compiler options to get large-file access to work. +dnl For more details about this brain damage please see: +dnl http://www.sas.com/standards/large.file/x_open.20Mar96.html + +dnl Written by Paul Eggert . + +dnl Internal subroutine of AC_SYS_LARGEFILE. +dnl AC_SYS_LARGEFILE_FLAGS(FLAGSNAME) +AC_DEFUN(AC_SYS_LARGEFILE_FLAGS, + [AC_CACHE_CHECK([for $1 value to request large file support], + ac_cv_sys_largefile_$1, + [if ($GETCONF LFS_$1) >conftest.1 2>conftest.2 && test ! -s conftest.2 + then + ac_cv_sys_largefile_$1=`cat conftest.1` + else + ac_cv_sys_largefile_$1=no + ifelse($1, CFLAGS, + [case "$host_os" in + # HP-UX 10.20 requires -D__STDC_EXT__ with gcc 2.95.1. +changequote(, )dnl + hpux10.[2-9][0-9]* | hpux1[1-9]* | hpux[2-9][0-9]*) +changequote([, ])dnl + if test "$GCC" = yes; then + ac_cv_sys_largefile_CFLAGS=-D__STDC_EXT__ + fi + ;; + # IRIX 6.2 and later require cc -n32. +changequote(, )dnl + irix6.[2-9]* | irix6.1[0-9]* | irix[7-9].* | irix[1-9][0-9]*) +changequote([, ])dnl + if test "$GCC" != yes; then + ac_cv_sys_largefile_CFLAGS=-n32 + fi + esac + if test "$ac_cv_sys_largefile_CFLAGS" != no; then + ac_save_CC="$CC" + CC="$CC $ac_cv_sys_largefile_CFLAGS" + AC_TRY_LINK(, , , ac_cv_sys_largefile_CFLAGS=no) + CC="$ac_save_CC" + fi]) + fi + rm -f conftest*])]) + +dnl Internal subroutine of AC_SYS_LARGEFILE. +dnl AC_SYS_LARGEFILE_SPACE_APPEND(VAR, VAL) +AC_DEFUN(AC_SYS_LARGEFILE_SPACE_APPEND, + [case $2 in + no) ;; + ?*) + case "[$]$1" in + '') $1=$2 ;; + *) $1=[$]$1' '$2 ;; + esac ;; + esac]) + +dnl Internal subroutine of AC_SYS_LARGEFILE. +dnl AC_SYS_LARGEFILE_MACRO_VALUE(C-MACRO, CACHE-VAR, COMMENT, CODE-TO-SET-DEFAULT) +AC_DEFUN(AC_SYS_LARGEFILE_MACRO_VALUE, + [AC_CACHE_CHECK([for $1], $2, + [$2=no +changequote(, )dnl + $4 + for ac_flag in $ac_cv_sys_largefile_CFLAGS no; do + case "$ac_flag" in + -D$1) + $2=1 ;; + -D$1=*) + $2=`expr " $ac_flag" : '[^=]*=\(.*\)'` ;; + esac + done +changequote([, ])dnl + ]) + if test "[$]$2" != no; then + AC_DEFINE_UNQUOTED([$1], [$]$2, [$3]) + fi]) + +AC_DEFUN(AC_SYS_LARGEFILE, + [AC_REQUIRE([AC_CANONICAL_HOST]) + AC_ARG_ENABLE(largefile, + [ --disable-largefile omit support for large files]) + if test "$enable_largefile" != no; then + AC_CHECK_TOOL(GETCONF, getconf) + AC_SYS_LARGEFILE_FLAGS(CFLAGS) + AC_SYS_LARGEFILE_FLAGS(LDFLAGS) + AC_SYS_LARGEFILE_FLAGS(LIBS) + + for ac_flag in $ac_cv_sys_largefile_CFLAGS no; do + case "$ac_flag" in + no) ;; + -D_FILE_OFFSET_BITS=*) ;; + -D_LARGEFILE_SOURCE | -D_LARGEFILE_SOURCE=*) ;; + -D_LARGE_FILES | -D_LARGE_FILES=*) ;; + -D?* | -I?*) + AC_SYS_LARGEFILE_SPACE_APPEND(CPPFLAGS, "$ac_flag") ;; + *) + AC_SYS_LARGEFILE_SPACE_APPEND(CFLAGS, "$ac_flag") ;; + esac + done + AC_SYS_LARGEFILE_SPACE_APPEND(LDFLAGS, "$ac_cv_sys_largefile_LDFLAGS") + AC_SYS_LARGEFILE_SPACE_APPEND(LIBS, "$ac_cv_sys_largefile_LIBS") + AC_SYS_LARGEFILE_MACRO_VALUE(_FILE_OFFSET_BITS, + ac_cv_sys_file_offset_bits, + [Number of bits in a file offset, on hosts where this is settable.], + [case "$host_os" in + # HP-UX 10.20 and later + hpux10.[2-9][0-9]* | hpux1[1-9]* | hpux[2-9][0-9]*) + ac_cv_sys_file_offset_bits=64 ;; + esac]) + AC_SYS_LARGEFILE_MACRO_VALUE(_LARGEFILE_SOURCE, + ac_cv_sys_largefile_source, + [Define to make fseeko etc. visible, on some hosts.], + [case "$host_os" in + # HP-UX 10.20 and later + hpux10.[2-9][0-9]* | hpux1[1-9]* | hpux[2-9][0-9]*) + ac_cv_sys_largefile_source=1 ;; + esac]) + AC_SYS_LARGEFILE_MACRO_VALUE(_LARGE_FILES, + ac_cv_sys_large_files, + [Define for large files, on AIX-style hosts.], + [case "$host_os" in + # AIX 4.2 and later + aix4.[2-9]* | aix4.1[0-9]* | aix[5-9].* | aix[1-9][0-9]*) + ac_cv_sys_large_files=1 ;; + esac]) + fi + ]) diff -Nru bzip2-1.0.1/bzip2.1 bzip2-1.0.1.new/bzip2.1 --- bzip2-1.0.1/bzip2.1 Sat Jun 24 20:13:27 2000 +++ bzip2-1.0.1.new/bzip2.1 Thu Jan 1 01:00:00 1970 @@ -1,439 +0,0 @@ -.PU -.TH bzip2 1 -.SH NAME -bzip2, bunzip2 \- a block-sorting file compressor, v1.0 -.br -bzcat \- decompresses files to stdout -.br -bzip2recover \- recovers data from damaged bzip2 files - -.SH SYNOPSIS -.ll +8 -.B bzip2 -.RB [ " \-cdfkqstvzVL123456789 " ] -[ -.I "filenames \&..." -] -.ll -8 -.br -.B bunzip2 -.RB [ " \-fkvsVL " ] -[ -.I "filenames \&..." -] -.br -.B bzcat -.RB [ " \-s " ] -[ -.I "filenames \&..." -] -.br -.B bzip2recover -.I "filename" - -.SH DESCRIPTION -.I bzip2 -compresses files using the Burrows-Wheeler block sorting -text compression algorithm, and Huffman coding. Compression is -generally considerably better than that achieved by more conventional -LZ77/LZ78-based compressors, and approaches the performance of the PPM -family of statistical compressors. - -The command-line options are deliberately very similar to -those of -.I GNU gzip, -but they are not identical. - -.I bzip2 -expects a list of file names to accompany the -command-line flags. Each file is replaced by a compressed version of -itself, with the name "original_name.bz2". -Each compressed file -has the same modification date, permissions, and, when possible, -ownership as the corresponding original, so that these properties can -be correctly restored at decompression time. File name handling is -naive in the sense that there is no mechanism for preserving original -file names, permissions, ownerships or dates in filesystems which lack -these concepts, or have serious file name length restrictions, such as -MS-DOS. - -.I bzip2 -and -.I bunzip2 -will by default not overwrite existing -files. If you want this to happen, specify the \-f flag. - -If no file names are specified, -.I bzip2 -compresses from standard -input to standard output. In this case, -.I bzip2 -will decline to -write compressed output to a terminal, as this would be entirely -incomprehensible and therefore pointless. - -.I bunzip2 -(or -.I bzip2 \-d) -decompresses all -specified files. Files which were not created by -.I bzip2 -will be detected and ignored, and a warning issued. -.I bzip2 -attempts to guess the filename for the decompressed file -from that of the compressed file as follows: - - filename.bz2 becomes filename - filename.bz becomes filename - filename.tbz2 becomes filename.tar - filename.tbz becomes filename.tar - anyothername becomes anyothername.out - -If the file does not end in one of the recognised endings, -.I .bz2, -.I .bz, -.I .tbz2 -or -.I .tbz, -.I bzip2 -complains that it cannot -guess the name of the original file, and uses the original name -with -.I .out -appended. - -As with compression, supplying no -filenames causes decompression from -standard input to standard output. - -.I bunzip2 -will correctly decompress a file which is the -concatenation of two or more compressed files. The result is the -concatenation of the corresponding uncompressed files. Integrity -testing (\-t) -of concatenated -compressed files is also supported. - -You can also compress or decompress files to the standard output by -giving the \-c flag. Multiple files may be compressed and -decompressed like this. The resulting outputs are fed sequentially to -stdout. Compression of multiple files -in this manner generates a stream -containing multiple compressed file representations. Such a stream -can be decompressed correctly only by -.I bzip2 -version 0.9.0 or -later. Earlier versions of -.I bzip2 -will stop after decompressing -the first file in the stream. - -.I bzcat -(or -.I bzip2 -dc) -decompresses all specified files to -the standard output. - -.I bzip2 -will read arguments from the environment variables -.I BZIP2 -and -.I BZIP, -in that order, and will process them -before any arguments read from the command line. This gives a -convenient way to supply default arguments. - -Compression is always performed, even if the compressed -file is slightly -larger than the original. Files of less than about one hundred bytes -tend to get larger, since the compression mechanism has a constant -overhead in the region of 50 bytes. Random data (including the output -of most file compressors) is coded at about 8.05 bits per byte, giving -an expansion of around 0.5%. - -As a self-check for your protection, -.I -bzip2 -uses 32-bit CRCs to -make sure that the decompressed version of a file is identical to the -original. This guards against corruption of the compressed data, and -against undetected bugs in -.I bzip2 -(hopefully very unlikely). The -chances of data corruption going undetected is microscopic, about one -chance in four billion for each file processed. Be aware, though, that -the check occurs upon decompression, so it can only tell you that -something is wrong. It can't help you -recover the original uncompressed -data. You can use -.I bzip2recover -to try to recover data from -damaged files. - -Return values: 0 for a normal exit, 1 for environmental problems (file -not found, invalid flags, I/O errors, &c), 2 to indicate a corrupt -compressed file, 3 for an internal consistency error (eg, bug) which -caused -.I bzip2 -to panic. - -.SH OPTIONS -.TP -.B \-c --stdout -Compress or decompress to standard output. -.TP -.B \-d --decompress -Force decompression. -.I bzip2, -.I bunzip2 -and -.I bzcat -are -really the same program, and the decision about what actions to take is -done on the basis of which name is used. This flag overrides that -mechanism, and forces -.I bzip2 -to decompress. -.TP -.B \-z --compress -The complement to \-d: forces compression, regardless of the -invokation name. -.TP -.B \-t --test -Check integrity of the specified file(s), but don't decompress them. -This really performs a trial decompression and throws away the result. -.TP -.B \-f --force -Force overwrite of output files. Normally, -.I bzip2 -will not overwrite -existing output files. Also forces -.I bzip2 -to break hard links -to files, which it otherwise wouldn't do. -.TP -.B \-k --keep -Keep (don't delete) input files during compression -or decompression. -.TP -.B \-s --small -Reduce memory usage, for compression, decompression and testing. Files -are decompressed and tested using a modified algorithm which only -requires 2.5 bytes per block byte. This means any file can be -decompressed in 2300k of memory, albeit at about half the normal speed. - -During compression, \-s selects a block size of 200k, which limits -memory use to around the same figure, at the expense of your compression -ratio. In short, if your machine is low on memory (8 megabytes or -less), use \-s for everything. See MEMORY MANAGEMENT below. -.TP -.B \-q --quiet -Suppress non-essential warning messages. Messages pertaining to -I/O errors and other critical events will not be suppressed. -.TP -.B \-v --verbose -Verbose mode -- show the compression ratio for each file processed. -Further \-v's increase the verbosity level, spewing out lots of -information which is primarily of interest for diagnostic purposes. -.TP -.B \-L --license -V --version -Display the software version, license terms and conditions. -.TP -.B \-1 to \-9 -Set the block size to 100 k, 200 k .. 900 k when compressing. Has no -effect when decompressing. See MEMORY MANAGEMENT below. -.TP -.B \-- -Treats all subsequent arguments as file names, even if they start -with a dash. This is so you can handle files with names beginning -with a dash, for example: bzip2 \-- \-myfilename. -.TP -.B \--repetitive-fast --repetitive-best -These flags are redundant in versions 0.9.5 and above. They provided -some coarse control over the behaviour of the sorting algorithm in -earlier versions, which was sometimes useful. 0.9.5 and above have an -improved algorithm which renders these flags irrelevant. - -.SH MEMORY MANAGEMENT -.I bzip2 -compresses large files in blocks. The block size affects -both the compression ratio achieved, and the amount of memory needed for -compression and decompression. The flags \-1 through \-9 -specify the block size to be 100,000 bytes through 900,000 bytes (the -default) respectively. At decompression time, the block size used for -compression is read from the header of the compressed file, and -.I bunzip2 -then allocates itself just enough memory to decompress -the file. Since block sizes are stored in compressed files, it follows -that the flags \-1 to \-9 are irrelevant to and so ignored -during decompression. - -Compression and decompression requirements, -in bytes, can be estimated as: - - Compression: 400k + ( 8 x block size ) - - Decompression: 100k + ( 4 x block size ), or - 100k + ( 2.5 x block size ) - -Larger block sizes give rapidly diminishing marginal returns. Most of -the compression comes from the first two or three hundred k of block -size, a fact worth bearing in mind when using -.I bzip2 -on small machines. -It is also important to appreciate that the decompression memory -requirement is set at compression time by the choice of block size. - -For files compressed with the default 900k block size, -.I bunzip2 -will require about 3700 kbytes to decompress. To support decompression -of any file on a 4 megabyte machine, -.I bunzip2 -has an option to -decompress using approximately half this amount of memory, about 2300 -kbytes. Decompression speed is also halved, so you should use this -option only where necessary. The relevant flag is -s. - -In general, try and use the largest block size memory constraints allow, -since that maximises the compression achieved. Compression and -decompression speed are virtually unaffected by block size. - -Another significant point applies to files which fit in a single block --- that means most files you'd encounter using a large block size. The -amount of real memory touched is proportional to the size of the file, -since the file is smaller than a block. For example, compressing a file -20,000 bytes long with the flag -9 will cause the compressor to -allocate around 7600k of memory, but only touch 400k + 20000 * 8 = 560 -kbytes of it. Similarly, the decompressor will allocate 3700k but only -touch 100k + 20000 * 4 = 180 kbytes. - -Here is a table which summarises the maximum memory usage for different -block sizes. Also recorded is the total compressed size for 14 files of -the Calgary Text Compression Corpus totalling 3,141,622 bytes. This -column gives some feel for how compression varies with block size. -These figures tend to understate the advantage of larger block sizes for -larger files, since the Corpus is dominated by smaller files. - - Compress Decompress Decompress Corpus - Flag usage usage -s usage Size - - -1 1200k 500k 350k 914704 - -2 2000k 900k 600k 877703 - -3 2800k 1300k 850k 860338 - -4 3600k 1700k 1100k 846899 - -5 4400k 2100k 1350k 845160 - -6 5200k 2500k 1600k 838626 - -7 6100k 2900k 1850k 834096 - -8 6800k 3300k 2100k 828642 - -9 7600k 3700k 2350k 828642 - -.SH RECOVERING DATA FROM DAMAGED FILES -.I bzip2 -compresses files in blocks, usually 900kbytes long. Each -block is handled independently. If a media or transmission error causes -a multi-block .bz2 -file to become damaged, it may be possible to -recover data from the undamaged blocks in the file. - -The compressed representation of each block is delimited by a 48-bit -pattern, which makes it possible to find the block boundaries with -reasonable certainty. Each block also carries its own 32-bit CRC, so -damaged blocks can be distinguished from undamaged ones. - -.I bzip2recover -is a simple program whose purpose is to search for -blocks in .bz2 files, and write each block out into its own .bz2 -file. You can then use -.I bzip2 -\-t -to test the -integrity of the resulting files, and decompress those which are -undamaged. - -.I bzip2recover -takes a single argument, the name of the damaged file, -and writes a number of files "rec0001file.bz2", -"rec0002file.bz2", etc, containing the extracted blocks. -The output filenames are designed so that the use of -wildcards in subsequent processing -- for example, -"bzip2 -dc rec*file.bz2 > recovered_data" -- lists the files in -the correct order. - -.I bzip2recover -should be of most use dealing with large .bz2 -files, as these will contain many blocks. It is clearly -futile to use it on damaged single-block files, since a -damaged block cannot be recovered. If you wish to minimise -any potential data loss through media or transmission errors, -you might consider compressing with a smaller -block size. - -.SH PERFORMANCE NOTES -The sorting phase of compression gathers together similar strings in the -file. Because of this, files containing very long runs of repeated -symbols, like "aabaabaabaab ..." (repeated several hundred times) may -compress more slowly than normal. Versions 0.9.5 and above fare much -better than previous versions in this respect. The ratio between -worst-case and average-case compression time is in the region of 10:1. -For previous versions, this figure was more like 100:1. You can use the -\-vvvv option to monitor progress in great detail, if you want. - -Decompression speed is unaffected by these phenomena. - -.I bzip2 -usually allocates several megabytes of memory to operate -in, and then charges all over it in a fairly random fashion. This means -that performance, both for compressing and decompressing, is largely -determined by the speed at which your machine can service cache misses. -Because of this, small changes to the code to reduce the miss rate have -been observed to give disproportionately large performance improvements. -I imagine -.I bzip2 -will perform best on machines with very large caches. - -.SH CAVEATS -I/O error messages are not as helpful as they could be. -.I bzip2 -tries hard to detect I/O errors and exit cleanly, but the details of -what the problem is sometimes seem rather misleading. - -This manual page pertains to version 1.0 of -.I bzip2. -Compressed -data created by this version is entirely forwards and backwards -compatible with the previous public releases, versions 0.1pl2, 0.9.0 -and 0.9.5, -but with the following exception: 0.9.0 and above can correctly -decompress multiple concatenated compressed files. 0.1pl2 cannot do -this; it will stop after decompressing just the first file in the -stream. - -.I bzip2recover -uses 32-bit integers to represent bit positions in -compressed files, so it cannot handle compressed files more than 512 -megabytes long. This could easily be fixed. - -.SH AUTHOR -Julian Seward, jseward@acm.org. - -http://sourceware.cygnus.com/bzip2 -http://www.muraroa.demon.co.uk - -The ideas embodied in -.I bzip2 -are due to (at least) the following -people: Michael Burrows and David Wheeler (for the block sorting -transformation), David Wheeler (again, for the Huffman coder), Peter -Fenwick (for the structured coding model in the original -.I bzip, -and many refinements), and Alistair Moffat, Radford Neal and Ian Witten -(for the arithmetic coder in the original -.I bzip). -I am much -indebted for their help, support and advice. See the manual in the -source distribution for pointers to sources of documentation. Christian -von Roques encouraged me to look for faster sorting algorithms, so as to -speed up compression. Bela Lubkin encouraged me to improve the -worst-case compression performance. Many people sent patches, helped -with portability problems, lent machines, gave advice and were generally -helpful. diff -Nru bzip2-1.0.1/bzip2.1.preformatted bzip2-1.0.1.new/bzip2.1.preformatted --- bzip2-1.0.1/bzip2.1.preformatted Sat Jun 24 20:13:27 2000 +++ bzip2-1.0.1.new/bzip2.1.preformatted Thu Jan 1 01:00:00 1970 @@ -1,462 +0,0 @@ - - - -bzip2(1) bzip2(1) - - -NNAAMMEE - bzip2, bunzip2 - a block-sorting file compressor, v1.0 - bzcat - decompresses files to stdout - bzip2recover - recovers data from damaged bzip2 files - - -SSYYNNOOPPSSIISS - bbzziipp22 [ --ccddffkkqqssttvvzzVVLL112233445566778899 ] [ _f_i_l_e_n_a_m_e_s _._._. ] - bbuunnzziipp22 [ --ffkkvvssVVLL ] [ _f_i_l_e_n_a_m_e_s _._._. ] - bbzzccaatt [ --ss ] [ _f_i_l_e_n_a_m_e_s _._._. ] - bbzziipp22rreeccoovveerr _f_i_l_e_n_a_m_e - - -DDEESSCCRRIIPPTTIIOONN - _b_z_i_p_2 compresses files using the Burrows-Wheeler block - sorting text compression algorithm, and Huffman coding. - Compression is generally considerably better than that - achieved by more conventional LZ77/LZ78-based compressors, - and approaches the performance of the PPM family of sta- - tistical compressors. - - The command-line options are deliberately very similar to - those of _G_N_U _g_z_i_p_, but they are not identical. - - _b_z_i_p_2 expects a list of file names to accompany the com- - mand-line flags. Each file is replaced by a compressed - version of itself, with the name "original_name.bz2". - Each compressed file has the same modification date, per- - missions, and, when possible, ownership as the correspond- - ing original, so that these properties can be correctly - restored at decompression time. File name handling is - naive in the sense that there is no mechanism for preserv- - ing original file names, permissions, ownerships or dates - in filesystems which lack these concepts, or have serious - file name length restrictions, such as MS-DOS. - - _b_z_i_p_2 and _b_u_n_z_i_p_2 will by default not overwrite existing - files. If you want this to happen, specify the -f flag. - - If no file names are specified, _b_z_i_p_2 compresses from - standard input to standard output. In this case, _b_z_i_p_2 - will decline to write compressed output to a terminal, as - this would be entirely incomprehensible and therefore - pointless. - - _b_u_n_z_i_p_2 (or _b_z_i_p_2 _-_d_) decompresses all specified files. - Files which were not created by _b_z_i_p_2 will be detected and - ignored, and a warning issued. _b_z_i_p_2 attempts to guess - the filename for the decompressed file from that of the - compressed file as follows: - - filename.bz2 becomes filename - filename.bz becomes filename - filename.tbz2 becomes filename.tar - - - - 1 - - - - - -bzip2(1) bzip2(1) - - - filename.tbz becomes filename.tar - anyothername becomes anyothername.out - - If the file does not end in one of the recognised endings, - _._b_z_2_, _._b_z_, _._t_b_z_2 or _._t_b_z_, _b_z_i_p_2 complains that it cannot - guess the name of the original file, and uses the original - name with _._o_u_t appended. - - As with compression, supplying no filenames causes decom- - pression from standard input to standard output. - - _b_u_n_z_i_p_2 will correctly decompress a file which is the con- - catenation of two or more compressed files. The result is - the concatenation of the corresponding uncompressed files. - Integrity testing (-t) of concatenated compressed files is - also supported. - - You can also compress or decompress files to the standard - output by giving the -c flag. Multiple files may be com- - pressed and decompressed like this. The resulting outputs - are fed sequentially to stdout. Compression of multiple - files in this manner generates a stream containing multi- - ple compressed file representations. Such a stream can be - decompressed correctly only by _b_z_i_p_2 version 0.9.0 or - later. Earlier versions of _b_z_i_p_2 will stop after decom- - pressing the first file in the stream. - - _b_z_c_a_t (or _b_z_i_p_2 _-_d_c_) decompresses all specified files to - the standard output. - - _b_z_i_p_2 will read arguments from the environment variables - _B_Z_I_P_2 and _B_Z_I_P_, in that order, and will process them - before any arguments read from the command line. This - gives a convenient way to supply default arguments. - - Compression is always performed, even if the compressed - file is slightly larger than the original. Files of less - than about one hundred bytes tend to get larger, since the - compression mechanism has a constant overhead in the - region of 50 bytes. Random data (including the output of - most file compressors) is coded at about 8.05 bits per - byte, giving an expansion of around 0.5%. - - As a self-check for your protection, _b_z_i_p_2 uses 32-bit - CRCs to make sure that the decompressed version of a file - is identical to the original. This guards against corrup- - tion of the compressed data, and against undetected bugs - in _b_z_i_p_2 (hopefully very unlikely). The chances of data - corruption going undetected is microscopic, about one - chance in four billion for each file processed. Be aware, - though, that the check occurs upon decompression, so it - can only tell you that something is wrong. It can't help - you recover the original uncompressed data. You can use - _b_z_i_p_2_r_e_c_o_v_e_r to try to recover data from damaged files. - - - - 2 - - - - - -bzip2(1) bzip2(1) - - - Return values: 0 for a normal exit, 1 for environmental - problems (file not found, invalid flags, I/O errors, &c), - 2 to indicate a corrupt compressed file, 3 for an internal - consistency error (eg, bug) which caused _b_z_i_p_2 to panic. - - -OOPPTTIIOONNSS - --cc ----ssttddoouutt - Compress or decompress to standard output. - - --dd ----ddeeccoommpprreessss - Force decompression. _b_z_i_p_2_, _b_u_n_z_i_p_2 and _b_z_c_a_t are - really the same program, and the decision about - what actions to take is done on the basis of which - name is used. This flag overrides that mechanism, - and forces _b_z_i_p_2 to decompress. - - --zz ----ccoommpprreessss - The complement to -d: forces compression, regard- - less of the invokation name. - - --tt ----tteesstt - Check integrity of the specified file(s), but don't - decompress them. This really performs a trial - decompression and throws away the result. - - --ff ----ffoorrccee - Force overwrite of output files. Normally, _b_z_i_p_2 - will not overwrite existing output files. Also - forces _b_z_i_p_2 to break hard links to files, which it - otherwise wouldn't do. - - --kk ----kkeeeepp - Keep (don't delete) input files during compression - or decompression. - - --ss ----ssmmaallll - Reduce memory usage, for compression, decompression - and testing. Files are decompressed and tested - using a modified algorithm which only requires 2.5 - bytes per block byte. This means any file can be - decompressed in 2300k of memory, albeit at about - half the normal speed. - - During compression, -s selects a block size of - 200k, which limits memory use to around the same - figure, at the expense of your compression ratio. - In short, if your machine is low on memory (8 - megabytes or less), use -s for everything. See - MEMORY MANAGEMENT below. - - --qq ----qquuiieett - Suppress non-essential warning messages. Messages - pertaining to I/O errors and other critical events - - - - 3 - - - - - -bzip2(1) bzip2(1) - - - will not be suppressed. - - --vv ----vveerrbboossee - Verbose mode -- show the compression ratio for each - file processed. Further -v's increase the ver- - bosity level, spewing out lots of information which - is primarily of interest for diagnostic purposes. - - --LL ----lliicceennssee --VV ----vveerrssiioonn - Display the software version, license terms and - conditions. - - --11 ttoo --99 - Set the block size to 100 k, 200 k .. 900 k when - compressing. Has no effect when decompressing. - See MEMORY MANAGEMENT below. - - ---- Treats all subsequent arguments as file names, even - if they start with a dash. This is so you can han- - dle files with names beginning with a dash, for - example: bzip2 -- -myfilename. - - ----rreeppeettiittiivvee--ffaasstt ----rreeppeettiittiivvee--bbeesstt - These flags are redundant in versions 0.9.5 and - above. They provided some coarse control over the - behaviour of the sorting algorithm in earlier ver- - sions, which was sometimes useful. 0.9.5 and above - have an improved algorithm which renders these - flags irrelevant. - - -MMEEMMOORRYY MMAANNAAGGEEMMEENNTT - _b_z_i_p_2 compresses large files in blocks. The block size - affects both the compression ratio achieved, and the - amount of memory needed for compression and decompression. - The flags -1 through -9 specify the block size to be - 100,000 bytes through 900,000 bytes (the default) respec- - tively. At decompression time, the block size used for - compression is read from the header of the compressed - file, and _b_u_n_z_i_p_2 then allocates itself just enough memory - to decompress the file. Since block sizes are stored in - compressed files, it follows that the flags -1 to -9 are - irrelevant to and so ignored during decompression. - - Compression and decompression requirements, in bytes, can - be estimated as: - - Compression: 400k + ( 8 x block size ) - - Decompression: 100k + ( 4 x block size ), or - 100k + ( 2.5 x block size ) - - Larger block sizes give rapidly diminishing marginal - returns. Most of the compression comes from the first two - - - - 4 - - - - - -bzip2(1) bzip2(1) - - - or three hundred k of block size, a fact worth bearing in - mind when using _b_z_i_p_2 on small machines. It is also - important to appreciate that the decompression memory - requirement is set at compression time by the choice of - block size. - - For files compressed with the default 900k block size, - _b_u_n_z_i_p_2 will require about 3700 kbytes to decompress. To - support decompression of any file on a 4 megabyte machine, - _b_u_n_z_i_p_2 has an option to decompress using approximately - half this amount of memory, about 2300 kbytes. Decompres- - sion speed is also halved, so you should use this option - only where necessary. The relevant flag is -s. - - In general, try and use the largest block size memory con- - straints allow, since that maximises the compression - achieved. Compression and decompression speed are virtu- - ally unaffected by block size. - - Another significant point applies to files which fit in a - single block -- that means most files you'd encounter - using a large block size. The amount of real memory - touched is proportional to the size of the file, since the - file is smaller than a block. For example, compressing a - file 20,000 bytes long with the flag -9 will cause the - compressor to allocate around 7600k of memory, but only - touch 400k + 20000 * 8 = 560 kbytes of it. Similarly, the - decompressor will allocate 3700k but only touch 100k + - 20000 * 4 = 180 kbytes. - - Here is a table which summarises the maximum memory usage - for different block sizes. Also recorded is the total - compressed size for 14 files of the Calgary Text Compres- - sion Corpus totalling 3,141,622 bytes. This column gives - some feel for how compression varies with block size. - These figures tend to understate the advantage of larger - block sizes for larger files, since the Corpus is domi- - nated by smaller files. - - Compress Decompress Decompress Corpus - Flag usage usage -s usage Size - - -1 1200k 500k 350k 914704 - -2 2000k 900k 600k 877703 - -3 2800k 1300k 850k 860338 - -4 3600k 1700k 1100k 846899 - -5 4400k 2100k 1350k 845160 - -6 5200k 2500k 1600k 838626 - -7 6100k 2900k 1850k 834096 - -8 6800k 3300k 2100k 828642 - -9 7600k 3700k 2350k 828642 - - - - - - - 5 - - - - - -bzip2(1) bzip2(1) - - -RREECCOOVVEERRIINNGG DDAATTAA FFRROOMM DDAAMMAAGGEEDD FFIILLEESS - _b_z_i_p_2 compresses files in blocks, usually 900kbytes long. - Each block is handled independently. If a media or trans- - mission error causes a multi-block .bz2 file to become - damaged, it may be possible to recover data from the - undamaged blocks in the file. - - The compressed representation of each block is delimited - by a 48-bit pattern, which makes it possible to find the - block boundaries with reasonable certainty. Each block - also carries its own 32-bit CRC, so damaged blocks can be - distinguished from undamaged ones. - - _b_z_i_p_2_r_e_c_o_v_e_r is a simple program whose purpose is to - search for blocks in .bz2 files, and write each block out - into its own .bz2 file. You can then use _b_z_i_p_2 -t to test - the integrity of the resulting files, and decompress those - which are undamaged. - - _b_z_i_p_2_r_e_c_o_v_e_r takes a single argument, the name of the dam- - aged file, and writes a number of files "rec0001file.bz2", - "rec0002file.bz2", etc, containing the extracted blocks. - The output filenames are designed so that the use of - wildcards in subsequent processing -- for example, "bzip2 - -dc rec*file.bz2 > recovered_data" -- lists the files in - the correct order. - - _b_z_i_p_2_r_e_c_o_v_e_r should be of most use dealing with large .bz2 - files, as these will contain many blocks. It is clearly - futile to use it on damaged single-block files, since a - damaged block cannot be recovered. If you wish to min- - imise any potential data loss through media or transmis- - sion errors, you might consider compressing with a smaller - block size. - - -PPEERRFFOORRMMAANNCCEE NNOOTTEESS - The sorting phase of compression gathers together similar - strings in the file. Because of this, files containing - very long runs of repeated symbols, like "aabaabaabaab - ..." (repeated several hundred times) may compress more - slowly than normal. Versions 0.9.5 and above fare much - better than previous versions in this respect. The ratio - between worst-case and average-case compression time is in - the region of 10:1. For previous versions, this figure - was more like 100:1. You can use the -vvvv option to mon- - itor progress in great detail, if you want. - - Decompression speed is unaffected by these phenomena. - - _b_z_i_p_2 usually allocates several megabytes of memory to - operate in, and then charges all over it in a fairly ran- - dom fashion. This means that performance, both for com- - pressing and decompressing, is largely determined by the - - - - 6 - - - - - -bzip2(1) bzip2(1) - - - speed at which your machine can service cache misses. - Because of this, small changes to the code to reduce the - miss rate have been observed to give disproportionately - large performance improvements. I imagine _b_z_i_p_2 will per- - form best on machines with very large caches. - - -CCAAVVEEAATTSS - I/O error messages are not as helpful as they could be. - _b_z_i_p_2 tries hard to detect I/O errors and exit cleanly, - but the details of what the problem is sometimes seem - rather misleading. - - This manual page pertains to version 1.0 of _b_z_i_p_2_. Com- - pressed data created by this version is entirely forwards - and backwards compatible with the previous public - releases, versions 0.1pl2, 0.9.0 and 0.9.5, but with the - following exception: 0.9.0 and above can correctly decom- - press multiple concatenated compressed files. 0.1pl2 can- - not do this; it will stop after decompressing just the - first file in the stream. - - _b_z_i_p_2_r_e_c_o_v_e_r uses 32-bit integers to represent bit posi- - tions in compressed files, so it cannot handle compressed - files more than 512 megabytes long. This could easily be - fixed. - - -AAUUTTHHOORR - Julian Seward, jseward@acm.org. - - http://sourceware.cygnus.com/bzip2 - http://www.muraroa.demon.co.uk - - The ideas embodied in _b_z_i_p_2 are due to (at least) the fol- - lowing people: Michael Burrows and David Wheeler (for the - block sorting transformation), David Wheeler (again, for - the Huffman coder), Peter Fenwick (for the structured cod- - ing model in the original _b_z_i_p_, and many refinements), and - Alistair Moffat, Radford Neal and Ian Witten (for the - arithmetic coder in the original _b_z_i_p_)_. I am much - indebted for their help, support and advice. See the man- - ual in the source distribution for pointers to sources of - documentation. Christian von Roques encouraged me to look - for faster sorting algorithms, so as to speed up compres- - sion. Bela Lubkin encouraged me to improve the worst-case - compression performance. Many people sent patches, helped - with portability problems, lent machines, gave advice and - were generally helpful. - - - - - - - - - 7 - - diff -Nru bzip2-1.0.1/bzless bzip2-1.0.1.new/bzless --- bzip2-1.0.1/bzless Thu Jan 1 01:00:00 1970 +++ bzip2-1.0.1.new/bzless Sat Jun 24 20:16:09 2000 @@ -0,0 +1,2 @@ +#!/bin/sh +%{_bindir}/bunzip2 -c "\$@" | /usr/bin/less diff -Nru bzip2-1.0.1/config.h.in bzip2-1.0.1.new/config.h.in --- bzip2-1.0.1/config.h.in Thu Jan 1 01:00:00 1970 +++ bzip2-1.0.1.new/config.h.in Sat Jun 24 20:13:06 2000 @@ -0,0 +1,17 @@ +/* config.h.in. Generated automatically from configure.in by autoheader. */ + +/* Name of package */ +#undef PACKAGE + +/* Version number of package */ +#undef VERSION + +/* Number of bits in a file offset, on hosts where this is settable. */ +#undef _FILE_OFFSET_BITS + +/* Define to make fseeko etc. visible, on some hosts. */ +#undef _LARGEFILE_SOURCE + +/* Define for large files, on AIX-style hosts. */ +#undef _LARGE_FILES + diff -Nru bzip2-1.0.1/configure.in bzip2-1.0.1.new/configure.in --- bzip2-1.0.1/configure.in Thu Jan 1 01:00:00 1970 +++ bzip2-1.0.1.new/configure.in Sat Jun 24 20:13:06 2000 @@ -0,0 +1,10 @@ +AC_INIT(bzip2.c) +AM_INIT_AUTOMAKE(bzip2,1.0.1) +AM_CONFIG_HEADER(config.h) +AC_PROG_CC +AM_PROG_LIBTOOL +AC_PROG_LN_S +AC_SYS_LARGEFILE +AC_OUTPUT(Makefile + doc/Makefile + doc/pl/Makefile) diff -Nru bzip2-1.0.1/crctable.c bzip2-1.0.1.new/crctable.c --- bzip2-1.0.1/crctable.c Sat Jun 24 20:13:27 2000 +++ bzip2-1.0.1.new/crctable.c Sat Jun 24 20:13:06 2000 @@ -58,6 +58,10 @@ For more information on these sources, see the manual. --*/ +#ifdef HAVE_CONFIG_H +#include +#endif + #include "bzlib_private.h" diff -Nru bzip2-1.0.1/decompress.c bzip2-1.0.1.new/decompress.c --- bzip2-1.0.1/decompress.c Sat Jun 24 20:13:27 2000 +++ bzip2-1.0.1.new/decompress.c Sat Jun 24 20:13:06 2000 @@ -58,6 +58,10 @@ For more information on these sources, see the manual. --*/ +#ifdef HAVE_CONFIG_H +#include +#endif + #include "bzlib_private.h" diff -Nru bzip2-1.0.1/dlltest.c bzip2-1.0.1.new/dlltest.c --- bzip2-1.0.1/dlltest.c Sat Jun 24 20:13:27 2000 +++ bzip2-1.0.1.new/dlltest.c Sat Jun 24 20:13:06 2000 @@ -8,6 +8,10 @@ usage: minibz2 [-d] [-{1,2,..9}] [[srcfilename] destfilename] */ +#ifdef HAVE_CONFIG_H +#include +#endif + #define BZ_IMPORT #include #include diff -Nru bzip2-1.0.1/doc/Makefile.am bzip2-1.0.1.new/doc/Makefile.am --- bzip2-1.0.1/doc/Makefile.am Thu Jan 1 01:00:00 1970 +++ bzip2-1.0.1.new/doc/Makefile.am Sat Jun 24 20:14:43 2000 @@ -0,0 +1,5 @@ + +SUBDIRS = pl + +man_MANS = bzip2.1 bunzip2.1 bzcat.1 bzip2recover.1 +#info_TEXINFOS = bzip2.texi diff -Nru bzip2-1.0.1/doc/bunzip2.1 bzip2-1.0.1.new/doc/bunzip2.1 --- bzip2-1.0.1/doc/bunzip2.1 Thu Jan 1 01:00:00 1970 +++ bzip2-1.0.1.new/doc/bunzip2.1 Sat Jun 24 20:13:06 2000 @@ -0,0 +1 @@ +.so bzip2.1 \ No newline at end of file diff -Nru bzip2-1.0.1/doc/bzcat.1 bzip2-1.0.1.new/doc/bzcat.1 --- bzip2-1.0.1/doc/bzcat.1 Thu Jan 1 01:00:00 1970 +++ bzip2-1.0.1.new/doc/bzcat.1 Sat Jun 24 20:13:06 2000 @@ -0,0 +1 @@ +.so bzip2.1 \ No newline at end of file diff -Nru bzip2-1.0.1/doc/bzip2.1 bzip2-1.0.1.new/doc/bzip2.1 --- bzip2-1.0.1/doc/bzip2.1 Thu Jan 1 01:00:00 1970 +++ bzip2-1.0.1.new/doc/bzip2.1 Sat Jun 24 20:13:06 2000 @@ -0,0 +1,439 @@ +.PU +.TH bzip2 1 +.SH NAME +bzip2, bunzip2 \- a block-sorting file compressor, v1.0 +.br +bzcat \- decompresses files to stdout +.br +bzip2recover \- recovers data from damaged bzip2 files + +.SH SYNOPSIS +.ll +8 +.B bzip2 +.RB [ " \-cdfkqstvzVL123456789 " ] +[ +.I "filenames \&..." +] +.ll -8 +.br +.B bunzip2 +.RB [ " \-fkvsVL " ] +[ +.I "filenames \&..." +] +.br +.B bzcat +.RB [ " \-s " ] +[ +.I "filenames \&..." +] +.br +.B bzip2recover +.I "filename" + +.SH DESCRIPTION +.I bzip2 +compresses files using the Burrows-Wheeler block sorting +text compression algorithm, and Huffman coding. Compression is +generally considerably better than that achieved by more conventional +LZ77/LZ78-based compressors, and approaches the performance of the PPM +family of statistical compressors. + +The command-line options are deliberately very similar to +those of +.I GNU gzip, +but they are not identical. + +.I bzip2 +expects a list of file names to accompany the +command-line flags. Each file is replaced by a compressed version of +itself, with the name "original_name.bz2". +Each compressed file +has the same modification date, permissions, and, when possible, +ownership as the corresponding original, so that these properties can +be correctly restored at decompression time. File name handling is +naive in the sense that there is no mechanism for preserving original +file names, permissions, ownerships or dates in filesystems which lack +these concepts, or have serious file name length restrictions, such as +MS-DOS. + +.I bzip2 +and +.I bunzip2 +will by default not overwrite existing +files. If you want this to happen, specify the \-f flag. + +If no file names are specified, +.I bzip2 +compresses from standard +input to standard output. In this case, +.I bzip2 +will decline to +write compressed output to a terminal, as this would be entirely +incomprehensible and therefore pointless. + +.I bunzip2 +(or +.I bzip2 \-d) +decompresses all +specified files. Files which were not created by +.I bzip2 +will be detected and ignored, and a warning issued. +.I bzip2 +attempts to guess the filename for the decompressed file +from that of the compressed file as follows: + + filename.bz2 becomes filename + filename.bz becomes filename + filename.tbz2 becomes filename.tar + filename.tbz becomes filename.tar + anyothername becomes anyothername.out + +If the file does not end in one of the recognised endings, +.I .bz2, +.I .bz, +.I .tbz2 +or +.I .tbz, +.I bzip2 +complains that it cannot +guess the name of the original file, and uses the original name +with +.I .out +appended. + +As with compression, supplying no +filenames causes decompression from +standard input to standard output. + +.I bunzip2 +will correctly decompress a file which is the +concatenation of two or more compressed files. The result is the +concatenation of the corresponding uncompressed files. Integrity +testing (\-t) +of concatenated +compressed files is also supported. + +You can also compress or decompress files to the standard output by +giving the \-c flag. Multiple files may be compressed and +decompressed like this. The resulting outputs are fed sequentially to +stdout. Compression of multiple files +in this manner generates a stream +containing multiple compressed file representations. Such a stream +can be decompressed correctly only by +.I bzip2 +version 0.9.0 or +later. Earlier versions of +.I bzip2 +will stop after decompressing +the first file in the stream. + +.I bzcat +(or +.I bzip2 -dc) +decompresses all specified files to +the standard output. + +.I bzip2 +will read arguments from the environment variables +.I BZIP2 +and +.I BZIP, +in that order, and will process them +before any arguments read from the command line. This gives a +convenient way to supply default arguments. + +Compression is always performed, even if the compressed +file is slightly +larger than the original. Files of less than about one hundred bytes +tend to get larger, since the compression mechanism has a constant +overhead in the region of 50 bytes. Random data (including the output +of most file compressors) is coded at about 8.05 bits per byte, giving +an expansion of around 0.5%. + +As a self-check for your protection, +.I +bzip2 +uses 32-bit CRCs to +make sure that the decompressed version of a file is identical to the +original. This guards against corruption of the compressed data, and +against undetected bugs in +.I bzip2 +(hopefully very unlikely). The +chances of data corruption going undetected is microscopic, about one +chance in four billion for each file processed. Be aware, though, that +the check occurs upon decompression, so it can only tell you that +something is wrong. It can't help you +recover the original uncompressed +data. You can use +.I bzip2recover +to try to recover data from +damaged files. + +Return values: 0 for a normal exit, 1 for environmental problems (file +not found, invalid flags, I/O errors, &c), 2 to indicate a corrupt +compressed file, 3 for an internal consistency error (eg, bug) which +caused +.I bzip2 +to panic. + +.SH OPTIONS +.TP +.B \-c --stdout +Compress or decompress to standard output. +.TP +.B \-d --decompress +Force decompression. +.I bzip2, +.I bunzip2 +and +.I bzcat +are +really the same program, and the decision about what actions to take is +done on the basis of which name is used. This flag overrides that +mechanism, and forces +.I bzip2 +to decompress. +.TP +.B \-z --compress +The complement to \-d: forces compression, regardless of the +invokation name. +.TP +.B \-t --test +Check integrity of the specified file(s), but don't decompress them. +This really performs a trial decompression and throws away the result. +.TP +.B \-f --force +Force overwrite of output files. Normally, +.I bzip2 +will not overwrite +existing output files. Also forces +.I bzip2 +to break hard links +to files, which it otherwise wouldn't do. +.TP +.B \-k --keep +Keep (don't delete) input files during compression +or decompression. +.TP +.B \-s --small +Reduce memory usage, for compression, decompression and testing. Files +are decompressed and tested using a modified algorithm which only +requires 2.5 bytes per block byte. This means any file can be +decompressed in 2300k of memory, albeit at about half the normal speed. + +During compression, \-s selects a block size of 200k, which limits +memory use to around the same figure, at the expense of your compression +ratio. In short, if your machine is low on memory (8 megabytes or +less), use \-s for everything. See MEMORY MANAGEMENT below. +.TP +.B \-q --quiet +Suppress non-essential warning messages. Messages pertaining to +I/O errors and other critical events will not be suppressed. +.TP +.B \-v --verbose +Verbose mode -- show the compression ratio for each file processed. +Further \-v's increase the verbosity level, spewing out lots of +information which is primarily of interest for diagnostic purposes. +.TP +.B \-L --license -V --version +Display the software version, license terms and conditions. +.TP +.B \-1 to \-9 +Set the block size to 100 k, 200 k .. 900 k when compressing. Has no +effect when decompressing. See MEMORY MANAGEMENT below. +.TP +.B \-- +Treats all subsequent arguments as file names, even if they start +with a dash. This is so you can handle files with names beginning +with a dash, for example: bzip2 \-- \-myfilename. +.TP +.B \--repetitive-fast --repetitive-best +These flags are redundant in versions 0.9.5 and above. They provided +some coarse control over the behaviour of the sorting algorithm in +earlier versions, which was sometimes useful. 0.9.5 and above have an +improved algorithm which renders these flags irrelevant. + +.SH MEMORY MANAGEMENT +.I bzip2 +compresses large files in blocks. The block size affects +both the compression ratio achieved, and the amount of memory needed for +compression and decompression. The flags \-1 through \-9 +specify the block size to be 100,000 bytes through 900,000 bytes (the +default) respectively. At decompression time, the block size used for +compression is read from the header of the compressed file, and +.I bunzip2 +then allocates itself just enough memory to decompress +the file. Since block sizes are stored in compressed files, it follows +that the flags \-1 to \-9 are irrelevant to and so ignored +during decompression. + +Compression and decompression requirements, +in bytes, can be estimated as: + + Compression: 400k + ( 8 x block size ) + + Decompression: 100k + ( 4 x block size ), or + 100k + ( 2.5 x block size ) + +Larger block sizes give rapidly diminishing marginal returns. Most of +the compression comes from the first two or three hundred k of block +size, a fact worth bearing in mind when using +.I bzip2 +on small machines. +It is also important to appreciate that the decompression memory +requirement is set at compression time by the choice of block size. + +For files compressed with the default 900k block size, +.I bunzip2 +will require about 3700 kbytes to decompress. To support decompression +of any file on a 4 megabyte machine, +.I bunzip2 +has an option to +decompress using approximately half this amount of memory, about 2300 +kbytes. Decompression speed is also halved, so you should use this +option only where necessary. The relevant flag is -s. + +In general, try and use the largest block size memory constraints allow, +since that maximises the compression achieved. Compression and +decompression speed are virtually unaffected by block size. + +Another significant point applies to files which fit in a single block +-- that means most files you'd encounter using a large block size. The +amount of real memory touched is proportional to the size of the file, +since the file is smaller than a block. For example, compressing a file +20,000 bytes long with the flag -9 will cause the compressor to +allocate around 7600k of memory, but only touch 400k + 20000 * 8 = 560 +kbytes of it. Similarly, the decompressor will allocate 3700k but only +touch 100k + 20000 * 4 = 180 kbytes. + +Here is a table which summarises the maximum memory usage for different +block sizes. Also recorded is the total compressed size for 14 files of +the Calgary Text Compression Corpus totalling 3,141,622 bytes. This +column gives some feel for how compression varies with block size. +These figures tend to understate the advantage of larger block sizes for +larger files, since the Corpus is dominated by smaller files. + + Compress Decompress Decompress Corpus + Flag usage usage -s usage Size + + -1 1200k 500k 350k 914704 + -2 2000k 900k 600k 877703 + -3 2800k 1300k 850k 860338 + -4 3600k 1700k 1100k 846899 + -5 4400k 2100k 1350k 845160 + -6 5200k 2500k 1600k 838626 + -7 6100k 2900k 1850k 834096 + -8 6800k 3300k 2100k 828642 + -9 7600k 3700k 2350k 828642 + +.SH RECOVERING DATA FROM DAMAGED FILES +.I bzip2 +compresses files in blocks, usually 900kbytes long. Each +block is handled independently. If a media or transmission error causes +a multi-block .bz2 +file to become damaged, it may be possible to +recover data from the undamaged blocks in the file. + +The compressed representation of each block is delimited by a 48-bit +pattern, which makes it possible to find the block boundaries with +reasonable certainty. Each block also carries its own 32-bit CRC, so +damaged blocks can be distinguished from undamaged ones. + +.I bzip2recover +is a simple program whose purpose is to search for +blocks in .bz2 files, and write each block out into its own .bz2 +file. You can then use +.I bzip2 +\-t +to test the +integrity of the resulting files, and decompress those which are +undamaged. + +.I bzip2recover +takes a single argument, the name of the damaged file, +and writes a number of files "rec0001file.bz2", +"rec0002file.bz2", etc, containing the extracted blocks. +The output filenames are designed so that the use of +wildcards in subsequent processing -- for example, +"bzip2 -dc rec*file.bz2 > recovered_data" -- lists the files in +the correct order. + +.I bzip2recover +should be of most use dealing with large .bz2 +files, as these will contain many blocks. It is clearly +futile to use it on damaged single-block files, since a +damaged block cannot be recovered. If you wish to minimise +any potential data loss through media or transmission errors, +you might consider compressing with a smaller +block size. + +.SH PERFORMANCE NOTES +The sorting phase of compression gathers together similar strings in the +file. Because of this, files containing very long runs of repeated +symbols, like "aabaabaabaab ..." (repeated several hundred times) may +compress more slowly than normal. Versions 0.9.5 and above fare much +better than previous versions in this respect. The ratio between +worst-case and average-case compression time is in the region of 10:1. +For previous versions, this figure was more like 100:1. You can use the +\-vvvv option to monitor progress in great detail, if you want. + +Decompression speed is unaffected by these phenomena. + +.I bzip2 +usually allocates several megabytes of memory to operate +in, and then charges all over it in a fairly random fashion. This means +that performance, both for compressing and decompressing, is largely +determined by the speed at which your machine can service cache misses. +Because of this, small changes to the code to reduce the miss rate have +been observed to give disproportionately large performance improvements. +I imagine +.I bzip2 +will perform best on machines with very large caches. + +.SH CAVEATS +I/O error messages are not as helpful as they could be. +.I bzip2 +tries hard to detect I/O errors and exit cleanly, but the details of +what the problem is sometimes seem rather misleading. + +This manual page pertains to version 1.0 of +.I bzip2. +Compressed +data created by this version is entirely forwards and backwards +compatible with the previous public releases, versions 0.1pl2, 0.9.0 +and 0.9.5, +but with the following exception: 0.9.0 and above can correctly +decompress multiple concatenated compressed files. 0.1pl2 cannot do +this; it will stop after decompressing just the first file in the +stream. + +.I bzip2recover +uses 32-bit integers to represent bit positions in +compressed files, so it cannot handle compressed files more than 512 +megabytes long. This could easily be fixed. + +.SH AUTHOR +Julian Seward, jseward@acm.org. + +http://sourceware.cygnus.com/bzip2 +http://www.muraroa.demon.co.uk + +The ideas embodied in +.I bzip2 +are due to (at least) the following +people: Michael Burrows and David Wheeler (for the block sorting +transformation), David Wheeler (again, for the Huffman coder), Peter +Fenwick (for the structured coding model in the original +.I bzip, +and many refinements), and Alistair Moffat, Radford Neal and Ian Witten +(for the arithmetic coder in the original +.I bzip). +I am much +indebted for their help, support and advice. See the manual in the +source distribution for pointers to sources of documentation. Christian +von Roques encouraged me to look for faster sorting algorithms, so as to +speed up compression. Bela Lubkin encouraged me to improve the +worst-case compression performance. Many people sent patches, helped +with portability problems, lent machines, gave advice and were generally +helpful. diff -Nru bzip2-1.0.1/doc/bzip2.texi bzip2-1.0.1.new/doc/bzip2.texi --- bzip2-1.0.1/doc/bzip2.texi Thu Jan 1 01:00:00 1970 +++ bzip2-1.0.1.new/doc/bzip2.texi Sat Jun 24 20:13:06 2000 @@ -0,0 +1,2217 @@ +\input texinfo @c -*- Texinfo -*- +@setfilename bzip2.info + +@ignore +This file documents bzip2 version 1.0, and associated library +libbzip2, written by Julian Seward (jseward@acm.org). + +Copyright (C) 1996-2000 Julian R Seward + +Permission is granted to make and distribute verbatim copies of +this manual provided the copyright notice and this permission notice +are preserved on all copies. + +Permission is granted to copy and distribute translations of this manual +into another language, under the above conditions for verbatim copies. +@end ignore + +@ifinfo +@format +@dircategory File utilities: +* Bzip2: (bzip2). A program and library for data + compression +@end direntry +@end format +@end ifinfo + +@iftex +@c @finalout +@settitle bzip2 and libbzip2 +@titlepage +@title bzip2 and libbzip2 +@subtitle a program and library for data compression +@subtitle copyright (C) 1996-2000 Julian Seward +@subtitle version 1.0 of 21 March 2000 +@author Julian Seward + +@end titlepage + +@parindent 0mm +@parskip 2mm + +@end iftex +@node Top, Overview, (dir), (dir) + +@top bzip2 + +This program, @code{bzip2}, +and associated library @code{libbzip2}, are +Copyright (C) 1996-2000 Julian R Seward. All rights reserved. + +Redistribution and use in source and binary forms, with or without +modification, are permitted provided that the following conditions +are met: +@itemize @bullet +@item + Redistributions of source code must retain the above copyright + notice, this list of conditions and the following disclaimer. +@item + The origin of this software must not be misrepresented; you must + not claim that you wrote the original software. If you use this + software in a product, an acknowledgment in the product + documentation would be appreciated but is not required. +@item + Altered source versions must be plainly marked as such, and must + not be misrepresented as being the original software. +@item + The name of the author may not be used to endorse or promote + products derived from this software without specific prior written + permission. +@end itemize +THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS +OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED +WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY +DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE +GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS +INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, +WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING +NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS +SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + +Julian Seward, Cambridge, UK. + +@code{jseward@@acm.org} + +@code{http://sourceware.cygnus.com/bzip2} + +@code{http://www.cacheprof.org} + +@code{http://www.muraroa.demon.co.uk} + +@code{bzip2}/@code{libbzip2} version 1.0 of 21 March 2000. + +PATENTS: To the best of my knowledge, @code{bzip2} does not use any patented +algorithms. However, I do not have the resources available to carry out +a full patent search. Therefore I cannot give any guarantee of the +above statement. + + + + + + + +@node Overview, Implementation, Top, Top +@chapter Introduction + +@code{bzip2} compresses files using the Burrows-Wheeler +block-sorting text compression algorithm, and Huffman coding. +Compression is generally considerably better than that +achieved by more conventional LZ77/LZ78-based compressors, +and approaches the performance of the PPM family of statistical compressors. + +@code{bzip2} is built on top of @code{libbzip2}, a flexible library +for handling compressed data in the @code{bzip2} format. This manual +describes both how to use the program and +how to work with the library interface. Most of the +manual is devoted to this library, not the program, +which is good news if your interest is only in the program. + +Chapter 2 describes how to use @code{bzip2}; this is the only part +you need to read if you just want to know how to operate the program. +Chapter 3 describes the programming interfaces in detail, and +Chapter 4 records some miscellaneous notes which I thought +ought to be recorded somewhere. + + +@chapter How to use @code{bzip2} + +This chapter contains a copy of the @code{bzip2} man page, +and nothing else. + +@quotation + +@unnumberedsubsubsec NAME +@itemize +@item @code{bzip2}, @code{bunzip2} +- a block-sorting file compressor, v1.0 +@item @code{bzcat} +- decompresses files to stdout +@item @code{bzip2recover} +- recovers data from damaged bzip2 files +@end itemize + +@unnumberedsubsubsec SYNOPSIS +@itemize +@item @code{bzip2} [ -cdfkqstvzVL123456789 ] [ filenames ... ] +@item @code{bunzip2} [ -fkvsVL ] [ filenames ... ] +@item @code{bzcat} [ -s ] [ filenames ... ] +@item @code{bzip2recover} filename +@end itemize + +@unnumberedsubsubsec DESCRIPTION + +@code{bzip2} compresses files using the Burrows-Wheeler block sorting +text compression algorithm, and Huffman coding. Compression is +generally considerably better than that achieved by more conventional +LZ77/LZ78-based compressors, and approaches the performance of the PPM +family of statistical compressors. + +The command-line options are deliberately very similar to those of GNU +@code{gzip}, but they are not identical. + +@code{bzip2} expects a list of file names to accompany the command-line +flags. Each file is replaced by a compressed version of itself, with +the name @code{original_name.bz2}. Each compressed file has the same +modification date, permissions, and, when possible, ownership as the +corresponding original, so that these properties can be correctly +restored at decompression time. File name handling is naive in the +sense that there is no mechanism for preserving original file names, +permissions, ownerships or dates in filesystems which lack these +concepts, or have serious file name length restrictions, such as MS-DOS. + +@code{bzip2} and @code{bunzip2} will by default not overwrite existing +files. If you want this to happen, specify the @code{-f} flag. + +If no file names are specified, @code{bzip2} compresses from standard +input to standard output. In this case, @code{bzip2} will decline to +write compressed output to a terminal, as this would be entirely +incomprehensible and therefore pointless. + +@code{bunzip2} (or @code{bzip2 -d}) decompresses all +specified files. Files which were not created by @code{bzip2} +will be detected and ignored, and a warning issued. +@code{bzip2} attempts to guess the filename for the decompressed file +from that of the compressed file as follows: +@itemize +@item @code{filename.bz2 } becomes @code{filename} +@item @code{filename.bz } becomes @code{filename} +@item @code{filename.tbz2} becomes @code{filename.tar} +@item @code{filename.tbz } becomes @code{filename.tar} +@item @code{anyothername } becomes @code{anyothername.out} +@end itemize +If the file does not end in one of the recognised endings, +@code{.bz2}, @code{.bz}, +@code{.tbz2} or @code{.tbz}, @code{bzip2} complains that it cannot +guess the name of the original file, and uses the original name +with @code{.out} appended. + +As with compression, supplying no +filenames causes decompression from standard input to standard output. + +@code{bunzip2} will correctly decompress a file which is the +concatenation of two or more compressed files. The result is the +concatenation of the corresponding uncompressed files. Integrity +testing (@code{-t}) of concatenated compressed files is also supported. + +You can also compress or decompress files to the standard output by +giving the @code{-c} flag. Multiple files may be compressed and +decompressed like this. The resulting outputs are fed sequentially to +stdout. Compression of multiple files in this manner generates a stream +containing multiple compressed file representations. Such a stream +can be decompressed correctly only by @code{bzip2} version 0.9.0 or +later. Earlier versions of @code{bzip2} will stop after decompressing +the first file in the stream. + +@code{bzcat} (or @code{bzip2 -dc}) decompresses all specified files to +the standard output. + +@code{bzip2} will read arguments from the environment variables +@code{BZIP2} and @code{BZIP}, in that order, and will process them +before any arguments read from the command line. This gives a +convenient way to supply default arguments. + +Compression is always performed, even if the compressed file is slightly +larger than the original. Files of less than about one hundred bytes +tend to get larger, since the compression mechanism has a constant +overhead in the region of 50 bytes. Random data (including the output +of most file compressors) is coded at about 8.05 bits per byte, giving +an expansion of around 0.5%. + +As a self-check for your protection, @code{bzip2} uses 32-bit CRCs to +make sure that the decompressed version of a file is identical to the +original. This guards against corruption of the compressed data, and +against undetected bugs in @code{bzip2} (hopefully very unlikely). The +chances of data corruption going undetected is microscopic, about one +chance in four billion for each file processed. Be aware, though, that +the check occurs upon decompression, so it can only tell you that +something is wrong. It can't help you recover the original uncompressed +data. You can use @code{bzip2recover} to try to recover data from +damaged files. + +Return values: 0 for a normal exit, 1 for environmental problems (file +not found, invalid flags, I/O errors, &c), 2 to indicate a corrupt +compressed file, 3 for an internal consistency error (eg, bug) which +caused @code{bzip2} to panic. + + +@unnumberedsubsubsec OPTIONS +@table @code +@item -c --stdout +Compress or decompress to standard output. +@item -d --decompress +Force decompression. @code{bzip2}, @code{bunzip2} and @code{bzcat} are +really the same program, and the decision about what actions to take is +done on the basis of which name is used. This flag overrides that +mechanism, and forces bzip2 to decompress. +@item -z --compress +The complement to @code{-d}: forces compression, regardless of the +invokation name. +@item -t --test +Check integrity of the specified file(s), but don't decompress them. +This really performs a trial decompression and throws away the result. +@item -f --force +Force overwrite of output files. Normally, @code{bzip2} will not overwrite +existing output files. Also forces @code{bzip2} to break hard links +to files, which it otherwise wouldn't do. +@item -k --keep +Keep (don't delete) input files during compression +or decompression. +@item -s --small +Reduce memory usage, for compression, decompression and testing. Files +are decompressed and tested using a modified algorithm which only +requires 2.5 bytes per block byte. This means any file can be +decompressed in 2300k of memory, albeit at about half the normal speed. + +During compression, @code{-s} selects a block size of 200k, which limits +memory use to around the same figure, at the expense of your compression +ratio. In short, if your machine is low on memory (8 megabytes or +less), use -s for everything. See MEMORY MANAGEMENT below. +@item -q --quiet +Suppress non-essential warning messages. Messages pertaining to +I/O errors and other critical events will not be suppressed. +@item -v --verbose +Verbose mode -- show the compression ratio for each file processed. +Further @code{-v}'s increase the verbosity level, spewing out lots of +information which is primarily of interest for diagnostic purposes. +@item -L --license -V --version +Display the software version, license terms and conditions. +@item -1 to -9 +Set the block size to 100 k, 200 k .. 900 k when compressing. Has no +effect when decompressing. See MEMORY MANAGEMENT below. +@item -- +Treats all subsequent arguments as file names, even if they start +with a dash. This is so you can handle files with names beginning +with a dash, for example: @code{bzip2 -- -myfilename}. +@item --repetitive-fast +@item --repetitive-best +These flags are redundant in versions 0.9.5 and above. They provided +some coarse control over the behaviour of the sorting algorithm in +earlier versions, which was sometimes useful. 0.9.5 and above have an +improved algorithm which renders these flags irrelevant. +@end table + + +@unnumberedsubsubsec MEMORY MANAGEMENT + +@code{bzip2} compresses large files in blocks. The block size affects +both the compression ratio achieved, and the amount of memory needed for +compression and decompression. The flags @code{-1} through @code{-9} +specify the block size to be 100,000 bytes through 900,000 bytes (the +default) respectively. At decompression time, the block size used for +compression is read from the header of the compressed file, and +@code{bunzip2} then allocates itself just enough memory to decompress +the file. Since block sizes are stored in compressed files, it follows +that the flags @code{-1} to @code{-9} are irrelevant to and so ignored +during decompression. + +Compression and decompression requirements, in bytes, can be estimated +as: +@example + Compression: 400k + ( 8 x block size ) + + Decompression: 100k + ( 4 x block size ), or + 100k + ( 2.5 x block size ) +@end example +Larger block sizes give rapidly diminishing marginal returns. Most of +the compression comes from the first two or three hundred k of block +size, a fact worth bearing in mind when using @code{bzip2} on small machines. +It is also important to appreciate that the decompression memory +requirement is set at compression time by the choice of block size. + +For files compressed with the default 900k block size, @code{bunzip2} +will require about 3700 kbytes to decompress. To support decompression +of any file on a 4 megabyte machine, @code{bunzip2} has an option to +decompress using approximately half this amount of memory, about 2300 +kbytes. Decompression speed is also halved, so you should use this +option only where necessary. The relevant flag is @code{-s}. + +In general, try and use the largest block size memory constraints allow, +since that maximises the compression achieved. Compression and +decompression speed are virtually unaffected by block size. + +Another significant point applies to files which fit in a single block +-- that means most files you'd encounter using a large block size. The +amount of real memory touched is proportional to the size of the file, +since the file is smaller than a block. For example, compressing a file +20,000 bytes long with the flag @code{-9} will cause the compressor to +allocate around 7600k of memory, but only touch 400k + 20000 * 8 = 560 +kbytes of it. Similarly, the decompressor will allocate 3700k but only +touch 100k + 20000 * 4 = 180 kbytes. + +Here is a table which summarises the maximum memory usage for different +block sizes. Also recorded is the total compressed size for 14 files of +the Calgary Text Compression Corpus totalling 3,141,622 bytes. This +column gives some feel for how compression varies with block size. +These figures tend to understate the advantage of larger block sizes for +larger files, since the Corpus is dominated by smaller files. +@example + Compress Decompress Decompress Corpus + Flag usage usage -s usage Size + + -1 1200k 500k 350k 914704 + -2 2000k 900k 600k 877703 + -3 2800k 1300k 850k 860338 + -4 3600k 1700k 1100k 846899 + -5 4400k 2100k 1350k 845160 + -6 5200k 2500k 1600k 838626 + -7 6100k 2900k 1850k 834096 + -8 6800k 3300k 2100k 828642 + -9 7600k 3700k 2350k 828642 +@end example + +@unnumberedsubsubsec RECOVERING DATA FROM DAMAGED FILES + +@code{bzip2} compresses files in blocks, usually 900kbytes long. Each +block is handled independently. If a media or transmission error causes +a multi-block @code{.bz2} file to become damaged, it may be possible to +recover data from the undamaged blocks in the file. + +The compressed representation of each block is delimited by a 48-bit +pattern, which makes it possible to find the block boundaries with +reasonable certainty. Each block also carries its own 32-bit CRC, so +damaged blocks can be distinguished from undamaged ones. + +@code{bzip2recover} is a simple program whose purpose is to search for +blocks in @code{.bz2} files, and write each block out into its own +@code{.bz2} file. You can then use @code{bzip2 -t} to test the +integrity of the resulting files, and decompress those which are +undamaged. + +@code{bzip2recover} +takes a single argument, the name of the damaged file, +and writes a number of files @code{rec0001file.bz2}, + @code{rec0002file.bz2}, etc, containing the extracted blocks. + The output filenames are designed so that the use of + wildcards in subsequent processing -- for example, +@code{bzip2 -dc rec*file.bz2 > recovered_data} -- lists the files in + the correct order. + +@code{bzip2recover} should be of most use dealing with large @code{.bz2} + files, as these will contain many blocks. It is clearly + futile to use it on damaged single-block files, since a + damaged block cannot be recovered. If you wish to minimise +any potential data loss through media or transmission errors, +you might consider compressing with a smaller + block size. + + +@unnumberedsubsubsec PERFORMANCE NOTES + +The sorting phase of compression gathers together similar strings in the +file. Because of this, files containing very long runs of repeated +symbols, like "aabaabaabaab ..." (repeated several hundred times) may +compress more slowly than normal. Versions 0.9.5 and above fare much +better than previous versions in this respect. The ratio between +worst-case and average-case compression time is in the region of 10:1. +For previous versions, this figure was more like 100:1. You can use the +@code{-vvvv} option to monitor progress in great detail, if you want. + +Decompression speed is unaffected by these phenomena. + +@code{bzip2} usually allocates several megabytes of memory to operate +in, and then charges all over it in a fairly random fashion. This means +that performance, both for compressing and decompressing, is largely +determined by the speed at which your machine can service cache misses. +Because of this, small changes to the code to reduce the miss rate have +been observed to give disproportionately large performance improvements. +I imagine @code{bzip2} will perform best on machines with very large +caches. + + +@unnumberedsubsubsec CAVEATS + +I/O error messages are not as helpful as they could be. @code{bzip2} +tries hard to detect I/O errors and exit cleanly, but the details of +what the problem is sometimes seem rather misleading. + +This manual page pertains to version 1.0 of @code{bzip2}. Compressed +data created by this version is entirely forwards and backwards +compatible with the previous public releases, versions 0.1pl2, 0.9.0 and +0.9.5, but with the following exception: 0.9.0 and above can correctly +decompress multiple concatenated compressed files. 0.1pl2 cannot do +this; it will stop after decompressing just the first file in the +stream. + +@code{bzip2recover} uses 32-bit integers to represent bit positions in +compressed files, so it cannot handle compressed files more than 512 +megabytes long. This could easily be fixed. + + +@unnumberedsubsubsec AUTHOR +Julian Seward, @code{jseward@@acm.org}. + +The ideas embodied in @code{bzip2} are due to (at least) the following +people: Michael Burrows and David Wheeler (for the block sorting +transformation), David Wheeler (again, for the Huffman coder), Peter +Fenwick (for the structured coding model in the original @code{bzip}, +and many refinements), and Alistair Moffat, Radford Neal and Ian Witten +(for the arithmetic coder in the original @code{bzip}). I am much +indebted for their help, support and advice. See the manual in the +source distribution for pointers to sources of documentation. Christian +von Roques encouraged me to look for faster sorting algorithms, so as to +speed up compression. Bela Lubkin encouraged me to improve the +worst-case compression performance. Many people sent patches, helped +with portability problems, lent machines, gave advice and were generally +helpful. + +@end quotation + + + + +@chapter Programming with @code{libbzip2} + +This chapter describes the programming interface to @code{libbzip2}. + +For general background information, particularly about memory +use and performance aspects, you'd be well advised to read Chapter 2 +as well. + +@section Top-level structure + +@code{libbzip2} is a flexible library for compressing and decompressing +data in the @code{bzip2} data format. Although packaged as a single +entity, it helps to regard the library as three separate parts: the low +level interface, and the high level interface, and some utility +functions. + +The structure of @code{libbzip2}'s interfaces is similar to +that of Jean-loup Gailly's and Mark Adler's excellent @code{zlib} +library. + +All externally visible symbols have names beginning @code{BZ2_}. +This is new in version 1.0. The intention is to minimise pollution +of the namespaces of library clients. + +@subsection Low-level summary + +This interface provides services for compressing and decompressing +data in memory. There's no provision for dealing with files, streams +or any other I/O mechanisms, just straight memory-to-memory work. +In fact, this part of the library can be compiled without inclusion +of @code{stdio.h}, which may be helpful for embedded applications. + +The low-level part of the library has no global variables and +is therefore thread-safe. + +Six routines make up the low level interface: +@code{BZ2_bzCompressInit}, @code{BZ2_bzCompress}, and @* @code{BZ2_bzCompressEnd} +for compression, +and a corresponding trio @code{BZ2_bzDecompressInit}, @* @code{BZ2_bzDecompress} +and @code{BZ2_bzDecompressEnd} for decompression. +The @code{*Init} functions allocate +memory for compression/decompression and do other +initialisations, whilst the @code{*End} functions close down operations +and release memory. + +The real work is done by @code{BZ2_bzCompress} and @code{BZ2_bzDecompress}. +These compress and decompress data from a user-supplied input buffer +to a user-supplied output buffer. These buffers can be any size; +arbitrary quantities of data are handled by making repeated calls +to these functions. This is a flexible mechanism allowing a +consumer-pull style of activity, or producer-push, or a mixture of +both. + + + +@subsection High-level summary + +This interface provides some handy wrappers around the low-level +interface to facilitate reading and writing @code{bzip2} format +files (@code{.bz2} files). The routines provide hooks to facilitate +reading files in which the @code{bzip2} data stream is embedded +within some larger-scale file structure, or where there are +multiple @code{bzip2} data streams concatenated end-to-end. + +For reading files, @code{BZ2_bzReadOpen}, @code{BZ2_bzRead}, +@code{BZ2_bzReadClose} and @* @code{BZ2_bzReadGetUnused} are supplied. For +writing files, @code{BZ2_bzWriteOpen}, @code{BZ2_bzWrite} and +@code{BZ2_bzWriteFinish} are available. + +As with the low-level library, no global variables are used +so the library is per se thread-safe. However, if I/O errors +occur whilst reading or writing the underlying compressed files, +you may have to consult @code{errno} to determine the cause of +the error. In that case, you'd need a C library which correctly +supports @code{errno} in a multithreaded environment. + +To make the library a little simpler and more portable, +@code{BZ2_bzReadOpen} and @code{BZ2_bzWriteOpen} require you to pass them file +handles (@code{FILE*}s) which have previously been opened for reading or +writing respectively. That avoids portability problems associated with +file operations and file attributes, whilst not being much of an +imposition on the programmer. + + + +@subsection Utility functions summary +For very simple needs, @code{BZ2_bzBuffToBuffCompress} and +@code{BZ2_bzBuffToBuffDecompress} are provided. These compress +data in memory from one buffer to another buffer in a single +function call. You should assess whether these functions +fulfill your memory-to-memory compression/decompression +requirements before investing effort in understanding the more +general but more complex low-level interface. + +Yoshioka Tsuneo (@code{QWF00133@@niftyserve.or.jp} / +@code{tsuneo-y@@is.aist-nara.ac.jp}) has contributed some functions to +give better @code{zlib} compatibility. These functions are +@code{BZ2_bzopen}, @code{BZ2_bzread}, @code{BZ2_bzwrite}, @code{BZ2_bzflush}, +@code{BZ2_bzclose}, +@code{BZ2_bzerror} and @code{BZ2_bzlibVersion}. You may find these functions +more convenient for simple file reading and writing, than those in the +high-level interface. These functions are not (yet) officially part of +the library, and are minimally documented here. If they break, you +get to keep all the pieces. I hope to document them properly when time +permits. + +Yoshioka also contributed modifications to allow the library to be +built as a Windows DLL. + + +@section Error handling + +The library is designed to recover cleanly in all situations, including +the worst-case situation of decompressing random data. I'm not +100% sure that it can always do this, so you might want to add +a signal handler to catch segmentation violations during decompression +if you are feeling especially paranoid. I would be interested in +hearing more about the robustness of the library to corrupted +compressed data. + +Version 1.0 is much more robust in this respect than +0.9.0 or 0.9.5. Investigations with Checker (a tool for +detecting problems with memory management, similar to Purify) +indicate that, at least for the few files I tested, all single-bit +errors in the decompressed data are caught properly, with no +segmentation faults, no reads of uninitialised data and no +out of range reads or writes. So it's certainly much improved, +although I wouldn't claim it to be totally bombproof. + +The file @code{bzlib.h} contains all definitions needed to use +the library. In particular, you should definitely not include +@code{bzlib_private.h}. + +In @code{bzlib.h}, the various return values are defined. The following +list is not intended as an exhaustive description of the circumstances +in which a given value may be returned -- those descriptions are given +later. Rather, it is intended to convey the rough meaning of each +return value. The first five actions are normal and not intended to +denote an error situation. +@table @code +@item BZ_OK +The requested action was completed successfully. +@item BZ_RUN_OK +@itemx BZ_FLUSH_OK +@itemx BZ_FINISH_OK +In @code{BZ2_bzCompress}, the requested flush/finish/nothing-special action +was completed successfully. +@item BZ_STREAM_END +Compression of data was completed, or the logical stream end was +detected during decompression. +@end table + +The following return values indicate an error of some kind. +@table @code +@item BZ_CONFIG_ERROR +Indicates that the library has been improperly compiled on your +platform -- a major configuration error. Specifically, it means +that @code{sizeof(char)}, @code{sizeof(short)} and @code{sizeof(int)} +are not 1, 2 and 4 respectively, as they should be. Note that the +library should still work properly on 64-bit platforms which follow +the LP64 programming model -- that is, where @code{sizeof(long)} +and @code{sizeof(void*)} are 8. Under LP64, @code{sizeof(int)} is +still 4, so @code{libbzip2}, which doesn't use the @code{long} type, +is OK. +@item BZ_SEQUENCE_ERROR +When using the library, it is important to call the functions in the +correct sequence and with data structures (buffers etc) in the correct +states. @code{libbzip2} checks as much as it can to ensure this is +happening, and returns @code{BZ_SEQUENCE_ERROR} if not. Code which +complies precisely with the function semantics, as detailed below, +should never receive this value; such an event denotes buggy code +which you should investigate. +@item BZ_PARAM_ERROR +Returned when a parameter to a function call is out of range +or otherwise manifestly incorrect. As with @code{BZ_SEQUENCE_ERROR}, +this denotes a bug in the client code. The distinction between +@code{BZ_PARAM_ERROR} and @code{BZ_SEQUENCE_ERROR} is a bit hazy, but still worth +making. +@item BZ_MEM_ERROR +Returned when a request to allocate memory failed. Note that the +quantity of memory needed to decompress a stream cannot be determined +until the stream's header has been read. So @code{BZ2_bzDecompress} and +@code{BZ2_bzRead} may return @code{BZ_MEM_ERROR} even though some of +the compressed data has been read. The same is not true for +compression; once @code{BZ2_bzCompressInit} or @code{BZ2_bzWriteOpen} have +successfully completed, @code{BZ_MEM_ERROR} cannot occur. +@item BZ_DATA_ERROR +Returned when a data integrity error is detected during decompression. +Most importantly, this means when stored and computed CRCs for the +data do not match. This value is also returned upon detection of any +other anomaly in the compressed data. +@item BZ_DATA_ERROR_MAGIC +As a special case of @code{BZ_DATA_ERROR}, it is sometimes useful to +know when the compressed stream does not start with the correct +magic bytes (@code{'B' 'Z' 'h'}). +@item BZ_IO_ERROR +Returned by @code{BZ2_bzRead} and @code{BZ2_bzWrite} when there is an error +reading or writing in the compressed file, and by @code{BZ2_bzReadOpen} +and @code{BZ2_bzWriteOpen} for attempts to use a file for which the +error indicator (viz, @code{ferror(f)}) is set. +On receipt of @code{BZ_IO_ERROR}, the caller should consult +@code{errno} and/or @code{perror} to acquire operating-system +specific information about the problem. +@item BZ_UNEXPECTED_EOF +Returned by @code{BZ2_bzRead} when the compressed file finishes +before the logical end of stream is detected. +@item BZ_OUTBUFF_FULL +Returned by @code{BZ2_bzBuffToBuffCompress} and +@code{BZ2_bzBuffToBuffDecompress} to indicate that the output data +will not fit into the output buffer provided. +@end table + + + +@section Low-level interface + +@subsection @code{BZ2_bzCompressInit} +@example +typedef + struct @{ + char *next_in; + unsigned int avail_in; + unsigned int total_in_lo32; + unsigned int total_in_hi32; + + char *next_out; + unsigned int avail_out; + unsigned int total_out_lo32; + unsigned int total_out_hi32; + + void *state; + + void *(*bzalloc)(void *,int,int); + void (*bzfree)(void *,void *); + void *opaque; + @} + bz_stream; + +int BZ2_bzCompressInit ( bz_stream *strm, + int blockSize100k, + int verbosity, + int workFactor ); + +@end example + +Prepares for compression. The @code{bz_stream} structure +holds all data pertaining to the compression activity. +A @code{bz_stream} structure should be allocated and initialised +prior to the call. +The fields of @code{bz_stream} +comprise the entirety of the user-visible data. @code{state} +is a pointer to the private data structures required for compression. + +Custom memory allocators are supported, via fields @code{bzalloc}, +@code{bzfree}, +and @code{opaque}. The value +@code{opaque} is passed to as the first argument to +all calls to @code{bzalloc} and @code{bzfree}, but is +otherwise ignored by the library. +The call @code{bzalloc ( opaque, n, m )} is expected to return a +pointer @code{p} to +@code{n * m} bytes of memory, and @code{bzfree ( opaque, p )} +should free +that memory. + +If you don't want to use a custom memory allocator, set @code{bzalloc}, +@code{bzfree} and +@code{opaque} to @code{NULL}, +and the library will then use the standard @code{malloc}/@code{free} +routines. + +Before calling @code{BZ2_bzCompressInit}, fields @code{bzalloc}, +@code{bzfree} and @code{opaque} should +be filled appropriately, as just described. Upon return, the internal +state will have been allocated and initialised, and @code{total_in_lo32}, +@code{total_in_hi32}, @code{total_out_lo32} and +@code{total_out_hi32} will have been set to zero. +These four fields are used by the library +to inform the caller of the total amount of data passed into and out of +the library, respectively. You should not try to change them. +As of version 1.0, 64-bit counts are maintained, even on 32-bit +platforms, using the @code{_hi32} fields to store the upper 32 bits +of the count. So, for example, the total amount of data in +is @code{(total_in_hi32 << 32) + total_in_lo32}. + +Parameter @code{blockSize100k} specifies the block size to be used for +compression. It should be a value between 1 and 9 inclusive, and the +actual block size used is 100000 x this figure. 9 gives the best +compression but takes most memory. + +Parameter @code{verbosity} should be set to a number between 0 and 4 +inclusive. 0 is silent, and greater numbers give increasingly verbose +monitoring/debugging output. If the library has been compiled with +@code{-DBZ_NO_STDIO}, no such output will appear for any verbosity +setting. + +Parameter @code{workFactor} controls how the compression phase behaves +when presented with worst case, highly repetitive, input data. If +compression runs into difficulties caused by repetitive data, the +library switches from the standard sorting algorithm to a fallback +algorithm. The fallback is slower than the standard algorithm by +perhaps a factor of three, but always behaves reasonably, no matter how +bad the input. + +Lower values of @code{workFactor} reduce the amount of effort the +standard algorithm will expend before resorting to the fallback. You +should set this parameter carefully; too low, and many inputs will be +handled by the fallback algorithm and so compress rather slowly, too +high, and your average-to-worst case compression times can become very +large. The default value of 30 gives reasonable behaviour over a wide +range of circumstances. + +Allowable values range from 0 to 250 inclusive. 0 is a special case, +equivalent to using the default value of 30. + +Note that the compressed output generated is the same regardless of +whether or not the fallback algorithm is used. + +Be aware also that this parameter may disappear entirely in future +versions of the library. In principle it should be possible to devise a +good way to automatically choose which algorithm to use. Such a +mechanism would render the parameter obsolete. + +Possible return values: +@display + @code{BZ_CONFIG_ERROR} + if the library has been mis-compiled + @code{BZ_PARAM_ERROR} + if @code{strm} is @code{NULL} + or @code{blockSize} < 1 or @code{blockSize} > 9 + or @code{verbosity} < 0 or @code{verbosity} > 4 + or @code{workFactor} < 0 or @code{workFactor} > 250 + @code{BZ_MEM_ERROR} + if not enough memory is available + @code{BZ_OK} + otherwise +@end display +Allowable next actions: +@display + @code{BZ2_bzCompress} + if @code{BZ_OK} is returned + no specific action needed in case of error +@end display + +@subsection @code{BZ2_bzCompress} +@example + int BZ2_bzCompress ( bz_stream *strm, int action ); +@end example +Provides more input and/or output buffer space for the library. The +caller maintains input and output buffers, and calls @code{BZ2_bzCompress} to +transfer data between them. + +Before each call to @code{BZ2_bzCompress}, @code{next_in} should point at +the data to be compressed, and @code{avail_in} should indicate how many +bytes the library may read. @code{BZ2_bzCompress} updates @code{next_in}, +@code{avail_in} and @code{total_in} to reflect the number of bytes it +has read. + +Similarly, @code{next_out} should point to a buffer in which the +compressed data is to be placed, with @code{avail_out} indicating how +much output space is available. @code{BZ2_bzCompress} updates +@code{next_out}, @code{avail_out} and @code{total_out} to reflect the +number of bytes output. + +You may provide and remove as little or as much data as you like on each +call of @code{BZ2_bzCompress}. In the limit, it is acceptable to supply and +remove data one byte at a time, although this would be terribly +inefficient. You should always ensure that at least one byte of output +space is available at each call. + +A second purpose of @code{BZ2_bzCompress} is to request a change of mode of the +compressed stream. + +Conceptually, a compressed stream can be in one of four states: IDLE, +RUNNING, FLUSHING and FINISHING. Before initialisation +(@code{BZ2_bzCompressInit}) and after termination (@code{BZ2_bzCompressEnd}), a +stream is regarded as IDLE. + +Upon initialisation (@code{BZ2_bzCompressInit}), the stream is placed in the +RUNNING state. Subsequent calls to @code{BZ2_bzCompress} should pass +@code{BZ_RUN} as the requested action; other actions are illegal and +will result in @code{BZ_SEQUENCE_ERROR}. + +At some point, the calling program will have provided all the input data +it wants to. It will then want to finish up -- in effect, asking the +library to process any data it might have buffered internally. In this +state, @code{BZ2_bzCompress} will no longer attempt to read data from +@code{next_in}, but it will want to write data to @code{next_out}. +Because the output buffer supplied by the user can be arbitrarily small, +the finishing-up operation cannot necessarily be done with a single call +of @code{BZ2_bzCompress}. + +Instead, the calling program passes @code{BZ_FINISH} as an action to +@code{BZ2_bzCompress}. This changes the stream's state to FINISHING. Any +remaining input (ie, @code{next_in[0 .. avail_in-1]}) is compressed and +transferred to the output buffer. To do this, @code{BZ2_bzCompress} must be +called repeatedly until all the output has been consumed. At that +point, @code{BZ2_bzCompress} returns @code{BZ_STREAM_END}, and the stream's +state is set back to IDLE. @code{BZ2_bzCompressEnd} should then be +called. + +Just to make sure the calling program does not cheat, the library makes +a note of @code{avail_in} at the time of the first call to +@code{BZ2_bzCompress} which has @code{BZ_FINISH} as an action (ie, at the +time the program has announced its intention to not supply any more +input). By comparing this value with that of @code{avail_in} over +subsequent calls to @code{BZ2_bzCompress}, the library can detect any +attempts to slip in more data to compress. Any calls for which this is +detected will return @code{BZ_SEQUENCE_ERROR}. This indicates a +programming mistake which should be corrected. + +Instead of asking to finish, the calling program may ask +@code{BZ2_bzCompress} to take all the remaining input, compress it and +terminate the current (Burrows-Wheeler) compression block. This could +be useful for error control purposes. The mechanism is analogous to +that for finishing: call @code{BZ2_bzCompress} with an action of +@code{BZ_FLUSH}, remove output data, and persist with the +@code{BZ_FLUSH} action until the value @code{BZ_RUN} is returned. As +with finishing, @code{BZ2_bzCompress} detects any attempt to provide more +input data once the flush has begun. + +Once the flush is complete, the stream returns to the normal RUNNING +state. + +This all sounds pretty complex, but isn't really. Here's a table +which shows which actions are allowable in each state, what action +will be taken, what the next state is, and what the non-error return +values are. Note that you can't explicitly ask what state the +stream is in, but nor do you need to -- it can be inferred from the +values returned by @code{BZ2_bzCompress}. +@display +IDLE/@code{any} + Illegal. IDLE state only exists after @code{BZ2_bzCompressEnd} or + before @code{BZ2_bzCompressInit}. + Return value = @code{BZ_SEQUENCE_ERROR} + +RUNNING/@code{BZ_RUN} + Compress from @code{next_in} to @code{next_out} as much as possible. + Next state = RUNNING + Return value = @code{BZ_RUN_OK} + +RUNNING/@code{BZ_FLUSH} + Remember current value of @code{next_in}. Compress from @code{next_in} + to @code{next_out} as much as possible, but do not accept any more input. + Next state = FLUSHING + Return value = @code{BZ_FLUSH_OK} + +RUNNING/@code{BZ_FINISH} + Remember current value of @code{next_in}. Compress from @code{next_in} + to @code{next_out} as much as possible, but do not accept any more input. + Next state = FINISHING + Return value = @code{BZ_FINISH_OK} + +FLUSHING/@code{BZ_FLUSH} + Compress from @code{next_in} to @code{next_out} as much as possible, + but do not accept any more input. + If all the existing input has been used up and all compressed + output has been removed + Next state = RUNNING; Return value = @code{BZ_RUN_OK} + else + Next state = FLUSHING; Return value = @code{BZ_FLUSH_OK} + +FLUSHING/other + Illegal. + Return value = @code{BZ_SEQUENCE_ERROR} + +FINISHING/@code{BZ_FINISH} + Compress from @code{next_in} to @code{next_out} as much as possible, + but to not accept any more input. + If all the existing input has been used up and all compressed + output has been removed + Next state = IDLE; Return value = @code{BZ_STREAM_END} + else + Next state = FINISHING; Return value = @code{BZ_FINISHING} + +FINISHING/other + Illegal. + Return value = @code{BZ_SEQUENCE_ERROR} +@end display + +That still looks complicated? Well, fair enough. The usual sequence +of calls for compressing a load of data is: +@itemize @bullet +@item Get started with @code{BZ2_bzCompressInit}. +@item Shovel data in and shlurp out its compressed form using zero or more +calls of @code{BZ2_bzCompress} with action = @code{BZ_RUN}. +@item Finish up. +Repeatedly call @code{BZ2_bzCompress} with action = @code{BZ_FINISH}, +copying out the compressed output, until @code{BZ_STREAM_END} is returned. +@item Close up and go home. Call @code{BZ2_bzCompressEnd}. +@end itemize +If the data you want to compress fits into your input buffer all +at once, you can skip the calls of @code{BZ2_bzCompress ( ..., BZ_RUN )} and +just do the @code{BZ2_bzCompress ( ..., BZ_FINISH )} calls. + +All required memory is allocated by @code{BZ2_bzCompressInit}. The +compression library can accept any data at all (obviously). So you +shouldn't get any error return values from the @code{BZ2_bzCompress} calls. +If you do, they will be @code{BZ_SEQUENCE_ERROR}, and indicate a bug in +your programming. + +Trivial other possible return values: +@display + @code{BZ_PARAM_ERROR} + if @code{strm} is @code{NULL}, or @code{strm->s} is @code{NULL} +@end display + +@subsection @code{BZ2_bzCompressEnd} +@example +int BZ2_bzCompressEnd ( bz_stream *strm ); +@end example +Releases all memory associated with a compression stream. + +Possible return values: +@display + @code{BZ_PARAM_ERROR} if @code{strm} is @code{NULL} or @code{strm->s} is @code{NULL} + @code{BZ_OK} otherwise +@end display + + +@subsection @code{BZ2_bzDecompressInit} +@example +int BZ2_bzDecompressInit ( bz_stream *strm, int verbosity, int small ); +@end example +Prepares for decompression. As with @code{BZ2_bzCompressInit}, a +@code{bz_stream} record should be allocated and initialised before the +call. Fields @code{bzalloc}, @code{bzfree} and @code{opaque} should be +set if a custom memory allocator is required, or made @code{NULL} for +the normal @code{malloc}/@code{free} routines. Upon return, the internal +state will have been initialised, and @code{total_in} and +@code{total_out} will be zero. + +For the meaning of parameter @code{verbosity}, see @code{BZ2_bzCompressInit}. + +If @code{small} is nonzero, the library will use an alternative +decompression algorithm which uses less memory but at the cost of +decompressing more slowly (roughly speaking, half the speed, but the +maximum memory requirement drops to around 2300k). See Chapter 2 for +more information on memory management. + +Note that the amount of memory needed to decompress +a stream cannot be determined until the stream's header has been read, +so even if @code{BZ2_bzDecompressInit} succeeds, a subsequent +@code{BZ2_bzDecompress} could fail with @code{BZ_MEM_ERROR}. + +Possible return values: +@display + @code{BZ_CONFIG_ERROR} + if the library has been mis-compiled + @code{BZ_PARAM_ERROR} + if @code{(small != 0 && small != 1)} + or @code{(verbosity < 0 || verbosity > 4)} + @code{BZ_MEM_ERROR} + if insufficient memory is available +@end display + +Allowable next actions: +@display + @code{BZ2_bzDecompress} + if @code{BZ_OK} was returned + no specific action required in case of error +@end display + + + +@subsection @code{BZ2_bzDecompress} +@example +int BZ2_bzDecompress ( bz_stream *strm ); +@end example +Provides more input and/out output buffer space for the library. The +caller maintains input and output buffers, and uses @code{BZ2_bzDecompress} +to transfer data between them. + +Before each call to @code{BZ2_bzDecompress}, @code{next_in} +should point at the compressed data, +and @code{avail_in} should indicate how many bytes the library +may read. @code{BZ2_bzDecompress} updates @code{next_in}, @code{avail_in} +and @code{total_in} +to reflect the number of bytes it has read. + +Similarly, @code{next_out} should point to a buffer in which the uncompressed +output is to be placed, with @code{avail_out} indicating how much output space +is available. @code{BZ2_bzCompress} updates @code{next_out}, +@code{avail_out} and @code{total_out} to reflect +the number of bytes output. + +You may provide and remove as little or as much data as you like on +each call of @code{BZ2_bzDecompress}. +In the limit, it is acceptable to +supply and remove data one byte at a time, although this would be +terribly inefficient. You should always ensure that at least one +byte of output space is available at each call. + +Use of @code{BZ2_bzDecompress} is simpler than @code{BZ2_bzCompress}. + +You should provide input and remove output as described above, and +repeatedly call @code{BZ2_bzDecompress} until @code{BZ_STREAM_END} is +returned. Appearance of @code{BZ_STREAM_END} denotes that +@code{BZ2_bzDecompress} has detected the logical end of the compressed +stream. @code{BZ2_bzDecompress} will not produce @code{BZ_STREAM_END} until +all output data has been placed into the output buffer, so once +@code{BZ_STREAM_END} appears, you are guaranteed to have available all +the decompressed output, and @code{BZ2_bzDecompressEnd} can safely be +called. + +If case of an error return value, you should call @code{BZ2_bzDecompressEnd} +to clean up and release memory. + +Possible return values: +@display + @code{BZ_PARAM_ERROR} + if @code{strm} is @code{NULL} or @code{strm->s} is @code{NULL} + or @code{strm->avail_out < 1} + @code{BZ_DATA_ERROR} + if a data integrity error is detected in the compressed stream + @code{BZ_DATA_ERROR_MAGIC} + if the compressed stream doesn't begin with the right magic bytes + @code{BZ_MEM_ERROR} + if there wasn't enough memory available + @code{BZ_STREAM_END} + if the logical end of the data stream was detected and all + output in has been consumed, eg @code{s->avail_out > 0} + @code{BZ_OK} + otherwise +@end display +Allowable next actions: +@display + @code{BZ2_bzDecompress} + if @code{BZ_OK} was returned + @code{BZ2_bzDecompressEnd} + otherwise +@end display + + +@subsection @code{BZ2_bzDecompressEnd} +@example +int BZ2_bzDecompressEnd ( bz_stream *strm ); +@end example +Releases all memory associated with a decompression stream. + +Possible return values: +@display + @code{BZ_PARAM_ERROR} + if @code{strm} is @code{NULL} or @code{strm->s} is @code{NULL} + @code{BZ_OK} + otherwise +@end display + +Allowable next actions: +@display + None. +@end display + + +@section High-level interface + +This interface provides functions for reading and writing +@code{bzip2} format files. First, some general points. + +@itemize @bullet +@item All of the functions take an @code{int*} first argument, + @code{bzerror}. + After each call, @code{bzerror} should be consulted first to determine + the outcome of the call. If @code{bzerror} is @code{BZ_OK}, + the call completed + successfully, and only then should the return value of the function + (if any) be consulted. If @code{bzerror} is @code{BZ_IO_ERROR}, + there was an error + reading/writing the underlying compressed file, and you should + then consult @code{errno}/@code{perror} to determine the + cause of the difficulty. + @code{bzerror} may also be set to various other values; precise details are + given on a per-function basis below. +@item If @code{bzerror} indicates an error + (ie, anything except @code{BZ_OK} and @code{BZ_STREAM_END}), + you should immediately call @code{BZ2_bzReadClose} (or @code{BZ2_bzWriteClose}, + depending on whether you are attempting to read or to write) + to free up all resources associated + with the stream. Once an error has been indicated, behaviour of all calls + except @code{BZ2_bzReadClose} (@code{BZ2_bzWriteClose}) is undefined. + The implication is that (1) @code{bzerror} should + be checked after each call, and (2) if @code{bzerror} indicates an error, + @code{BZ2_bzReadClose} (@code{BZ2_bzWriteClose}) should then be called to clean up. +@item The @code{FILE*} arguments passed to + @code{BZ2_bzReadOpen}/@code{BZ2_bzWriteOpen} + should be set to binary mode. + Most Unix systems will do this by default, but other platforms, + including Windows and Mac, will not. If you omit this, you may + encounter problems when moving code to new platforms. +@item Memory allocation requests are handled by + @code{malloc}/@code{free}. + At present + there is no facility for user-defined memory allocators in the file I/O + functions (could easily be added, though). +@end itemize + + + +@subsection @code{BZ2_bzReadOpen} +@example + typedef void BZFILE; + + BZFILE *BZ2_bzReadOpen ( int *bzerror, FILE *f, + int small, int verbosity, + void *unused, int nUnused ); +@end example +Prepare to read compressed data from file handle @code{f}. @code{f} +should refer to a file which has been opened for reading, and for which +the error indicator (@code{ferror(f)})is not set. If @code{small} is 1, +the library will try to decompress using less memory, at the expense of +speed. + +For reasons explained below, @code{BZ2_bzRead} will decompress the +@code{nUnused} bytes starting at @code{unused}, before starting to read +from the file @code{f}. At most @code{BZ_MAX_UNUSED} bytes may be +supplied like this. If this facility is not required, you should pass +@code{NULL} and @code{0} for @code{unused} and n@code{Unused} +respectively. + +For the meaning of parameters @code{small} and @code{verbosity}, +see @code{BZ2_bzDecompressInit}. + +The amount of memory needed to decompress a file cannot be determined +until the file's header has been read. So it is possible that +@code{BZ2_bzReadOpen} returns @code{BZ_OK} but a subsequent call of +@code{BZ2_bzRead} will return @code{BZ_MEM_ERROR}. + +Possible assignments to @code{bzerror}: +@display + @code{BZ_CONFIG_ERROR} + if the library has been mis-compiled + @code{BZ_PARAM_ERROR} + if @code{f} is @code{NULL} + or @code{small} is neither @code{0} nor @code{1} + or @code{(unused == NULL && nUnused != 0)} + or @code{(unused != NULL && !(0 <= nUnused <= BZ_MAX_UNUSED))} + @code{BZ_IO_ERROR} + if @code{ferror(f)} is nonzero + @code{BZ_MEM_ERROR} + if insufficient memory is available + @code{BZ_OK} + otherwise. +@end display + +Possible return values: +@display + Pointer to an abstract @code{BZFILE} + if @code{bzerror} is @code{BZ_OK} + @code{NULL} + otherwise +@end display + +Allowable next actions: +@display + @code{BZ2_bzRead} + if @code{bzerror} is @code{BZ_OK} + @code{BZ2_bzClose} + otherwise +@end display + + +@subsection @code{BZ2_bzRead} +@example + int BZ2_bzRead ( int *bzerror, BZFILE *b, void *buf, int len ); +@end example +Reads up to @code{len} (uncompressed) bytes from the compressed file +@code{b} into +the buffer @code{buf}. If the read was successful, +@code{bzerror} is set to @code{BZ_OK} +and the number of bytes read is returned. If the logical end-of-stream +was detected, @code{bzerror} will be set to @code{BZ_STREAM_END}, +and the number +of bytes read is returned. All other @code{bzerror} values denote an error. + +@code{BZ2_bzRead} will supply @code{len} bytes, +unless the logical stream end is detected +or an error occurs. Because of this, it is possible to detect the +stream end by observing when the number of bytes returned is +less than the number +requested. Nevertheless, this is regarded as inadvisable; you should +instead check @code{bzerror} after every call and watch out for +@code{BZ_STREAM_END}. + +Internally, @code{BZ2_bzRead} copies data from the compressed file in chunks +of size @code{BZ_MAX_UNUSED} bytes +before decompressing it. If the file contains more bytes than strictly +needed to reach the logical end-of-stream, @code{BZ2_bzRead} will almost certainly +read some of the trailing data before signalling @code{BZ_SEQUENCE_END}. +To collect the read but unused data once @code{BZ_SEQUENCE_END} has +appeared, call @code{BZ2_bzReadGetUnused} immediately before @code{BZ2_bzReadClose}. + +Possible assignments to @code{bzerror}: +@display + @code{BZ_PARAM_ERROR} + if @code{b} is @code{NULL} or @code{buf} is @code{NULL} or @code{len < 0} + @code{BZ_SEQUENCE_ERROR} + if @code{b} was opened with @code{BZ2_bzWriteOpen} + @code{BZ_IO_ERROR} + if there is an error reading from the compressed file + @code{BZ_UNEXPECTED_EOF} + if the compressed file ended before the logical end-of-stream was detected + @code{BZ_DATA_ERROR} + if a data integrity error was detected in the compressed stream + @code{BZ_DATA_ERROR_MAGIC} + if the stream does not begin with the requisite header bytes (ie, is not + a @code{bzip2} data file). This is really a special case of @code{BZ_DATA_ERROR}. + @code{BZ_MEM_ERROR} + if insufficient memory was available + @code{BZ_STREAM_END} + if the logical end of stream was detected. + @code{BZ_OK} + otherwise. +@end display + +Possible return values: +@display + number of bytes read + if @code{bzerror} is @code{BZ_OK} or @code{BZ_STREAM_END} + undefined + otherwise +@end display + +Allowable next actions: +@display + collect data from @code{buf}, then @code{BZ2_bzRead} or @code{BZ2_bzReadClose} + if @code{bzerror} is @code{BZ_OK} + collect data from @code{buf}, then @code{BZ2_bzReadClose} or @code{BZ2_bzReadGetUnused} + if @code{bzerror} is @code{BZ_SEQUENCE_END} + @code{BZ2_bzReadClose} + otherwise +@end display + + + +@subsection @code{BZ2_bzReadGetUnused} +@example + void BZ2_bzReadGetUnused ( int* bzerror, BZFILE *b, + void** unused, int* nUnused ); +@end example +Returns data which was read from the compressed file but was not needed +to get to the logical end-of-stream. @code{*unused} is set to the address +of the data, and @code{*nUnused} to the number of bytes. @code{*nUnused} will +be set to a value between @code{0} and @code{BZ_MAX_UNUSED} inclusive. + +This function may only be called once @code{BZ2_bzRead} has signalled +@code{BZ_STREAM_END} but before @code{BZ2_bzReadClose}. + +Possible assignments to @code{bzerror}: +@display + @code{BZ_PARAM_ERROR} + if @code{b} is @code{NULL} + or @code{unused} is @code{NULL} or @code{nUnused} is @code{NULL} + @code{BZ_SEQUENCE_ERROR} + if @code{BZ_STREAM_END} has not been signalled + or if @code{b} was opened with @code{BZ2_bzWriteOpen} + @code{BZ_OK} + otherwise +@end display + +Allowable next actions: +@display + @code{BZ2_bzReadClose} +@end display + + +@subsection @code{BZ2_bzReadClose} +@example + void BZ2_bzReadClose ( int *bzerror, BZFILE *b ); +@end example +Releases all memory pertaining to the compressed file @code{b}. +@code{BZ2_bzReadClose} does not call @code{fclose} on the underlying file +handle, so you should do that yourself if appropriate. +@code{BZ2_bzReadClose} should be called to clean up after all error +situations. + +Possible assignments to @code{bzerror}: +@display + @code{BZ_SEQUENCE_ERROR} + if @code{b} was opened with @code{BZ2_bzOpenWrite} + @code{BZ_OK} + otherwise +@end display + +Allowable next actions: +@display + none +@end display + + + +@subsection @code{BZ2_bzWriteOpen} +@example + BZFILE *BZ2_bzWriteOpen ( int *bzerror, FILE *f, + int blockSize100k, int verbosity, + int workFactor ); +@end example +Prepare to write compressed data to file handle @code{f}. +@code{f} should refer to +a file which has been opened for writing, and for which the error +indicator (@code{ferror(f)})is not set. + +For the meaning of parameters @code{blockSize100k}, +@code{verbosity} and @code{workFactor}, see +@* @code{BZ2_bzCompressInit}. + +All required memory is allocated at this stage, so if the call +completes successfully, @code{BZ_MEM_ERROR} cannot be signalled by a +subsequent call to @code{BZ2_bzWrite}. + +Possible assignments to @code{bzerror}: +@display + @code{BZ_CONFIG_ERROR} + if the library has been mis-compiled + @code{BZ_PARAM_ERROR} + if @code{f} is @code{NULL} + or @code{blockSize100k < 1} or @code{blockSize100k > 9} + @code{BZ_IO_ERROR} + if @code{ferror(f)} is nonzero + @code{BZ_MEM_ERROR} + if insufficient memory is available + @code{BZ_OK} + otherwise +@end display + +Possible return values: +@display + Pointer to an abstract @code{BZFILE} + if @code{bzerror} is @code{BZ_OK} + @code{NULL} + otherwise +@end display + +Allowable next actions: +@display + @code{BZ2_bzWrite} + if @code{bzerror} is @code{BZ_OK} + (you could go directly to @code{BZ2_bzWriteClose}, but this would be pretty pointless) + @code{BZ2_bzWriteClose} + otherwise +@end display + + + +@subsection @code{BZ2_bzWrite} +@example + void BZ2_bzWrite ( int *bzerror, BZFILE *b, void *buf, int len ); +@end example +Absorbs @code{len} bytes from the buffer @code{buf}, eventually to be +compressed and written to the file. + +Possible assignments to @code{bzerror}: +@display + @code{BZ_PARAM_ERROR} + if @code{b} is @code{NULL} or @code{buf} is @code{NULL} or @code{len < 0} + @code{BZ_SEQUENCE_ERROR} + if b was opened with @code{BZ2_bzReadOpen} + @code{BZ_IO_ERROR} + if there is an error writing the compressed file. + @code{BZ_OK} + otherwise +@end display + + + + +@subsection @code{BZ2_bzWriteClose} +@example + void BZ2_bzWriteClose ( int *bzerror, BZFILE* f, + int abandon, + unsigned int* nbytes_in, + unsigned int* nbytes_out ); + + void BZ2_bzWriteClose64 ( int *bzerror, BZFILE* f, + int abandon, + unsigned int* nbytes_in_lo32, + unsigned int* nbytes_in_hi32, + unsigned int* nbytes_out_lo32, + unsigned int* nbytes_out_hi32 ); +@end example + +Compresses and flushes to the compressed file all data so far supplied +by @code{BZ2_bzWrite}. The logical end-of-stream markers are also written, so +subsequent calls to @code{BZ2_bzWrite} are illegal. All memory associated +with the compressed file @code{b} is released. +@code{fflush} is called on the +compressed file, but it is not @code{fclose}'d. + +If @code{BZ2_bzWriteClose} is called to clean up after an error, the only +action is to release the memory. The library records the error codes +issued by previous calls, so this situation will be detected +automatically. There is no attempt to complete the compression +operation, nor to @code{fflush} the compressed file. You can force this +behaviour to happen even in the case of no error, by passing a nonzero +value to @code{abandon}. + +If @code{nbytes_in} is non-null, @code{*nbytes_in} will be set to be the +total volume of uncompressed data handled. Similarly, @code{nbytes_out} +will be set to the total volume of compressed data written. For +compatibility with older versions of the library, @code{BZ2_bzWriteClose} +only yields the lower 32 bits of these counts. Use +@code{BZ2_bzWriteClose64} if you want the full 64 bit counts. These +two functions are otherwise absolutely identical. + + +Possible assignments to @code{bzerror}: +@display + @code{BZ_SEQUENCE_ERROR} + if @code{b} was opened with @code{BZ2_bzReadOpen} + @code{BZ_IO_ERROR} + if there is an error writing the compressed file + @code{BZ_OK} + otherwise +@end display + +@subsection Handling embedded compressed data streams + +The high-level library facilitates use of +@code{bzip2} data streams which form some part of a surrounding, larger +data stream. +@itemize @bullet +@item For writing, the library takes an open file handle, writes +compressed data to it, @code{fflush}es it but does not @code{fclose} it. +The calling application can write its own data before and after the +compressed data stream, using that same file handle. +@item Reading is more complex, and the facilities are not as general +as they could be since generality is hard to reconcile with efficiency. +@code{BZ2_bzRead} reads from the compressed file in blocks of size +@code{BZ_MAX_UNUSED} bytes, and in doing so probably will overshoot +the logical end of compressed stream. +To recover this data once decompression has +ended, call @code{BZ2_bzReadGetUnused} after the last call of @code{BZ2_bzRead} +(the one returning @code{BZ_STREAM_END}) but before calling +@code{BZ2_bzReadClose}. +@end itemize + +This mechanism makes it easy to decompress multiple @code{bzip2} +streams placed end-to-end. As the end of one stream, when @code{BZ2_bzRead} +returns @code{BZ_STREAM_END}, call @code{BZ2_bzReadGetUnused} to collect the +unused data (copy it into your own buffer somewhere). +That data forms the start of the next compressed stream. +To start uncompressing that next stream, call @code{BZ2_bzReadOpen} again, +feeding in the unused data via the @code{unused}/@code{nUnused} +parameters. +Keep doing this until @code{BZ_STREAM_END} return coincides with the +physical end of file (@code{feof(f)}). In this situation +@code{BZ2_bzReadGetUnused} +will of course return no data. + +This should give some feel for how the high-level interface can be used. +If you require extra flexibility, you'll have to bite the bullet and get +to grips with the low-level interface. + +@subsection Standard file-reading/writing code +Here's how you'd write data to a compressed file: +@example @code +FILE* f; +BZFILE* b; +int nBuf; +char buf[ /* whatever size you like */ ]; +int bzerror; +int nWritten; + +f = fopen ( "myfile.bz2", "w" ); +if (!f) @{ + /* handle error */ +@} +b = BZ2_bzWriteOpen ( &bzerror, f, 9 ); +if (bzerror != BZ_OK) @{ + BZ2_bzWriteClose ( b ); + /* handle error */ +@} + +while ( /* condition */ ) @{ + /* get data to write into buf, and set nBuf appropriately */ + nWritten = BZ2_bzWrite ( &bzerror, b, buf, nBuf ); + if (bzerror == BZ_IO_ERROR) @{ + BZ2_bzWriteClose ( &bzerror, b ); + /* handle error */ + @} +@} + +BZ2_bzWriteClose ( &bzerror, b ); +if (bzerror == BZ_IO_ERROR) @{ + /* handle error */ +@} +@end example +And to read from a compressed file: +@example +FILE* f; +BZFILE* b; +int nBuf; +char buf[ /* whatever size you like */ ]; +int bzerror; +int nWritten; + +f = fopen ( "myfile.bz2", "r" ); +if (!f) @{ + /* handle error */ +@} +b = BZ2_bzReadOpen ( &bzerror, f, 0, NULL, 0 ); +if (bzerror != BZ_OK) @{ + BZ2_bzReadClose ( &bzerror, b ); + /* handle error */ +@} + +bzerror = BZ_OK; +while (bzerror == BZ_OK && /* arbitrary other conditions */) @{ + nBuf = BZ2_bzRead ( &bzerror, b, buf, /* size of buf */ ); + if (bzerror == BZ_OK) @{ + /* do something with buf[0 .. nBuf-1] */ + @} +@} +if (bzerror != BZ_STREAM_END) @{ + BZ2_bzReadClose ( &bzerror, b ); + /* handle error */ +@} else @{ + BZ2_bzReadClose ( &bzerror ); +@} +@end example + + + +@section Utility functions +@subsection @code{BZ2_bzBuffToBuffCompress} +@example + int BZ2_bzBuffToBuffCompress( char* dest, + unsigned int* destLen, + char* source, + unsigned int sourceLen, + int blockSize100k, + int verbosity, + int workFactor ); +@end example +Attempts to compress the data in @code{source[0 .. sourceLen-1]} +into the destination buffer, @code{dest[0 .. *destLen-1]}. +If the destination buffer is big enough, @code{*destLen} is +set to the size of the compressed data, and @code{BZ_OK} is +returned. If the compressed data won't fit, @code{*destLen} +is unchanged, and @code{BZ_OUTBUFF_FULL} is returned. + +Compression in this manner is a one-shot event, done with a single call +to this function. The resulting compressed data is a complete +@code{bzip2} format data stream. There is no mechanism for making +additional calls to provide extra input data. If you want that kind of +mechanism, use the low-level interface. + +For the meaning of parameters @code{blockSize100k}, @code{verbosity} +and @code{workFactor}, @* see @code{BZ2_bzCompressInit}. + +To guarantee that the compressed data will fit in its buffer, allocate +an output buffer of size 1% larger than the uncompressed data, plus +six hundred extra bytes. + +@code{BZ2_bzBuffToBuffDecompress} will not write data at or +beyond @code{dest[*destLen]}, even in case of buffer overflow. + +Possible return values: +@display + @code{BZ_CONFIG_ERROR} + if the library has been mis-compiled + @code{BZ_PARAM_ERROR} + if @code{dest} is @code{NULL} or @code{destLen} is @code{NULL} + or @code{blockSize100k < 1} or @code{blockSize100k > 9} + or @code{verbosity < 0} or @code{verbosity > 4} + or @code{workFactor < 0} or @code{workFactor > 250} + @code{BZ_MEM_ERROR} + if insufficient memory is available + @code{BZ_OUTBUFF_FULL} + if the size of the compressed data exceeds @code{*destLen} + @code{BZ_OK} + otherwise +@end display + + + +@subsection @code{BZ2_bzBuffToBuffDecompress} +@example + int BZ2_bzBuffToBuffDecompress ( char* dest, + unsigned int* destLen, + char* source, + unsigned int sourceLen, + int small, + int verbosity ); +@end example +Attempts to decompress the data in @code{source[0 .. sourceLen-1]} +into the destination buffer, @code{dest[0 .. *destLen-1]}. +If the destination buffer is big enough, @code{*destLen} is +set to the size of the uncompressed data, and @code{BZ_OK} is +returned. If the compressed data won't fit, @code{*destLen} +is unchanged, and @code{BZ_OUTBUFF_FULL} is returned. + +@code{source} is assumed to hold a complete @code{bzip2} format +data stream. @* @code{BZ2_bzBuffToBuffDecompress} tries to decompress +the entirety of the stream into the output buffer. + +For the meaning of parameters @code{small} and @code{verbosity}, +see @code{BZ2_bzDecompressInit}. + +Because the compression ratio of the compressed data cannot be known in +advance, there is no easy way to guarantee that the output buffer will +be big enough. You may of course make arrangements in your code to +record the size of the uncompressed data, but such a mechanism is beyond +the scope of this library. + +@code{BZ2_bzBuffToBuffDecompress} will not write data at or +beyond @code{dest[*destLen]}, even in case of buffer overflow. + +Possible return values: +@display + @code{BZ_CONFIG_ERROR} + if the library has been mis-compiled + @code{BZ_PARAM_ERROR} + if @code{dest} is @code{NULL} or @code{destLen} is @code{NULL} + or @code{small != 0 && small != 1} + or @code{verbosity < 0} or @code{verbosity > 4} + @code{BZ_MEM_ERROR} + if insufficient memory is available + @code{BZ_OUTBUFF_FULL} + if the size of the compressed data exceeds @code{*destLen} + @code{BZ_DATA_ERROR} + if a data integrity error was detected in the compressed data + @code{BZ_DATA_ERROR_MAGIC} + if the compressed data doesn't begin with the right magic bytes + @code{BZ_UNEXPECTED_EOF} + if the compressed data ends unexpectedly + @code{BZ_OK} + otherwise +@end display + + + +@section @code{zlib} compatibility functions +Yoshioka Tsuneo has contributed some functions to +give better @code{zlib} compatibility. These functions are +@code{BZ2_bzopen}, @code{BZ2_bzread}, @code{BZ2_bzwrite}, @code{BZ2_bzflush}, +@code{BZ2_bzclose}, +@code{BZ2_bzerror} and @code{BZ2_bzlibVersion}. +These functions are not (yet) officially part of +the library. If they break, you get to keep all the pieces. +Nevertheless, I think they work ok. +@example +typedef void BZFILE; + +const char * BZ2_bzlibVersion ( void ); +@end example +Returns a string indicating the library version. +@example +BZFILE * BZ2_bzopen ( const char *path, const char *mode ); +BZFILE * BZ2_bzdopen ( int fd, const char *mode ); +@end example +Opens a @code{.bz2} file for reading or writing, using either its name +or a pre-existing file descriptor. +Analogous to @code{fopen} and @code{fdopen}. +@example +int BZ2_bzread ( BZFILE* b, void* buf, int len ); +int BZ2_bzwrite ( BZFILE* b, void* buf, int len ); +@end example +Reads/writes data from/to a previously opened @code{BZFILE}. +Analogous to @code{fread} and @code{fwrite}. +@example +int BZ2_bzflush ( BZFILE* b ); +void BZ2_bzclose ( BZFILE* b ); +@end example +Flushes/closes a @code{BZFILE}. @code{BZ2_bzflush} doesn't actually do +anything. Analogous to @code{fflush} and @code{fclose}. + +@example +const char * BZ2_bzerror ( BZFILE *b, int *errnum ) +@end example +Returns a string describing the more recent error status of +@code{b}, and also sets @code{*errnum} to its numerical value. + + +@section Using the library in a @code{stdio}-free environment + +@subsection Getting rid of @code{stdio} + +In a deeply embedded application, you might want to use just +the memory-to-memory functions. You can do this conveniently +by compiling the library with preprocessor symbol @code{BZ_NO_STDIO} +defined. Doing this gives you a library containing only the following +eight functions: + +@code{BZ2_bzCompressInit}, @code{BZ2_bzCompress}, @code{BZ2_bzCompressEnd} @* +@code{BZ2_bzDecompressInit}, @code{BZ2_bzDecompress}, @code{BZ2_bzDecompressEnd} @* +@code{BZ2_bzBuffToBuffCompress}, @code{BZ2_bzBuffToBuffDecompress} + +When compiled like this, all functions will ignore @code{verbosity} +settings. + +@subsection Critical error handling +@code{libbzip2} contains a number of internal assertion checks which +should, needless to say, never be activated. Nevertheless, if an +assertion should fail, behaviour depends on whether or not the library +was compiled with @code{BZ_NO_STDIO} set. + +For a normal compile, an assertion failure yields the message +@example + bzip2/libbzip2: internal error number N. + This is a bug in bzip2/libbzip2, 1.0 of 21-Mar-2000. + Please report it to me at: jseward@@acm.org. If this happened + when you were using some program which uses libbzip2 as a + component, you should also report this bug to the author(s) + of that program. Please make an effort to report this bug; + timely and accurate bug reports eventually lead to higher + quality software. Thanks. Julian Seward, 21 March 2000. +@end example +where @code{N} is some error code number. @code{exit(3)} +is then called. + +For a @code{stdio}-free library, assertion failures result +in a call to a function declared as: +@example + extern void bz_internal_error ( int errcode ); +@end example +The relevant code is passed as a parameter. You should supply +such a function. + +In either case, once an assertion failure has occurred, any +@code{bz_stream} records involved can be regarded as invalid. +You should not attempt to resume normal operation with them. + +You may, of course, change critical error handling to suit +your needs. As I said above, critical errors indicate bugs +in the library and should not occur. All "normal" error +situations are indicated via error return codes from functions, +and can be recovered from. + + +@section Making a Windows DLL +Everything related to Windows has been contributed by Yoshioka Tsuneo +@* (@code{QWF00133@@niftyserve.or.jp} / +@code{tsuneo-y@@is.aist-nara.ac.jp}), so you should send your queries to +him (but perhaps Cc: me, @code{jseward@@acm.org}). + +My vague understanding of what to do is: using Visual C++ 5.0, +open the project file @code{libbz2.dsp}, and build. That's all. + +If you can't +open the project file for some reason, make a new one, naming these files: +@code{blocksort.c}, @code{bzlib.c}, @code{compress.c}, +@code{crctable.c}, @code{decompress.c}, @code{huffman.c}, @* +@code{randtable.c} and @code{libbz2.def}. You will also need +to name the header files @code{bzlib.h} and @code{bzlib_private.h}. + +If you don't use VC++, you may need to define the proprocessor symbol +@code{_WIN32}. + +Finally, @code{dlltest.c} is a sample program using the DLL. It has a +project file, @code{dlltest.dsp}. + +If you just want a makefile for Visual C, have a look at +@code{makefile.msc}. + +Be aware that if you compile @code{bzip2} itself on Win32, you must set +@code{BZ_UNIX} to 0 and @code{BZ_LCCWIN32} to 1, in the file +@code{bzip2.c}, before compiling. Otherwise the resulting binary won't +work correctly. + +I haven't tried any of this stuff myself, but it all looks plausible. + + + +@chapter Miscellanea + +These are just some random thoughts of mine. Your mileage may +vary. + +@section Limitations of the compressed file format +@code{bzip2-1.0}, @code{0.9.5} and @code{0.9.0} +use exactly the same file format as the previous +version, @code{bzip2-0.1}. This decision was made in the interests of +stability. Creating yet another incompatible compressed file format +would create further confusion and disruption for users. + +Nevertheless, this is not a painless decision. Development +work since the release of @code{bzip2-0.1} in August 1997 +has shown complexities in the file format which slow down +decompression and, in retrospect, are unnecessary. These are: +@itemize @bullet +@item The run-length encoder, which is the first of the + compression transformations, is entirely irrelevant. + The original purpose was to protect the sorting algorithm + from the very worst case input: a string of repeated + symbols. But algorithm steps Q6a and Q6b in the original + Burrows-Wheeler technical report (SRC-124) show how + repeats can be handled without difficulty in block + sorting. +@item The randomisation mechanism doesn't really need to be + there. Udi Manber and Gene Myers published a suffix + array construction algorithm a few years back, which + can be employed to sort any block, no matter how + repetitive, in O(N log N) time. Subsequent work by + Kunihiko Sadakane has produced a derivative O(N (log N)^2) + algorithm which usually outperforms the Manber-Myers + algorithm. + + I could have changed to Sadakane's algorithm, but I find + it to be slower than @code{bzip2}'s existing algorithm for + most inputs, and the randomisation mechanism protects + adequately against bad cases. I didn't think it was + a good tradeoff to make. Partly this is due to the fact + that I was not flooded with email complaints about + @code{bzip2-0.1}'s performance on repetitive data, so + perhaps it isn't a problem for real inputs. + + Probably the best long-term solution, + and the one I have incorporated into 0.9.5 and above, + is to use the existing sorting + algorithm initially, and fall back to a O(N (log N)^2) + algorithm if the standard algorithm gets into difficulties. +@item The compressed file format was never designed to be + handled by a library, and I have had to jump though + some hoops to produce an efficient implementation of + decompression. It's a bit hairy. Try passing + @code{decompress.c} through the C preprocessor + and you'll see what I mean. Much of this complexity + could have been avoided if the compressed size of + each block of data was recorded in the data stream. +@item An Adler-32 checksum, rather than a CRC32 checksum, + would be faster to compute. +@end itemize +It would be fair to say that the @code{bzip2} format was frozen +before I properly and fully understood the performance +consequences of doing so. + +Improvements which I was able to incorporate into +0.9.0, despite using the same file format, are: +@itemize @bullet +@item Single array implementation of the inverse BWT. This + significantly speeds up decompression, presumably + because it reduces the number of cache misses. +@item Faster inverse MTF transform for large MTF values. The + new implementation is based on the notion of sliding blocks + of values. +@item @code{bzip2-0.9.0} now reads and writes files with @code{fread} + and @code{fwrite}; version 0.1 used @code{putc} and @code{getc}. + Duh! Well, you live and learn. + +@end itemize +Further ahead, it would be nice +to be able to do random access into files. This will +require some careful design of compressed file formats. + + + +@section Portability issues +After some consideration, I have decided not to use +GNU @code{autoconf} to configure 0.9.5 or 1.0. + +@code{autoconf}, admirable and wonderful though it is, +mainly assists with portability problems between Unix-like +platforms. But @code{bzip2} doesn't have much in the way +of portability problems on Unix; most of the difficulties appear +when porting to the Mac, or to Microsoft's operating systems. +@code{autoconf} doesn't help in those cases, and brings in a +whole load of new complexity. + +Most people should be able to compile the library and program +under Unix straight out-of-the-box, so to speak, especially +if you have a version of GNU C available. + +There are a couple of @code{__inline__} directives in the code. GNU C +(@code{gcc}) should be able to handle them. If you're not using +GNU C, your C compiler shouldn't see them at all. +If your compiler does, for some reason, see them and doesn't +like them, just @code{#define} @code{__inline__} to be @code{/* */}. One +easy way to do this is to compile with the flag @code{-D__inline__=}, +which should be understood by most Unix compilers. + +If you still have difficulties, try compiling with the macro +@code{BZ_STRICT_ANSI} defined. This should enable you to build the +library in a strictly ANSI compliant environment. Building the program +itself like this is dangerous and not supported, since you remove +@code{bzip2}'s checks against compressing directories, symbolic links, +devices, and other not-really-a-file entities. This could cause +filesystem corruption! + +One other thing: if you create a @code{bzip2} binary for public +distribution, please try and link it statically (@code{gcc -s}). This +avoids all sorts of library-version issues that others may encounter +later on. + +If you build @code{bzip2} on Win32, you must set @code{BZ_UNIX} to 0 and +@code{BZ_LCCWIN32} to 1, in the file @code{bzip2.c}, before compiling. +Otherwise the resulting binary won't work correctly. + + + +@section Reporting bugs +I tried pretty hard to make sure @code{bzip2} is +bug free, both by design and by testing. Hopefully +you'll never need to read this section for real. + +Nevertheless, if @code{bzip2} dies with a segmentation +fault, a bus error or an internal assertion failure, it +will ask you to email me a bug report. Experience with +version 0.1 shows that almost all these problems can +be traced to either compiler bugs or hardware problems. +@itemize @bullet +@item +Recompile the program with no optimisation, and see if it +works. And/or try a different compiler. +I heard all sorts of stories about various flavours +of GNU C (and other compilers) generating bad code for +@code{bzip2}, and I've run across two such examples myself. + +2.7.X versions of GNU C are known to generate bad code from +time to time, at high optimisation levels. +If you get problems, try using the flags +@code{-O2} @code{-fomit-frame-pointer} @code{-fno-strength-reduce}. +You should specifically @emph{not} use @code{-funroll-loops}. + +You may notice that the Makefile runs six tests as part of +the build process. If the program passes all of these, it's +a pretty good (but not 100%) indication that the compiler has +done its job correctly. +@item +If @code{bzip2} crashes randomly, and the crashes are not +repeatable, you may have a flaky memory subsystem. @code{bzip2} +really hammers your memory hierarchy, and if it's a bit marginal, +you may get these problems. Ditto if your disk or I/O subsystem +is slowly failing. Yup, this really does happen. + +Try using a different machine of the same type, and see if +you can repeat the problem. +@item This isn't really a bug, but ... If @code{bzip2} tells +you your file is corrupted on decompression, and you +obtained the file via FTP, there is a possibility that you +forgot to tell FTP to do a binary mode transfer. That absolutely +will cause the file to be non-decompressible. You'll have to transfer +it again. +@end itemize + +If you've incorporated @code{libbzip2} into your own program +and are getting problems, please, please, please, check that the +parameters you are passing in calls to the library, are +correct, and in accordance with what the documentation says +is allowable. I have tried to make the library robust against +such problems, but I'm sure I haven't succeeded. + +Finally, if the above comments don't help, you'll have to send +me a bug report. Now, it's just amazing how many people will +send me a bug report saying something like +@display + bzip2 crashed with segmentation fault on my machine +@end display +and absolutely nothing else. Needless to say, a such a report +is @emph{totally, utterly, completely and comprehensively 100% useless; +a waste of your time, my time, and net bandwidth}. +With no details at all, there's no way I can possibly begin +to figure out what the problem is. + +The rules of the game are: facts, facts, facts. Don't omit +them because "oh, they won't be relevant". At the bare +minimum: +@display + Machine type. Operating system version. + Exact version of @code{bzip2} (do @code{bzip2 -V}). + Exact version of the compiler used. + Flags passed to the compiler. +@end display +However, the most important single thing that will help me is +the file that you were trying to compress or decompress at the +time the problem happened. Without that, my ability to do anything +more than speculate about the cause, is limited. + +Please remember that I connect to the Internet with a modem, so +you should contact me before mailing me huge files. + + +@section Did you get the right package? + +@code{bzip2} is a resource hog. It soaks up large amounts of CPU cycles +and memory. Also, it gives very large latencies. In the worst case, you +can feed many megabytes of uncompressed data into the library before +getting any compressed output, so this probably rules out applications +requiring interactive behaviour. + +These aren't faults of my implementation, I hope, but more +an intrinsic property of the Burrows-Wheeler transform (unfortunately). +Maybe this isn't what you want. + +If you want a compressor and/or library which is faster, uses less +memory but gets pretty good compression, and has minimal latency, +consider Jean-loup +Gailly's and Mark Adler's work, @code{zlib-1.1.2} and +@code{gzip-1.2.4}. Look for them at + +@code{http://www.cdrom.com/pub/infozip/zlib} and +@code{http://www.gzip.org} respectively. + +For something faster and lighter still, you might try Markus F X J +Oberhumer's @code{LZO} real-time compression/decompression library, at +@* @code{http://wildsau.idv.uni-linz.ac.at/mfx/lzo.html}. + +If you want to use the @code{bzip2} algorithms to compress small blocks +of data, 64k bytes or smaller, for example on an on-the-fly disk +compressor, you'd be well advised not to use this library. Instead, +I've made a special library tuned for that kind of use. It's part of +@code{e2compr-0.40}, an on-the-fly disk compressor for the Linux +@code{ext2} filesystem. Look at +@code{http://www.netspace.net.au/~reiter/e2compr}. + + + +@section Testing + +A record of the tests I've done. + +First, some data sets: +@itemize @bullet +@item B: a directory containing 6001 files, one for every length in the + range 0 to 6000 bytes. The files contain random lowercase + letters. 18.7 megabytes. +@item H: my home directory tree. Documents, source code, mail files, + compressed data. H contains B, and also a directory of + files designed as boundary cases for the sorting; mostly very + repetitive, nasty files. 565 megabytes. +@item A: directory tree holding various applications built from source: + @code{egcs}, @code{gcc-2.8.1}, KDE, GTK, Octave, etc. + 2200 megabytes. +@end itemize +The tests conducted are as follows. Each test means compressing +(a copy of) each file in the data set, decompressing it and +comparing it against the original. + +First, a bunch of tests with block sizes and internal buffer +sizes set very small, +to detect any problems with the +blocking and buffering mechanisms. +This required modifying the source code so as to try to +break it. +@enumerate +@item Data set H, with + buffer size of 1 byte, and block size of 23 bytes. +@item Data set B, buffer sizes 1 byte, block size 1 byte. +@item As (2) but small-mode decompression. +@item As (2) with block size 2 bytes. +@item As (2) with block size 3 bytes. +@item As (2) with block size 4 bytes. +@item As (2) with block size 5 bytes. +@item As (2) with block size 6 bytes and small-mode decompression. +@item H with buffer size of 1 byte, but normal block + size (up to 900000 bytes). +@end enumerate +Then some tests with unmodified source code. +@enumerate +@item H, all settings normal. +@item As (1), with small-mode decompress. +@item H, compress with flag @code{-1}. +@item H, compress with flag @code{-s}, decompress with flag @code{-s}. +@item Forwards compatibility: H, @code{bzip2-0.1pl2} compressing, + @code{bzip2-0.9.5} decompressing, all settings normal. +@item Backwards compatibility: H, @code{bzip2-0.9.5} compressing, + @code{bzip2-0.1pl2} decompressing, all settings normal. +@item Bigger tests: A, all settings normal. +@item As (7), using the fallback (Sadakane-like) sorting algorithm. +@item As (8), compress with flag @code{-1}, decompress with flag + @code{-s}. +@item H, using the fallback sorting algorithm. +@item Forwards compatibility: A, @code{bzip2-0.1pl2} compressing, + @code{bzip2-0.9.5} decompressing, all settings normal. +@item Backwards compatibility: A, @code{bzip2-0.9.5} compressing, + @code{bzip2-0.1pl2} decompressing, all settings normal. +@item Misc test: about 400 megabytes of @code{.tar} files with + @code{bzip2} compiled with Checker (a memory access error + detector, like Purify). +@item Misc tests to make sure it builds and runs ok on non-Linux/x86 + platforms. +@end enumerate +These tests were conducted on a 225 MHz IDT WinChip machine, running +Linux 2.0.36. They represent nearly a week of continuous computation. +All tests completed successfully. + + +@section Further reading +@code{bzip2} is not research work, in the sense that it doesn't present +any new ideas. Rather, it's an engineering exercise based on existing +ideas. + +Four documents describe essentially all the ideas behind @code{bzip2}: +@example +Michael Burrows and D. J. Wheeler: + "A block-sorting lossless data compression algorithm" + 10th May 1994. + Digital SRC Research Report 124. + ftp://ftp.digital.com/pub/DEC/SRC/research-reports/SRC-124.ps.gz + If you have trouble finding it, try searching at the + New Zealand Digital Library, http://www.nzdl.org. + +Daniel S. Hirschberg and Debra A. LeLewer + "Efficient Decoding of Prefix Codes" + Communications of the ACM, April 1990, Vol 33, Number 4. + You might be able to get an electronic copy of this + from the ACM Digital Library. + +David J. Wheeler + Program bred3.c and accompanying document bred3.ps. + This contains the idea behind the multi-table Huffman + coding scheme. + ftp://ftp.cl.cam.ac.uk/users/djw3/ + +Jon L. Bentley and Robert Sedgewick + "Fast Algorithms for Sorting and Searching Strings" + Available from Sedgewick's web page, + www.cs.princeton.edu/~rs +@end example +The following paper gives valuable additional insights into the +algorithm, but is not immediately the basis of any code +used in bzip2. +@example +Peter Fenwick: + Block Sorting Text Compression + Proceedings of the 19th Australasian Computer Science Conference, + Melbourne, Australia. Jan 31 - Feb 2, 1996. + ftp://ftp.cs.auckland.ac.nz/pub/peter-f/ACSC96paper.ps +@end example +Kunihiko Sadakane's sorting algorithm, mentioned above, +is available from: +@example +http://naomi.is.s.u-tokyo.ac.jp/~sada/papers/Sada98b.ps.gz +@end example +The Manber-Myers suffix array construction +algorithm is described in a paper +available from: +@example +http://www.cs.arizona.edu/people/gene/PAPERS/suffix.ps +@end example +Finally, the following paper documents some recent investigations +I made into the performance of sorting algorithms: +@example +Julian Seward: + On the Performance of BWT Sorting Algorithms + Proceedings of the IEEE Data Compression Conference 2000 + Snowbird, Utah. 28-30 March 2000. +@end example + + +@contents + +@bye + diff -Nru bzip2-1.0.1/doc/bzip2recover.1 bzip2-1.0.1.new/doc/bzip2recover.1 --- bzip2-1.0.1/doc/bzip2recover.1 Thu Jan 1 01:00:00 1970 +++ bzip2-1.0.1.new/doc/bzip2recover.1 Sat Jun 24 20:13:06 2000 @@ -0,0 +1 @@ +.so bzip2.1 \ No newline at end of file diff -Nru bzip2-1.0.1/doc/pl/Makefile.am bzip2-1.0.1.new/doc/pl/Makefile.am --- bzip2-1.0.1/doc/pl/Makefile.am Thu Jan 1 01:00:00 1970 +++ bzip2-1.0.1.new/doc/pl/Makefile.am Sat Jun 24 20:13:06 2000 @@ -0,0 +1,4 @@ + +mandir = @mandir@/pl +man_MANS = bzip2.1 bunzip2.1 bzcat.1 bzip2recover.1 + diff -Nru bzip2-1.0.1/doc/pl/bunzip2.1 bzip2-1.0.1.new/doc/pl/bunzip2.1 --- bzip2-1.0.1/doc/pl/bunzip2.1 Thu Jan 1 01:00:00 1970 +++ bzip2-1.0.1.new/doc/pl/bunzip2.1 Sat Jun 24 20:13:06 2000 @@ -0,0 +1 @@ +.so bzip2.1 \ No newline at end of file diff -Nru bzip2-1.0.1/doc/pl/bzcat.1 bzip2-1.0.1.new/doc/pl/bzcat.1 --- bzip2-1.0.1/doc/pl/bzcat.1 Thu Jan 1 01:00:00 1970 +++ bzip2-1.0.1.new/doc/pl/bzcat.1 Sat Jun 24 20:13:06 2000 @@ -0,0 +1 @@ +.so bzip2.1 \ No newline at end of file diff -Nru bzip2-1.0.1/doc/pl/bzip2.1 bzip2-1.0.1.new/doc/pl/bzip2.1 --- bzip2-1.0.1/doc/pl/bzip2.1 Thu Jan 1 01:00:00 1970 +++ bzip2-1.0.1.new/doc/pl/bzip2.1 Sat Jun 24 20:13:06 2000 @@ -0,0 +1,384 @@ +.\" T³umaczenie Maciej Wojciechowski wojciech@staszic.waw.pl +.PU +.TH bzip2 1 "" "" "wersja 1.0" +.SH NAZWA +bzip2, bunzip2 \- sortuj±cy bloki kompresor/dekompresor plików, v1.0 +.br +bzcat \- dekompresuje pliki na standardowe wyj¶cie +.br +bzip2recover \- odzyskuje dane ze zniszczonych archiwów bzip2 +.SH SK£ADNIA +.ll +8 +.B bzip2 +.RB [ \-cdfkqstvzVL123456789 ] +.RI [ nazwy_plików \&...] +.ll -8 +.br +.B bunzip2 +.RB [ \-fkvsVL ] +.RI [ nazwy_plików \&...] +.br +.B bzcat +.RB [ \-s ] +.RI [ nazwy_plików \&...] +.br +.B bzip2recover +.I nazwa_pliku +.SH OPIS +.I bzip2 +kompresuje pliki u¿ywaj±c algorytmu sortowania bloków Burrowsa-Wheelera i +kodu Huffmana. Kompresja jest generalnie sporo lepsza od konwencjonalnych +kompresorów opartych o metodê LZ77/LZ78, i jest porównywalna z +osi±gniêciami statystycznych kompresorów z rodziny PPM. + +Opcje linii poleceñ s± w wiêkszo¶ci bardzo podobne do tych z +.IR "GNU gzip" , +ale nie s± identyczne. + +.I bzip2 +oczekuje listy plików towarzysz±cych parametrom linii poleceñ. Ka¿dy plik jest +zastêpowany przez swoj± skompresowan± wersjê, z nazw± +"oryginalny_plik.bz2". Ka¿dy skompresowany plik ma ten sam czas modyfikacji, +uprawnienia i, je¶li to mo¿liwe, w³a¶ciciela co orygina³, po to, aby te +ustawienia mog³y zostaæ odtworzone podczas dekompresji. Utrzymywanie nazwy +plików nie jest do koñca dok³adne w tym sensie, ¿e nie ma mo¿liwo¶ci +przetrzymywania daty, uprawnieñ, w³a¶ciciela i nazw plików na systemach, na +których brakuje tych mo¿liwo¶ci lub maj± ograniczenia co do d³ugo¶ci nazwy, +tak np. jak MS-DOS. + +.I bzip2 +i +.I bunzip2 +standardowo nie nadpisuj± istniej±cych ju¿ plików. Je¶li chcesz aby to +robi³y, musisz u¿yæ parametru \-f. + +Je¶li nie podano ¿adnej nazwy pliku, +.I bzip2 +kompresuje ze standardowego wej¶cia na standardowe wyj¶cie. Odmiawia wówczas +wypisywania skompresowanego wyj¶cie na terminal, gdy¿ by³oby to +ca³kiem niezrozumia³e i przez to bez wiêkszego sensu. + +.I bunzip2 +(lub +.IR bzip2 \-d ) +dekompresuje wszystkie podane pliki. Pliki, które nie by³y +utworzone przez +.I bzip2 +zostan± wykryte i zignorowane, a na ekranie pojawi siê komunikat +ostrzegawczy. +.I bzip2 +próbuje zgadn±æ nazwê dla dekompresowanego pliku w nastêpuj±cy sposób: +.nf + nazwa_pliku.bz2 staje siê nazwa_pliku + nazwa_pliku.bz staje siê nazwa_pliku + nazwa_pliku.tbz2 staje siê nazwa_pliku.tar + nazwa_pliku.tbz staje siê nazwa_pliku.tar + inna_nazwa staje siê inna_nazwa.out +.fi +Je¶li plik nie ma jednego z nastêpuj±cych rozpoznawalnych rozszerzeñ, +.IR .bz2 , +.IR .bz , +.I .tbz2 +lub +.IR .tbz , +to +.I bzip2 +napisze, ¿e nie mo¿e zgadn±æ nazwy pierwotnego pliku, i u¿yje +oryginalnej nazwy z dodanym rozszerzeniem +.IR .out . + +Tak jak kompresja, nie posiadaj±ca ¿adnych plików, powoduje kompresjê ze +standardowego wej¶cia na standardowe wyj¶cie. + +.I bunzip2 +poprawnie zdekompresuje plik, który jest po³aczeniem dwóch lub wiêcej +skompresowanych plików. Rezultatem jest po³±czony odpowiedni +nieskompresowany plik. Obs³ugiwane jest równie¿ sprawdzanie spójno¶ci +(\-t) po³±czonych skompresowanych plików. + +Mo¿esz równie¿ kompresowaæ lub dekompresowaæ pliki na standardowe wyj¶cie +u¿ywaj±c parametru \-c. W ten w³a¶nie sposób mo¿na przeprowadzaæ kompresjê +wielu plików równocze¶nie. +Powsta³e wyniki s± przesy³ane sekwencyjnie na standardowe wyj¶cie. +W ten sposób kompresja wielu plików generuje strumieñ +zawieraj±cy reprezentacje kilku skompresowanych plików. Taki strumieñ mo¿e +byæ zdekompresowany poprawnie tylko przez +.I bzip2 +w wersji 0.9.0 lub pó¼niejszej. Wcze¶niejsze wersje +.I bzip2 +zatrzymaj± siê po zdekmpresowaniu pierwszego pliku w strumieniu. + +.I bzcat +(lub +.I bzip2 -dc) +dekompresuje wszystkie wybrane pliki na standardowe wyj¶cie. + +.I bzip2 +czyta argumenty ze zmiennych ¶rodowiskowych +.I BZIP2 +i +.I BZIP, +w podanej kolejno¶ci, i przetwarza je przed jakimikolwiek argumentami +przeczytanymi z linii poleceñ. To dobra metoda na specyfikowanie +standardowych ustawieñ. + +Kompresja stosowana jest zawsze, nawet je¶li skompresowany plik jest +nieznaczniej wiêkszy od pliku oryginalnego. Pliki mniejsze ni¿ mniej wiêcej +sto bajtów staj± siê wiêksze, poniewa¿ mechanizm kompresji ma sta³y +nag³ówek wynosz±cy oko³o 50 bajtów. Przypadkowe dane (w³±czaj±c wyj¶cie +wiêkszo¶ci kompresorów plików) d± kodowane na mniej wiêcej 8.05 bitu na +bajt, daj±c zysk oko³o 0.5%. + +Jako samosprawdzenie dla twojej ochrony +.I bzip2 +u¿ywa 32-bitowego CRC aby upewniæ siê, ¿e zdekompresowana wersja pliku jest +identyczna z oryginaln±. To strze¿e przed stratami w skompresowanych danych +i przed niewykrytymi b³êdami w +.I bzip2 +(na szczê¶cie bardzo rzadkich). Mo¿liwo¶æ niewykrycia utraty danych +jest mikroskopijna, mniej wiêcej jedna szansa na cztery biliony dla ka¿dego +pliku. Uwa¿aj jednak, gdy¿ sprawdzenie jest dokonywane przed dekompresj±, +wiêc dowiesz siê tylko tego, ¿e co¶ jest nie w porz±dku. Nie pomo¿e ci to odzyskaæ +oryginalnych nieskompresowanych danych. Mo¿esz u¿yæ +.I bzip2recover +aby spróbowaæ odzyskaæ dane z uszkodzonych plików. + +Zwracane warto¶ci: 0 dla normalnego wyj¶cia, 1 dla problemów technicznych +(plik nie znaleziony, niew³a¶ciwy parametr, b³±d wyj¶cia/wyj¶cia itp.), 2 dla +zasygnalizowania b³êdu skompresowanego pliku, 3 dla wewnêtrznego b³êdu (np. +bug), który zmusi³ \fIbzip2\fP do przerwania. + +.SH OPCJE +.TP +.B \-c --stdout +Kompresuje lub dekompresuje na standardowe wyj¶cie. +.TP +.B \-d --decompress +Wymusza dekompresjê. +.IR bzip2 , +.I bunzip2 +i +.I bzcat +s± tak naprawdê tymi samymi programami i decyzja jakie akcje bêd± wykonane +jest wykonywana na podstawie nazwy jaka zosta³a u¿yta. Ten parametr ma wy¿szy +priorytet i wymusza na \fIbzip2\fP dekompresjê. +.TP +.B \-z --compress +Podobne do \-d: wymusza kompresjê, bez wzglêdu na sposób wywo³ania. +.TP +.B \-t --test +Sprawdza integralno¶æ wybranego pliku(ów), ale nie dekompresuje ich. Wymusza +to próbn± dekompresjê i mówi, jaki jest rezultat. +.TP +.B \-f --force +Wymusza zastêpowanie plików wyj¶ciowych. Normalnie, \fIbzip2\fP nie +zastêpuje istniej±cych plików wyj¶ciowych. Wymusza równie¿ na \fIbzip2\fP +³amanie dowi±zañ twardych, czego normalnie nie robi. +.TP +.B \-k --keep +Zatrzymaj (nie kasuj) pliki wej¶ciowe przy kompresji lub dekompresji. +.TP +.B \-s --small +Zredukuj u¿ycie pamiêci na kompresjê, dekompresjê i testowanie. Pliki s± +dekompresowane i testowane przy u¿yciu zmodyfikowanego algorytmu, który +potrzebuje tylko 2.5 bajtu na blok bajtów. Oznacza to, ¿e ka¿dy plik mo¿e +byæ zdekompresowany przy u¿yciu oko³o 2300k pamiêci, jednak trac±c oko³o po³owê +normalnej szybko¶ci. + +Podczas kompresji, \-s wybiera bloki wielko¶ci 200k, których limity +pamiêci wynosz± mniej wiêcej tyle samo, w zamian za jako¶æ kompresji. W +skrócie, je¶li twój komputer ma ma³o pamiêci (8 megabajtów lub mniej), +u¿ywaj opcji \-s do wszystkiego. Zobacz \fBzarz±dzanie pamiêci±\fP poni¿ej. +.TP +.B \-q --quiet +Wy³±cza wszystkie nieistotne komunikaty ostrzegawcze. +Nie s± eliminowane komunikaty dotycz±ce b³êdów wej¶cia/wyj¶cia i innych +zdarzeñ krytycznych. +.TP +.B \-v --verbose +Tryb gadatliwy -- pokazuje stopieñ kompresji dla ka¿dego pliku. Nastêpne +\fB\-v\fP zwiêkszaj± stopieñ gadatliwo¶ci, powoduj±c wy¶wietlanie du¿ej +ilo¶ci informacji, przydatnych g³ównie przy diagnostyce. +.TP +.B \-L --license -V --version +Wy¶wietla wersjê programu i warunki licencji. +.TP +.B \-1 to \-9 +Ustawia wielko¶æ bloku na 100 k, 200 k .. 900 k przy kompresji. Nie ma +¿adnego znaczenia przy dekompresji. Zobacz \fBzarz±dzanie pamiêci±\fP +poni¿ej. +.TP +.B \-- +Traktuje wszystkie nastêpuj±ce po nim argumenty jako nazwy plików, nawet je¶li +zaczynaj± siê one od my¶lnika. Mo¿esz wiêc kompresowaæ i dekompresowaæ +pliki, których nazwa zaczyna siê od my¶lnika, na przyk³ad: bzip2 \-- +\-mój_plik. +.TP +.B \--repetitive-fast --repetitive-best +Te parametry nie maj± znaczenia w wersjach 0.9.5 i wy¿szych. Umo¿liwia³y one +pewn± infantyln± kontrolê nad zachowaniem algorytmu sortuj±cego we +wcze¶niejszych wersjach, co by³o czasami u¿yteczne. Wersje 0.9.5 i wy¿sze +maj± usprawniony algorytm, który powoduje bezu¿yteczno¶æ tej funkcji. + +.SH ZARZ¡DZANIE PAMIÊCI¡ +.I bzip2 +kompresuje du¿e pliki w blokach. Rozmiar bloku ma wp³yw zarówno na stopieñ +osi±ganej kompresji, jak równie¿ na ilo¶æ pamiêci potrzebnej do kompresji +i dekompresji. Parametry od \-1 do \-9 wybieraj± rozmiar bloku odpowiednio +od 100,000 bajtów a¿ do 900,000 bajtów (standardowo). W czasie dekompresji, +rozmiar bloku u¿ytego do kompresji jest odczytywany z nag³ówku pliku +skompresowanego i +.I bunzip2 +sam zajmuje odpowiedni± do dekompresji ilo¶æ pamiêci. Poniewa¿ rozmiar +bloków jest przetrzymywany w pliku skompresowanym, parametry od \-1 do \-9 +nie maj± przy dekompresji ¿adnego znaczenia. + +Wymagania kompresji i dekompresji w bajtach, mog± byæ wyliczone przez: + + Kompresja : 400k + ( 8 x rozmiar bloku ) + + Dekompresja : 100k + ( 4 x rozmiar bloku ) lub + 100k + ( 2.5 x rozmiar bloku ) + +Wiêksze bloki daj± du¿e zmniejszenie zwrotów marginalnych. Wiêkszo¶æ +kompresji pochodzi z pierwszych stu lub dwustu kilobajtów rozmiaru bloku. +Warto o tym pamiêtaæ u¿ywaj±c \fIbzip2\fP na wolnych +komputerach. Warto równie¿ podkre¶liæ, ¿e rozmiar pamiêci potrzebnej do +dekompresji jest wybierany poprzez ustawienie odpowiedniej +wielko¶ci bloku przy kompresji. + +Dla plików skompresowanych standardowym blokiem wielko¶ci 900k, +\fIbunzip2\fP bêdzie wymaga³ oko³o 3700 kilobajtów do dekompresji. Aby +umo¿liwiæ dekompresjê na komputerze wyposa¿onym jedynie w 4 megabajty +pamiêci, \fIbunzip2\fP ma opcjê, która mo¿e zmniejszyæ wymagania prawie do +po³owy, tzn. oko³o 2300 kilobajtów. Prêdko¶æ dekompresji jest równie¿ bardzo +zmiejszona, wiêc u¿ywaj tej opcji tylko wtedy, kiedy jest to konieczne. Tym +parametrem jest -s. + +Generalnie, próbuj i u¿ywaj najwiêkszych rozmiarów bloków, je¶li ilo¶æ +pamiêci ci na to pozwala. Prêdko¶æ kompresji i dekompresji w zasadzie nie +zale¿y od wielko¶ci u¿ytego bloku. + +Inna wa¿na rzecz dotyczy plików, które mieszcz± siê w pojedyñczym bloku -- +oznacza to wiêkszo¶æ plików na które siê natkniesz u¿ywaj±c du¿ych bloków. +Rozmiar realny pamiêci zabieranej jest proporcjonalny do wielko¶ci pliku, +je¶li plik jest mniejszy ni¿ blok. Na przyk³ad, kompresja pliku o +wielko¶ci 20,000 bajtów z parametrem -9 wymusi na kompresorze odnalezienie +7600 k pamiêci, ale zajêcie tylko 400k + 20000 * 8 = 560 kilobajtów z +tego. Podobnie, dekompresor odnajdzie 3700k, ale zajmie tylko 100k + 20000 +* 4 = 180 kilobajtów. + +Tu jest tabela, która podsumowuje maksymalne u¿ycie pamiêci dla ró¿nych +rozmiarów bloków. Podano te¿ ca³kowity rozmiar skompresowanych 14 +plików tekstowych (Calgary Text Compressione Corpus) zajmuj±cych razem +3,141,622 bajtów. Ta kolumna daje pewne pojêcie o tym, jaki wp³yw na +kompresjê ma wielko¶æ bloków. Ta tabela uzmys³awia równie¿ przewagê u¿ycia +wiêkszych bloków dla wiêkszych plików, poniewa¿ "Corpus" jest zdominowany +przez mniejsze pliki. +.nf + U¿ycie U¿ycie U¿ycie Corpus + Parametr kompresji dekompresji dekompresji -s Size + + -1 1200k 500k 350k 914704 + -2 2000k 900k 600k 877703 + -3 2800k 1300k 850k 860338 + -4 3600k 1700k 1100k 846899 + -5 4400k 2100k 1350k 845160 + -6 5200k 2500k 1600k 838626 + -7 6100k 2900k 1850k 834096 + -8 6800k 3300k 2100k 828642 + -9 7600k 3700k 2350k 828642 +.fi +.SH ODZYSKIWANIE DANYCH ZE ZNISZCZONYCH PLIKÓW BZIP2 +.I bzip2 +kompresuje pliki w blokach, zazwyczaj 900 kilbajtowych. Ka¿dy blok jest +trzymany osobno. Je¶li b³êdy transmisji lub no¶nika uszkodz± plik +wieloblokowy .bz2, mo¿liwe jest odtworzenie danych zawartych w +niezniszczonych blokach pliku. + +Ka¿dy blok jest reprezentowany przez 48-bitowy wzorzec, który umo¿liwia +znajdowanie przyporz±dkowañ bloków z rozs±dn± pewno¶ci±. Ka¿dy blok +ma równie¿ swój 32-bitowy CRC, wiêc bloki uszkodzone mog± byæ ³atwo +odseparowane od poprawnych. + +.I bzip2recover +jest oddzielnym programem, którego zadaniem jest poszukiwanie bloków w +plikach .bz2 i zapisywanie ich do w³asnego pliku .bz2. Mo¿esz potem u¿yæ +\fIbzip2\fP \-t aby sprawdziæ spójno¶æ wyj¶ciowego pliku i zdekompresowaæ +te, które nie s± uszkodzone. + +.I bzip2recover +pobiera pojedynczy argument, nazwê uszkodzonego pliku, i tworzy pewn± liczbê +plików "rec0001plik.bz2", "rec0002plik.bz2", itd., przetrzymuj±ce odzyskane +bloki. Wyj¶ciowe nazwy plików s± tak tworzone, aby ³atwo by³o potem u¿ywaæ +ich razem za pomoc± gwiazdek -- na przyk³ad, "bzip2 -dc rec*plik.bz2 > +odzyskany_plik" -- wylistuje pliki we w³a¶ciwej kolejno¶ci. + +.I bzip2recover +powinien byæ u¿ywany najczê¶ciej z du¿ymi plikami .bz2, jako i¿ one +zawieraj± najczê¶ciej du¿o bloków. Jest czystym bezsensem u¿ywaæ go na +uszkodzonym jedno-blokowym pliku, poniewa¿ uszkodzony blok nie mo¿e byæ +odzyskany. Je¶li chcesz zminimalizowaæ jakiekolwiek mo¿liwe straty danych +poprzez no¶nik lub transmisjê, powiniene¶ zastanowiæ siê nad u¿yciem +mniejszych bloków. + +.SH OPISY WYNIKÓW +Etap sortuj±cy kompresji ³±czy razem podobne ci±gi znaków w pliku. Przez +to, pliki zawieraj±ce bardzo d³ugie ci±gi powtarzaj±cych siê symboli, jak +"aabaabaabaab ..." (powtórzone kilkaset razy) mog± byæ kompresowane wolniej +ni¿ normalnie. Wersje 0.9.5 i wy¿sze zachowuj± siê du¿o lepiej w tej +sytuacji ni¿ wersje poprzednie. Ró¿nica stopnia kompresji pomiêdzy +najgorszym i najlepszym przypadkiem kompresji wynosi oko³o 10:1. Dla +wcze¶niejszych wersji by³o to nawet oko³o 100:1. Je¶li chcesz, mo¿esz u¿yæ +parametru \-vvvv aby monitorowaæ postêpy bardzo szczegó³owo. + +Prêdko¶æ dekompresji nie jest zmieniana przez to zjawisko. + +.I bzip2 +zazwyczaj rezerwuje kilka megabajtów pamiêci do dzia³ania a +potem wykorzystuje j± w sposób zupe³nie przypadkowy. +Oznacza to, ¿e zarówno prêdko¶æ kompresji jak i dekompresji jest w +du¿ej czê¶ci zale¿na od prêdko¶ci, z jak± twój komputer mo¿e naprawiaæ braki +bufora podrêcznego. Z tego powodu, wprowadzone zosta³y ma³e zmiany kody aby +zmniejszyæ straty, które da³y nieproporcjonalnie du¿y wzrost osi±gniêæ. +My¶lê, ¿e +.I bzip2 +bêdzie dzia³a³ najlepiej na komputerach z du¿ymi buforami podrêcznymi. + +.SH ZAKAMARKI +Wiadomo¶ci o b³êdach wej¶cia/wyj¶cia nie s± a¿ tak pomocne, jak mog³yby byæ. +.I bzip2 +stara siê wykryæ b³±d wej¶cia/wyj¶cia i wyj¶æ "czysto", ale +szczegó³y tego, jaki to problem mog± byæ czasami bardzo myl±ce. + +Ta strona podrêcznika odnosi siê do wersji 1.0 programu \fIbzip2\fP. +Skompresowane pliki utworzone przez tê wersjê s± kompatybilne zarówno z +w przód jak i wstecznie z poprzednimi publicznymi wydaniami, +wersjami 0.1pl2, 0.9.0 i 0.9.5 ale z ma³ymi wyj±tkami: 0.9.0 i wy¿sze potrafi± +poprawnie dekompresowaæ wiele skompresowanych plików z³±czonych w jeden. +0.1pl2 nie potrafi tego; zatrzyma siê ju¿ po dekompresji pierwszego pliku w +strumieniu. + +.I bzip2recover +u¿ywa 32-bitowych liczb do reprezentacji pozycji bitu w skompresowanym +pliku, wiêc nie mo¿e przetwarzaæ skompresowanych plików d³u¿szych ni¿ 512 +megabajtów. Mo¿na to ³atwo naprawiæ. + +.SH AUTOR +Julian Seward, jseward@acm.org. + +http://www.muraroa.demon.co.uk +http://sourceware.cygnus.com/bzip2 + +Idee zawarte w \fIbzip2\fP s± podzielone (przynajmniej) pomiêdzy +nastepuj±cy ludzi: Michael Burrows i David Wheeler (transformacja +sortuj±c± bloki), David Wheeler (znów, koder Huffmana), Peter Fenwick +(struktura kodowania modelu w oryginalnym \fIbzip2\fP, i wiele +udoskonaleñ), i Alistair Moffar, Radford Neal i Ian Witten (arytmetyczny +koder w oryginalnym \fIbzip2\fP). Jestem im bardzo wdziêczny za ich pomoc, +wsparcie i porady. Zobacz stronê manuala w ¼ród³owej dystrybucji po +wska¼niki do ¼róde³ dokumentacji. Christian von Roques zachêci³ mnie do +wymy¶lenia szybszego algorytmu sortuj±cego, po to ¿eby przyspieszyæ +kompresjê. Bela Lubkin zachêci³a mnie do polepszenia najgorszych wyników +kompresji. Wiele ludzi przys³a³o ³atki, pomog³o w ró¿nych problemach, +po¿yczy³o komputerów, da³o rady i by³o ogólnie pomocnych. diff -Nru bzip2-1.0.1/doc/pl/bzip2recover.1 bzip2-1.0.1.new/doc/pl/bzip2recover.1 --- bzip2-1.0.1/doc/pl/bzip2recover.1 Thu Jan 1 01:00:00 1970 +++ bzip2-1.0.1.new/doc/pl/bzip2recover.1 Sat Jun 24 20:13:06 2000 @@ -0,0 +1 @@ +.so bzip2.1 \ No newline at end of file diff -Nru bzip2-1.0.1/huffman.c bzip2-1.0.1.new/huffman.c --- bzip2-1.0.1/huffman.c Sat Jun 24 20:13:27 2000 +++ bzip2-1.0.1.new/huffman.c Sat Jun 24 20:13:06 2000 @@ -58,6 +58,10 @@ For more information on these sources, see the manual. --*/ +#ifdef HAVE_CONFIG_H +#include +#endif + #include "bzlib_private.h" diff -Nru bzip2-1.0.1/makefile.msc bzip2-1.0.1.new/makefile.msc --- bzip2-1.0.1/makefile.msc Sat Jun 24 20:13:27 2000 +++ bzip2-1.0.1.new/makefile.msc Thu Jan 1 01:00:00 1970 @@ -1,63 +0,0 @@ -# Makefile for Microsoft Visual C++ 6.0 -# usage: nmake -f makefile.msc -# K.M. Syring (syring@gsf.de) -# Fixed up by JRS for bzip2-0.9.5d release. - -CC=cl -CFLAGS= -DWIN32 -MD -Ox -D_FILE_OFFSET_BITS=64 - -OBJS= blocksort.obj \ - huffman.obj \ - crctable.obj \ - randtable.obj \ - compress.obj \ - decompress.obj \ - bzlib.obj - -all: lib bzip2 test - -bzip2: lib - $(CC) $(CFLAGS) -o bzip2 bzip2.c libbz2.lib setargv.obj - $(CC) $(CFLAGS) -o bzip2recover bzip2recover.c - -lib: $(OBJS) - lib /out:libbz2.lib $(OBJS) - -test: bzip2 - type words1 - .\\bzip2 -1 < sample1.ref > sample1.rb2 - .\\bzip2 -2 < sample2.ref > sample2.rb2 - .\\bzip2 -3 < sample3.ref > sample3.rb2 - .\\bzip2 -d < sample1.bz2 > sample1.tst - .\\bzip2 -d < sample2.bz2 > sample2.tst - .\\bzip2 -ds < sample3.bz2 > sample3.tst - @echo All six of the fc's should find no differences. - @echo If fc finds an error on sample3.bz2, this could be - @echo because WinZip's 'TAR file smart CR/LF conversion' - @echo is too clever for its own good. Disable this option. - @echo The correct size for sample3.ref is 120,244. If it - @echo is 150,251, WinZip has messed it up. - fc sample1.bz2 sample1.rb2 - fc sample2.bz2 sample2.rb2 - fc sample3.bz2 sample3.rb2 - fc sample1.tst sample1.ref - fc sample2.tst sample2.ref - fc sample3.tst sample3.ref - - - -clean: - del *.obj - del libbz2.lib - del bzip2.exe - del bzip2recover.exe - del sample1.rb2 - del sample2.rb2 - del sample3.rb2 - del sample1.tst - del sample2.tst - del sample3.tst - -.c.obj: - $(CC) $(CFLAGS) -c $*.c -o $*.obj - diff -Nru bzip2-1.0.1/manual.ps bzip2-1.0.1.new/manual.ps --- bzip2-1.0.1/manual.ps Sat Jun 24 20:13:27 2000 +++ bzip2-1.0.1.new/manual.ps Thu Jan 1 01:00:00 1970 @@ -1,3808 +0,0 @@ -%!PS-Adobe-2.0 -%%Creator: dvips(k) 5.78 Copyright 1998 Radical Eye Software (www.radicaleye.com) -%%Title: manual.dvi -%%Pages: 39 -%%PageOrder: Ascend -%%BoundingBox: 0 0 596 842 -%%EndComments -%DVIPSCommandLine: dvips -o manual.ps manual.dvi -%DVIPSParameters: dpi=600, compressed -%DVIPSSource: TeX output 2000.03.23:2343 -%%BeginProcSet: texc.pro 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y(As)j(with)f(compression,)h(supplying)c(no)k -(\014lenames)f(causes)i(decompression)e(from)h(stan-)390 -1321 y(dard)d(input)g(to)i(standard)e(output.)390 1472 -y Fj(bunzip2)k Fl(will)g(correctly)j(decompress)e(a)i(\014le)e(whic)m -(h)g(is)h(the)g(concatenation)i(of)e(t)m(w)m(o)i(or)390 -1576 y(more)j(compressed)f(\014les.)67 b(The)39 b(result)g(is)g(the)g -(concatenation)i(of)f(the)g(corresp)s(onding)390 1680 -y(uncompressed)c(\014les.)59 b(In)m(tegrit)m(y)38 b(testing)f(\()p -Fj(-t)p Fl(\))g(of)g(concatenated)i(compressed)e(\014les)f(is)390 -1784 y(also)30 b(supp)s(orted.)390 1935 y(Y)-8 b(ou)40 -b(can)g(also)f(compress)g(or)g(decompress)g(\014les)g(to)h(the)f -(standard)g(output)g(b)m(y)g(giving)390 2039 y(the)30 -b Fj(-c)g Fl(\015ag.)40 b(Multiple)28 b(\014les)h(ma)m(y)i(b)s(e)e -(compressed)h(and)f(decompressed)h(lik)m(e)f(this.)39 -b(The)390 2142 y(resulting)31 b(outputs)i(are)h(fed)f(sequen)m(tially)f -(to)i(stdout.)49 b(Compression)32 b(of)h(m)m(ultiple)e(\014les)390 -2246 y(in)24 b(this)g(manner)h(generates)h(a)g(stream)f(con)m(taining)g -(m)m(ultiple)e(compressed)i(\014le)f(represen-)390 2350 -y(tations.)58 b(Suc)m(h)36 b(a)g(stream)g(can)h(b)s(e)e(decompressed)h -(correctly)h(only)e(b)m(y)h Fj(bzip2)e Fl(v)m(ersion)390 -2454 y(0.9.0)g(or)e(later.)47 b(Earlier)30 b(v)m(ersions)i(of)g -Fj(bzip2)f Fl(will)f(stop)i(after)h(decompressing)e(the)i(\014rst)390 -2558 y(\014le)c(in)h(the)g(stream.)390 2709 y Fj(bzcat)f -Fl(\(or)i Fj(bzip2)e(-dc)p Fl(\))g(decompresses)i(all)e(sp)s(eci\014ed) -g(\014les)g(to)i(the)g(standard)e(output.)390 2860 y -Fj(bzip2)f Fl(will)g(read)i(argumen)m(ts)g(from)f(the)h(en)m(vironmen)m -(t)g(v)-5 b(ariables)28 b Fj(BZIP2)h Fl(and)g Fj(BZIP)p -Fl(,)g(in)390 2963 y(that)24 b(order,)g(and)f(will)e(pro)s(cess)i(them) -g(b)s(efore)g(an)m(y)h(argumen)m(ts)f(read)h(from)f(the)g(command)390 -3067 y(line.)39 b(This)29 b(giv)m(es)h(a)h(con)m(v)m(enien)m(t)h(w)m(a) -m(y)f(to)g(supply)d(default)i(argumen)m(ts.)390 3218 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b(against)h(undetected)g(bugs)e(in)390 -4096 y Fj(bzip2)35 b Fl(\(hop)s(efully)e(v)m(ery)k(unlik)m(ely\).)56 -b(The)36 b(c)m(hances)h(of)f(data)h(corruption)e(going)h(unde-)390 -4199 y(tected)g(is)e(microscopic,)h(ab)s(out)f(one)h(c)m(hance)g(in)f -(four)g(billion)d(for)j(eac)m(h)i(\014le)d(pro)s(cessed.)390 -4303 y(Be)38 b(a)m(w)m(are,)k(though,)d(that)f(the)g(c)m(hec)m(k)i(o)s -(ccurs)d(up)s(on)f(decompression,)j(so)f(it)f(can)h(only)390 -4407 y(tell)28 b(y)m(ou)g(that)i(something)d(is)h(wrong.)40 -b(It)28 b(can't)i(help)d(y)m(ou)i(reco)m(v)m(er)h(the)e(original)f -(uncom-)390 4511 y(pressed)h(data.)41 b(Y)-8 b(ou)30 -b(can)f(use)g Fj(bzip2recover)d Fl(to)k(try)f(to)h(reco)m(v)m(er)h -(data)f(from)e(damaged)390 4614 y(\014les.)390 4766 y(Return)22 -b(v)-5 b(alues:)37 b(0)23 b(for)g(a)g(normal)f(exit,)j(1)e(for)g(en)m -(vironmen)m(tal)f(problems)f(\(\014le)i(not)g(found,)390 -4869 y(in)m(v)-5 b(alid)30 b(\015ags,)k(I/O)f(errors,)g(&c\),)h(2)f(to) 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-b(compression,)h(regardless)d(of)i(the)g(in-)870 1334 -y(v)m(ok)-5 b(ation)31 b(name.)390 1488 y Fj(-t)f(--test)8 -b Fl(Chec)m(k)33 b(in)m(tegrit)m(y)j(of)f(the)g(sp)s(eci\014ed)e -(\014le\(s\),)k(but)d(don't)h(decompress)g(them.)870 -1591 y(This)40 b(really)g(p)s(erforms)g(a)i(trial)e(decompression)h -(and)g(thro)m(ws)g(a)m(w)m(a)m(y)j(the)870 1695 y(result.)390 -1849 y Fj(-f)30 b(--force)870 1953 y Fl(F)-8 b(orce)31 -b(o)m(v)m(erwrite)f(of)g(output)f(\014les.)40 b(Normally)-8 -b(,)29 b Fj(bzip2)f Fl(will)f(not)j(o)m(v)m(erwrite)870 -2057 y(existing)e(output)g(\014les.)39 b(Also)28 b(forces)h -Fj(bzip2)e Fl(to)i(break)g(hard)e(links)f(to)k(\014les,)870 -2161 y(whic)m(h)f(it)h(otherwise)g(w)m(ouldn't)f(do.)390 -2315 y Fj(-k)h(--keep)8 b Fl(Keep)24 b(\(don't)i(delete\))h(input)d -(\014les)g(during)g(compression)h(or)h(decompression.)390 -2469 y Fj(-s)k(--small)870 2573 y Fl(Reduce)23 b(memory)f(usage,)j(for) -d(compression,)h(decompression)f(and)g(testing.)870 2676 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b(p)s(ertaining)33 b(to)870 3893 y(I/O)d(errors)g(and)g -(other)h(critical)e(ev)m(en)m(ts)j(will)27 b(not)k(b)s(e)f(suppressed.) -390 4047 y Fj(-v)g(--verbose)870 4151 y Fl(V)-8 b(erb)s(ose)28 -b(mo)s(de)f({)i(sho)m(w)e(the)h(compression)f(ratio)h(for)f(eac)m(h)i -(\014le)e(pro)s(cessed.)870 4255 y(F)-8 b(urther)30 b -Fj(-v)p Fl('s)g(increase)g(the)g(v)m(erb)s(osit)m(y)g(lev)m(el,)h(sp)s -(ewing)d(out)j(lots)f(of)g(infor-)870 4359 y(mation)g(whic)m(h)f(is)h -(primarily)d(of)j(in)m(terest)h(for)f(diagnostic)g(purp)s(oses.)390 -4513 y Fj(-L)g(--license)e(-V)h(--version)870 4617 y -Fl(Displa)m(y)h(the)g(soft)m(w)m(are)i(v)m(ersion,)e(license)f(terms)i -(and)e(conditions.)390 4771 y Fj(-1)h(to)g(-9)72 b Fl(Set)35 -b(the)g(blo)s(c)m(k)f(size)h(to)g(100)h(k,)g(200)g(k)f(..)53 -b(900)36 b(k)f(when)f(compressing.)53 b(Has)870 4875 -y(no)41 b(e\013ect)h(when)d(decompressing.)71 b(See)41 -b(MEMOR)-8 b(Y)41 b(MANA)m(GEMENT)870 4978 y(b)s(elo)m(w.)390 -5132 y Fj(--)324 b Fl(T)-8 b(reats)25 b(all)e(subsequen)m(t)g(argumen)m -(ts)i(as)f(\014le)g(names,)h(ev)m(en)g(if)e(they)i(start)f(with)870 -5236 y(a)32 b(dash.)43 b(This)29 b(is)h(so)i(y)m(ou)g(can)f(handle)f -(\014les)g(with)g(names)i(b)s(eginning)c(with)870 5340 -y(a)j(dash,)f(for)g(example:)40 b Fj(bzip2)29 b(--)h(-myfilename)p -Fl(.)p eop -%%Page: 6 7 -6 6 bop 150 -116 a Fl(Chapter)30 b(2:)41 b(Ho)m(w)31 -b(to)g(use)f Fj(bzip2)2375 b Fl(6)390 299 y Fj(--repetitive-fast)390 -427 y(--repetitive-best)870 530 y Fl(These)34 b(\015ags)g(are)h -(redundan)m(t)e(in)g(v)m(ersions)g(0.9.5)j(and)e(ab)s(o)m(v)m(e.)53 -b(They)34 b(pro-)870 634 y(vided)h(some)i(coarse)g(con)m(trol)g(o)m(v)m -(er)g(the)g(b)s(eha)m(viour)e(of)h(the)g(sorting)g(algo-)870 -738 y(rithm)h(in)h(earlier)g(v)m(ersions,)j(whic)m(h)d(w)m(as)h -(sometimes)h(useful.)65 b(0.9.5)41 b(and)870 842 y(ab)s(o)m(v)m(e)34 -b(ha)m(v)m(e)g(an)f(impro)m(v)m(ed)g(algorithm)f(whic)m(h)f(renders)h -(these)h(\015ags)h(irrel-)870 946 y(ev)-5 b(an)m(t.)390 -1190 y Ff(MEMOR)-10 b(Y)40 b(MANA)m(GEMENT)390 1377 y -Fj(bzip2)25 b Fl(compresses)i(large)g(\014les)e(in)g(blo)s(c)m(ks.)39 -b(The)26 b(blo)s(c)m(k)h(size)f(a\013ects)i(b)s(oth)e(the)h(compres-) -390 1481 y(sion)39 b(ratio)g(ac)m(hiev)m(ed,)k(and)d(the)f(amoun)m(t)i -(of)e(memory)h(needed)f(for)h(compression)f(and)390 1585 -y(decompression.)59 b(The)36 b(\015ags)h Fj(-1)f Fl(through)h -Fj(-9)f Fl(sp)s(ecify)f(the)i(blo)s(c)m(k)g(size)f(to)i(b)s(e)e -(100,000)390 1688 y(b)m(ytes)29 b(through)e(900,000)k(b)m(ytes)d(\(the) -h(default\))e(resp)s(ectiv)m(ely)-8 b(.)40 b(A)m(t)29 -b(decompression)e(time,)390 1792 y(the)32 b(blo)s(c)m(k)g(size)g(used)g -(for)g(compression)f(is)g(read)h(from)g(the)g(header)g(of)h(the)f -(compressed)390 1896 y(\014le,)j(and)f Fj(bunzip2)e Fl(then)i(allo)s -(cates)h(itself)e(just)h(enough)g(memory)g(to)i(decompress)e(the)390 -2000 y(\014le.)39 b(Since)29 b(blo)s(c)m(k)g(sizes)g(are)h(stored)f(in) -f(compressed)h(\014les,)g(it)g(follo)m(ws)f(that)i(the)g(\015ags)g -Fj(-1)390 2103 y Fl(to)h Fj(-9)f Fl(are)h(irrelev)-5 -b(an)m(t)29 b(to)i(and)f(so)h(ignored)e(during)f(decompression.)390 -2255 y(Compression)h(and)g(decompression)h(requiremen)m(ts,)f(in)g(b)m -(ytes,)j(can)e(b)s(e)g(estimated)h(as:)869 2406 y Fj(Compression:)140 -b(400k)46 b(+)i(\()f(8)h(x)f(block)f(size)h(\))869 2613 -y(Decompression:)d(100k)i(+)i(\()f(4)h(x)f(block)f(size)h(\),)g(or)1585 -2717 y(100k)f(+)i(\()f(2.5)g(x)g(block)g(size)f(\))390 -2868 y Fl(Larger)29 b(blo)s(c)m(k)f(sizes)h(giv)m(e)g(rapidly)d -(diminishing)e(marginal)k(returns.)39 b(Most)29 b(of)g(the)g(com-)390 -2972 y(pression)d(comes)j(from)f(the)g(\014rst)g(t)m(w)m(o)h(or)f -(three)h(h)m(undred)d(k)i(of)g(blo)s(c)m(k)g(size,)g(a)h(fact)g(w)m -(orth)390 3075 y(b)s(earing)j(in)f(mind)g(when)h(using)f -Fj(bzip2)h Fl(on)g(small)g(mac)m(hines.)47 b(It)33 b(is)f(also)h(imp)s -(ortan)m(t)f(to)390 3179 y(appreciate)j(that)h(the)f(decompression)f -(memory)h(requiremen)m(t)f(is)h(set)g(at)h(compression)390 -3283 y(time)30 b(b)m(y)g(the)h(c)m(hoice)g(of)g(blo)s(c)m(k)f(size.)390 -3434 y(F)-8 b(or)45 b(\014les)f(compressed)g(with)g(the)g(default)g -(900k)i(blo)s(c)m(k)e(size,)49 b Fj(bunzip2)42 b Fl(will)g(require)390 -3538 y(ab)s(out)29 b(3700)j(kb)m(ytes)e(to)h(decompress.)40 -b(T)-8 b(o)30 b(supp)s(ort)e(decompression)h(of)h(an)m(y)g(\014le)f(on) -g(a)i(4)390 3642 y(megab)m(yte)h(mac)m(hine,)d Fj(bunzip2)f -Fl(has)i(an)g(option)f(to)i(decompress)e(using)g(appro)m(ximately)390 -3745 y(half)k(this)g(amoun)m(t)i(of)f(memory)-8 b(,)36 -b(ab)s(out)e(2300)i(kb)m(ytes.)53 b(Decompression)34 -b(sp)s(eed)g(is)f(also)390 3849 y(halv)m(ed,)i(so)f(y)m(ou)h(should)d -(use)h(this)g(option)h(only)f(where)h(necessary)-8 b(.)53 -b(The)33 b(relev)-5 b(an)m(t)35 b(\015ag)390 3953 y(is)29 -b Fj(-s)p Fl(.)390 4104 y(In)34 b(general,)i(try)f(and)f(use)g(the)h -(largest)h(blo)s(c)m(k)e(size)h(memory)f(constrain)m(ts)h(allo)m(w,)h -(since)390 4208 y(that)45 b(maximises)f(the)h(compression)f(ac)m(hiev)m -(ed.)85 b(Compression)43 b(and)h(decompression)390 4311 -y(sp)s(eed)30 b(are)g(virtually)e(una\013ected)j(b)m(y)f(blo)s(c)m(k)g -(size.)390 4463 y(Another)25 b(signi\014can)m(t)f(p)s(oin)m(t)g -(applies)f(to)j(\014les)e(whic)m(h)g(\014t)h(in)e(a)j(single)d(blo)s(c) -m(k)i({)g(that)h(means)390 4566 y(most)g(\014les)g(y)m(ou'd)g(encoun)m -(ter)h(using)d(a)j(large)f(blo)s(c)m(k)g(size.)39 b(The)25 -b(amoun)m(t)i(of)f(real)g(memory)390 4670 y(touc)m(hed)38 -b(is)e(prop)s(ortional)f(to)j(the)f(size)g(of)h(the)f(\014le,)h(since)f -(the)g(\014le)g(is)f(smaller)g(than)h(a)390 4774 y(blo)s(c)m(k.)49 -b(F)-8 b(or)35 b(example,)f(compressing)e(a)i(\014le)e(20,000)k(b)m -(ytes)e(long)f(with)f(the)i(\015ag)g Fj(-9)f Fl(will)390 -4878 y(cause)28 b(the)f(compressor)g(to)h(allo)s(cate)f(around)f(7600k) -j(of)e(memory)-8 b(,)28 b(but)f(only)f(touc)m(h)i(400k)390 -4981 y Fj(+)h Fl(20000)j(*)e(8)g(=)f(560)i(kb)m(ytes)f(of)g(it.)40 -b(Similarly)-8 b(,)26 b(the)k(decompressor)f(will)e(allo)s(cate)j -(3700k)390 5085 y(but)g(only)f(touc)m(h)i(100k)h Fj(+)e -Fl(20000)i(*)f(4)g(=)f(180)i(kb)m(ytes.)390 5236 y(Here)41 -b(is)f(a)i(table)f(whic)m(h)e(summarises)g(the)j(maxim)m(um)d(memory)i -(usage)h(for)e(di\013eren)m(t)390 5340 y(blo)s(c)m(k)25 -b(sizes.)38 b(Also)25 b(recorded)g(is)f(the)i(total)g(compressed)e -(size)h(for)g(14)h(\014les)e(of)i(the)f(Calgary)p eop -%%Page: 7 8 -7 7 bop 150 -116 a Fl(Chapter)30 b(2:)41 b(Ho)m(w)31 -b(to)g(use)f Fj(bzip2)2375 b Fl(7)390 299 y(T)-8 b(ext)38 -b(Compression)d(Corpus)h(totalling)h(3,141,622)k(b)m(ytes.)61 -b(This)36 b(column)g(giv)m(es)i(some)390 403 y(feel)23 -b(for)f(ho)m(w)h(compression)f(v)-5 b(aries)23 b(with)e(blo)s(c)m(k)i -(size.)38 b(These)23 b(\014gures)f(tend)g(to)i(understate)390 -506 y(the)g(adv)-5 b(an)m(tage)26 b(of)e(larger)f(blo)s(c)m(k)h(sizes)f -(for)h(larger)f(\014les,)h(since)g(the)g(Corpus)e(is)h(dominated)390 -610 y(b)m(y)30 b(smaller)f(\014les.)1107 761 y Fj(Compress)141 -b(Decompress)g(Decompress)f(Corpus)773 865 y(Flag)238 -b(usage)285 b(usage)332 b(-s)48 b(usage)237 b(Size)821 -1073 y(-1)286 b(1200k)332 b(500k)429 b(350k)285 b(914704)821 -1176 y(-2)h(2000k)332 b(900k)429 b(600k)285 b(877703)821 -1280 y(-3)h(2800k)f(1300k)428 b(850k)285 b(860338)821 -1384 y(-4)h(3600k)f(1700k)380 b(1100k)285 b(846899)821 -1488 y(-5)h(4400k)f(2100k)380 b(1350k)285 b(845160)821 -1591 y(-6)h(5200k)f(2500k)380 b(1600k)285 b(838626)821 -1695 y(-7)h(6100k)f(2900k)380 b(1850k)285 b(834096)821 -1799 y(-8)h(6800k)f(3300k)380 b(2100k)285 b(828642)821 -1903 y(-9)h(7600k)f(3700k)380 b(2350k)285 b(828642)390 -2147 y Ff(RECO)m(VERING)37 b(D)m(A)-10 b(T)g(A)40 b(FR)m(OM)h(D)m(AMA)m -(GED)e(FILES)390 2333 y Fj(bzip2)25 b Fl(compresses)h(\014les)g(in)f -(blo)s(c)m(ks,)h(usually)e(900kb)m(ytes)29 b(long.)39 -b(Eac)m(h)27 b(blo)s(c)m(k)e(is)h(handled)390 2437 y(indep)s(enden)m -(tly)-8 b(.)47 b(If)32 b(a)i(media)e(or)h(transmission)e(error)i -(causes)h(a)f(m)m(ulti-blo)s(c)m(k)f Fj(.bz2)g Fl(\014le)390 -2541 y(to)k(b)s(ecome)h(damaged,)g(it)e(ma)m(y)i(b)s(e)e(p)s(ossible)e -(to)k(reco)m(v)m(er)g(data)f(from)g(the)f(undamaged)390 -2645 y(blo)s(c)m(ks)30 b(in)f(the)h(\014le.)390 2796 -y(The)j(compressed)h(represen)m(tation)f(of)h(eac)m(h)h(blo)s(c)m(k)e -(is)g(delimited)e(b)m(y)j(a)g(48-bit)g(pattern,)390 2900 -y(whic)m(h)27 b(mak)m(es)j(it)e(p)s(ossible)e(to)j(\014nd)e(the)i(blo)s -(c)m(k)f(b)s(oundaries)e(with)i(reasonable)g(certain)m(t)m(y)-8 -b(.)390 3003 y(Eac)m(h)34 b(blo)s(c)m(k)f(also)g(carries)g(its)g(o)m -(wn)g(32-bit)g(CR)m(C,)h(so)f(damaged)h(blo)s(c)m(ks)f(can)g(b)s(e)g -(distin-)390 3107 y(guished)c(from)h(undamaged)g(ones.)390 -3258 y Fj(bzip2recover)37 b Fl(is)j(a)h(simple)e(program)h(whose)g -(purp)s(ose)f(is)h(to)i(searc)m(h)f(for)f(blo)s(c)m(ks)g(in)390 -3362 y Fj(.bz2)34 b Fl(\014les,)i(and)f(write)f(eac)m(h)j(blo)s(c)m(k)d -(out)i(in)m(to)f(its)g(o)m(wn)g Fj(.bz2)f Fl(\014le.)55 -b(Y)-8 b(ou)36 b(can)f(then)g(use)390 3466 y Fj(bzip2)29 -b(-t)c Fl(to)i(test)f(the)g(in)m(tegrit)m(y)g(of)g(the)g(resulting)e -(\014les,)i(and)f(decompress)h(those)g(whic)m(h)390 3569 -y(are)31 b(undamaged.)390 3721 y Fj(bzip2recover)41 b -Fl(tak)m(es)46 b(a)f(single)e(argumen)m(t,)49 b(the)44 -b(name)h(of)g(the)f(damaged)h(\014le,)j(and)390 3824 -y(writes)33 b(a)i(n)m(um)m(b)s(er)d(of)j(\014les)e Fj(rec0001file.bz2)p -Fl(,)e Fj(rec0002file.bz2)p Fl(,)g(etc,)36 b(con)m(taining)390 -3928 y(the)42 b(extracted)g(blo)s(c)m(ks.)74 b(The)41 -b(output)g(\014lenames)f(are)i(designed)e(so)i(that)g(the)g(use)f(of) -390 4032 y(wildcards)30 b(in)h(subsequen)m(t)h(pro)s(cessing)f({)i(for) -g(example,)g Fj(bzip2)c(-dc)g(rec*file.bz2)e(>)390 4136 -y(recovered_data)f Fl({)31 b(lists)e(the)i(\014les)e(in)g(the)i -(correct)g(order.)390 4287 y Fj(bzip2recover)38 b Fl(should)i(b)s(e)g -(of)i(most)g(use)f(dealing)f(with)g(large)i Fj(.bz2)e -Fl(\014les,)k(as)d(these)390 4390 y(will)29 b(con)m(tain)j(man)m(y)g -(blo)s(c)m(ks.)45 b(It)32 b(is)f(clearly)g(futile)f(to)i(use)g(it)f(on) -h(damaged)g(single-blo)s(c)m(k)390 4494 y(\014les,)g(since)f(a)h -(damaged)h(blo)s(c)m(k)e(cannot)i(b)s(e)e(reco)m(v)m(ered.)47 -b(If)32 b(y)m(ou)g(wish)e(to)j(minimise)c(an)m(y)390 -4598 y(p)s(oten)m(tial)36 b(data)i(loss)e(through)g(media)h(or)f -(transmission)f(errors,)j(y)m(ou)f(migh)m(t)g(consider)390 -4702 y(compressing)29 b(with)g(a)i(smaller)e(blo)s(c)m(k)h(size.)390 -4946 y Ff(PERF)m(ORMANCE)39 b(NOTES)390 5132 y Fl(The)f(sorting)f -(phase)h(of)h(compression)e(gathers)i(together)h(similar)35 -b(strings)i(in)g(the)i(\014le.)390 5236 y(Because)54 -b(of)f(this,)58 b(\014les)52 b(con)m(taining)g(v)m(ery)h(long)g(runs)e -(of)i(rep)s(eated)g(sym)m(b)s(ols,)58 b(lik)m(e)390 5340 -y Fj(")p Fl(aabaabaabaab)e(...)p Fj(")g Fl(\(rep)s(eated)g(sev)m(eral)f -(h)m(undred)e(times\))i(ma)m(y)h(compress)f(more)p eop -%%Page: 8 9 -8 8 bop 150 -116 a Fl(Chapter)30 b(2:)41 b(Ho)m(w)31 -b(to)g(use)f Fj(bzip2)2375 b Fl(8)390 299 y(slo)m(wly)33 -b(than)g(normal.)50 b(V)-8 b(ersions)33 b(0.9.5)i(and)f(ab)s(o)m(v)m(e) -h(fare)e(m)m(uc)m(h)h(b)s(etter)g(than)f(previous)390 -403 y(v)m(ersions)i(in)g(this)f(resp)s(ect.)57 b(The)35 -b(ratio)h(b)s(et)m(w)m(een)h(w)m(orst-case)g(and)e(a)m(v)m(erage-case) -40 b(com-)390 506 y(pression)e(time)h(is)f(in)g(the)h(region)g(of)h -(10:1.)69 b(F)-8 b(or)40 b(previous)e(v)m(ersions,)j(this)d(\014gure)h -(w)m(as)390 610 y(more)f(lik)m(e)g(100:1.)66 b(Y)-8 b(ou)38 -b(can)h(use)e(the)i Fj(-vvvv)d Fl(option)i(to)h(monitor)e(progress)h -(in)f(great)390 714 y(detail,)30 b(if)f(y)m(ou)i(w)m(an)m(t.)390 -865 y(Decompression)f(sp)s(eed)g(is)f(una\013ected)i(b)m(y)f(these)h -(phenomena.)390 1016 y Fj(bzip2)i Fl(usually)g(allo)s(cates)i(sev)m -(eral)f(megab)m(ytes)j(of)d(memory)h(to)g(op)s(erate)h(in,)e(and)g -(then)390 1120 y(c)m(harges)k(all)d(o)m(v)m(er)j(it)f(in)e(a)i(fairly)e -(random)h(fashion.)59 b(This)34 b(means)j(that)g(p)s(erformance,)390 -1224 y(b)s(oth)27 b(for)h(compressing)f(and)g(decompressing,)h(is)f -(largely)g(determined)g(b)m(y)h(the)g(sp)s(eed)f(at)390 -1327 y(whic)m(h)35 b(y)m(our)h(mac)m(hine)g(can)g(service)g(cac)m(he)i -(misses.)57 b(Because)37 b(of)g(this,)f(small)f(c)m(hanges)390 -1431 y(to)f(the)f(co)s(de)h(to)f(reduce)g(the)h(miss)d(rate)j(ha)m(v)m -(e)h(b)s(een)d(observ)m(ed)h(to)h(giv)m(e)g(disprop)s(ortion-)390 -1535 y(ately)i(large)f(p)s(erformance)f(impro)m(v)m(emen)m(ts.)56 -b(I)35 b(imagine)f Fj(bzip2)g Fl(will)e(p)s(erform)i(b)s(est)h(on)390 -1639 y(mac)m(hines)30 b(with)f(v)m(ery)i(large)f(cac)m(hes.)390 -1885 y Ff(CA)-14 b(VEA)k(TS)390 2072 y Fl(I/O)38 b(error)g(messages)h -(are)f(not)h(as)f(helpful)e(as)i(they)g(could)f(b)s(e.)64 -b Fj(bzip2)37 b Fl(tries)g(hard)g(to)390 2176 y(detect)29 -b(I/O)e(errors)g(and)f(exit)i(cleanly)-8 b(,)27 b(but)g(the)h(details)e -(of)h(what)h(the)f(problem)f(is)g(some-)390 2280 y(times)k(seem)h -(rather)f(misleading.)390 2431 y(This)j(man)m(ual)g(page)i(p)s(ertains) -e(to)i(v)m(ersion)f(1.0)i(of)e Fj(bzip2)p Fl(.)51 b(Compressed)34 -b(data)h(created)390 2534 y(b)m(y)25 b(this)e(v)m(ersion)i(is)e(en)m -(tirely)h(forw)m(ards)h(and)f(bac)m(kw)m(ards)h(compatible)f(with)f -(the)i(previous)390 2638 y(public)18 b(releases,)24 b(v)m(ersions)c -(0.1pl2,)k(0.9.0)e(and)f(0.9.5,)k(but)20 b(with)g(the)h(follo)m(wing)e -(exception:)390 2742 y(0.9.0)43 b(and)e(ab)s(o)m(v)m(e)h(can)g -(correctly)f(decompress)g(m)m(ultiple)e(concatenated)k(compressed)390 -2846 y(\014les.)c(0.1pl2)30 b(cannot)g(do)f(this;)f(it)h(will)e(stop)i -(after)h(decompressing)e(just)g(the)i(\014rst)e(\014le)g(in)390 -2949 y(the)j(stream.)390 3100 y Fj(bzip2recover)20 b -Fl(uses)k(32-bit)g(in)m(tegers)f(to)i(represen)m(t)f(bit)e(p)s -(ositions)g(in)g(compressed)i(\014les,)390 3204 y(so)j(it)f(cannot)i -(handle)d(compressed)i(\014les)f(more)h(than)f(512)i(megab)m(ytes)h -(long.)39 b(This)25 b(could)390 3308 y(easily)30 b(b)s(e)f(\014xed.)390 -3555 y Ff(A)m(UTHOR)390 3741 y Fl(Julian)f(Sew)m(ard,)i -Fj(jseward@acm.org)p Fl(.)390 3892 y(The)24 b(ideas)f(em)m(b)s(o)s -(died)f(in)h Fj(bzip2)f Fl(are)j(due)e(to)i(\(at)g(least\))g(the)f -(follo)m(wing)e(p)s(eople:)37 b(Mic)m(hael)390 3996 y(Burro)m(ws)48 -b(and)g(Da)m(vid)h(Wheeler)f(\(for)h(the)g(blo)s(c)m(k)f(sorting)g -(transformation\),)53 b(Da)m(vid)390 4100 y(Wheeler)45 -b(\(again,)50 b(for)45 b(the)g(Hu\013man)g(co)s(der\),)k(P)m(eter)d(F) --8 b(en)m(wic)m(k)46 b(\(for)g(the)f(structured)390 4204 -y(co)s(ding)26 b(mo)s(del)g(in)f(the)i(original)e Fj(bzip)p -Fl(,)i(and)f(man)m(y)h(re\014nemen)m(ts\),)h(and)e(Alistair)f -(Mo\013at,)390 4307 y(Radford)34 b(Neal)h(and)f(Ian)h(Witten)g(\(for)f -(the)h(arithmetic)g(co)s(der)f(in)g(the)h(original)d -Fj(bzip)p Fl(\).)390 4411 y(I)41 b(am)g(m)m(uc)m(h)h(indebted)e(for)h -(their)f(help,)j(supp)s(ort)c(and)i(advice.)74 b(See)41 -b(the)h(man)m(ual)e(in)390 4515 y(the)28 b(source)g(distribution)23 -b(for)28 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b(.)36 b(In)150 5202 y(principle)20 b(it)j(should)e(b)s(e)h -(p)s(ossible)f(to)j(devise)f(a)g(go)s(o)s(d)g(w)m(a)m(y)i(to)f -(automatically)f(c)m(ho)s(ose)h(whic)m(h)e(algorithm)150 -5312 y(to)31 b(use.)41 b(Suc)m(h)29 b(a)i(mec)m(hanism)f(w)m(ould)f -(render)g(the)i(parameter)g(obsolete.)p eop -%%Page: 14 15 -14 14 bop 150 -116 a Fl(Chapter)30 b(3:)41 b(Programming)29 -b(with)g Fj(libbzip2)1881 b Fl(14)150 299 y(P)m(ossible)29 -b(return)h(v)-5 b(alues:)572 450 y Fj(BZ_CONFIG_ERROR)663 -554 y Fl(if)29 b(the)i(library)d(has)i(b)s(een)f(mis-compiled)572 -657 y Fj(BZ_PARAM_ERROR)663 761 y Fl(if)g Fj(strm)g Fl(is)h -Fj(NULL)663 865 y Fl(or)g Fj(blockSize)e(<)i Fl(1)h(or)f -Fj(blockSize)e(>)i Fl(9)663 969 y(or)g Fj(verbosity)e(<)i -Fl(0)h(or)f Fj(verbosity)e(>)i Fl(4)663 1073 y(or)g Fj(workFactor)e(<)i -Fl(0)g(or)h Fj(workFactor)c(>)j Fl(250)572 1176 y Fj(BZ_MEM_ERROR)663 -1280 y Fl(if)f(not)i(enough)f(memory)g(is)f(a)m(v)-5 -b(ailable)572 1384 y Fj(BZ_OK)663 1488 y Fl(otherwise)150 -1645 y(Allo)m(w)m(able)30 b(next)g(actions:)572 1796 -y Fj(BZ2_bzCompress)663 1899 y Fl(if)f Fj(BZ_OK)g Fl(is)g(returned)572 -2003 y(no)h(sp)s(eci\014c)f(action)i(needed)f(in)f(case)i(of)g(error) -150 2255 y Ff(3.3.2)63 b Fe(BZ2_bzCompress)533 2441 y -Fj(int)47 b(BZ2_bzCompress)d(\()j(bz_stream)f(*strm,)g(int)h(action)f -(\);)150 2598 y Fl(Pro)m(vides)28 b(more)g(input)f(and/or)h(output)g -(bu\013er)g(space)h(for)f(the)h(library)-8 b(.)38 b(The)28 -b(caller)g(main)m(tains)f(input)150 2708 y(and)j(output)g(bu\013ers,)f -(and)h(calls)g Fj(BZ2_bzCompress)c Fl(to)31 b(transfer)f(data)h(b)s(et) -m(w)m(een)g(them.)150 2865 y(Before)j(eac)m(h)g(call)e(to)i -Fj(BZ2_bzCompress)p Fl(,)c Fj(next_in)h Fl(should)g(p)s(oin)m(t)h(at)h -(the)g(data)h(to)g(b)s(e)e(compressed,)150 2974 y(and)41 -b Fj(avail_in)f Fl(should)g(indicate)h(ho)m(w)h(man)m(y)f(b)m(ytes)i -(the)f(library)d(ma)m(y)k(read.)75 b Fj(BZ2_bzCompress)150 -3084 y Fl(up)s(dates)29 b Fj(next_in)p Fl(,)g Fj(avail_in)f -Fl(and)i Fj(total_in)e Fl(to)j(re\015ect)g(the)g(n)m(um)m(b)s(er)e(of)h -(b)m(ytes)h(it)f(has)g(read.)150 3241 y(Similarly)-8 -b(,)27 b Fj(next_out)h Fl(should)g(p)s(oin)m(t)h(to)i(a)f(bu\013er)f -(in)g(whic)m(h)g(the)h(compressed)g(data)h(is)e(to)i(b)s(e)e(placed,) -150 3350 y(with)i Fj(avail_out)f Fl(indicating)h(ho)m(w)h(m)m(uc)m(h)h -(output)f(space)h(is)f(a)m(v)-5 b(ailable.)46 b Fj(BZ2_bzCompress)29 -b Fl(up)s(dates)150 3460 y Fj(next_out)p Fl(,)f Fj(avail_out)g -Fl(and)i Fj(total_out)e Fl(to)j(re\015ect)g(the)f(n)m(um)m(b)s(er)g(of) -g(b)m(ytes)h(output.)150 3617 y(Y)-8 b(ou)40 b(ma)m(y)g(pro)m(vide)e -(and)h(remo)m(v)m(e)i(as)f(little)e(or)h(as)h(m)m(uc)m(h)f(data)h(as)g -(y)m(ou)f(lik)m(e)g(on)g(eac)m(h)i(call)e(of)g Fj(BZ2_)150 -3726 y(bzCompress)p Fl(.)48 b(In)33 b(the)h(limit,)f(it)h(is)f -(acceptable)h(to)h(supply)c(and)j(remo)m(v)m(e)h(data)g(one)f(b)m(yte)g -(at)h(a)f(time,)150 3836 y(although)28 b(this)f(w)m(ould)g(b)s(e)h -(terribly)e(ine\016cien)m(t.)39 b(Y)-8 b(ou)29 b(should)e(alw)m(a)m(ys) -h(ensure)g(that)h(at)g(least)g(one)f(b)m(yte)150 3946 -y(of)j(output)f(space)g(is)g(a)m(v)-5 b(ailable)30 b(at)h(eac)m(h)g -(call.)150 4102 y(A)38 b(second)h(purp)s(ose)d(of)j Fj(BZ2_bzCompress) -34 b Fl(is)j(to)i(request)f(a)h(c)m(hange)g(of)g(mo)s(de)e(of)i(the)f -(compressed)150 4212 y(stream.)150 4369 y(Conceptually)-8 -b(,)24 b(a)g(compressed)g(stream)g(can)f(b)s(e)g(in)g(one)h(of)f(four)g -(states:)39 b(IDLE,)24 b(R)m(UNNING,)h(FLUSH-)150 4478 -y(ING)37 b(and)g(FINISHING.)g(Before)i(initialisation)33 -b(\()p Fj(BZ2_bzCompressInit)p Fl(\))g(and)j(after)i(termination)150 -4588 y(\()p Fj(BZ2_bzCompressEnd)p Fl(\),)27 b(a)j(stream)h(is)f -(regarded)g(as)g(IDLE.)150 4745 y(Up)s(on)35 b(initialisation)e(\()p -Fj(BZ2_bzCompressInit)p Fl(\),)h(the)i(stream)h(is)e(placed)h(in)e(the) -j(R)m(UNNING)g(state.)150 4854 y(Subsequen)m(t)j(calls)g(to)i -Fj(BZ2_bzCompress)37 b Fl(should)j(pass)g Fj(BZ_RUN)g -Fl(as)h(the)g(requested)h(action;)47 b(other)150 4964 -y(actions)31 b(are)f(illegal)f(and)h(will)d(result)j(in)f -Fj(BZ_SEQUENCE_ERROR)p Fl(.)150 5121 y(A)m(t)38 b(some)f(p)s(oin)m(t,)h -(the)f(calling)e(program)i(will)d(ha)m(v)m(e)k(pro)m(vided)e(all)f(the) -i(input)e(data)j(it)e(w)m(an)m(ts)i(to.)61 b(It)150 5230 -y(will)28 b(then)h(w)m(an)m(t)i(to)g(\014nish)d(up)h({)i(in)d -(e\013ect,)k(asking)e(the)g(library)e(to)j(pro)s(cess)f(an)m(y)g(data)h -(it)f(migh)m(t)g(ha)m(v)m(e)150 5340 y(bu\013ered)25 -b(in)m(ternally)-8 b(.)38 b(In)25 b(this)g(state,)k Fj(BZ2_bzCompress) -22 b Fl(will)i(no)i(longer)g(attempt)h(to)g(read)f(data)h(from)p -eop -%%Page: 15 16 -15 15 bop 150 -116 a Fl(Chapter)30 b(3:)41 b(Programming)29 -b(with)g Fj(libbzip2)1881 b Fl(15)150 299 y Fj(next_in)p -Fl(,)33 b(but)g(it)h(will)d(w)m(an)m(t)k(to)g(write)e(data)h(to)h -Fj(next_out)p Fl(.)49 b(Because)36 b(the)e(output)f(bu\013er)g -(supplied)150 408 y(b)m(y)e(the)h(user)e(can)i(b)s(e)f(arbitrarily)d -(small,)j(the)g(\014nishing-up)d(op)s(eration)i(cannot)i(necessarily)e -(b)s(e)h(done)150 518 y(with)e(a)i(single)e(call)h(of)g -Fj(BZ2_bzCompress)p Fl(.)150 675 y(Instead,)47 b(the)d(calling)f -(program)g(passes)h Fj(BZ_FINISH)d Fl(as)j(an)g(action)g(to)h -Fj(BZ2_bzCompress)p Fl(.)77 b(This)150 784 y(c)m(hanges)30 -b(the)f(stream's)g(state)h(to)f(FINISHING.)g(An)m(y)g(remaining)e -(input)g(\(ie,)i Fj(next_in[0)f(..)i(avail_)150 894 y(in-1])p -Fl(\))36 b(is)f(compressed)i(and)f(transferred)g(to)h(the)g(output)g -(bu\013er.)58 b(T)-8 b(o)38 b(do)e(this,)i Fj(BZ2_bzCompress)150 -1004 y Fl(m)m(ust)h(b)s(e)f(called)g(rep)s(eatedly)h(un)m(til)e(all)h -(the)h(output)f(has)h(b)s(een)f(consumed.)66 b(A)m(t)40 -b(that)g(p)s(oin)m(t,)g Fj(BZ2_)150 1113 y(bzCompress)h -Fl(returns)h Fj(BZ_STREAM_END)p Fl(,)i(and)f(the)h(stream's)g(state)h -(is)d(set)j(bac)m(k)f(to)g(IDLE.)g Fj(BZ2_)150 1223 y(bzCompressEnd)27 -b Fl(should)h(then)i(b)s(e)g(called.)150 1380 y(Just)25 -b(to)i(mak)m(e)g(sure)e(the)i(calling)d(program)i(do)s(es)g(not)g(c)m -(heat,)i(the)f(library)c(mak)m(es)k(a)f(note)h(of)f Fj(avail_in)150 -1489 y Fl(at)g(the)g(time)f(of)g(the)g(\014rst)g(call)g(to)h -Fj(BZ2_bzCompress)21 b Fl(whic)m(h)j(has)h Fj(BZ_FINISH)e -Fl(as)i(an)h(action)f(\(ie,)i(at)f(the)150 1599 y(time)d(the)h(program) -g(has)f(announced)g(its)h(in)m(ten)m(tion)f(to)h(not)g(supply)e(an)m(y) -i(more)g(input\).)37 b(By)24 b(comparing)150 1708 y(this)k(v)-5 -b(alue)28 b(with)g(that)h(of)h Fj(avail_in)c Fl(o)m(v)m(er)k(subsequen) -m(t)f(calls)f(to)h Fj(BZ2_bzCompress)p Fl(,)d(the)j(library)e(can)150 -1818 y(detect)33 b(an)m(y)e(attempts)i(to)f(slip)d(in)h(more)h(data)h -(to)h(compress.)43 b(An)m(y)31 b(calls)g(for)g(whic)m(h)f(this)g(is)h -(detected)150 1928 y(will)j(return)h Fj(BZ_SEQUENCE_ERROR)p -Fl(.)55 b(This)34 b(indicates)i(a)h(programming)e(mistak)m(e)i(whic)m -(h)e(should)g(b)s(e)150 2037 y(corrected.)150 2194 y(Instead)i(of)g -(asking)f(to)h(\014nish,)f(the)h(calling)f(program)g(ma)m(y)h(ask)g -Fj(BZ2_bzCompress)c Fl(to)38 b(tak)m(e)g(all)e(the)150 -2304 y(remaining)j(input,)i(compress)f(it)g(and)g(terminate)h(the)g -(curren)m(t)f(\(Burro)m(ws-Wheeler\))h(compression)150 -2413 y(blo)s(c)m(k.)e(This)26 b(could)h(b)s(e)g(useful)f(for)h(error)h -(con)m(trol)g(purp)s(oses.)38 b(The)27 b(mec)m(hanism)g(is)g(analogous) -h(to)g(that)150 2523 y(for)35 b(\014nishing:)46 b(call)35 -b Fj(BZ2_bzCompress)c Fl(with)i(an)i(action)g(of)g Fj(BZ_FLUSH)p -Fl(,)g(remo)m(v)m(e)h(output)f(data,)i(and)150 2632 y(p)s(ersist)h -(with)g(the)i Fj(BZ_FLUSH)e Fl(action)i(un)m(til)e(the)i(v)-5 -b(alue)39 b Fj(BZ_RUN)f Fl(is)h(returned.)68 b(As)39 -b(with)g(\014nishing,)150 2742 y Fj(BZ2_bzCompress)23 -b Fl(detects)28 b(an)m(y)f(attempt)h(to)f(pro)m(vide)f(more)h(input)e -(data)i(once)g(the)g(\015ush)e(has)i(b)s(egun.)150 2899 -y(Once)j(the)h(\015ush)e(is)g(complete,)i(the)g(stream)f(returns)g(to)h -(the)f(normal)g(R)m(UNNING)h(state.)150 3056 y(This)f(all)h(sounds)g -(prett)m(y)h(complex,)h(but)e(isn't)g(really)-8 b(.)45 -b(Here's)33 b(a)f(table)g(whic)m(h)f(sho)m(ws)h(whic)m(h)f(actions)150 -3165 y(are)e(allo)m(w)m(able)f(in)f(eac)m(h)j(state,)g(what)f(action)g -(will)c(b)s(e)j(tak)m(en,)j(what)d(the)h(next)f(state)i(is,)e(and)g -(what)h(the)150 3275 y(non-error)h(return)f(v)-5 b(alues)29 -b(are.)41 b(Note)32 b(that)e(y)m(ou)h(can't)g(explicitly)d(ask)i(what)g -(state)i(the)e(stream)h(is)e(in,)150 3384 y(but)h(nor)g(do)g(y)m(ou)h -(need)f(to)h({)g(it)e(can)i(b)s(e)f(inferred)e(from)i(the)h(v)-5 -b(alues)29 b(returned)h(b)m(y)g Fj(BZ2_bzCompress)p Fl(.)390 -3535 y(IDLE/)p Fj(any)572 3639 y Fl(Illegal.)60 b(IDLE)30 -b(state)i(only)d(exists)h(after)h Fj(BZ2_bzCompressEnd)26 -b Fl(or)572 3743 y(b)s(efore)k Fj(BZ2_bzCompressInit)p -Fl(.)572 3847 y(Return)f(v)-5 b(alue)30 b(=)g Fj(BZ_SEQUENCE_ERROR)390 -4054 y Fl(R)m(UNNING/)p Fj(BZ_RUN)572 4158 y Fl(Compress)f(from)h -Fj(next_in)f Fl(to)i Fj(next_out)d Fl(as)i(m)m(uc)m(h)h(as)f(p)s -(ossible.)572 4262 y(Next)h(state)h(=)e(R)m(UNNING)572 -4366 y(Return)f(v)-5 b(alue)30 b(=)g Fj(BZ_RUN_OK)390 -4573 y Fl(R)m(UNNING/)p Fj(BZ_FLUSH)572 4677 y Fl(Remem)m(b)s(er)g -(curren)m(t)g(v)-5 b(alue)30 b(of)g Fj(next_in)p Fl(.)59 -b(Compress)30 b(from)g Fj(next_in)572 4781 y Fl(to)h -Fj(next_out)d Fl(as)j(m)m(uc)m(h)f(as)h(p)s(ossible,)d(but)i(do)g(not)g -(accept)i(an)m(y)f(more)f(input.)572 4885 y(Next)h(state)h(=)e -(FLUSHING)572 4988 y(Return)f(v)-5 b(alue)30 b(=)g Fj(BZ_FLUSH_OK)390 -5196 y Fl(R)m(UNNING/)p Fj(BZ_FINISH)572 5300 y Fl(Remem)m(b)s(er)g -(curren)m(t)g(v)-5 b(alue)30 b(of)g Fj(next_in)p Fl(.)59 -b(Compress)30 b(from)g Fj(next_in)p eop -%%Page: 16 17 -16 16 bop 150 -116 a Fl(Chapter)30 b(3:)41 b(Programming)29 -b(with)g Fj(libbzip2)1881 b Fl(16)572 299 y(to)31 b Fj(next_out)d -Fl(as)j(m)m(uc)m(h)f(as)h(p)s(ossible,)d(but)i(do)g(not)g(accept)i(an)m -(y)f(more)f(input.)572 403 y(Next)h(state)h(=)e(FINISHING)572 -506 y(Return)f(v)-5 b(alue)30 b(=)g Fj(BZ_FINISH_OK)390 -714 y Fl(FLUSHING/)p Fj(BZ_FLUSH)572 818 y Fl(Compress)f(from)h -Fj(next_in)f Fl(to)i Fj(next_out)d Fl(as)i(m)m(uc)m(h)h(as)f(p)s -(ossible,)572 922 y(but)f(do)i(not)f(accept)i(an)m(y)f(more)f(input.) -572 1025 y(If)g(all)f(the)i(existing)e(input)f(has)i(b)s(een)g(used)g -(up)f(and)h(all)f(compressed)572 1129 y(output)h(has)g(b)s(een)g(remo)m -(v)m(ed)663 1233 y(Next)h(state)h(=)e(R)m(UNNING;)i(Return)d(v)-5 -b(alue)30 b(=)g Fj(BZ_RUN_OK)572 1337 y Fl(else)663 1440 -y(Next)h(state)h(=)e(FLUSHING;)h(Return)e(v)-5 b(alue)30 -b(=)g Fj(BZ_FLUSH_OK)390 1648 y Fl(FLUSHING/other)572 -1752 y(Illegal.)572 1856 y(Return)f(v)-5 b(alue)30 b(=)g -Fj(BZ_SEQUENCE_ERROR)390 2063 y Fl(FINISHING/)p Fj(BZ_FINISH)572 -2167 y Fl(Compress)f(from)h Fj(next_in)f Fl(to)i Fj(next_out)d -Fl(as)i(m)m(uc)m(h)h(as)f(p)s(ossible,)572 2271 y(but)f(to)j(not)e -(accept)i(an)m(y)f(more)f(input.)572 2374 y(If)g(all)f(the)i(existing)e -(input)f(has)i(b)s(een)g(used)g(up)f(and)h(all)f(compressed)572 -2478 y(output)h(has)g(b)s(een)g(remo)m(v)m(ed)663 2582 -y(Next)h(state)h(=)e(IDLE;)g(Return)g(v)-5 b(alue)30 -b(=)g Fj(BZ_STREAM_END)572 2686 y Fl(else)663 2790 y(Next)h(state)h(=)e -(FINISHING;)g(Return)g(v)-5 b(alue)30 b(=)g Fj(BZ_FINISHING)390 -2997 y Fl(FINISHING/other)572 3101 y(Illegal.)572 3205 -y(Return)f(v)-5 b(alue)30 b(=)g Fj(BZ_SEQUENCE_ERROR)150 -3361 y Fl(That)24 b(still)f(lo)s(oks)g(complicated?)39 -b(W)-8 b(ell,)25 b(fair)f(enough.)38 b(The)24 b(usual)f(sequence)i(of)f -(calls)g(for)g(compressing)150 3471 y(a)31 b(load)f(of)g(data)h(is:)225 -3628 y Fi(\017)60 b Fl(Get)31 b(started)g(with)e Fj(BZ2_bzCompressInit) -p Fl(.)225 3774 y Fi(\017)60 b Fl(Sho)m(v)m(el)38 b(data)h(in)e(and)g -(shlurp)e(out)k(its)e(compressed)h(form)g(using)e(zero)j(or)f(more)h -(calls)e(of)h Fj(BZ2_)330 3884 y(bzCompress)28 b Fl(with)h(action)h(=)g -Fj(BZ_RUN)p Fl(.)225 4030 y Fi(\017)60 b Fl(Finish)23 -b(up.)38 b(Rep)s(eatedly)25 b(call)f Fj(BZ2_bzCompress)e -Fl(with)i(action)h(=)g Fj(BZ_FINISH)p Fl(,)f(cop)m(ying)h(out)h(the)330 -4139 y(compressed)k(output,)g(un)m(til)f Fj(BZ_STREAM_END)e -Fl(is)i(returned.)225 4285 y Fi(\017)60 b Fl(Close)30 -b(up)f(and)h(go)h(home.)41 b(Call)29 b Fj(BZ2_bzCompressEnd)p -Fl(.)150 4478 y(If)23 b(the)h(data)h(y)m(ou)f(w)m(an)m(t)h(to)f -(compress)g(\014ts)f(in)m(to)h(y)m(our)g(input)e(bu\013er)h(all)f(at)j -(once,)h(y)m(ou)e(can)g(skip)f(the)h(calls)150 4588 y(of)37 -b Fj(BZ2_bzCompress)26 b(\()k(...,)f(BZ_RUN)g(\))36 b -Fl(and)g(just)g(do)h(the)g Fj(BZ2_bzCompress)26 b(\()k(...,)f -(BZ_FINISH)150 4698 y(\))h Fl(calls.)150 4854 y(All)36 -b(required)g(memory)h(is)f(allo)s(cated)i(b)m(y)f Fj -(BZ2_bzCompressInit)p Fl(.)56 b(The)37 b(compression)g(library)e(can) -150 4964 y(accept)g(an)m(y)f(data)h(at)g(all)d(\(ob)m(viously\).)51 -b(So)34 b(y)m(ou)g(shouldn't)e(get)j(an)m(y)f(error)f(return)g(v)-5 -b(alues)33 b(from)h(the)150 5074 y Fj(BZ2_bzCompress)29 -b Fl(calls.)46 b(If)32 b(y)m(ou)h(do,)g(they)g(will)d(b)s(e)i -Fj(BZ_SEQUENCE_ERROR)p Fl(,)d(and)j(indicate)f(a)i(bug)f(in)150 -5183 y(y)m(our)e(programming.)150 5340 y(T)-8 b(rivial)28 -b(other)j(p)s(ossible)d(return)h(v)-5 b(alues:)p eop -%%Page: 17 18 -17 17 bop 150 -116 a Fl(Chapter)30 b(3:)41 b(Programming)29 -b(with)g Fj(libbzip2)1881 b Fl(17)572 299 y Fj(BZ_PARAM_ERROR)663 -403 y Fl(if)29 b Fj(strm)g Fl(is)h Fj(NULL)p Fl(,)f(or)i -Fj(strm->s)d Fl(is)h Fj(NULL)150 652 y Ff(3.3.3)63 b -Fe(BZ2_bzCompressEnd)390 839 y Fj(int)47 b(BZ2_bzCompressEnd)c(\()k -(bz_stream)f(*strm)g(\);)150 996 y Fl(Releases)31 b(all)e(memory)h -(asso)s(ciated)h(with)e(a)i(compression)e(stream.)150 -1153 y(P)m(ossible)g(return)h(v)-5 b(alues:)481 1304 -y Fj(BZ_PARAM_ERROR)117 b Fl(if)30 b Fj(strm)f Fl(is)g -Fj(NULL)g Fl(or)i Fj(strm->s)d Fl(is)i Fj(NULL)481 1408 -y(BZ_OK)120 b Fl(otherwise)150 1657 y Ff(3.3.4)63 b Fe -(BZ2_bzDecompressInit)390 1844 y Fj(int)47 b(BZ2_bzDecompressInit)42 -b(\()48 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Fl(should)h(p)s(oin)m(t)g(at)h(the)h(compressed)e -(data,)j(and)150 675 y Fj(avail_in)h Fl(should)h(indicate)h(ho)m(w)h -(man)m(y)f(b)m(ytes)i(the)e(library)f(ma)m(y)i(read.)56 -b Fj(BZ2_bzDecompress)32 b Fl(up-)150 784 y(dates)f Fj(next_in)p -Fl(,)e Fj(avail_in)f Fl(and)h Fj(total_in)g Fl(to)i(re\015ect)g(the)f -(n)m(um)m(b)s(er)f(of)i(b)m(ytes)g(it)f(has)g(read.)150 -941 y(Similarly)-8 b(,)37 b Fj(next_out)f Fl(should)g(p)s(oin)m(t)i(to) -g(a)h(bu\013er)e(in)g(whic)m(h)g(the)i(uncompressed)e(output)g(is)h(to) -h(b)s(e)150 1051 y(placed,)d(with)e Fj(avail_out)f Fl(indicating)g(ho)m -(w)i(m)m(uc)m(h)g(output)g(space)h(is)e(a)m(v)-5 b(ailable.)55 -b Fj(BZ2_bzCompress)150 1160 y Fl(up)s(dates)29 b Fj(next_out)p -Fl(,)g Fj(avail_out)f Fl(and)h Fj(total_out)f Fl(to)j(re\015ect)g(the)g -(n)m(um)m(b)s(er)e(of)h(b)m(ytes)h(output.)150 1317 y(Y)-8 -b(ou)40 b(ma)m(y)g(pro)m(vide)e(and)h(remo)m(v)m(e)i(as)f(little)e(or)h -(as)h(m)m(uc)m(h)f(data)h(as)g(y)m(ou)f(lik)m(e)g(on)g(eac)m(h)i(call)e 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b(the)g(meaning)e(of)i(parameters)g -Fj(small)e Fl(and)g Fj(verbosity)p Fl(,)f(see)j Fj -(BZ2_bzDecompressInit)p Fl(.)150 1474 y(The)k(amoun)m(t)g(of)g(memory)g -(needed)g(to)g(decompress)g(a)h(\014le)e(cannot)h(b)s(e)g(determined)e -(un)m(til)h(the)h(\014le's)150 1584 y(header)22 b(has)f(b)s(een)g -(read.)38 b(So)22 b(it)f(is)g(p)s(ossible)e(that)k Fj(BZ2_bzReadOpen)17 -b Fl(returns)k Fj(BZ_OK)f Fl(but)h(a)i(subsequen)m(t)150 -1693 y(call)30 b(of)g Fj(BZ2_bzRead)e Fl(will)f(return)j -Fj(BZ_MEM_ERROR)p Fl(.)150 1850 y(P)m(ossible)f(assignmen)m(ts)h(to)h -Fj(bzerror)p Fl(:)572 2001 y Fj(BZ_CONFIG_ERROR)663 2105 -y Fl(if)e(the)i(library)d(has)i(b)s(een)f(mis-compiled)572 -2209 y Fj(BZ_PARAM_ERROR)663 2313 y Fl(if)g Fj(f)h Fl(is)g -Fj(NULL)663 2416 y Fl(or)g Fj(small)f Fl(is)g(neither)h -Fj(0)g Fl(nor)g Fj(1)663 2520 y Fl(or)g Fj(\(unused)46 -b(==)h(NULL)g(&&)g(nUnused)f(!=)h(0\))663 2624 y Fl(or)30 -b Fj(\(unused)46 b(!=)h(NULL)g(&&)g(!\(0)g(<=)g(nUnused)f(<=)h -(BZ_MAX_UNUSED\)\))572 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Fj(BZ_OK)e Fl(and)h(the)h(n)m(um)m(b)s -(er)e(of)i(b)m(ytes)g(read)f(is)g(returned.)p eop -%%Page: 21 22 -21 21 bop 150 -116 a Fl(Chapter)30 b(3:)41 b(Programming)29 -b(with)g Fj(libbzip2)1881 b Fl(21)150 299 y(If)33 b(the)g(logical)g -(end-of-stream)h(w)m(as)g(detected,)i Fj(bzerror)31 b -Fl(will)g(b)s(e)h(set)i(to)g Fj(BZ_STREAM_END)p Fl(,)d(and)i(the)150 -408 y(n)m(um)m(b)s(er)c(of)i(b)m(ytes)f(read)h(is)e(returned.)40 -b(All)29 b(other)h Fj(bzerror)f Fl(v)-5 b(alues)29 b(denote)i(an)g -(error.)150 565 y Fj(BZ2_bzRead)37 b Fl(will)f(supply)h -Fj(len)i Fl(b)m(ytes,)j(unless)c(the)i(logical)f(stream)h(end)e(is)h -(detected)i(or)e(an)g(error)150 675 y(o)s(ccurs.)75 b(Because)43 -b(of)f(this,)i(it)d(is)g(p)s(ossible)e(to)k(detect)g(the)f(stream)g -(end)f(b)m(y)h(observing)f(when)g(the)150 784 y(n)m(um)m(b)s(er)29 -b(of)h(b)m(ytes)g(returned)f(is)g(less)g(than)h(the)g(n)m(um)m(b)s(er)f -(requested.)40 b(Nev)m(ertheless,)31 b(this)e(is)g(regarded)150 -894 y(as)38 b(inadvisable;)g(y)m(ou)g(should)d(instead)i(c)m(hec)m(k)i -Fj(bzerror)d Fl(after)i(ev)m(ery)g(call)e(and)h(w)m(atc)m(h)i(out)f -(for)f Fj(BZ_)150 1004 y(STREAM_END)p Fl(.)150 1160 y(In)m(ternally)-8 -b(,)47 b Fj(BZ2_bzRead)41 b Fl(copies)j(data)g(from)g(the)g(compressed) -g(\014le)f(in)f(c)m(h)m(unks)i(of)g(size)g Fj(BZ_MAX_)150 -1270 y(UNUSED)31 b Fl(b)m(ytes)i(b)s(efore)f(decompressing)f(it.)47 -b(If)32 b(the)h(\014le)e(con)m(tains)i(more)g(b)m(ytes)g(than)f -(strictly)f(needed)150 1380 y(to)48 b(reac)m(h)f(the)g(logical)f -(end-of-stream,)52 b Fj(BZ2_bzRead)44 b Fl(will)g(almost)j(certainly)f -(read)h(some)g(of)g(the)150 1489 y(trailing)c(data)j(b)s(efore)e -(signalling)f Fj(BZ_SEQUENCE_END)p Fl(.)80 b(T)-8 b(o)46 -b(collect)f(the)g(read)g(but)g(un)m(used)e(data)150 1599 -y(once)29 b Fj(BZ_SEQUENCE_END)24 b Fl(has)k(app)s(eared,)g(call)f -Fj(BZ2_bzReadGetUnused)c Fl(immediately)j(b)s(efore)i -Fj(BZ2_)150 1708 y(bzReadClose)p Fl(.)150 1865 y(P)m(ossible)h -(assignmen)m(ts)h(to)h 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Fl(if)e(insu\016cien)m(t)g(memory)h(w)m(as)h(a)m(v)-5 -b(ailable)572 3573 y Fj(BZ_STREAM_END)663 3677 y Fl(if)29 -b(the)i(logical)e(end)h(of)h(stream)f(w)m(as)h(detected.)572 -3781 y Fj(BZ_OK)663 3884 y Fl(otherwise.)150 4041 y(P)m(ossible)e -(return)h(v)-5 b(alues:)572 4192 y(n)m(um)m(b)s(er)29 -b(of)h(b)m(ytes)h(read)663 4296 y(if)e Fj(bzerror)f Fl(is)i -Fj(BZ_OK)f Fl(or)h Fj(BZ_STREAM_END)572 4400 y Fl(unde\014ned)663 -4503 y(otherwise)150 4660 y(Allo)m(w)m(able)g(next)g(actions:)572 -4811 y(collect)h(data)g(from)f Fj(buf)p Fl(,)f(then)h -Fj(BZ2_bzRead)e Fl(or)i Fj(BZ2_bzReadClose)663 4915 y -Fl(if)f Fj(bzerror)f Fl(is)i Fj(BZ_OK)572 5019 y Fl(collect)h(data)g -(from)f Fj(buf)p Fl(,)f(then)h Fj(BZ2_bzReadClose)d Fl(or)j -Fj(BZ2_bzReadGetUnused)663 5123 y Fl(if)f Fj(bzerror)f -Fl(is)i Fj(BZ_SEQUENCE_END)572 5226 y(BZ2_bzReadClose)663 -5330 y Fl(otherwise)p eop -%%Page: 22 23 -22 22 bop 150 -116 a Fl(Chapter)30 b(3:)41 b(Programming)29 -b(with)g Fj(libbzip2)1881 b Fl(22)150 299 y Ff(3.4.3)63 -b Fe(BZ2_bzReadGetUnused)533 486 y Fj(void)47 b(BZ2_bzReadGetUnused)42 -b(\()48 b(int*)e(bzerror,)g(BZFILE)g(*b,)1822 589 y(void**)g(unused,)g -(int*)g(nUnused)g(\);)150 746 y Fl(Returns)36 b(data)i(whic)m(h)d(w)m -(as)j(read)f(from)f(the)h(compressed)g(\014le)f(but)g(w)m(as)h(not)h -(needed)e(to)i(get)g(to)g(the)150 856 y(logical)k(end-of-stream.)78 -b Fj(*unused)41 b Fl(is)h(set)h(to)g(the)g(address)f(of)g(the)h(data,)k -(and)42 b Fj(*nUnused)e Fl(to)k(the)150 965 y(n)m(um)m(b)s(er)29 -b(of)i(b)m(ytes.)41 b Fj(*nUnused)28 b Fl(will)g(b)s(e)h(set)i(to)g(a)g -(v)-5 b(alue)30 b(b)s(et)m(w)m(een)h Fj(0)f Fl(and)g -Fj(BZ_MAX_UNUSED)d Fl(inclusiv)m(e.)150 1122 y(This)d(function)h(ma)m -(y)h(only)g(b)s(e)f(called)g(once)i Fj(BZ2_bzRead)c Fl(has)j(signalled) -e Fj(BZ_STREAM_END)e Fl(but)j(b)s(efore)150 1232 y Fj(BZ2_bzReadClose)p -Fl(.)150 1389 y(P)m(ossible)k(assignmen)m(ts)h(to)h Fj(bzerror)p -Fl(:)572 1540 y Fj(BZ_PARAM_ERROR)663 1644 y Fl(if)e -Fj(b)h Fl(is)g Fj(NULL)663 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b(su\016x)e(arra)m(y)h(construction)f(algorithm)g(a)h(few)g(y)m -(ears)h(bac)m(k,)g(whic)m(h)d(can)j(b)s(e)330 2628 y(emplo)m(y)m(ed)27 -b(to)h(sort)g(an)m(y)f(blo)s(c)m(k,)h(no)f(matter)h(ho)m(w)f(rep)s -(etitiv)m(e,)h(in)d(O\(N)j(log)f(N\))h(time.)39 b(Subsequen)m(t)330 -2737 y(w)m(ork)25 b(b)m(y)f(Kunihik)m(o)f(Sadak)-5 b(ane)24 -b(has)h(pro)s(duced)e(a)i(deriv)-5 b(ativ)m(e)24 b(O\(N)h(\(log)g(N\))p -Fj(^)p Fl(2\))h(algorithm)d(whic)m(h)330 2847 y(usually)28 -b(outp)s(erforms)h(the)i(Man)m(b)s(er-My)m(ers)g(algorithm.)330 -2988 y(I)g(could)g(ha)m(v)m(e)i(c)m(hanged)f(to)g(Sadak)-5 -b(ane's)32 b(algorithm,)f(but)g(I)g(\014nd)f(it)h(to)h(b)s(e)f(slo)m(w) -m(er)h(than)f Fj(bzip2)p Fl('s)330 3098 y(existing)38 -b(algorithm)g(for)h(most)h(inputs,)f(and)g(the)g(randomisation)f(mec)m -(hanism)g(protects)i(ade-)330 3208 y(quately)34 b(against)f(bad)g -(cases.)52 b(I)33 b(didn't)f(think)g(it)i(w)m(as)g(a)g(go)s(o)s(d)f -(tradeo\013)i(to)f(mak)m(e.)51 b(P)m(artly)34 b(this)330 -3317 y(is)39 b(due)h(to)h(the)f(fact)h(that)g(I)f(w)m(as)g(not)h(\015o) -s(o)s(ded)e(with)g(email)g(complain)m(ts)g(ab)s(out)h -Fj(bzip2-0.1)p Fl('s)330 3427 y(p)s(erformance)30 b(on)g(rep)s(etitiv)m -(e)g(data,)h(so)g(p)s(erhaps)d(it)i(isn't)g(a)h(problem)d(for)j(real)f -(inputs.)330 3568 y(Probably)i(the)h(b)s(est)g(long-term)g(solution,)g -(and)g(the)g(one)h(I)f(ha)m(v)m(e)h(incorp)s(orated)e(in)m(to)i(0.9.5)h -(and)330 3678 y(ab)s(o)m(v)m(e,)42 b(is)c(to)h(use)f(the)h(existing)f -(sorting)g(algorithm)f(initially)-8 b(,)38 b(and)g(fall)f(bac)m(k)i(to) -h(a)f(O\(N)f(\(log)330 3787 y(N\))p Fj(^)p Fl(2\))31 -b(algorithm)f(if)f(the)i(standard)e(algorithm)h(gets)h(in)m(to)f -(di\016culties.)225 3929 y Fi(\017)60 b Fl(The)31 b(compressed)f -(\014le)g(format)i(w)m(as)f(nev)m(er)h(designed)d(to)j(b)s(e)f(handled) -e(b)m(y)i(a)g(library)-8 b(,)29 b(and)i(I)g(ha)m(v)m(e)330 -4039 y(had)d(to)i(jump)e(though)g(some)i(ho)s(ops)e(to)i(pro)s(duce)e -(an)h(e\016cien)m(t)g(implemen)m(tation)f(of)h(decompres-)330 -4148 y(sion.)38 b(It's)26 b(a)h(bit)e(hairy)-8 b(.)38 -b(T)-8 b(ry)26 b(passing)f Fj(decompress.c)d Fl(through)k(the)g(C)f -(prepro)s(cessor)g(and)h(y)m(ou'll)330 4258 y(see)32 -b(what)g(I)f(mean.)45 b(Muc)m(h)32 b(of)g(this)e(complexit)m(y)i(could) -f(ha)m(v)m(e)i(b)s(een)e(a)m(v)m(oided)h(if)e(the)i(compressed)330 -4367 y(size)e(of)h(eac)m(h)g(blo)s(c)m(k)f(of)h(data)g(w)m(as)g -(recorded)f(in)f(the)h(data)h(stream.)225 4509 y Fi(\017)60 -b Fl(An)30 b(Adler-32)g(c)m(hec)m(ksum,)i(rather)e(than)g(a)h(CR)m(C32) -g(c)m(hec)m(ksum,)g(w)m(ould)e(b)s(e)h(faster)h(to)g(compute.)150 -4698 y(It)e(w)m(ould)f(b)s(e)g(fair)g(to)h(sa)m(y)h(that)g(the)f -Fj(bzip2)e Fl(format)i(w)m(as)h(frozen)f(b)s(efore)f(I)h(prop)s(erly)d -(and)j(fully)d(under-)150 4807 y(sto)s(o)s(d)k(the)h(p)s(erformance)e -(consequences)i(of)g(doing)e(so.)150 4964 y(Impro)m(v)m(emen)m(ts)d -(whic)m(h)e(I)i(w)m(as)g(able)f(to)h(incorp)s(orate)f(in)m(to)g(0.9.0,) -k(despite)24 b(using)g(the)i(same)g(\014le)e(format,)150 -5074 y(are:)225 5230 y Fi(\017)60 b Fl(Single)30 b(arra)m(y)i(implemen) -m(tation)e(of)h(the)h(in)m(v)m(erse)f(BWT.)h(This)e(signi\014can)m(tly) -f(sp)s(eeds)i(up)f(decom-)330 5340 y(pression,)f(presumably)f(b)s -(ecause)i(it)g(reduces)g(the)h(n)m(um)m(b)s(er)e(of)i(cac)m(he)h -(misses.)p eop -%%Page: 32 33 -32 32 bop 150 -116 a Fl(Chapter)30 b(4:)41 b(Miscellanea)2586 -b(32)225 299 y Fi(\017)60 b Fl(F)-8 b(aster)27 b(in)m(v)m(erse)e(MTF)h -(transform)f(for)g(large)h(MTF)f(v)-5 b(alues.)39 b(The)25 -b(new)g(implemen)m(tation)f(is)g(based)330 408 y(on)30 -b(the)h(notion)f(of)g(sliding)e(blo)s(c)m(ks)h(of)i(v)-5 -b(alues.)225 544 y Fi(\017)60 b Fj(bzip2-0.9.0)24 b Fl(no)m(w)k(reads)f -(and)f(writes)h(\014les)f(with)g Fj(fread)g Fl(and)h -Fj(fwrite)p Fl(;)f(v)m(ersion)h(0.1)i(used)d Fj(putc)330 -653 y Fl(and)k Fj(getc)p Fl(.)39 b(Duh!)h(W)-8 b(ell,)31 -b(y)m(ou)f(liv)m(e)g(and)g(learn.)150 836 y(F)-8 b(urther)30 -b(ahead,)g(it)f(w)m(ould)g(b)s(e)g(nice)h(to)g(b)s(e)g(able)f(to)i(do)e -(random)g(access)j(in)m(to)d(\014les.)40 b(This)28 b(will)f(require)150 -945 y(some)k(careful)e(design)h(of)g(compressed)g(\014le)g(formats.)150 -1227 y Fk(4.2)68 b(P)l(ortabilit)l(y)47 b(issues)150 -1419 y Fl(After)36 b(some)g(consideration,)g(I)f(ha)m(v)m(e)i(decided)d -(not)i(to)g(use)g(GNU)g Fj(autoconf)d Fl(to)j(con\014gure)g(0.9.5)h(or) -150 1529 y(1.0.)150 1686 y Fj(autoconf)p Fl(,)31 b(admirable)g(and)h(w) -m(onderful)f(though)i(it)f(is,)h(mainly)d(assists)j(with)e(p)s -(ortabilit)m(y)g(problems)150 1795 y(b)s(et)m(w)m(een)f(Unix-lik)m(e)d -(platforms.)40 b(But)29 b Fj(bzip2)f Fl(do)s(esn't)h(ha)m(v)m(e)h(m)m -(uc)m(h)f(in)f(the)h(w)m(a)m(y)h(of)g(p)s(ortabilit)m(y)d(prob-)150 -1905 y(lems)35 b(on)h(Unix;)j(most)d(of)g(the)h(di\016culties)d(app)s -(ear)h(when)g(p)s(orting)g(to)i(the)f(Mac,)j(or)d(to)h(Microsoft's)150 -2015 y(op)s(erating)26 b(systems.)40 b Fj(autoconf)25 -b Fl(do)s(esn't)h(help)g(in)f(those)j(cases,)h(and)d(brings)f(in)g(a)j -(whole)e(load)g(of)h(new)150 2124 y(complexit)m(y)-8 -b(.)150 2281 y(Most)28 b(p)s(eople)f(should)f(b)s(e)h(able)g(to)h -(compile)e(the)i(library)d(and)i(program)h(under)e(Unix)g(straigh)m(t)i -(out-of-)150 2391 y(the-b)s(o)m(x,)j(so)g(to)g(sp)s(eak,)f(esp)s -(ecially)f(if)g(y)m(ou)i(ha)m(v)m(e)g(a)g(v)m(ersion)f(of)g(GNU)h(C)f -(a)m(v)-5 b(ailable.)150 2547 y(There)32 b(are)h(a)g(couple)f(of)h -Fj(__inline__)d Fl(directiv)m(es)i(in)f(the)i(co)s(de.)48 -b(GNU)33 b(C)f(\()p Fj(gcc)p Fl(\))g(should)f(b)s(e)h(able)g(to)150 -2657 y(handle)24 b(them.)39 b(If)25 b(y)m(ou're)i(not)e(using)g(GNU)h -(C,)f(y)m(our)h(C)f(compiler)f(shouldn't)g(see)i(them)f(at)i(all.)38 -b(If)25 b(y)m(our)150 2767 y(compiler)k(do)s(es,)i(for)g(some)g -(reason,)h(see)f(them)g(and)f(do)s(esn't)h(lik)m(e)f(them,)i(just)e -Fj(#define)f(__inline__)150 2876 y Fl(to)37 b(b)s(e)f -Fj(/*)30 b(*/)p Fl(.)58 b(One)36 b(easy)h(w)m(a)m(y)g(to)h(do)e(this)f -(is)h(to)h(compile)e(with)g(the)i(\015ag)g Fj(-D__inline__=)p -Fl(,)d(whic)m(h)150 2986 y(should)28 b(b)s(e)i(understo)s(o)s(d)f(b)m -(y)h(most)h(Unix)e(compilers.)150 3143 y(If)35 b(y)m(ou)g(still)e(ha)m -(v)m(e)j(di\016culties,)e(try)h(compiling)e(with)g(the)j(macro)f -Fj(BZ_STRICT_ANSI)c Fl(de\014ned.)54 b(This)150 3252 -y(should)28 b(enable)i(y)m(ou)h(to)g(build)d(the)i(library)e(in)h(a)i -(strictly)f(ANSI)g(complian)m(t)f(en)m(vironmen)m(t.)41 -b(Building)150 3362 y(the)25 b(program)f(itself)f(lik)m(e)g(this)h(is)f -(dangerous)h(and)g(not)g(supp)s(orted,)g(since)g(y)m(ou)h(remo)m(v)m(e) -g Fj(bzip2)p Fl('s)e(c)m(hec)m(ks)150 3471 y(against)30 -b(compressing)f(directories,)g(sym)m(b)s(olic)g(links,)f(devices,)i -(and)f(other)h(not-really-a-\014le)g(en)m(tities.)150 -3581 y(This)f(could)g(cause)i(\014lesystem)f(corruption!)150 -3738 y(One)e(other)i(thing:)39 b(if)27 b(y)m(ou)j(create)g(a)f -Fj(bzip2)f Fl(binary)f(for)i(public)d(distribution,)g(please)i(try)h -(and)g(link)d(it)150 3847 y(statically)g(\()p Fj(gcc)k(-s)p -Fl(\).)39 b(This)25 b(a)m(v)m(oids)i(all)f(sorts)h(of)g(library-v)m -(ersion)d(issues)h(that)i(others)g(ma)m(y)g(encoun)m(ter)150 -3957 y(later)j(on.)150 4114 y(If)f(y)m(ou)g(build)e Fj(bzip2)h -Fl(on)h(Win32,)h(y)m(ou)f(m)m(ust)g(set)h Fj(BZ_UNIX)e -Fl(to)i(0)f(and)g Fj(BZ_LCCWIN32)d Fl(to)k(1,)g(in)e(the)i(\014le)150 -4223 y Fj(bzip2.c)p Fl(,)f(b)s(efore)h(compiling.)38 -b(Otherwise)29 b(the)i(resulting)d(binary)h(w)m(on't)i(w)m(ork)f -(correctly)-8 b(.)150 4505 y Fk(4.3)68 b(Rep)t(orting)46 -b(bugs)150 4698 y Fl(I)25 b(tried)f(prett)m(y)i(hard)e(to)i(mak)m(e)g -(sure)f Fj(bzip2)e Fl(is)i(bug)f(free,)j(b)s(oth)d(b)m(y)h(design)f -(and)h(b)m(y)g(testing.)39 b(Hop)s(efully)150 4807 y(y)m(ou'll)29 -b(nev)m(er)i(need)f(to)h(read)g(this)e(section)h(for)h(real.)150 -4964 y(Nev)m(ertheless,)36 b(if)c Fj(bzip2)h Fl(dies)g(with)f(a)i -(segmen)m(tation)h(fault,)g(a)f(bus)f(error)g(or)h(an)g(in)m(ternal)e -(assertion)150 5074 y(failure,)i(it)h(will)d(ask)j(y)m(ou)g(to)g(email) -f(me)h(a)g(bug)f(rep)s(ort.)54 b(Exp)s(erience)33 b(with)h(v)m(ersion)g -(0.1)i(sho)m(ws)e(that)150 5183 y(almost)c(all)g(these)h(problems)d -(can)j(b)s(e)f(traced)h(to)g(either)f(compiler)e(bugs)i(or)g(hardw)m -(are)g(problems.)225 5340 y Fi(\017)60 b Fl(Recompile)22 -b(the)h(program)g(with)f(no)h(optimisation,)g(and)f(see)i(if)e(it)g(w)m -(orks.)39 b(And/or)22 b(try)h(a)g(di\013eren)m(t)p eop -%%Page: 33 34 -33 33 bop 150 -116 a Fl(Chapter)30 b(4:)41 b(Miscellanea)2586 -b(33)330 299 y(compiler.)77 b(I)43 b(heard)f(all)g(sorts)h(of)h -(stories)e(ab)s(out)h(v)-5 b(arious)42 b(\015a)m(v)m(ours)h(of)h(GNU)f -(C)g(\(and)g(other)330 408 y(compilers\))20 b(generating)i(bad)e(co)s -(de)i(for)f Fj(bzip2)p Fl(,)h(and)f(I'v)m(e)h(run)e(across)i(t)m(w)m(o) -g(suc)m(h)f(examples)g(m)m(yself.)330 606 y(2.7.X)35 -b(v)m(ersions)e(of)g(GNU)h(C)f(are)h(kno)m(wn)f(to)h(generate)h(bad)d -(co)s(de)i(from)f(time)g(to)h(time,)g(at)g(high)330 716 -y(optimisation)20 b(lev)m(els.)37 b(If)21 b(y)m(ou)g(get)i(problems,)e 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-b(if)f(y)m(our)h(disk)e(or)h(I/O)h(subsystem)e(is)h(slo)m(wly)330 -1768 y(failing.)39 b(Y)-8 b(up,)30 b(this)f(really)g(do)s(es)h(happ)s -(en.)330 1966 y(T)-8 b(ry)28 b(using)f(a)i(di\013eren)m(t)f(mac)m(hine) -g(of)h(the)g(same)f(t)m(yp)s(e,)i(and)e(see)h(if)e(y)m(ou)i(can)g(rep)s -(eat)g(the)f(problem.)225 2163 y Fi(\017)60 b Fl(This)21 -b(isn't)i(really)f(a)h(bug,)i(but)d(...)39 b(If)23 b -Fj(bzip2)f Fl(tells)g(y)m(ou)h(y)m(our)h(\014le)e(is)g(corrupted)h(on)g -(decompression,)330 2273 y(and)29 b(y)m(ou)g(obtained)f(the)i(\014le)e -(via)h(FTP)-8 b(,)29 b(there)h(is)e(a)h(p)s(ossibilit)m(y)d(that)k(y)m -(ou)f(forgot)h(to)g(tell)e(FTP)h(to)330 2383 y(do)23 -b(a)g(binary)e(mo)s(de)i(transfer.)38 b(That)23 b(absolutely)f(will)e -(cause)j(the)h(\014le)e(to)h(b)s(e)g(non-decompressible.)330 -2492 y(Y)-8 b(ou'll)30 b(ha)m(v)m(e)h(to)g(transfer)f(it)g(again.)150 -2737 y(If)i(y)m(ou'v)m(e)h(incorp)s(orated)e Fj(libbzip2)f -Fl(in)m(to)i(y)m(our)g(o)m(wn)g(program)g(and)g(are)g(getting)h 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-(.)g(.)g(.)g(.)g(.)g(.)g(.)g(.)g(.)g(.)g(.)g(.)g(.)g(.)g(.)g(.)g(.)g(.) -g(.)g(.)g(.)g(.)g(.)g(.)g(.)g(.)g(.)g(.)g(.)g(.)h(.)f(.)51 -b Fl(35)p eop -%%Trailer -end -userdict /end-hook known{end-hook}if -%%EOF diff -Nru bzip2-1.0.1/manual.texi bzip2-1.0.1.new/manual.texi --- bzip2-1.0.1/manual.texi Sat Jun 24 20:13:27 2000 +++ bzip2-1.0.1.new/manual.texi Thu Jan 1 01:00:00 1970 @@ -1,2215 +0,0 @@ -\input texinfo @c -*- Texinfo -*- -@setfilename bzip2.info - -@ignore -This file documents bzip2 version 1.0, and associated library -libbzip2, written by Julian Seward (jseward@acm.org). - -Copyright (C) 1996-2000 Julian R Seward - -Permission is granted to make and distribute verbatim copies of -this manual provided the copyright notice and this permission notice -are preserved on all copies. - -Permission is granted to copy and distribute translations of this manual -into another language, under the above conditions for verbatim copies. -@end ignore - -@ifinfo -@format -START-INFO-DIR-ENTRY -* Bzip2: (bzip2). A program and library for data compression. -END-INFO-DIR-ENTRY -@end format - -@end ifinfo - -@iftex -@c @finalout -@settitle bzip2 and libbzip2 -@titlepage -@title bzip2 and libbzip2 -@subtitle a program and library for data compression -@subtitle copyright (C) 1996-2000 Julian Seward -@subtitle version 1.0 of 21 March 2000 -@author Julian Seward - -@end titlepage - -@parindent 0mm -@parskip 2mm - -@end iftex -@node Top, Overview, (dir), (dir) - -This program, @code{bzip2}, -and associated library @code{libbzip2}, are -Copyright (C) 1996-2000 Julian R Seward. All rights reserved. - -Redistribution and use in source and binary forms, with or without -modification, are permitted provided that the following conditions -are met: -@itemize @bullet -@item - Redistributions of source code must retain the above copyright - notice, this list of conditions and the following disclaimer. -@item - The origin of this software must not be misrepresented; you must - not claim that you wrote the original software. If you use this - software in a product, an acknowledgment in the product - documentation would be appreciated but is not required. -@item - Altered source versions must be plainly marked as such, and must - not be misrepresented as being the original software. -@item - The name of the author may not be used to endorse or promote - products derived from this software without specific prior written - permission. -@end itemize -THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS -OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED -WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE -ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY -DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL -DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE -GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS -INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, -WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING -NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS -SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. - -Julian Seward, Cambridge, UK. - -@code{jseward@@acm.org} - -@code{http://sourceware.cygnus.com/bzip2} - -@code{http://www.cacheprof.org} - -@code{http://www.muraroa.demon.co.uk} - -@code{bzip2}/@code{libbzip2} version 1.0 of 21 March 2000. - -PATENTS: To the best of my knowledge, @code{bzip2} does not use any patented -algorithms. However, I do not have the resources available to carry out -a full patent search. Therefore I cannot give any guarantee of the -above statement. - - - - - - - -@node Overview, Implementation, Top, Top -@chapter Introduction - -@code{bzip2} compresses files using the Burrows-Wheeler -block-sorting text compression algorithm, and Huffman coding. -Compression is generally considerably better than that -achieved by more conventional LZ77/LZ78-based compressors, -and approaches the performance of the PPM family of statistical compressors. - -@code{bzip2} is built on top of @code{libbzip2}, a flexible library -for handling compressed data in the @code{bzip2} format. This manual -describes both how to use the program and -how to work with the library interface. Most of the -manual is devoted to this library, not the program, -which is good news if your interest is only in the program. - -Chapter 2 describes how to use @code{bzip2}; this is the only part -you need to read if you just want to know how to operate the program. -Chapter 3 describes the programming interfaces in detail, and -Chapter 4 records some miscellaneous notes which I thought -ought to be recorded somewhere. - - -@chapter How to use @code{bzip2} - -This chapter contains a copy of the @code{bzip2} man page, -and nothing else. - -@quotation - -@unnumberedsubsubsec NAME -@itemize -@item @code{bzip2}, @code{bunzip2} -- a block-sorting file compressor, v1.0 -@item @code{bzcat} -- decompresses files to stdout -@item @code{bzip2recover} -- recovers data from damaged bzip2 files -@end itemize - -@unnumberedsubsubsec SYNOPSIS -@itemize -@item @code{bzip2} [ -cdfkqstvzVL123456789 ] [ filenames ... ] -@item @code{bunzip2} [ -fkvsVL ] [ filenames ... ] -@item @code{bzcat} [ -s ] [ filenames ... ] -@item @code{bzip2recover} filename -@end itemize - -@unnumberedsubsubsec DESCRIPTION - -@code{bzip2} compresses files using the Burrows-Wheeler block sorting -text compression algorithm, and Huffman coding. Compression is -generally considerably better than that achieved by more conventional -LZ77/LZ78-based compressors, and approaches the performance of the PPM -family of statistical compressors. - -The command-line options are deliberately very similar to those of GNU -@code{gzip}, but they are not identical. - -@code{bzip2} expects a list of file names to accompany the command-line -flags. Each file is replaced by a compressed version of itself, with -the name @code{original_name.bz2}. Each compressed file has the same -modification date, permissions, and, when possible, ownership as the -corresponding original, so that these properties can be correctly -restored at decompression time. File name handling is naive in the -sense that there is no mechanism for preserving original file names, -permissions, ownerships or dates in filesystems which lack these -concepts, or have serious file name length restrictions, such as MS-DOS. - -@code{bzip2} and @code{bunzip2} will by default not overwrite existing -files. If you want this to happen, specify the @code{-f} flag. - -If no file names are specified, @code{bzip2} compresses from standard -input to standard output. In this case, @code{bzip2} will decline to -write compressed output to a terminal, as this would be entirely -incomprehensible and therefore pointless. - -@code{bunzip2} (or @code{bzip2 -d}) decompresses all -specified files. Files which were not created by @code{bzip2} -will be detected and ignored, and a warning issued. -@code{bzip2} attempts to guess the filename for the decompressed file -from that of the compressed file as follows: -@itemize -@item @code{filename.bz2 } becomes @code{filename} -@item @code{filename.bz } becomes @code{filename} -@item @code{filename.tbz2} becomes @code{filename.tar} -@item @code{filename.tbz } becomes @code{filename.tar} -@item @code{anyothername } becomes @code{anyothername.out} -@end itemize -If the file does not end in one of the recognised endings, -@code{.bz2}, @code{.bz}, -@code{.tbz2} or @code{.tbz}, @code{bzip2} complains that it cannot -guess the name of the original file, and uses the original name -with @code{.out} appended. - -As with compression, supplying no -filenames causes decompression from standard input to standard output. - -@code{bunzip2} will correctly decompress a file which is the -concatenation of two or more compressed files. The result is the -concatenation of the corresponding uncompressed files. Integrity -testing (@code{-t}) of concatenated compressed files is also supported. - -You can also compress or decompress files to the standard output by -giving the @code{-c} flag. Multiple files may be compressed and -decompressed like this. The resulting outputs are fed sequentially to -stdout. Compression of multiple files in this manner generates a stream -containing multiple compressed file representations. Such a stream -can be decompressed correctly only by @code{bzip2} version 0.9.0 or -later. Earlier versions of @code{bzip2} will stop after decompressing -the first file in the stream. - -@code{bzcat} (or @code{bzip2 -dc}) decompresses all specified files to -the standard output. - -@code{bzip2} will read arguments from the environment variables -@code{BZIP2} and @code{BZIP}, in that order, and will process them -before any arguments read from the command line. This gives a -convenient way to supply default arguments. - -Compression is always performed, even if the compressed file is slightly -larger than the original. Files of less than about one hundred bytes -tend to get larger, since the compression mechanism has a constant -overhead in the region of 50 bytes. Random data (including the output -of most file compressors) is coded at about 8.05 bits per byte, giving -an expansion of around 0.5%. - -As a self-check for your protection, @code{bzip2} uses 32-bit CRCs to -make sure that the decompressed version of a file is identical to the -original. This guards against corruption of the compressed data, and -against undetected bugs in @code{bzip2} (hopefully very unlikely). The -chances of data corruption going undetected is microscopic, about one -chance in four billion for each file processed. Be aware, though, that -the check occurs upon decompression, so it can only tell you that -something is wrong. It can't help you recover the original uncompressed -data. You can use @code{bzip2recover} to try to recover data from -damaged files. - -Return values: 0 for a normal exit, 1 for environmental problems (file -not found, invalid flags, I/O errors, &c), 2 to indicate a corrupt -compressed file, 3 for an internal consistency error (eg, bug) which -caused @code{bzip2} to panic. - - -@unnumberedsubsubsec OPTIONS -@table @code -@item -c --stdout -Compress or decompress to standard output. -@item -d --decompress -Force decompression. @code{bzip2}, @code{bunzip2} and @code{bzcat} are -really the same program, and the decision about what actions to take is -done on the basis of which name is used. This flag overrides that -mechanism, and forces bzip2 to decompress. -@item -z --compress -The complement to @code{-d}: forces compression, regardless of the -invokation name. -@item -t --test -Check integrity of the specified file(s), but don't decompress them. -This really performs a trial decompression and throws away the result. -@item -f --force -Force overwrite of output files. Normally, @code{bzip2} will not overwrite -existing output files. Also forces @code{bzip2} to break hard links -to files, which it otherwise wouldn't do. -@item -k --keep -Keep (don't delete) input files during compression -or decompression. -@item -s --small -Reduce memory usage, for compression, decompression and testing. Files -are decompressed and tested using a modified algorithm which only -requires 2.5 bytes per block byte. This means any file can be -decompressed in 2300k of memory, albeit at about half the normal speed. - -During compression, @code{-s} selects a block size of 200k, which limits -memory use to around the same figure, at the expense of your compression -ratio. In short, if your machine is low on memory (8 megabytes or -less), use -s for everything. See MEMORY MANAGEMENT below. -@item -q --quiet -Suppress non-essential warning messages. Messages pertaining to -I/O errors and other critical events will not be suppressed. -@item -v --verbose -Verbose mode -- show the compression ratio for each file processed. -Further @code{-v}'s increase the verbosity level, spewing out lots of -information which is primarily of interest for diagnostic purposes. -@item -L --license -V --version -Display the software version, license terms and conditions. -@item -1 to -9 -Set the block size to 100 k, 200 k .. 900 k when compressing. Has no -effect when decompressing. See MEMORY MANAGEMENT below. -@item -- -Treats all subsequent arguments as file names, even if they start -with a dash. This is so you can handle files with names beginning -with a dash, for example: @code{bzip2 -- -myfilename}. -@item --repetitive-fast -@item --repetitive-best -These flags are redundant in versions 0.9.5 and above. They provided -some coarse control over the behaviour of the sorting algorithm in -earlier versions, which was sometimes useful. 0.9.5 and above have an -improved algorithm which renders these flags irrelevant. -@end table - - -@unnumberedsubsubsec MEMORY MANAGEMENT - -@code{bzip2} compresses large files in blocks. The block size affects -both the compression ratio achieved, and the amount of memory needed for -compression and decompression. The flags @code{-1} through @code{-9} -specify the block size to be 100,000 bytes through 900,000 bytes (the -default) respectively. At decompression time, the block size used for -compression is read from the header of the compressed file, and -@code{bunzip2} then allocates itself just enough memory to decompress -the file. Since block sizes are stored in compressed files, it follows -that the flags @code{-1} to @code{-9} are irrelevant to and so ignored -during decompression. - -Compression and decompression requirements, in bytes, can be estimated -as: -@example - Compression: 400k + ( 8 x block size ) - - Decompression: 100k + ( 4 x block size ), or - 100k + ( 2.5 x block size ) -@end example -Larger block sizes give rapidly diminishing marginal returns. Most of -the compression comes from the first two or three hundred k of block -size, a fact worth bearing in mind when using @code{bzip2} on small machines. -It is also important to appreciate that the decompression memory -requirement is set at compression time by the choice of block size. - -For files compressed with the default 900k block size, @code{bunzip2} -will require about 3700 kbytes to decompress. To support decompression -of any file on a 4 megabyte machine, @code{bunzip2} has an option to -decompress using approximately half this amount of memory, about 2300 -kbytes. Decompression speed is also halved, so you should use this -option only where necessary. The relevant flag is @code{-s}. - -In general, try and use the largest block size memory constraints allow, -since that maximises the compression achieved. Compression and -decompression speed are virtually unaffected by block size. - -Another significant point applies to files which fit in a single block --- that means most files you'd encounter using a large block size. The -amount of real memory touched is proportional to the size of the file, -since the file is smaller than a block. For example, compressing a file -20,000 bytes long with the flag @code{-9} will cause the compressor to -allocate around 7600k of memory, but only touch 400k + 20000 * 8 = 560 -kbytes of it. Similarly, the decompressor will allocate 3700k but only -touch 100k + 20000 * 4 = 180 kbytes. - -Here is a table which summarises the maximum memory usage for different -block sizes. Also recorded is the total compressed size for 14 files of -the Calgary Text Compression Corpus totalling 3,141,622 bytes. This -column gives some feel for how compression varies with block size. -These figures tend to understate the advantage of larger block sizes for -larger files, since the Corpus is dominated by smaller files. -@example - Compress Decompress Decompress Corpus - Flag usage usage -s usage Size - - -1 1200k 500k 350k 914704 - -2 2000k 900k 600k 877703 - -3 2800k 1300k 850k 860338 - -4 3600k 1700k 1100k 846899 - -5 4400k 2100k 1350k 845160 - -6 5200k 2500k 1600k 838626 - -7 6100k 2900k 1850k 834096 - -8 6800k 3300k 2100k 828642 - -9 7600k 3700k 2350k 828642 -@end example - -@unnumberedsubsubsec RECOVERING DATA FROM DAMAGED FILES - -@code{bzip2} compresses files in blocks, usually 900kbytes long. Each -block is handled independently. If a media or transmission error causes -a multi-block @code{.bz2} file to become damaged, it may be possible to -recover data from the undamaged blocks in the file. - -The compressed representation of each block is delimited by a 48-bit -pattern, which makes it possible to find the block boundaries with -reasonable certainty. Each block also carries its own 32-bit CRC, so -damaged blocks can be distinguished from undamaged ones. - -@code{bzip2recover} is a simple program whose purpose is to search for -blocks in @code{.bz2} files, and write each block out into its own -@code{.bz2} file. You can then use @code{bzip2 -t} to test the -integrity of the resulting files, and decompress those which are -undamaged. - -@code{bzip2recover} -takes a single argument, the name of the damaged file, -and writes a number of files @code{rec0001file.bz2}, - @code{rec0002file.bz2}, etc, containing the extracted blocks. - The output filenames are designed so that the use of - wildcards in subsequent processing -- for example, -@code{bzip2 -dc rec*file.bz2 > recovered_data} -- lists the files in - the correct order. - -@code{bzip2recover} should be of most use dealing with large @code{.bz2} - files, as these will contain many blocks. It is clearly - futile to use it on damaged single-block files, since a - damaged block cannot be recovered. If you wish to minimise -any potential data loss through media or transmission errors, -you might consider compressing with a smaller - block size. - - -@unnumberedsubsubsec PERFORMANCE NOTES - -The sorting phase of compression gathers together similar strings in the -file. Because of this, files containing very long runs of repeated -symbols, like "aabaabaabaab ..." (repeated several hundred times) may -compress more slowly than normal. Versions 0.9.5 and above fare much -better than previous versions in this respect. The ratio between -worst-case and average-case compression time is in the region of 10:1. -For previous versions, this figure was more like 100:1. You can use the -@code{-vvvv} option to monitor progress in great detail, if you want. - -Decompression speed is unaffected by these phenomena. - -@code{bzip2} usually allocates several megabytes of memory to operate -in, and then charges all over it in a fairly random fashion. This means -that performance, both for compressing and decompressing, is largely -determined by the speed at which your machine can service cache misses. -Because of this, small changes to the code to reduce the miss rate have -been observed to give disproportionately large performance improvements. -I imagine @code{bzip2} will perform best on machines with very large -caches. - - -@unnumberedsubsubsec CAVEATS - -I/O error messages are not as helpful as they could be. @code{bzip2} -tries hard to detect I/O errors and exit cleanly, but the details of -what the problem is sometimes seem rather misleading. - -This manual page pertains to version 1.0 of @code{bzip2}. Compressed -data created by this version is entirely forwards and backwards -compatible with the previous public releases, versions 0.1pl2, 0.9.0 and -0.9.5, but with the following exception: 0.9.0 and above can correctly -decompress multiple concatenated compressed files. 0.1pl2 cannot do -this; it will stop after decompressing just the first file in the -stream. - -@code{bzip2recover} uses 32-bit integers to represent bit positions in -compressed files, so it cannot handle compressed files more than 512 -megabytes long. This could easily be fixed. - - -@unnumberedsubsubsec AUTHOR -Julian Seward, @code{jseward@@acm.org}. - -The ideas embodied in @code{bzip2} are due to (at least) the following -people: Michael Burrows and David Wheeler (for the block sorting -transformation), David Wheeler (again, for the Huffman coder), Peter -Fenwick (for the structured coding model in the original @code{bzip}, -and many refinements), and Alistair Moffat, Radford Neal and Ian Witten -(for the arithmetic coder in the original @code{bzip}). I am much -indebted for their help, support and advice. See the manual in the -source distribution for pointers to sources of documentation. Christian -von Roques encouraged me to look for faster sorting algorithms, so as to -speed up compression. Bela Lubkin encouraged me to improve the -worst-case compression performance. Many people sent patches, helped -with portability problems, lent machines, gave advice and were generally -helpful. - -@end quotation - - - - -@chapter Programming with @code{libbzip2} - -This chapter describes the programming interface to @code{libbzip2}. - -For general background information, particularly about memory -use and performance aspects, you'd be well advised to read Chapter 2 -as well. - -@section Top-level structure - -@code{libbzip2} is a flexible library for compressing and decompressing -data in the @code{bzip2} data format. Although packaged as a single -entity, it helps to regard the library as three separate parts: the low -level interface, and the high level interface, and some utility -functions. - -The structure of @code{libbzip2}'s interfaces is similar to -that of Jean-loup Gailly's and Mark Adler's excellent @code{zlib} -library. - -All externally visible symbols have names beginning @code{BZ2_}. -This is new in version 1.0. The intention is to minimise pollution -of the namespaces of library clients. - -@subsection Low-level summary - -This interface provides services for compressing and decompressing -data in memory. There's no provision for dealing with files, streams -or any other I/O mechanisms, just straight memory-to-memory work. -In fact, this part of the library can be compiled without inclusion -of @code{stdio.h}, which may be helpful for embedded applications. - -The low-level part of the library has no global variables and -is therefore thread-safe. - -Six routines make up the low level interface: -@code{BZ2_bzCompressInit}, @code{BZ2_bzCompress}, and @* @code{BZ2_bzCompressEnd} -for compression, -and a corresponding trio @code{BZ2_bzDecompressInit}, @* @code{BZ2_bzDecompress} -and @code{BZ2_bzDecompressEnd} for decompression. -The @code{*Init} functions allocate -memory for compression/decompression and do other -initialisations, whilst the @code{*End} functions close down operations -and release memory. - -The real work is done by @code{BZ2_bzCompress} and @code{BZ2_bzDecompress}. -These compress and decompress data from a user-supplied input buffer -to a user-supplied output buffer. These buffers can be any size; -arbitrary quantities of data are handled by making repeated calls -to these functions. This is a flexible mechanism allowing a -consumer-pull style of activity, or producer-push, or a mixture of -both. - - - -@subsection High-level summary - -This interface provides some handy wrappers around the low-level -interface to facilitate reading and writing @code{bzip2} format -files (@code{.bz2} files). The routines provide hooks to facilitate -reading files in which the @code{bzip2} data stream is embedded -within some larger-scale file structure, or where there are -multiple @code{bzip2} data streams concatenated end-to-end. - -For reading files, @code{BZ2_bzReadOpen}, @code{BZ2_bzRead}, -@code{BZ2_bzReadClose} and @* @code{BZ2_bzReadGetUnused} are supplied. For -writing files, @code{BZ2_bzWriteOpen}, @code{BZ2_bzWrite} and -@code{BZ2_bzWriteFinish} are available. - -As with the low-level library, no global variables are used -so the library is per se thread-safe. However, if I/O errors -occur whilst reading or writing the underlying compressed files, -you may have to consult @code{errno} to determine the cause of -the error. In that case, you'd need a C library which correctly -supports @code{errno} in a multithreaded environment. - -To make the library a little simpler and more portable, -@code{BZ2_bzReadOpen} and @code{BZ2_bzWriteOpen} require you to pass them file -handles (@code{FILE*}s) which have previously been opened for reading or -writing respectively. That avoids portability problems associated with -file operations and file attributes, whilst not being much of an -imposition on the programmer. - - - -@subsection Utility functions summary -For very simple needs, @code{BZ2_bzBuffToBuffCompress} and -@code{BZ2_bzBuffToBuffDecompress} are provided. These compress -data in memory from one buffer to another buffer in a single -function call. You should assess whether these functions -fulfill your memory-to-memory compression/decompression -requirements before investing effort in understanding the more -general but more complex low-level interface. - -Yoshioka Tsuneo (@code{QWF00133@@niftyserve.or.jp} / -@code{tsuneo-y@@is.aist-nara.ac.jp}) has contributed some functions to -give better @code{zlib} compatibility. These functions are -@code{BZ2_bzopen}, @code{BZ2_bzread}, @code{BZ2_bzwrite}, @code{BZ2_bzflush}, -@code{BZ2_bzclose}, -@code{BZ2_bzerror} and @code{BZ2_bzlibVersion}. You may find these functions -more convenient for simple file reading and writing, than those in the -high-level interface. These functions are not (yet) officially part of -the library, and are minimally documented here. If they break, you -get to keep all the pieces. I hope to document them properly when time -permits. - -Yoshioka also contributed modifications to allow the library to be -built as a Windows DLL. - - -@section Error handling - -The library is designed to recover cleanly in all situations, including -the worst-case situation of decompressing random data. I'm not -100% sure that it can always do this, so you might want to add -a signal handler to catch segmentation violations during decompression -if you are feeling especially paranoid. I would be interested in -hearing more about the robustness of the library to corrupted -compressed data. - -Version 1.0 is much more robust in this respect than -0.9.0 or 0.9.5. Investigations with Checker (a tool for -detecting problems with memory management, similar to Purify) -indicate that, at least for the few files I tested, all single-bit -errors in the decompressed data are caught properly, with no -segmentation faults, no reads of uninitialised data and no -out of range reads or writes. So it's certainly much improved, -although I wouldn't claim it to be totally bombproof. - -The file @code{bzlib.h} contains all definitions needed to use -the library. In particular, you should definitely not include -@code{bzlib_private.h}. - -In @code{bzlib.h}, the various return values are defined. The following -list is not intended as an exhaustive description of the circumstances -in which a given value may be returned -- those descriptions are given -later. Rather, it is intended to convey the rough meaning of each -return value. The first five actions are normal and not intended to -denote an error situation. -@table @code -@item BZ_OK -The requested action was completed successfully. -@item BZ_RUN_OK -@itemx BZ_FLUSH_OK -@itemx BZ_FINISH_OK -In @code{BZ2_bzCompress}, the requested flush/finish/nothing-special action -was completed successfully. -@item BZ_STREAM_END -Compression of data was completed, or the logical stream end was -detected during decompression. -@end table - -The following return values indicate an error of some kind. -@table @code -@item BZ_CONFIG_ERROR -Indicates that the library has been improperly compiled on your -platform -- a major configuration error. Specifically, it means -that @code{sizeof(char)}, @code{sizeof(short)} and @code{sizeof(int)} -are not 1, 2 and 4 respectively, as they should be. Note that the -library should still work properly on 64-bit platforms which follow -the LP64 programming model -- that is, where @code{sizeof(long)} -and @code{sizeof(void*)} are 8. Under LP64, @code{sizeof(int)} is -still 4, so @code{libbzip2}, which doesn't use the @code{long} type, -is OK. -@item BZ_SEQUENCE_ERROR -When using the library, it is important to call the functions in the -correct sequence and with data structures (buffers etc) in the correct -states. @code{libbzip2} checks as much as it can to ensure this is -happening, and returns @code{BZ_SEQUENCE_ERROR} if not. Code which -complies precisely with the function semantics, as detailed below, -should never receive this value; such an event denotes buggy code -which you should investigate. -@item BZ_PARAM_ERROR -Returned when a parameter to a function call is out of range -or otherwise manifestly incorrect. As with @code{BZ_SEQUENCE_ERROR}, -this denotes a bug in the client code. The distinction between -@code{BZ_PARAM_ERROR} and @code{BZ_SEQUENCE_ERROR} is a bit hazy, but still worth -making. -@item BZ_MEM_ERROR -Returned when a request to allocate memory failed. Note that the -quantity of memory needed to decompress a stream cannot be determined -until the stream's header has been read. So @code{BZ2_bzDecompress} and -@code{BZ2_bzRead} may return @code{BZ_MEM_ERROR} even though some of -the compressed data has been read. The same is not true for -compression; once @code{BZ2_bzCompressInit} or @code{BZ2_bzWriteOpen} have -successfully completed, @code{BZ_MEM_ERROR} cannot occur. -@item BZ_DATA_ERROR -Returned when a data integrity error is detected during decompression. -Most importantly, this means when stored and computed CRCs for the -data do not match. This value is also returned upon detection of any -other anomaly in the compressed data. -@item BZ_DATA_ERROR_MAGIC -As a special case of @code{BZ_DATA_ERROR}, it is sometimes useful to -know when the compressed stream does not start with the correct -magic bytes (@code{'B' 'Z' 'h'}). -@item BZ_IO_ERROR -Returned by @code{BZ2_bzRead} and @code{BZ2_bzWrite} when there is an error -reading or writing in the compressed file, and by @code{BZ2_bzReadOpen} -and @code{BZ2_bzWriteOpen} for attempts to use a file for which the -error indicator (viz, @code{ferror(f)}) is set. -On receipt of @code{BZ_IO_ERROR}, the caller should consult -@code{errno} and/or @code{perror} to acquire operating-system -specific information about the problem. -@item BZ_UNEXPECTED_EOF -Returned by @code{BZ2_bzRead} when the compressed file finishes -before the logical end of stream is detected. -@item BZ_OUTBUFF_FULL -Returned by @code{BZ2_bzBuffToBuffCompress} and -@code{BZ2_bzBuffToBuffDecompress} to indicate that the output data -will not fit into the output buffer provided. -@end table - - - -@section Low-level interface - -@subsection @code{BZ2_bzCompressInit} -@example -typedef - struct @{ - char *next_in; - unsigned int avail_in; - unsigned int total_in_lo32; - unsigned int total_in_hi32; - - char *next_out; - unsigned int avail_out; - unsigned int total_out_lo32; - unsigned int total_out_hi32; - - void *state; - - void *(*bzalloc)(void *,int,int); - void (*bzfree)(void *,void *); - void *opaque; - @} - bz_stream; - -int BZ2_bzCompressInit ( bz_stream *strm, - int blockSize100k, - int verbosity, - int workFactor ); - -@end example - -Prepares for compression. The @code{bz_stream} structure -holds all data pertaining to the compression activity. -A @code{bz_stream} structure should be allocated and initialised -prior to the call. -The fields of @code{bz_stream} -comprise the entirety of the user-visible data. @code{state} -is a pointer to the private data structures required for compression. - -Custom memory allocators are supported, via fields @code{bzalloc}, -@code{bzfree}, -and @code{opaque}. The value -@code{opaque} is passed to as the first argument to -all calls to @code{bzalloc} and @code{bzfree}, but is -otherwise ignored by the library. -The call @code{bzalloc ( opaque, n, m )} is expected to return a -pointer @code{p} to -@code{n * m} bytes of memory, and @code{bzfree ( opaque, p )} -should free -that memory. - -If you don't want to use a custom memory allocator, set @code{bzalloc}, -@code{bzfree} and -@code{opaque} to @code{NULL}, -and the library will then use the standard @code{malloc}/@code{free} -routines. - -Before calling @code{BZ2_bzCompressInit}, fields @code{bzalloc}, -@code{bzfree} and @code{opaque} should -be filled appropriately, as just described. Upon return, the internal -state will have been allocated and initialised, and @code{total_in_lo32}, -@code{total_in_hi32}, @code{total_out_lo32} and -@code{total_out_hi32} will have been set to zero. -These four fields are used by the library -to inform the caller of the total amount of data passed into and out of -the library, respectively. You should not try to change them. -As of version 1.0, 64-bit counts are maintained, even on 32-bit -platforms, using the @code{_hi32} fields to store the upper 32 bits -of the count. So, for example, the total amount of data in -is @code{(total_in_hi32 << 32) + total_in_lo32}. - -Parameter @code{blockSize100k} specifies the block size to be used for -compression. It should be a value between 1 and 9 inclusive, and the -actual block size used is 100000 x this figure. 9 gives the best -compression but takes most memory. - -Parameter @code{verbosity} should be set to a number between 0 and 4 -inclusive. 0 is silent, and greater numbers give increasingly verbose -monitoring/debugging output. If the library has been compiled with -@code{-DBZ_NO_STDIO}, no such output will appear for any verbosity -setting. - -Parameter @code{workFactor} controls how the compression phase behaves -when presented with worst case, highly repetitive, input data. If -compression runs into difficulties caused by repetitive data, the -library switches from the standard sorting algorithm to a fallback -algorithm. The fallback is slower than the standard algorithm by -perhaps a factor of three, but always behaves reasonably, no matter how -bad the input. - -Lower values of @code{workFactor} reduce the amount of effort the -standard algorithm will expend before resorting to the fallback. You -should set this parameter carefully; too low, and many inputs will be -handled by the fallback algorithm and so compress rather slowly, too -high, and your average-to-worst case compression times can become very -large. The default value of 30 gives reasonable behaviour over a wide -range of circumstances. - -Allowable values range from 0 to 250 inclusive. 0 is a special case, -equivalent to using the default value of 30. - -Note that the compressed output generated is the same regardless of -whether or not the fallback algorithm is used. - -Be aware also that this parameter may disappear entirely in future -versions of the library. In principle it should be possible to devise a -good way to automatically choose which algorithm to use. Such a -mechanism would render the parameter obsolete. - -Possible return values: -@display - @code{BZ_CONFIG_ERROR} - if the library has been mis-compiled - @code{BZ_PARAM_ERROR} - if @code{strm} is @code{NULL} - or @code{blockSize} < 1 or @code{blockSize} > 9 - or @code{verbosity} < 0 or @code{verbosity} > 4 - or @code{workFactor} < 0 or @code{workFactor} > 250 - @code{BZ_MEM_ERROR} - if not enough memory is available - @code{BZ_OK} - otherwise -@end display -Allowable next actions: -@display - @code{BZ2_bzCompress} - if @code{BZ_OK} is returned - no specific action needed in case of error -@end display - -@subsection @code{BZ2_bzCompress} -@example - int BZ2_bzCompress ( bz_stream *strm, int action ); -@end example -Provides more input and/or output buffer space for the library. The -caller maintains input and output buffers, and calls @code{BZ2_bzCompress} to -transfer data between them. - -Before each call to @code{BZ2_bzCompress}, @code{next_in} should point at -the data to be compressed, and @code{avail_in} should indicate how many -bytes the library may read. @code{BZ2_bzCompress} updates @code{next_in}, -@code{avail_in} and @code{total_in} to reflect the number of bytes it -has read. - -Similarly, @code{next_out} should point to a buffer in which the -compressed data is to be placed, with @code{avail_out} indicating how -much output space is available. @code{BZ2_bzCompress} updates -@code{next_out}, @code{avail_out} and @code{total_out} to reflect the -number of bytes output. - -You may provide and remove as little or as much data as you like on each -call of @code{BZ2_bzCompress}. In the limit, it is acceptable to supply and -remove data one byte at a time, although this would be terribly -inefficient. You should always ensure that at least one byte of output -space is available at each call. - -A second purpose of @code{BZ2_bzCompress} is to request a change of mode of the -compressed stream. - -Conceptually, a compressed stream can be in one of four states: IDLE, -RUNNING, FLUSHING and FINISHING. Before initialisation -(@code{BZ2_bzCompressInit}) and after termination (@code{BZ2_bzCompressEnd}), a -stream is regarded as IDLE. - -Upon initialisation (@code{BZ2_bzCompressInit}), the stream is placed in the -RUNNING state. Subsequent calls to @code{BZ2_bzCompress} should pass -@code{BZ_RUN} as the requested action; other actions are illegal and -will result in @code{BZ_SEQUENCE_ERROR}. - -At some point, the calling program will have provided all the input data -it wants to. It will then want to finish up -- in effect, asking the -library to process any data it might have buffered internally. In this -state, @code{BZ2_bzCompress} will no longer attempt to read data from -@code{next_in}, but it will want to write data to @code{next_out}. -Because the output buffer supplied by the user can be arbitrarily small, -the finishing-up operation cannot necessarily be done with a single call -of @code{BZ2_bzCompress}. - -Instead, the calling program passes @code{BZ_FINISH} as an action to -@code{BZ2_bzCompress}. This changes the stream's state to FINISHING. Any -remaining input (ie, @code{next_in[0 .. avail_in-1]}) is compressed and -transferred to the output buffer. To do this, @code{BZ2_bzCompress} must be -called repeatedly until all the output has been consumed. At that -point, @code{BZ2_bzCompress} returns @code{BZ_STREAM_END}, and the stream's -state is set back to IDLE. @code{BZ2_bzCompressEnd} should then be -called. - -Just to make sure the calling program does not cheat, the library makes -a note of @code{avail_in} at the time of the first call to -@code{BZ2_bzCompress} which has @code{BZ_FINISH} as an action (ie, at the -time the program has announced its intention to not supply any more -input). By comparing this value with that of @code{avail_in} over -subsequent calls to @code{BZ2_bzCompress}, the library can detect any -attempts to slip in more data to compress. Any calls for which this is -detected will return @code{BZ_SEQUENCE_ERROR}. This indicates a -programming mistake which should be corrected. - -Instead of asking to finish, the calling program may ask -@code{BZ2_bzCompress} to take all the remaining input, compress it and -terminate the current (Burrows-Wheeler) compression block. This could -be useful for error control purposes. The mechanism is analogous to -that for finishing: call @code{BZ2_bzCompress} with an action of -@code{BZ_FLUSH}, remove output data, and persist with the -@code{BZ_FLUSH} action until the value @code{BZ_RUN} is returned. As -with finishing, @code{BZ2_bzCompress} detects any attempt to provide more -input data once the flush has begun. - -Once the flush is complete, the stream returns to the normal RUNNING -state. - -This all sounds pretty complex, but isn't really. Here's a table -which shows which actions are allowable in each state, what action -will be taken, what the next state is, and what the non-error return -values are. Note that you can't explicitly ask what state the -stream is in, but nor do you need to -- it can be inferred from the -values returned by @code{BZ2_bzCompress}. -@display -IDLE/@code{any} - Illegal. IDLE state only exists after @code{BZ2_bzCompressEnd} or - before @code{BZ2_bzCompressInit}. - Return value = @code{BZ_SEQUENCE_ERROR} - -RUNNING/@code{BZ_RUN} - Compress from @code{next_in} to @code{next_out} as much as possible. - Next state = RUNNING - Return value = @code{BZ_RUN_OK} - -RUNNING/@code{BZ_FLUSH} - Remember current value of @code{next_in}. Compress from @code{next_in} - to @code{next_out} as much as possible, but do not accept any more input. - Next state = FLUSHING - Return value = @code{BZ_FLUSH_OK} - -RUNNING/@code{BZ_FINISH} - Remember current value of @code{next_in}. Compress from @code{next_in} - to @code{next_out} as much as possible, but do not accept any more input. - Next state = FINISHING - Return value = @code{BZ_FINISH_OK} - -FLUSHING/@code{BZ_FLUSH} - Compress from @code{next_in} to @code{next_out} as much as possible, - but do not accept any more input. - If all the existing input has been used up and all compressed - output has been removed - Next state = RUNNING; Return value = @code{BZ_RUN_OK} - else - Next state = FLUSHING; Return value = @code{BZ_FLUSH_OK} - -FLUSHING/other - Illegal. - Return value = @code{BZ_SEQUENCE_ERROR} - -FINISHING/@code{BZ_FINISH} - Compress from @code{next_in} to @code{next_out} as much as possible, - but to not accept any more input. - If all the existing input has been used up and all compressed - output has been removed - Next state = IDLE; Return value = @code{BZ_STREAM_END} - else - Next state = FINISHING; Return value = @code{BZ_FINISHING} - -FINISHING/other - Illegal. - Return value = @code{BZ_SEQUENCE_ERROR} -@end display - -That still looks complicated? Well, fair enough. The usual sequence -of calls for compressing a load of data is: -@itemize @bullet -@item Get started with @code{BZ2_bzCompressInit}. -@item Shovel data in and shlurp out its compressed form using zero or more -calls of @code{BZ2_bzCompress} with action = @code{BZ_RUN}. -@item Finish up. -Repeatedly call @code{BZ2_bzCompress} with action = @code{BZ_FINISH}, -copying out the compressed output, until @code{BZ_STREAM_END} is returned. -@item Close up and go home. Call @code{BZ2_bzCompressEnd}. -@end itemize -If the data you want to compress fits into your input buffer all -at once, you can skip the calls of @code{BZ2_bzCompress ( ..., BZ_RUN )} and -just do the @code{BZ2_bzCompress ( ..., BZ_FINISH )} calls. - -All required memory is allocated by @code{BZ2_bzCompressInit}. The -compression library can accept any data at all (obviously). So you -shouldn't get any error return values from the @code{BZ2_bzCompress} calls. -If you do, they will be @code{BZ_SEQUENCE_ERROR}, and indicate a bug in -your programming. - -Trivial other possible return values: -@display - @code{BZ_PARAM_ERROR} - if @code{strm} is @code{NULL}, or @code{strm->s} is @code{NULL} -@end display - -@subsection @code{BZ2_bzCompressEnd} -@example -int BZ2_bzCompressEnd ( bz_stream *strm ); -@end example -Releases all memory associated with a compression stream. - -Possible return values: -@display - @code{BZ_PARAM_ERROR} if @code{strm} is @code{NULL} or @code{strm->s} is @code{NULL} - @code{BZ_OK} otherwise -@end display - - -@subsection @code{BZ2_bzDecompressInit} -@example -int BZ2_bzDecompressInit ( bz_stream *strm, int verbosity, int small ); -@end example -Prepares for decompression. As with @code{BZ2_bzCompressInit}, a -@code{bz_stream} record should be allocated and initialised before the -call. Fields @code{bzalloc}, @code{bzfree} and @code{opaque} should be -set if a custom memory allocator is required, or made @code{NULL} for -the normal @code{malloc}/@code{free} routines. Upon return, the internal -state will have been initialised, and @code{total_in} and -@code{total_out} will be zero. - -For the meaning of parameter @code{verbosity}, see @code{BZ2_bzCompressInit}. - -If @code{small} is nonzero, the library will use an alternative -decompression algorithm which uses less memory but at the cost of -decompressing more slowly (roughly speaking, half the speed, but the -maximum memory requirement drops to around 2300k). See Chapter 2 for -more information on memory management. - -Note that the amount of memory needed to decompress -a stream cannot be determined until the stream's header has been read, -so even if @code{BZ2_bzDecompressInit} succeeds, a subsequent -@code{BZ2_bzDecompress} could fail with @code{BZ_MEM_ERROR}. - -Possible return values: -@display - @code{BZ_CONFIG_ERROR} - if the library has been mis-compiled - @code{BZ_PARAM_ERROR} - if @code{(small != 0 && small != 1)} - or @code{(verbosity < 0 || verbosity > 4)} - @code{BZ_MEM_ERROR} - if insufficient memory is available -@end display - -Allowable next actions: -@display - @code{BZ2_bzDecompress} - if @code{BZ_OK} was returned - no specific action required in case of error -@end display - - - -@subsection @code{BZ2_bzDecompress} -@example -int BZ2_bzDecompress ( bz_stream *strm ); -@end example -Provides more input and/out output buffer space for the library. The -caller maintains input and output buffers, and uses @code{BZ2_bzDecompress} -to transfer data between them. - -Before each call to @code{BZ2_bzDecompress}, @code{next_in} -should point at the compressed data, -and @code{avail_in} should indicate how many bytes the library -may read. @code{BZ2_bzDecompress} updates @code{next_in}, @code{avail_in} -and @code{total_in} -to reflect the number of bytes it has read. - -Similarly, @code{next_out} should point to a buffer in which the uncompressed -output is to be placed, with @code{avail_out} indicating how much output space -is available. @code{BZ2_bzCompress} updates @code{next_out}, -@code{avail_out} and @code{total_out} to reflect -the number of bytes output. - -You may provide and remove as little or as much data as you like on -each call of @code{BZ2_bzDecompress}. -In the limit, it is acceptable to -supply and remove data one byte at a time, although this would be -terribly inefficient. You should always ensure that at least one -byte of output space is available at each call. - -Use of @code{BZ2_bzDecompress} is simpler than @code{BZ2_bzCompress}. - -You should provide input and remove output as described above, and -repeatedly call @code{BZ2_bzDecompress} until @code{BZ_STREAM_END} is -returned. Appearance of @code{BZ_STREAM_END} denotes that -@code{BZ2_bzDecompress} has detected the logical end of the compressed -stream. @code{BZ2_bzDecompress} will not produce @code{BZ_STREAM_END} until -all output data has been placed into the output buffer, so once -@code{BZ_STREAM_END} appears, you are guaranteed to have available all -the decompressed output, and @code{BZ2_bzDecompressEnd} can safely be -called. - -If case of an error return value, you should call @code{BZ2_bzDecompressEnd} -to clean up and release memory. - -Possible return values: -@display - @code{BZ_PARAM_ERROR} - if @code{strm} is @code{NULL} or @code{strm->s} is @code{NULL} - or @code{strm->avail_out < 1} - @code{BZ_DATA_ERROR} - if a data integrity error is detected in the compressed stream - @code{BZ_DATA_ERROR_MAGIC} - if the compressed stream doesn't begin with the right magic bytes - @code{BZ_MEM_ERROR} - if there wasn't enough memory available - @code{BZ_STREAM_END} - if the logical end of the data stream was detected and all - output in has been consumed, eg @code{s->avail_out > 0} - @code{BZ_OK} - otherwise -@end display -Allowable next actions: -@display - @code{BZ2_bzDecompress} - if @code{BZ_OK} was returned - @code{BZ2_bzDecompressEnd} - otherwise -@end display - - -@subsection @code{BZ2_bzDecompressEnd} -@example -int BZ2_bzDecompressEnd ( bz_stream *strm ); -@end example -Releases all memory associated with a decompression stream. - -Possible return values: -@display - @code{BZ_PARAM_ERROR} - if @code{strm} is @code{NULL} or @code{strm->s} is @code{NULL} - @code{BZ_OK} - otherwise -@end display - -Allowable next actions: -@display - None. -@end display - - -@section High-level interface - -This interface provides functions for reading and writing -@code{bzip2} format files. First, some general points. - -@itemize @bullet -@item All of the functions take an @code{int*} first argument, - @code{bzerror}. - After each call, @code{bzerror} should be consulted first to determine - the outcome of the call. If @code{bzerror} is @code{BZ_OK}, - the call completed - successfully, and only then should the return value of the function - (if any) be consulted. If @code{bzerror} is @code{BZ_IO_ERROR}, - there was an error - reading/writing the underlying compressed file, and you should - then consult @code{errno}/@code{perror} to determine the - cause of the difficulty. - @code{bzerror} may also be set to various other values; precise details are - given on a per-function basis below. -@item If @code{bzerror} indicates an error - (ie, anything except @code{BZ_OK} and @code{BZ_STREAM_END}), - you should immediately call @code{BZ2_bzReadClose} (or @code{BZ2_bzWriteClose}, - depending on whether you are attempting to read or to write) - to free up all resources associated - with the stream. Once an error has been indicated, behaviour of all calls - except @code{BZ2_bzReadClose} (@code{BZ2_bzWriteClose}) is undefined. - The implication is that (1) @code{bzerror} should - be checked after each call, and (2) if @code{bzerror} indicates an error, - @code{BZ2_bzReadClose} (@code{BZ2_bzWriteClose}) should then be called to clean up. -@item The @code{FILE*} arguments passed to - @code{BZ2_bzReadOpen}/@code{BZ2_bzWriteOpen} - should be set to binary mode. - Most Unix systems will do this by default, but other platforms, - including Windows and Mac, will not. If you omit this, you may - encounter problems when moving code to new platforms. -@item Memory allocation requests are handled by - @code{malloc}/@code{free}. - At present - there is no facility for user-defined memory allocators in the file I/O - functions (could easily be added, though). -@end itemize - - - -@subsection @code{BZ2_bzReadOpen} -@example - typedef void BZFILE; - - BZFILE *BZ2_bzReadOpen ( int *bzerror, FILE *f, - int small, int verbosity, - void *unused, int nUnused ); -@end example -Prepare to read compressed data from file handle @code{f}. @code{f} -should refer to a file which has been opened for reading, and for which -the error indicator (@code{ferror(f)})is not set. If @code{small} is 1, -the library will try to decompress using less memory, at the expense of -speed. - -For reasons explained below, @code{BZ2_bzRead} will decompress the -@code{nUnused} bytes starting at @code{unused}, before starting to read -from the file @code{f}. At most @code{BZ_MAX_UNUSED} bytes may be -supplied like this. If this facility is not required, you should pass -@code{NULL} and @code{0} for @code{unused} and n@code{Unused} -respectively. - -For the meaning of parameters @code{small} and @code{verbosity}, -see @code{BZ2_bzDecompressInit}. - -The amount of memory needed to decompress a file cannot be determined -until the file's header has been read. So it is possible that -@code{BZ2_bzReadOpen} returns @code{BZ_OK} but a subsequent call of -@code{BZ2_bzRead} will return @code{BZ_MEM_ERROR}. - -Possible assignments to @code{bzerror}: -@display - @code{BZ_CONFIG_ERROR} - if the library has been mis-compiled - @code{BZ_PARAM_ERROR} - if @code{f} is @code{NULL} - or @code{small} is neither @code{0} nor @code{1} - or @code{(unused == NULL && nUnused != 0)} - or @code{(unused != NULL && !(0 <= nUnused <= BZ_MAX_UNUSED))} - @code{BZ_IO_ERROR} - if @code{ferror(f)} is nonzero - @code{BZ_MEM_ERROR} - if insufficient memory is available - @code{BZ_OK} - otherwise. -@end display - -Possible return values: -@display - Pointer to an abstract @code{BZFILE} - if @code{bzerror} is @code{BZ_OK} - @code{NULL} - otherwise -@end display - -Allowable next actions: -@display - @code{BZ2_bzRead} - if @code{bzerror} is @code{BZ_OK} - @code{BZ2_bzClose} - otherwise -@end display - - -@subsection @code{BZ2_bzRead} -@example - int BZ2_bzRead ( int *bzerror, BZFILE *b, void *buf, int len ); -@end example -Reads up to @code{len} (uncompressed) bytes from the compressed file -@code{b} into -the buffer @code{buf}. If the read was successful, -@code{bzerror} is set to @code{BZ_OK} -and the number of bytes read is returned. If the logical end-of-stream -was detected, @code{bzerror} will be set to @code{BZ_STREAM_END}, -and the number -of bytes read is returned. All other @code{bzerror} values denote an error. - -@code{BZ2_bzRead} will supply @code{len} bytes, -unless the logical stream end is detected -or an error occurs. Because of this, it is possible to detect the -stream end by observing when the number of bytes returned is -less than the number -requested. Nevertheless, this is regarded as inadvisable; you should -instead check @code{bzerror} after every call and watch out for -@code{BZ_STREAM_END}. - -Internally, @code{BZ2_bzRead} copies data from the compressed file in chunks -of size @code{BZ_MAX_UNUSED} bytes -before decompressing it. If the file contains more bytes than strictly -needed to reach the logical end-of-stream, @code{BZ2_bzRead} will almost certainly -read some of the trailing data before signalling @code{BZ_SEQUENCE_END}. -To collect the read but unused data once @code{BZ_SEQUENCE_END} has -appeared, call @code{BZ2_bzReadGetUnused} immediately before @code{BZ2_bzReadClose}. - -Possible assignments to @code{bzerror}: -@display - @code{BZ_PARAM_ERROR} - if @code{b} is @code{NULL} or @code{buf} is @code{NULL} or @code{len < 0} - @code{BZ_SEQUENCE_ERROR} - if @code{b} was opened with @code{BZ2_bzWriteOpen} - @code{BZ_IO_ERROR} - if there is an error reading from the compressed file - @code{BZ_UNEXPECTED_EOF} - if the compressed file ended before the logical end-of-stream was detected - @code{BZ_DATA_ERROR} - if a data integrity error was detected in the compressed stream - @code{BZ_DATA_ERROR_MAGIC} - if the stream does not begin with the requisite header bytes (ie, is not - a @code{bzip2} data file). This is really a special case of @code{BZ_DATA_ERROR}. - @code{BZ_MEM_ERROR} - if insufficient memory was available - @code{BZ_STREAM_END} - if the logical end of stream was detected. - @code{BZ_OK} - otherwise. -@end display - -Possible return values: -@display - number of bytes read - if @code{bzerror} is @code{BZ_OK} or @code{BZ_STREAM_END} - undefined - otherwise -@end display - -Allowable next actions: -@display - collect data from @code{buf}, then @code{BZ2_bzRead} or @code{BZ2_bzReadClose} - if @code{bzerror} is @code{BZ_OK} - collect data from @code{buf}, then @code{BZ2_bzReadClose} or @code{BZ2_bzReadGetUnused} - if @code{bzerror} is @code{BZ_SEQUENCE_END} - @code{BZ2_bzReadClose} - otherwise -@end display - - - -@subsection @code{BZ2_bzReadGetUnused} -@example - void BZ2_bzReadGetUnused ( int* bzerror, BZFILE *b, - void** unused, int* nUnused ); -@end example -Returns data which was read from the compressed file but was not needed -to get to the logical end-of-stream. @code{*unused} is set to the address -of the data, and @code{*nUnused} to the number of bytes. @code{*nUnused} will -be set to a value between @code{0} and @code{BZ_MAX_UNUSED} inclusive. - -This function may only be called once @code{BZ2_bzRead} has signalled -@code{BZ_STREAM_END} but before @code{BZ2_bzReadClose}. - -Possible assignments to @code{bzerror}: -@display - @code{BZ_PARAM_ERROR} - if @code{b} is @code{NULL} - or @code{unused} is @code{NULL} or @code{nUnused} is @code{NULL} - @code{BZ_SEQUENCE_ERROR} - if @code{BZ_STREAM_END} has not been signalled - or if @code{b} was opened with @code{BZ2_bzWriteOpen} - @code{BZ_OK} - otherwise -@end display - -Allowable next actions: -@display - @code{BZ2_bzReadClose} -@end display - - -@subsection @code{BZ2_bzReadClose} -@example - void BZ2_bzReadClose ( int *bzerror, BZFILE *b ); -@end example -Releases all memory pertaining to the compressed file @code{b}. -@code{BZ2_bzReadClose} does not call @code{fclose} on the underlying file -handle, so you should do that yourself if appropriate. -@code{BZ2_bzReadClose} should be called to clean up after all error -situations. - -Possible assignments to @code{bzerror}: -@display - @code{BZ_SEQUENCE_ERROR} - if @code{b} was opened with @code{BZ2_bzOpenWrite} - @code{BZ_OK} - otherwise -@end display - -Allowable next actions: -@display - none -@end display - - - -@subsection @code{BZ2_bzWriteOpen} -@example - BZFILE *BZ2_bzWriteOpen ( int *bzerror, FILE *f, - int blockSize100k, int verbosity, - int workFactor ); -@end example -Prepare to write compressed data to file handle @code{f}. -@code{f} should refer to -a file which has been opened for writing, and for which the error -indicator (@code{ferror(f)})is not set. - -For the meaning of parameters @code{blockSize100k}, -@code{verbosity} and @code{workFactor}, see -@* @code{BZ2_bzCompressInit}. - -All required memory is allocated at this stage, so if the call -completes successfully, @code{BZ_MEM_ERROR} cannot be signalled by a -subsequent call to @code{BZ2_bzWrite}. - -Possible assignments to @code{bzerror}: -@display - @code{BZ_CONFIG_ERROR} - if the library has been mis-compiled - @code{BZ_PARAM_ERROR} - if @code{f} is @code{NULL} - or @code{blockSize100k < 1} or @code{blockSize100k > 9} - @code{BZ_IO_ERROR} - if @code{ferror(f)} is nonzero - @code{BZ_MEM_ERROR} - if insufficient memory is available - @code{BZ_OK} - otherwise -@end display - -Possible return values: -@display - Pointer to an abstract @code{BZFILE} - if @code{bzerror} is @code{BZ_OK} - @code{NULL} - otherwise -@end display - -Allowable next actions: -@display - @code{BZ2_bzWrite} - if @code{bzerror} is @code{BZ_OK} - (you could go directly to @code{BZ2_bzWriteClose}, but this would be pretty pointless) - @code{BZ2_bzWriteClose} - otherwise -@end display - - - -@subsection @code{BZ2_bzWrite} -@example - void BZ2_bzWrite ( int *bzerror, BZFILE *b, void *buf, int len ); -@end example -Absorbs @code{len} bytes from the buffer @code{buf}, eventually to be -compressed and written to the file. - -Possible assignments to @code{bzerror}: -@display - @code{BZ_PARAM_ERROR} - if @code{b} is @code{NULL} or @code{buf} is @code{NULL} or @code{len < 0} - @code{BZ_SEQUENCE_ERROR} - if b was opened with @code{BZ2_bzReadOpen} - @code{BZ_IO_ERROR} - if there is an error writing the compressed file. - @code{BZ_OK} - otherwise -@end display - - - - -@subsection @code{BZ2_bzWriteClose} -@example - void BZ2_bzWriteClose ( int *bzerror, BZFILE* f, - int abandon, - unsigned int* nbytes_in, - unsigned int* nbytes_out ); - - void BZ2_bzWriteClose64 ( int *bzerror, BZFILE* f, - int abandon, - unsigned int* nbytes_in_lo32, - unsigned int* nbytes_in_hi32, - unsigned int* nbytes_out_lo32, - unsigned int* nbytes_out_hi32 ); -@end example - -Compresses and flushes to the compressed file all data so far supplied -by @code{BZ2_bzWrite}. The logical end-of-stream markers are also written, so -subsequent calls to @code{BZ2_bzWrite} are illegal. All memory associated -with the compressed file @code{b} is released. -@code{fflush} is called on the -compressed file, but it is not @code{fclose}'d. - -If @code{BZ2_bzWriteClose} is called to clean up after an error, the only -action is to release the memory. The library records the error codes -issued by previous calls, so this situation will be detected -automatically. There is no attempt to complete the compression -operation, nor to @code{fflush} the compressed file. You can force this -behaviour to happen even in the case of no error, by passing a nonzero -value to @code{abandon}. - -If @code{nbytes_in} is non-null, @code{*nbytes_in} will be set to be the -total volume of uncompressed data handled. Similarly, @code{nbytes_out} -will be set to the total volume of compressed data written. For -compatibility with older versions of the library, @code{BZ2_bzWriteClose} -only yields the lower 32 bits of these counts. Use -@code{BZ2_bzWriteClose64} if you want the full 64 bit counts. These -two functions are otherwise absolutely identical. - - -Possible assignments to @code{bzerror}: -@display - @code{BZ_SEQUENCE_ERROR} - if @code{b} was opened with @code{BZ2_bzReadOpen} - @code{BZ_IO_ERROR} - if there is an error writing the compressed file - @code{BZ_OK} - otherwise -@end display - -@subsection Handling embedded compressed data streams - -The high-level library facilitates use of -@code{bzip2} data streams which form some part of a surrounding, larger -data stream. -@itemize @bullet -@item For writing, the library takes an open file handle, writes -compressed data to it, @code{fflush}es it but does not @code{fclose} it. -The calling application can write its own data before and after the -compressed data stream, using that same file handle. -@item Reading is more complex, and the facilities are not as general -as they could be since generality is hard to reconcile with efficiency. -@code{BZ2_bzRead} reads from the compressed file in blocks of size -@code{BZ_MAX_UNUSED} bytes, and in doing so probably will overshoot -the logical end of compressed stream. -To recover this data once decompression has -ended, call @code{BZ2_bzReadGetUnused} after the last call of @code{BZ2_bzRead} -(the one returning @code{BZ_STREAM_END}) but before calling -@code{BZ2_bzReadClose}. -@end itemize - -This mechanism makes it easy to decompress multiple @code{bzip2} -streams placed end-to-end. As the end of one stream, when @code{BZ2_bzRead} -returns @code{BZ_STREAM_END}, call @code{BZ2_bzReadGetUnused} to collect the -unused data (copy it into your own buffer somewhere). -That data forms the start of the next compressed stream. -To start uncompressing that next stream, call @code{BZ2_bzReadOpen} again, -feeding in the unused data via the @code{unused}/@code{nUnused} -parameters. -Keep doing this until @code{BZ_STREAM_END} return coincides with the -physical end of file (@code{feof(f)}). In this situation -@code{BZ2_bzReadGetUnused} -will of course return no data. - -This should give some feel for how the high-level interface can be used. -If you require extra flexibility, you'll have to bite the bullet and get -to grips with the low-level interface. - -@subsection Standard file-reading/writing code -Here's how you'd write data to a compressed file: -@example @code -FILE* f; -BZFILE* b; -int nBuf; -char buf[ /* whatever size you like */ ]; -int bzerror; -int nWritten; - -f = fopen ( "myfile.bz2", "w" ); -if (!f) @{ - /* handle error */ -@} -b = BZ2_bzWriteOpen ( &bzerror, f, 9 ); -if (bzerror != BZ_OK) @{ - BZ2_bzWriteClose ( b ); - /* handle error */ -@} - -while ( /* condition */ ) @{ - /* get data to write into buf, and set nBuf appropriately */ - nWritten = BZ2_bzWrite ( &bzerror, b, buf, nBuf ); - if (bzerror == BZ_IO_ERROR) @{ - BZ2_bzWriteClose ( &bzerror, b ); - /* handle error */ - @} -@} - -BZ2_bzWriteClose ( &bzerror, b ); -if (bzerror == BZ_IO_ERROR) @{ - /* handle error */ -@} -@end example -And to read from a compressed file: -@example -FILE* f; -BZFILE* b; -int nBuf; -char buf[ /* whatever size you like */ ]; -int bzerror; -int nWritten; - -f = fopen ( "myfile.bz2", "r" ); -if (!f) @{ - /* handle error */ -@} -b = BZ2_bzReadOpen ( &bzerror, f, 0, NULL, 0 ); -if (bzerror != BZ_OK) @{ - BZ2_bzReadClose ( &bzerror, b ); - /* handle error */ -@} - -bzerror = BZ_OK; -while (bzerror == BZ_OK && /* arbitrary other conditions */) @{ - nBuf = BZ2_bzRead ( &bzerror, b, buf, /* size of buf */ ); - if (bzerror == BZ_OK) @{ - /* do something with buf[0 .. nBuf-1] */ - @} -@} -if (bzerror != BZ_STREAM_END) @{ - BZ2_bzReadClose ( &bzerror, b ); - /* handle error */ -@} else @{ - BZ2_bzReadClose ( &bzerror ); -@} -@end example - - - -@section Utility functions -@subsection @code{BZ2_bzBuffToBuffCompress} -@example - int BZ2_bzBuffToBuffCompress( char* dest, - unsigned int* destLen, - char* source, - unsigned int sourceLen, - int blockSize100k, - int verbosity, - int workFactor ); -@end example -Attempts to compress the data in @code{source[0 .. sourceLen-1]} -into the destination buffer, @code{dest[0 .. *destLen-1]}. -If the destination buffer is big enough, @code{*destLen} is -set to the size of the compressed data, and @code{BZ_OK} is -returned. If the compressed data won't fit, @code{*destLen} -is unchanged, and @code{BZ_OUTBUFF_FULL} is returned. - -Compression in this manner is a one-shot event, done with a single call -to this function. The resulting compressed data is a complete -@code{bzip2} format data stream. There is no mechanism for making -additional calls to provide extra input data. If you want that kind of -mechanism, use the low-level interface. - -For the meaning of parameters @code{blockSize100k}, @code{verbosity} -and @code{workFactor}, @* see @code{BZ2_bzCompressInit}. - -To guarantee that the compressed data will fit in its buffer, allocate -an output buffer of size 1% larger than the uncompressed data, plus -six hundred extra bytes. - -@code{BZ2_bzBuffToBuffDecompress} will not write data at or -beyond @code{dest[*destLen]}, even in case of buffer overflow. - -Possible return values: -@display - @code{BZ_CONFIG_ERROR} - if the library has been mis-compiled - @code{BZ_PARAM_ERROR} - if @code{dest} is @code{NULL} or @code{destLen} is @code{NULL} - or @code{blockSize100k < 1} or @code{blockSize100k > 9} - or @code{verbosity < 0} or @code{verbosity > 4} - or @code{workFactor < 0} or @code{workFactor > 250} - @code{BZ_MEM_ERROR} - if insufficient memory is available - @code{BZ_OUTBUFF_FULL} - if the size of the compressed data exceeds @code{*destLen} - @code{BZ_OK} - otherwise -@end display - - - -@subsection @code{BZ2_bzBuffToBuffDecompress} -@example - int BZ2_bzBuffToBuffDecompress ( char* dest, - unsigned int* destLen, - char* source, - unsigned int sourceLen, - int small, - int verbosity ); -@end example -Attempts to decompress the data in @code{source[0 .. sourceLen-1]} -into the destination buffer, @code{dest[0 .. *destLen-1]}. -If the destination buffer is big enough, @code{*destLen} is -set to the size of the uncompressed data, and @code{BZ_OK} is -returned. If the compressed data won't fit, @code{*destLen} -is unchanged, and @code{BZ_OUTBUFF_FULL} is returned. - -@code{source} is assumed to hold a complete @code{bzip2} format -data stream. @* @code{BZ2_bzBuffToBuffDecompress} tries to decompress -the entirety of the stream into the output buffer. - -For the meaning of parameters @code{small} and @code{verbosity}, -see @code{BZ2_bzDecompressInit}. - -Because the compression ratio of the compressed data cannot be known in -advance, there is no easy way to guarantee that the output buffer will -be big enough. You may of course make arrangements in your code to -record the size of the uncompressed data, but such a mechanism is beyond -the scope of this library. - -@code{BZ2_bzBuffToBuffDecompress} will not write data at or -beyond @code{dest[*destLen]}, even in case of buffer overflow. - -Possible return values: -@display - @code{BZ_CONFIG_ERROR} - if the library has been mis-compiled - @code{BZ_PARAM_ERROR} - if @code{dest} is @code{NULL} or @code{destLen} is @code{NULL} - or @code{small != 0 && small != 1} - or @code{verbosity < 0} or @code{verbosity > 4} - @code{BZ_MEM_ERROR} - if insufficient memory is available - @code{BZ_OUTBUFF_FULL} - if the size of the compressed data exceeds @code{*destLen} - @code{BZ_DATA_ERROR} - if a data integrity error was detected in the compressed data - @code{BZ_DATA_ERROR_MAGIC} - if the compressed data doesn't begin with the right magic bytes - @code{BZ_UNEXPECTED_EOF} - if the compressed data ends unexpectedly - @code{BZ_OK} - otherwise -@end display - - - -@section @code{zlib} compatibility functions -Yoshioka Tsuneo has contributed some functions to -give better @code{zlib} compatibility. These functions are -@code{BZ2_bzopen}, @code{BZ2_bzread}, @code{BZ2_bzwrite}, @code{BZ2_bzflush}, -@code{BZ2_bzclose}, -@code{BZ2_bzerror} and @code{BZ2_bzlibVersion}. -These functions are not (yet) officially part of -the library. If they break, you get to keep all the pieces. -Nevertheless, I think they work ok. -@example -typedef void BZFILE; - -const char * BZ2_bzlibVersion ( void ); -@end example -Returns a string indicating the library version. -@example -BZFILE * BZ2_bzopen ( const char *path, const char *mode ); -BZFILE * BZ2_bzdopen ( int fd, const char *mode ); -@end example -Opens a @code{.bz2} file for reading or writing, using either its name -or a pre-existing file descriptor. -Analogous to @code{fopen} and @code{fdopen}. -@example -int BZ2_bzread ( BZFILE* b, void* buf, int len ); -int BZ2_bzwrite ( BZFILE* b, void* buf, int len ); -@end example -Reads/writes data from/to a previously opened @code{BZFILE}. -Analogous to @code{fread} and @code{fwrite}. -@example -int BZ2_bzflush ( BZFILE* b ); -void BZ2_bzclose ( BZFILE* b ); -@end example -Flushes/closes a @code{BZFILE}. @code{BZ2_bzflush} doesn't actually do -anything. Analogous to @code{fflush} and @code{fclose}. - -@example -const char * BZ2_bzerror ( BZFILE *b, int *errnum ) -@end example -Returns a string describing the more recent error status of -@code{b}, and also sets @code{*errnum} to its numerical value. - - -@section Using the library in a @code{stdio}-free environment - -@subsection Getting rid of @code{stdio} - -In a deeply embedded application, you might want to use just -the memory-to-memory functions. You can do this conveniently -by compiling the library with preprocessor symbol @code{BZ_NO_STDIO} -defined. Doing this gives you a library containing only the following -eight functions: - -@code{BZ2_bzCompressInit}, @code{BZ2_bzCompress}, @code{BZ2_bzCompressEnd} @* -@code{BZ2_bzDecompressInit}, @code{BZ2_bzDecompress}, @code{BZ2_bzDecompressEnd} @* -@code{BZ2_bzBuffToBuffCompress}, @code{BZ2_bzBuffToBuffDecompress} - -When compiled like this, all functions will ignore @code{verbosity} -settings. - -@subsection Critical error handling -@code{libbzip2} contains a number of internal assertion checks which -should, needless to say, never be activated. Nevertheless, if an -assertion should fail, behaviour depends on whether or not the library -was compiled with @code{BZ_NO_STDIO} set. - -For a normal compile, an assertion failure yields the message -@example - bzip2/libbzip2: internal error number N. - This is a bug in bzip2/libbzip2, 1.0 of 21-Mar-2000. - Please report it to me at: jseward@@acm.org. If this happened - when you were using some program which uses libbzip2 as a - component, you should also report this bug to the author(s) - of that program. Please make an effort to report this bug; - timely and accurate bug reports eventually lead to higher - quality software. Thanks. Julian Seward, 21 March 2000. -@end example -where @code{N} is some error code number. @code{exit(3)} -is then called. - -For a @code{stdio}-free library, assertion failures result -in a call to a function declared as: -@example - extern void bz_internal_error ( int errcode ); -@end example -The relevant code is passed as a parameter. You should supply -such a function. - -In either case, once an assertion failure has occurred, any -@code{bz_stream} records involved can be regarded as invalid. -You should not attempt to resume normal operation with them. - -You may, of course, change critical error handling to suit -your needs. As I said above, critical errors indicate bugs -in the library and should not occur. All "normal" error -situations are indicated via error return codes from functions, -and can be recovered from. - - -@section Making a Windows DLL -Everything related to Windows has been contributed by Yoshioka Tsuneo -@* (@code{QWF00133@@niftyserve.or.jp} / -@code{tsuneo-y@@is.aist-nara.ac.jp}), so you should send your queries to -him (but perhaps Cc: me, @code{jseward@@acm.org}). - -My vague understanding of what to do is: using Visual C++ 5.0, -open the project file @code{libbz2.dsp}, and build. That's all. - -If you can't -open the project file for some reason, make a new one, naming these files: -@code{blocksort.c}, @code{bzlib.c}, @code{compress.c}, -@code{crctable.c}, @code{decompress.c}, @code{huffman.c}, @* -@code{randtable.c} and @code{libbz2.def}. You will also need -to name the header files @code{bzlib.h} and @code{bzlib_private.h}. - -If you don't use VC++, you may need to define the proprocessor symbol -@code{_WIN32}. - -Finally, @code{dlltest.c} is a sample program using the DLL. It has a -project file, @code{dlltest.dsp}. - -If you just want a makefile for Visual C, have a look at -@code{makefile.msc}. - -Be aware that if you compile @code{bzip2} itself on Win32, you must set -@code{BZ_UNIX} to 0 and @code{BZ_LCCWIN32} to 1, in the file -@code{bzip2.c}, before compiling. Otherwise the resulting binary won't -work correctly. - -I haven't tried any of this stuff myself, but it all looks plausible. - - - -@chapter Miscellanea - -These are just some random thoughts of mine. Your mileage may -vary. - -@section Limitations of the compressed file format -@code{bzip2-1.0}, @code{0.9.5} and @code{0.9.0} -use exactly the same file format as the previous -version, @code{bzip2-0.1}. This decision was made in the interests of -stability. Creating yet another incompatible compressed file format -would create further confusion and disruption for users. - -Nevertheless, this is not a painless decision. Development -work since the release of @code{bzip2-0.1} in August 1997 -has shown complexities in the file format which slow down -decompression and, in retrospect, are unnecessary. These are: -@itemize @bullet -@item The run-length encoder, which is the first of the - compression transformations, is entirely irrelevant. - The original purpose was to protect the sorting algorithm - from the very worst case input: a string of repeated - symbols. But algorithm steps Q6a and Q6b in the original - Burrows-Wheeler technical report (SRC-124) show how - repeats can be handled without difficulty in block - sorting. -@item The randomisation mechanism doesn't really need to be - there. Udi Manber and Gene Myers published a suffix - array construction algorithm a few years back, which - can be employed to sort any block, no matter how - repetitive, in O(N log N) time. Subsequent work by - Kunihiko Sadakane has produced a derivative O(N (log N)^2) - algorithm which usually outperforms the Manber-Myers - algorithm. - - I could have changed to Sadakane's algorithm, but I find - it to be slower than @code{bzip2}'s existing algorithm for - most inputs, and the randomisation mechanism protects - adequately against bad cases. I didn't think it was - a good tradeoff to make. Partly this is due to the fact - that I was not flooded with email complaints about - @code{bzip2-0.1}'s performance on repetitive data, so - perhaps it isn't a problem for real inputs. - - Probably the best long-term solution, - and the one I have incorporated into 0.9.5 and above, - is to use the existing sorting - algorithm initially, and fall back to a O(N (log N)^2) - algorithm if the standard algorithm gets into difficulties. -@item The compressed file format was never designed to be - handled by a library, and I have had to jump though - some hoops to produce an efficient implementation of - decompression. It's a bit hairy. Try passing - @code{decompress.c} through the C preprocessor - and you'll see what I mean. Much of this complexity - could have been avoided if the compressed size of - each block of data was recorded in the data stream. -@item An Adler-32 checksum, rather than a CRC32 checksum, - would be faster to compute. -@end itemize -It would be fair to say that the @code{bzip2} format was frozen -before I properly and fully understood the performance -consequences of doing so. - -Improvements which I was able to incorporate into -0.9.0, despite using the same file format, are: -@itemize @bullet -@item Single array implementation of the inverse BWT. This - significantly speeds up decompression, presumably - because it reduces the number of cache misses. -@item Faster inverse MTF transform for large MTF values. The - new implementation is based on the notion of sliding blocks - of values. -@item @code{bzip2-0.9.0} now reads and writes files with @code{fread} - and @code{fwrite}; version 0.1 used @code{putc} and @code{getc}. - Duh! Well, you live and learn. - -@end itemize -Further ahead, it would be nice -to be able to do random access into files. This will -require some careful design of compressed file formats. - - - -@section Portability issues -After some consideration, I have decided not to use -GNU @code{autoconf} to configure 0.9.5 or 1.0. - -@code{autoconf}, admirable and wonderful though it is, -mainly assists with portability problems between Unix-like -platforms. But @code{bzip2} doesn't have much in the way -of portability problems on Unix; most of the difficulties appear -when porting to the Mac, or to Microsoft's operating systems. -@code{autoconf} doesn't help in those cases, and brings in a -whole load of new complexity. - -Most people should be able to compile the library and program -under Unix straight out-of-the-box, so to speak, especially -if you have a version of GNU C available. - -There are a couple of @code{__inline__} directives in the code. GNU C -(@code{gcc}) should be able to handle them. If you're not using -GNU C, your C compiler shouldn't see them at all. -If your compiler does, for some reason, see them and doesn't -like them, just @code{#define} @code{__inline__} to be @code{/* */}. One -easy way to do this is to compile with the flag @code{-D__inline__=}, -which should be understood by most Unix compilers. - -If you still have difficulties, try compiling with the macro -@code{BZ_STRICT_ANSI} defined. This should enable you to build the -library in a strictly ANSI compliant environment. Building the program -itself like this is dangerous and not supported, since you remove -@code{bzip2}'s checks against compressing directories, symbolic links, -devices, and other not-really-a-file entities. This could cause -filesystem corruption! - -One other thing: if you create a @code{bzip2} binary for public -distribution, please try and link it statically (@code{gcc -s}). This -avoids all sorts of library-version issues that others may encounter -later on. - -If you build @code{bzip2} on Win32, you must set @code{BZ_UNIX} to 0 and -@code{BZ_LCCWIN32} to 1, in the file @code{bzip2.c}, before compiling. -Otherwise the resulting binary won't work correctly. - - - -@section Reporting bugs -I tried pretty hard to make sure @code{bzip2} is -bug free, both by design and by testing. Hopefully -you'll never need to read this section for real. - -Nevertheless, if @code{bzip2} dies with a segmentation -fault, a bus error or an internal assertion failure, it -will ask you to email me a bug report. Experience with -version 0.1 shows that almost all these problems can -be traced to either compiler bugs or hardware problems. -@itemize @bullet -@item -Recompile the program with no optimisation, and see if it -works. And/or try a different compiler. -I heard all sorts of stories about various flavours -of GNU C (and other compilers) generating bad code for -@code{bzip2}, and I've run across two such examples myself. - -2.7.X versions of GNU C are known to generate bad code from -time to time, at high optimisation levels. -If you get problems, try using the flags -@code{-O2} @code{-fomit-frame-pointer} @code{-fno-strength-reduce}. -You should specifically @emph{not} use @code{-funroll-loops}. - -You may notice that the Makefile runs six tests as part of -the build process. If the program passes all of these, it's -a pretty good (but not 100%) indication that the compiler has -done its job correctly. -@item -If @code{bzip2} crashes randomly, and the crashes are not -repeatable, you may have a flaky memory subsystem. @code{bzip2} -really hammers your memory hierarchy, and if it's a bit marginal, -you may get these problems. Ditto if your disk or I/O subsystem -is slowly failing. Yup, this really does happen. - -Try using a different machine of the same type, and see if -you can repeat the problem. -@item This isn't really a bug, but ... If @code{bzip2} tells -you your file is corrupted on decompression, and you -obtained the file via FTP, there is a possibility that you -forgot to tell FTP to do a binary mode transfer. That absolutely -will cause the file to be non-decompressible. You'll have to transfer -it again. -@end itemize - -If you've incorporated @code{libbzip2} into your own program -and are getting problems, please, please, please, check that the -parameters you are passing in calls to the library, are -correct, and in accordance with what the documentation says -is allowable. I have tried to make the library robust against -such problems, but I'm sure I haven't succeeded. - -Finally, if the above comments don't help, you'll have to send -me a bug report. Now, it's just amazing how many people will -send me a bug report saying something like -@display - bzip2 crashed with segmentation fault on my machine -@end display -and absolutely nothing else. Needless to say, a such a report -is @emph{totally, utterly, completely and comprehensively 100% useless; -a waste of your time, my time, and net bandwidth}. -With no details at all, there's no way I can possibly begin -to figure out what the problem is. - -The rules of the game are: facts, facts, facts. Don't omit -them because "oh, they won't be relevant". At the bare -minimum: -@display - Machine type. Operating system version. - Exact version of @code{bzip2} (do @code{bzip2 -V}). - Exact version of the compiler used. - Flags passed to the compiler. -@end display -However, the most important single thing that will help me is -the file that you were trying to compress or decompress at the -time the problem happened. Without that, my ability to do anything -more than speculate about the cause, is limited. - -Please remember that I connect to the Internet with a modem, so -you should contact me before mailing me huge files. - - -@section Did you get the right package? - -@code{bzip2} is a resource hog. It soaks up large amounts of CPU cycles -and memory. Also, it gives very large latencies. In the worst case, you -can feed many megabytes of uncompressed data into the library before -getting any compressed output, so this probably rules out applications -requiring interactive behaviour. - -These aren't faults of my implementation, I hope, but more -an intrinsic property of the Burrows-Wheeler transform (unfortunately). -Maybe this isn't what you want. - -If you want a compressor and/or library which is faster, uses less -memory but gets pretty good compression, and has minimal latency, -consider Jean-loup -Gailly's and Mark Adler's work, @code{zlib-1.1.2} and -@code{gzip-1.2.4}. Look for them at - -@code{http://www.cdrom.com/pub/infozip/zlib} and -@code{http://www.gzip.org} respectively. - -For something faster and lighter still, you might try Markus F X J -Oberhumer's @code{LZO} real-time compression/decompression library, at -@* @code{http://wildsau.idv.uni-linz.ac.at/mfx/lzo.html}. - -If you want to use the @code{bzip2} algorithms to compress small blocks -of data, 64k bytes or smaller, for example on an on-the-fly disk -compressor, you'd be well advised not to use this library. Instead, -I've made a special library tuned for that kind of use. It's part of -@code{e2compr-0.40}, an on-the-fly disk compressor for the Linux -@code{ext2} filesystem. Look at -@code{http://www.netspace.net.au/~reiter/e2compr}. - - - -@section Testing - -A record of the tests I've done. - -First, some data sets: -@itemize @bullet -@item B: a directory containing 6001 files, one for every length in the - range 0 to 6000 bytes. The files contain random lowercase - letters. 18.7 megabytes. -@item H: my home directory tree. Documents, source code, mail files, - compressed data. H contains B, and also a directory of - files designed as boundary cases for the sorting; mostly very - repetitive, nasty files. 565 megabytes. -@item A: directory tree holding various applications built from source: - @code{egcs}, @code{gcc-2.8.1}, KDE, GTK, Octave, etc. - 2200 megabytes. -@end itemize -The tests conducted are as follows. Each test means compressing -(a copy of) each file in the data set, decompressing it and -comparing it against the original. - -First, a bunch of tests with block sizes and internal buffer -sizes set very small, -to detect any problems with the -blocking and buffering mechanisms. -This required modifying the source code so as to try to -break it. -@enumerate -@item Data set H, with - buffer size of 1 byte, and block size of 23 bytes. -@item Data set B, buffer sizes 1 byte, block size 1 byte. -@item As (2) but small-mode decompression. -@item As (2) with block size 2 bytes. -@item As (2) with block size 3 bytes. -@item As (2) with block size 4 bytes. -@item As (2) with block size 5 bytes. -@item As (2) with block size 6 bytes and small-mode decompression. -@item H with buffer size of 1 byte, but normal block - size (up to 900000 bytes). -@end enumerate -Then some tests with unmodified source code. -@enumerate -@item H, all settings normal. -@item As (1), with small-mode decompress. -@item H, compress with flag @code{-1}. -@item H, compress with flag @code{-s}, decompress with flag @code{-s}. -@item Forwards compatibility: H, @code{bzip2-0.1pl2} compressing, - @code{bzip2-0.9.5} decompressing, all settings normal. -@item Backwards compatibility: H, @code{bzip2-0.9.5} compressing, - @code{bzip2-0.1pl2} decompressing, all settings normal. -@item Bigger tests: A, all settings normal. -@item As (7), using the fallback (Sadakane-like) sorting algorithm. -@item As (8), compress with flag @code{-1}, decompress with flag - @code{-s}. -@item H, using the fallback sorting algorithm. -@item Forwards compatibility: A, @code{bzip2-0.1pl2} compressing, - @code{bzip2-0.9.5} decompressing, all settings normal. -@item Backwards compatibility: A, @code{bzip2-0.9.5} compressing, - @code{bzip2-0.1pl2} decompressing, all settings normal. -@item Misc test: about 400 megabytes of @code{.tar} files with - @code{bzip2} compiled with Checker (a memory access error - detector, like Purify). -@item Misc tests to make sure it builds and runs ok on non-Linux/x86 - platforms. -@end enumerate -These tests were conducted on a 225 MHz IDT WinChip machine, running -Linux 2.0.36. They represent nearly a week of continuous computation. -All tests completed successfully. - - -@section Further reading -@code{bzip2} is not research work, in the sense that it doesn't present -any new ideas. Rather, it's an engineering exercise based on existing -ideas. - -Four documents describe essentially all the ideas behind @code{bzip2}: -@example -Michael Burrows and D. J. Wheeler: - "A block-sorting lossless data compression algorithm" - 10th May 1994. - Digital SRC Research Report 124. - ftp://ftp.digital.com/pub/DEC/SRC/research-reports/SRC-124.ps.gz - If you have trouble finding it, try searching at the - New Zealand Digital Library, http://www.nzdl.org. - -Daniel S. Hirschberg and Debra A. LeLewer - "Efficient Decoding of Prefix Codes" - Communications of the ACM, April 1990, Vol 33, Number 4. - You might be able to get an electronic copy of this - from the ACM Digital Library. - -David J. Wheeler - Program bred3.c and accompanying document bred3.ps. - This contains the idea behind the multi-table Huffman - coding scheme. - ftp://ftp.cl.cam.ac.uk/users/djw3/ - -Jon L. Bentley and Robert Sedgewick - "Fast Algorithms for Sorting and Searching Strings" - Available from Sedgewick's web page, - www.cs.princeton.edu/~rs -@end example -The following paper gives valuable additional insights into the -algorithm, but is not immediately the basis of any code -used in bzip2. -@example -Peter Fenwick: - Block Sorting Text Compression - Proceedings of the 19th Australasian Computer Science Conference, - Melbourne, Australia. Jan 31 - Feb 2, 1996. - ftp://ftp.cs.auckland.ac.nz/pub/peter-f/ACSC96paper.ps -@end example -Kunihiko Sadakane's sorting algorithm, mentioned above, -is available from: -@example -http://naomi.is.s.u-tokyo.ac.jp/~sada/papers/Sada98b.ps.gz -@end example -The Manber-Myers suffix array construction -algorithm is described in a paper -available from: -@example -http://www.cs.arizona.edu/people/gene/PAPERS/suffix.ps -@end example -Finally, the following paper documents some recent investigations -I made into the performance of sorting algorithms: -@example -Julian Seward: - On the Performance of BWT Sorting Algorithms - Proceedings of the IEEE Data Compression Conference 2000 - Snowbird, Utah. 28-30 March 2000. -@end example - - -@contents - -@bye - diff -Nru bzip2-1.0.1/manual_1.html bzip2-1.0.1.new/manual_1.html --- bzip2-1.0.1/manual_1.html Sat Jun 24 20:13:27 2000 +++ bzip2-1.0.1.new/manual_1.html Thu Jan 1 01:00:00 1970 @@ -1,47 +0,0 @@ - - - - -bzip2 and libbzip2 - Introduction - - - - - -

Go to the first, previous, next, last section, table of contents. -

- - -

Introduction

- -

-bzip2 compresses files using the Burrows-Wheeler -block-sorting text compression algorithm, and Huffman coding. -Compression is generally considerably better than that -achieved by more conventional LZ77/LZ78-based compressors, -and approaches the performance of the PPM family of statistical compressors. - -

-

-bzip2 is built on top of libbzip2, a flexible library -for handling compressed data in the bzip2 format. This manual -describes both how to use the program and -how to work with the library interface. Most of the -manual is devoted to this library, not the program, -which is good news if your interest is only in the program. - -

-

-Chapter 2 describes how to use bzip2; this is the only part -you need to read if you just want to know how to operate the program. -Chapter 3 describes the programming interfaces in detail, and -Chapter 4 records some miscellaneous notes which I thought -ought to be recorded somewhere. - -

- -

-

Go to the first, previous, next, last section, table of contents. - - diff -Nru bzip2-1.0.1/manual_2.html bzip2-1.0.1.new/manual_2.html --- bzip2-1.0.1/manual_2.html Sat Jun 24 20:13:27 2000 +++ bzip2-1.0.1.new/manual_2.html Thu Jan 1 01:00:00 1970 @@ -1,484 +0,0 @@ - - - - -bzip2 and libbzip2 - How to use bzip2 - - - - - - -

Go to the first, previous, next, last section, table of contents. -

- - -

How to use bzip2

- -

-This chapter contains a copy of the bzip2 man page, -and nothing else. - -

- -
- - - -

NAME

- -
    -
  • bzip2, bunzip2 - -- a block-sorting file compressor, v1.0 -
  • bzcat - -- decompresses files to stdout -
  • bzip2recover - -- recovers data from damaged bzip2 files -
- - - -

SYNOPSIS

- -
    -
  • bzip2 [ -cdfkqstvzVL123456789 ] [ filenames ... ] - -
  • bunzip2 [ -fkvsVL ] [ filenames ... ] - -
  • bzcat [ -s ] [ filenames ... ] - -
  • bzip2recover filename - -
- - - -

DESCRIPTION

- -

-bzip2 compresses files using the Burrows-Wheeler block sorting -text compression algorithm, and Huffman coding. Compression is -generally considerably better than that achieved by more conventional -LZ77/LZ78-based compressors, and approaches the performance of the PPM -family of statistical compressors. - -

-

-The command-line options are deliberately very similar to those of GNU -gzip, but they are not identical. - -

-

-bzip2 expects a list of file names to accompany the command-line -flags. Each file is replaced by a compressed version of itself, with -the name original_name.bz2. Each compressed file has the same -modification date, permissions, and, when possible, ownership as the -corresponding original, so that these properties can be correctly -restored at decompression time. File name handling is naive in the -sense that there is no mechanism for preserving original file names, -permissions, ownerships or dates in filesystems which lack these -concepts, or have serious file name length restrictions, such as MS-DOS. - -

-

-bzip2 and bunzip2 will by default not overwrite existing -files. If you want this to happen, specify the -f flag. - -

-

-If no file names are specified, bzip2 compresses from standard -input to standard output. In this case, bzip2 will decline to -write compressed output to a terminal, as this would be entirely -incomprehensible and therefore pointless. - -

-

-bunzip2 (or bzip2 -d) decompresses all -specified files. Files which were not created by bzip2 -will be detected and ignored, and a warning issued. -bzip2 attempts to guess the filename for the decompressed file -from that of the compressed file as follows: - -

    -
  • filename.bz2 becomes filename - -
  • filename.bz becomes filename - -
  • filename.tbz2 becomes filename.tar - -
  • filename.tbz becomes filename.tar - -
  • anyothername becomes anyothername.out - -
- -

-If the file does not end in one of the recognised endings, -.bz2, .bz, -.tbz2 or .tbz, bzip2 complains that it cannot -guess the name of the original file, and uses the original name -with .out appended. - -

-

-As with compression, supplying no -filenames causes decompression from standard input to standard output. - -

-

-bunzip2 will correctly decompress a file which is the -concatenation of two or more compressed files. The result is the -concatenation of the corresponding uncompressed files. Integrity -testing (-t) of concatenated compressed files is also supported. - -

-

-You can also compress or decompress files to the standard output by -giving the -c flag. Multiple files may be compressed and -decompressed like this. The resulting outputs are fed sequentially to -stdout. Compression of multiple files in this manner generates a stream -containing multiple compressed file representations. Such a stream -can be decompressed correctly only by bzip2 version 0.9.0 or -later. Earlier versions of bzip2 will stop after decompressing -the first file in the stream. - -

-

-bzcat (or bzip2 -dc) decompresses all specified files to -the standard output. - -

-

-bzip2 will read arguments from the environment variables -BZIP2 and BZIP, in that order, and will process them -before any arguments read from the command line. This gives a -convenient way to supply default arguments. - -

-

-Compression is always performed, even if the compressed file is slightly -larger than the original. Files of less than about one hundred bytes -tend to get larger, since the compression mechanism has a constant -overhead in the region of 50 bytes. Random data (including the output -of most file compressors) is coded at about 8.05 bits per byte, giving -an expansion of around 0.5%. - -

-

-As a self-check for your protection, bzip2 uses 32-bit CRCs to -make sure that the decompressed version of a file is identical to the -original. This guards against corruption of the compressed data, and -against undetected bugs in bzip2 (hopefully very unlikely). The -chances of data corruption going undetected is microscopic, about one -chance in four billion for each file processed. Be aware, though, that -the check occurs upon decompression, so it can only tell you that -something is wrong. It can't help you recover the original uncompressed -data. You can use bzip2recover to try to recover data from -damaged files. - -

-

-Return values: 0 for a normal exit, 1 for environmental problems (file -not found, invalid flags, I/O errors, &c), 2 to indicate a corrupt -compressed file, 3 for an internal consistency error (eg, bug) which -caused bzip2 to panic. - -

- - - -

OPTIONS

-
- -
-c --stdout -
-Compress or decompress to standard output. -
-d --decompress -
-Force decompression. bzip2, bunzip2 and bzcat are -really the same program, and the decision about what actions to take is -done on the basis of which name is used. This flag overrides that -mechanism, and forces bzip2 to decompress. -
-z --compress -
-The complement to -d: forces compression, regardless of the -invokation name. -
-t --test -
-Check integrity of the specified file(s), but don't decompress them. -This really performs a trial decompression and throws away the result. -
-f --force -
-Force overwrite of output files. Normally, bzip2 will not overwrite -existing output files. Also forces bzip2 to break hard links -to files, which it otherwise wouldn't do. -
-k --keep -
-Keep (don't delete) input files during compression -or decompression. -
-s --small -
-Reduce memory usage, for compression, decompression and testing. Files -are decompressed and tested using a modified algorithm which only -requires 2.5 bytes per block byte. This means any file can be -decompressed in 2300k of memory, albeit at about half the normal speed. - -During compression, -s selects a block size of 200k, which limits -memory use to around the same figure, at the expense of your compression -ratio. In short, if your machine is low on memory (8 megabytes or -less), use -s for everything. See MEMORY MANAGEMENT below. -
-q --quiet -
-Suppress non-essential warning messages. Messages pertaining to -I/O errors and other critical events will not be suppressed. -
-v --verbose -
-Verbose mode -- show the compression ratio for each file processed. -Further -v's increase the verbosity level, spewing out lots of -information which is primarily of interest for diagnostic purposes. -
-L --license -V --version -
-Display the software version, license terms and conditions. -
-1 to -9 -
-Set the block size to 100 k, 200 k .. 900 k when compressing. Has no -effect when decompressing. See MEMORY MANAGEMENT below. -
-- -
-Treats all subsequent arguments as file names, even if they start -with a dash. This is so you can handle files with names beginning -with a dash, for example: bzip2 -- -myfilename. -
--repetitive-fast -
-
--repetitive-best -
-These flags are redundant in versions 0.9.5 and above. They provided -some coarse control over the behaviour of the sorting algorithm in -earlier versions, which was sometimes useful. 0.9.5 and above have an -improved algorithm which renders these flags irrelevant. -
- - - -

MEMORY MANAGEMENT

- -

-bzip2 compresses large files in blocks. The block size affects -both the compression ratio achieved, and the amount of memory needed for -compression and decompression. The flags -1 through -9 -specify the block size to be 100,000 bytes through 900,000 bytes (the -default) respectively. At decompression time, the block size used for -compression is read from the header of the compressed file, and -bunzip2 then allocates itself just enough memory to decompress -the file. Since block sizes are stored in compressed files, it follows -that the flags -1 to -9 are irrelevant to and so ignored -during decompression. - -

-

-Compression and decompression requirements, in bytes, can be estimated -as: - -

-     Compression:   400k + ( 8 x block size )
-
-     Decompression: 100k + ( 4 x block size ), or
-                    100k + ( 2.5 x block size )
-
- -

-Larger block sizes give rapidly diminishing marginal returns. Most of -the compression comes from the first two or three hundred k of block -size, a fact worth bearing in mind when using bzip2 on small machines. -It is also important to appreciate that the decompression memory -requirement is set at compression time by the choice of block size. - -

-

-For files compressed with the default 900k block size, bunzip2 -will require about 3700 kbytes to decompress. To support decompression -of any file on a 4 megabyte machine, bunzip2 has an option to -decompress using approximately half this amount of memory, about 2300 -kbytes. Decompression speed is also halved, so you should use this -option only where necessary. The relevant flag is -s. - -

-

-In general, try and use the largest block size memory constraints allow, -since that maximises the compression achieved. Compression and -decompression speed are virtually unaffected by block size. - -

-

-Another significant point applies to files which fit in a single block --- that means most files you'd encounter using a large block size. The -amount of real memory touched is proportional to the size of the file, -since the file is smaller than a block. For example, compressing a file -20,000 bytes long with the flag -9 will cause the compressor to -allocate around 7600k of memory, but only touch 400k + 20000 * 8 = 560 -kbytes of it. Similarly, the decompressor will allocate 3700k but only -touch 100k + 20000 * 4 = 180 kbytes. - -

-

-Here is a table which summarises the maximum memory usage for different -block sizes. Also recorded is the total compressed size for 14 files of -the Calgary Text Compression Corpus totalling 3,141,622 bytes. This -column gives some feel for how compression varies with block size. -These figures tend to understate the advantage of larger block sizes for -larger files, since the Corpus is dominated by smaller files. - -

-          Compress   Decompress   Decompress   Corpus
-   Flag     usage      usage       -s usage     Size
-
-    -1      1200k       500k         350k      914704
-    -2      2000k       900k         600k      877703
-    -3      2800k      1300k         850k      860338
-    -4      3600k      1700k        1100k      846899
-    -5      4400k      2100k        1350k      845160
-    -6      5200k      2500k        1600k      838626
-    -7      6100k      2900k        1850k      834096
-    -8      6800k      3300k        2100k      828642
-    -9      7600k      3700k        2350k      828642
-
- - - -

RECOVERING DATA FROM DAMAGED FILES

- -

-bzip2 compresses files in blocks, usually 900kbytes long. Each -block is handled independently. If a media or transmission error causes -a multi-block .bz2 file to become damaged, it may be possible to -recover data from the undamaged blocks in the file. - -

-

-The compressed representation of each block is delimited by a 48-bit -pattern, which makes it possible to find the block boundaries with -reasonable certainty. Each block also carries its own 32-bit CRC, so -damaged blocks can be distinguished from undamaged ones. - -

-

-bzip2recover is a simple program whose purpose is to search for -blocks in .bz2 files, and write each block out into its own -.bz2 file. You can then use bzip2 -t to test the -integrity of the resulting files, and decompress those which are -undamaged. - -

-

-bzip2recover -takes a single argument, the name of the damaged file, -and writes a number of files rec0001file.bz2, - rec0002file.bz2, etc, containing the extracted blocks. - The output filenames are designed so that the use of - wildcards in subsequent processing -- for example, -bzip2 -dc rec*file.bz2 > recovered_data -- lists the files in - the correct order. - -

-

-bzip2recover should be of most use dealing with large .bz2 - files, as these will contain many blocks. It is clearly - futile to use it on damaged single-block files, since a - damaged block cannot be recovered. If you wish to minimise -any potential data loss through media or transmission errors, -you might consider compressing with a smaller - block size. - -

- - - -

PERFORMANCE NOTES

- -

-The sorting phase of compression gathers together similar strings in the -file. Because of this, files containing very long runs of repeated -symbols, like "aabaabaabaab ..." (repeated several hundred times) may -compress more slowly than normal. Versions 0.9.5 and above fare much -better than previous versions in this respect. The ratio between -worst-case and average-case compression time is in the region of 10:1. -For previous versions, this figure was more like 100:1. You can use the --vvvv option to monitor progress in great detail, if you want. - -

-

-Decompression speed is unaffected by these phenomena. - -

-

-bzip2 usually allocates several megabytes of memory to operate -in, and then charges all over it in a fairly random fashion. This means -that performance, both for compressing and decompressing, is largely -determined by the speed at which your machine can service cache misses. -Because of this, small changes to the code to reduce the miss rate have -been observed to give disproportionately large performance improvements. -I imagine bzip2 will perform best on machines with very large -caches. - -

- - - -

CAVEATS

- -

-I/O error messages are not as helpful as they could be. bzip2 -tries hard to detect I/O errors and exit cleanly, but the details of -what the problem is sometimes seem rather misleading. - -

-

-This manual page pertains to version 1.0 of bzip2. Compressed -data created by this version is entirely forwards and backwards -compatible with the previous public releases, versions 0.1pl2, 0.9.0 and -0.9.5, but with the following exception: 0.9.0 and above can correctly -decompress multiple concatenated compressed files. 0.1pl2 cannot do -this; it will stop after decompressing just the first file in the -stream. - -

-

-bzip2recover uses 32-bit integers to represent bit positions in -compressed files, so it cannot handle compressed files more than 512 -megabytes long. This could easily be fixed. - -

- - - -

AUTHOR

-

-Julian Seward, jseward@acm.org. - -

-

-The ideas embodied in bzip2 are due to (at least) the following -people: Michael Burrows and David Wheeler (for the block sorting -transformation), David Wheeler (again, for the Huffman coder), Peter -Fenwick (for the structured coding model in the original bzip, -and many refinements), and Alistair Moffat, Radford Neal and Ian Witten -(for the arithmetic coder in the original bzip). I am much -indebted for their help, support and advice. See the manual in the -source distribution for pointers to sources of documentation. Christian -von Roques encouraged me to look for faster sorting algorithms, so as to -speed up compression. Bela Lubkin encouraged me to improve the -worst-case compression performance. Many people sent patches, helped -with portability problems, lent machines, gave advice and were generally -helpful. - -

-
- -

-

Go to the first, previous, next, last section, table of contents. - - diff -Nru bzip2-1.0.1/manual_3.html bzip2-1.0.1.new/manual_3.html --- bzip2-1.0.1/manual_3.html Sat Jun 24 20:13:27 2000 +++ bzip2-1.0.1.new/manual_3.html Thu Jan 1 01:00:00 1970 @@ -1,1773 +0,0 @@ - - - - -bzip2 and libbzip2 - Programming with libbzip2 - - - - - - -

Go to the first, previous, next, last section, table of contents. -

- - -

Programming with libbzip2

- -

-This chapter describes the programming interface to libbzip2. - -

-

-For general background information, particularly about memory -use and performance aspects, you'd be well advised to read Chapter 2 -as well. - -

- - -

Top-level structure

- -

-libbzip2 is a flexible library for compressing and decompressing -data in the bzip2 data format. Although packaged as a single -entity, it helps to regard the library as three separate parts: the low -level interface, and the high level interface, and some utility -functions. - -

-

-The structure of libbzip2's interfaces is similar to -that of Jean-loup Gailly's and Mark Adler's excellent zlib -library. - -

-

-All externally visible symbols have names beginning BZ2_. -This is new in version 1.0. The intention is to minimise pollution -of the namespaces of library clients. - -

- - -

Low-level summary

- -

-This interface provides services for compressing and decompressing -data in memory. There's no provision for dealing with files, streams -or any other I/O mechanisms, just straight memory-to-memory work. -In fact, this part of the library can be compiled without inclusion -of stdio.h, which may be helpful for embedded applications. - -

-

-The low-level part of the library has no global variables and -is therefore thread-safe. - -

-

-Six routines make up the low level interface: -BZ2_bzCompressInit, BZ2_bzCompress, and
BZ2_bzCompressEnd -for compression, -and a corresponding trio BZ2_bzDecompressInit,
BZ2_bzDecompress -and BZ2_bzDecompressEnd for decompression. -The *Init functions allocate -memory for compression/decompression and do other -initialisations, whilst the *End functions close down operations -and release memory. - -

-

-The real work is done by BZ2_bzCompress and BZ2_bzDecompress. -These compress and decompress data from a user-supplied input buffer -to a user-supplied output buffer. These buffers can be any size; -arbitrary quantities of data are handled by making repeated calls -to these functions. This is a flexible mechanism allowing a -consumer-pull style of activity, or producer-push, or a mixture of -both. - -

- - - -

High-level summary

- -

-This interface provides some handy wrappers around the low-level -interface to facilitate reading and writing bzip2 format -files (.bz2 files). The routines provide hooks to facilitate -reading files in which the bzip2 data stream is embedded -within some larger-scale file structure, or where there are -multiple bzip2 data streams concatenated end-to-end. - -

-

-For reading files, BZ2_bzReadOpen, BZ2_bzRead, -BZ2_bzReadClose and
BZ2_bzReadGetUnused are supplied. For -writing files, BZ2_bzWriteOpen, BZ2_bzWrite and -BZ2_bzWriteFinish are available. - -

-

-As with the low-level library, no global variables are used -so the library is per se thread-safe. However, if I/O errors -occur whilst reading or writing the underlying compressed files, -you may have to consult errno to determine the cause of -the error. In that case, you'd need a C library which correctly -supports errno in a multithreaded environment. - -

-

-To make the library a little simpler and more portable, -BZ2_bzReadOpen and BZ2_bzWriteOpen require you to pass them file -handles (FILE*s) which have previously been opened for reading or -writing respectively. That avoids portability problems associated with -file operations and file attributes, whilst not being much of an -imposition on the programmer. - -

- - - -

Utility functions summary

-

-For very simple needs, BZ2_bzBuffToBuffCompress and -BZ2_bzBuffToBuffDecompress are provided. These compress -data in memory from one buffer to another buffer in a single -function call. You should assess whether these functions -fulfill your memory-to-memory compression/decompression -requirements before investing effort in understanding the more -general but more complex low-level interface. - -

-

-Yoshioka Tsuneo (QWF00133@niftyserve.or.jp / -tsuneo-y@is.aist-nara.ac.jp) has contributed some functions to -give better zlib compatibility. These functions are -BZ2_bzopen, BZ2_bzread, BZ2_bzwrite, BZ2_bzflush, -BZ2_bzclose, -BZ2_bzerror and BZ2_bzlibVersion. You may find these functions -more convenient for simple file reading and writing, than those in the -high-level interface. These functions are not (yet) officially part of -the library, and are minimally documented here. If they break, you -get to keep all the pieces. I hope to document them properly when time -permits. - -

-

-Yoshioka also contributed modifications to allow the library to be -built as a Windows DLL. - -

- - - -

Error handling

- -

-The library is designed to recover cleanly in all situations, including -the worst-case situation of decompressing random data. I'm not -100% sure that it can always do this, so you might want to add -a signal handler to catch segmentation violations during decompression -if you are feeling especially paranoid. I would be interested in -hearing more about the robustness of the library to corrupted -compressed data. - -

-

-Version 1.0 is much more robust in this respect than -0.9.0 or 0.9.5. Investigations with Checker (a tool for -detecting problems with memory management, similar to Purify) -indicate that, at least for the few files I tested, all single-bit -errors in the decompressed data are caught properly, with no -segmentation faults, no reads of uninitialised data and no -out of range reads or writes. So it's certainly much improved, -although I wouldn't claim it to be totally bombproof. - -

-

-The file bzlib.h contains all definitions needed to use -the library. In particular, you should definitely not include -bzlib_private.h. - -

-

-In bzlib.h, the various return values are defined. The following -list is not intended as an exhaustive description of the circumstances -in which a given value may be returned -- those descriptions are given -later. Rather, it is intended to convey the rough meaning of each -return value. The first five actions are normal and not intended to -denote an error situation. -

- -
BZ_OK -
-The requested action was completed successfully. -
BZ_RUN_OK -
-
BZ_FLUSH_OK -
-
BZ_FINISH_OK -
-In BZ2_bzCompress, the requested flush/finish/nothing-special action -was completed successfully. -
BZ_STREAM_END -
-Compression of data was completed, or the logical stream end was -detected during decompression. -
- -

-The following return values indicate an error of some kind. -

- -
BZ_CONFIG_ERROR -
-Indicates that the library has been improperly compiled on your -platform -- a major configuration error. Specifically, it means -that sizeof(char), sizeof(short) and sizeof(int) -are not 1, 2 and 4 respectively, as they should be. Note that the -library should still work properly on 64-bit platforms which follow -the LP64 programming model -- that is, where sizeof(long) -and sizeof(void*) are 8. Under LP64, sizeof(int) is -still 4, so libbzip2, which doesn't use the long type, -is OK. -
BZ_SEQUENCE_ERROR -
-When using the library, it is important to call the functions in the -correct sequence and with data structures (buffers etc) in the correct -states. libbzip2 checks as much as it can to ensure this is -happening, and returns BZ_SEQUENCE_ERROR if not. Code which -complies precisely with the function semantics, as detailed below, -should never receive this value; such an event denotes buggy code -which you should investigate. -
BZ_PARAM_ERROR -
-Returned when a parameter to a function call is out of range -or otherwise manifestly incorrect. As with BZ_SEQUENCE_ERROR, -this denotes a bug in the client code. The distinction between -BZ_PARAM_ERROR and BZ_SEQUENCE_ERROR is a bit hazy, but still worth -making. -
BZ_MEM_ERROR -
-Returned when a request to allocate memory failed. Note that the -quantity of memory needed to decompress a stream cannot be determined -until the stream's header has been read. So BZ2_bzDecompress and -BZ2_bzRead may return BZ_MEM_ERROR even though some of -the compressed data has been read. The same is not true for -compression; once BZ2_bzCompressInit or BZ2_bzWriteOpen have -successfully completed, BZ_MEM_ERROR cannot occur. -
BZ_DATA_ERROR -
-Returned when a data integrity error is detected during decompression. -Most importantly, this means when stored and computed CRCs for the -data do not match. This value is also returned upon detection of any -other anomaly in the compressed data. -
BZ_DATA_ERROR_MAGIC -
-As a special case of BZ_DATA_ERROR, it is sometimes useful to -know when the compressed stream does not start with the correct -magic bytes ('B' 'Z' 'h'). -
BZ_IO_ERROR -
-Returned by BZ2_bzRead and BZ2_bzWrite when there is an error -reading or writing in the compressed file, and by BZ2_bzReadOpen -and BZ2_bzWriteOpen for attempts to use a file for which the -error indicator (viz, ferror(f)) is set. -On receipt of BZ_IO_ERROR, the caller should consult -errno and/or perror to acquire operating-system -specific information about the problem. -
BZ_UNEXPECTED_EOF -
-Returned by BZ2_bzRead when the compressed file finishes -before the logical end of stream is detected. -
BZ_OUTBUFF_FULL -
-Returned by BZ2_bzBuffToBuffCompress and -BZ2_bzBuffToBuffDecompress to indicate that the output data -will not fit into the output buffer provided. -
- - - -

Low-level interface

- - - -

BZ2_bzCompressInit

- -
-typedef 
-   struct {
-      char *next_in;
-      unsigned int avail_in;
-      unsigned int total_in_lo32;
-      unsigned int total_in_hi32;
-
-      char *next_out;
-      unsigned int avail_out;
-      unsigned int total_out_lo32;
-      unsigned int total_out_hi32;
-
-      void *state;
-
-      void *(*bzalloc)(void *,int,int);
-      void (*bzfree)(void *,void *);
-      void *opaque;
-   } 
-   bz_stream;
-
-int BZ2_bzCompressInit ( bz_stream *strm, 
-                         int blockSize100k, 
-                         int verbosity,
-                         int workFactor );
-
-
- -

-Prepares for compression. The bz_stream structure -holds all data pertaining to the compression activity. -A bz_stream structure should be allocated and initialised -prior to the call. -The fields of bz_stream -comprise the entirety of the user-visible data. state -is a pointer to the private data structures required for compression. - -

-

-Custom memory allocators are supported, via fields bzalloc, -bzfree, -and opaque. The value -opaque is passed to as the first argument to -all calls to bzalloc and bzfree, but is -otherwise ignored by the library. -The call bzalloc ( opaque, n, m ) is expected to return a -pointer p to -n * m bytes of memory, and bzfree ( opaque, p ) -should free -that memory. - -

-

-If you don't want to use a custom memory allocator, set bzalloc, -bzfree and -opaque to NULL, -and the library will then use the standard malloc/free -routines. - -

-

-Before calling BZ2_bzCompressInit, fields bzalloc, -bzfree and opaque should -be filled appropriately, as just described. Upon return, the internal -state will have been allocated and initialised, and total_in_lo32, -total_in_hi32, total_out_lo32 and -total_out_hi32 will have been set to zero. -These four fields are used by the library -to inform the caller of the total amount of data passed into and out of -the library, respectively. You should not try to change them. -As of version 1.0, 64-bit counts are maintained, even on 32-bit -platforms, using the _hi32 fields to store the upper 32 bits -of the count. So, for example, the total amount of data in -is (total_in_hi32 << 32) + total_in_lo32. - -

-

-Parameter blockSize100k specifies the block size to be used for -compression. It should be a value between 1 and 9 inclusive, and the -actual block size used is 100000 x this figure. 9 gives the best -compression but takes most memory. - -

-

-Parameter verbosity should be set to a number between 0 and 4 -inclusive. 0 is silent, and greater numbers give increasingly verbose -monitoring/debugging output. If the library has been compiled with --DBZ_NO_STDIO, no such output will appear for any verbosity -setting. - -

-

-Parameter workFactor controls how the compression phase behaves -when presented with worst case, highly repetitive, input data. If -compression runs into difficulties caused by repetitive data, the -library switches from the standard sorting algorithm to a fallback -algorithm. The fallback is slower than the standard algorithm by -perhaps a factor of three, but always behaves reasonably, no matter how -bad the input. - -

-

-Lower values of workFactor reduce the amount of effort the -standard algorithm will expend before resorting to the fallback. You -should set this parameter carefully; too low, and many inputs will be -handled by the fallback algorithm and so compress rather slowly, too -high, and your average-to-worst case compression times can become very -large. The default value of 30 gives reasonable behaviour over a wide -range of circumstances. - -

-

-Allowable values range from 0 to 250 inclusive. 0 is a special case, -equivalent to using the default value of 30. - -

-

-Note that the compressed output generated is the same regardless of -whether or not the fallback algorithm is used. - -

-

-Be aware also that this parameter may disappear entirely in future -versions of the library. In principle it should be possible to devise a -good way to automatically choose which algorithm to use. Such a -mechanism would render the parameter obsolete. - -

-

-Possible return values: - -

-      BZ_CONFIG_ERROR
-         if the library has been mis-compiled
-      BZ_PARAM_ERROR 
-         if strm is NULL 
-         or blockSize < 1 or blockSize > 9
-         or verbosity < 0 or verbosity > 4
-         or workFactor < 0 or workFactor > 250
-      BZ_MEM_ERROR 
-         if not enough memory is available
-      BZ_OK 
-         otherwise
-
- -

-Allowable next actions: - -

-      BZ2_bzCompress 
-         if BZ_OK is returned
-      no specific action needed in case of error
-
- - - -

BZ2_bzCompress

- -
-   int BZ2_bzCompress ( bz_stream *strm, int action );
-
- -

-Provides more input and/or output buffer space for the library. The -caller maintains input and output buffers, and calls BZ2_bzCompress to -transfer data between them. - -

-

-Before each call to BZ2_bzCompress, next_in should point at -the data to be compressed, and avail_in should indicate how many -bytes the library may read. BZ2_bzCompress updates next_in, -avail_in and total_in to reflect the number of bytes it -has read. - -

-

-Similarly, next_out should point to a buffer in which the -compressed data is to be placed, with avail_out indicating how -much output space is available. BZ2_bzCompress updates -next_out, avail_out and total_out to reflect the -number of bytes output. - -

-

-You may provide and remove as little or as much data as you like on each -call of BZ2_bzCompress. In the limit, it is acceptable to supply and -remove data one byte at a time, although this would be terribly -inefficient. You should always ensure that at least one byte of output -space is available at each call. - -

-

-A second purpose of BZ2_bzCompress is to request a change of mode of the -compressed stream. - -

-

-Conceptually, a compressed stream can be in one of four states: IDLE, -RUNNING, FLUSHING and FINISHING. Before initialisation -(BZ2_bzCompressInit) and after termination (BZ2_bzCompressEnd), a -stream is regarded as IDLE. - -

-

-Upon initialisation (BZ2_bzCompressInit), the stream is placed in the -RUNNING state. Subsequent calls to BZ2_bzCompress should pass -BZ_RUN as the requested action; other actions are illegal and -will result in BZ_SEQUENCE_ERROR. - -

-

-At some point, the calling program will have provided all the input data -it wants to. It will then want to finish up -- in effect, asking the -library to process any data it might have buffered internally. In this -state, BZ2_bzCompress will no longer attempt to read data from -next_in, but it will want to write data to next_out. -Because the output buffer supplied by the user can be arbitrarily small, -the finishing-up operation cannot necessarily be done with a single call -of BZ2_bzCompress. - -

-

-Instead, the calling program passes BZ_FINISH as an action to -BZ2_bzCompress. This changes the stream's state to FINISHING. Any -remaining input (ie, next_in[0 .. avail_in-1]) is compressed and -transferred to the output buffer. To do this, BZ2_bzCompress must be -called repeatedly until all the output has been consumed. At that -point, BZ2_bzCompress returns BZ_STREAM_END, and the stream's -state is set back to IDLE. BZ2_bzCompressEnd should then be -called. - -

-

-Just to make sure the calling program does not cheat, the library makes -a note of avail_in at the time of the first call to -BZ2_bzCompress which has BZ_FINISH as an action (ie, at the -time the program has announced its intention to not supply any more -input). By comparing this value with that of avail_in over -subsequent calls to BZ2_bzCompress, the library can detect any -attempts to slip in more data to compress. Any calls for which this is -detected will return BZ_SEQUENCE_ERROR. This indicates a -programming mistake which should be corrected. - -

-

-Instead of asking to finish, the calling program may ask -BZ2_bzCompress to take all the remaining input, compress it and -terminate the current (Burrows-Wheeler) compression block. This could -be useful for error control purposes. The mechanism is analogous to -that for finishing: call BZ2_bzCompress with an action of -BZ_FLUSH, remove output data, and persist with the -BZ_FLUSH action until the value BZ_RUN is returned. As -with finishing, BZ2_bzCompress detects any attempt to provide more -input data once the flush has begun. - -

-

-Once the flush is complete, the stream returns to the normal RUNNING -state. - -

-

-This all sounds pretty complex, but isn't really. Here's a table -which shows which actions are allowable in each state, what action -will be taken, what the next state is, and what the non-error return -values are. Note that you can't explicitly ask what state the -stream is in, but nor do you need to -- it can be inferred from the -values returned by BZ2_bzCompress. - -

-IDLE/any           
-      Illegal.  IDLE state only exists after BZ2_bzCompressEnd or
-      before BZ2_bzCompressInit.
-      Return value = BZ_SEQUENCE_ERROR
-
-RUNNING/BZ_RUN     
-      Compress from next_in to next_out as much as possible.
-      Next state = RUNNING
-      Return value = BZ_RUN_OK
-
-RUNNING/BZ_FLUSH   
-      Remember current value of next_in.  Compress from next_in
-      to next_out as much as possible, but do not accept any more input.  
-      Next state = FLUSHING
-      Return value = BZ_FLUSH_OK
-
-RUNNING/BZ_FINISH  
-      Remember current value of next_in.  Compress from next_in
-      to next_out as much as possible, but do not accept any more input.
-      Next state = FINISHING
-      Return value = BZ_FINISH_OK
-
-FLUSHING/BZ_FLUSH  
-      Compress from next_in to next_out as much as possible, 
-      but do not accept any more input.  
-      If all the existing input has been used up and all compressed
-      output has been removed
-         Next state = RUNNING; Return value = BZ_RUN_OK
-      else
-         Next state = FLUSHING; Return value = BZ_FLUSH_OK
-
-FLUSHING/other     
-      Illegal.
-      Return value = BZ_SEQUENCE_ERROR
-
-FINISHING/BZ_FINISH  
-      Compress from next_in to next_out as much as possible,
-      but to not accept any more input.  
-      If all the existing input has been used up and all compressed
-      output has been removed
-         Next state = IDLE; Return value = BZ_STREAM_END
-      else
-         Next state = FINISHING; Return value = BZ_FINISHING
-
-FINISHING/other
-      Illegal.
-      Return value = BZ_SEQUENCE_ERROR
-
- -

-That still looks complicated? Well, fair enough. The usual sequence -of calls for compressing a load of data is: - -

    -
  • Get started with BZ2_bzCompressInit. - -
  • Shovel data in and shlurp out its compressed form using zero or more - -calls of BZ2_bzCompress with action = BZ_RUN. -
  • Finish up. - -Repeatedly call BZ2_bzCompress with action = BZ_FINISH, -copying out the compressed output, until BZ_STREAM_END is returned. -
  • Close up and go home. Call BZ2_bzCompressEnd. - -
- -

-If the data you want to compress fits into your input buffer all -at once, you can skip the calls of BZ2_bzCompress ( ..., BZ_RUN ) and -just do the BZ2_bzCompress ( ..., BZ_FINISH ) calls. - -

-

-All required memory is allocated by BZ2_bzCompressInit. The -compression library can accept any data at all (obviously). So you -shouldn't get any error return values from the BZ2_bzCompress calls. -If you do, they will be BZ_SEQUENCE_ERROR, and indicate a bug in -your programming. - -

-

-Trivial other possible return values: - -

-      BZ_PARAM_ERROR   
-         if strm is NULL, or strm->s is NULL
-
- - - -

BZ2_bzCompressEnd

- -
-int BZ2_bzCompressEnd ( bz_stream *strm );
-
- -

-Releases all memory associated with a compression stream. - -

-

-Possible return values: - -

-   BZ_PARAM_ERROR    if strm is NULL or strm->s is NULL
-   BZ_OK    otherwise
-
- - - -

BZ2_bzDecompressInit

- -
-int BZ2_bzDecompressInit ( bz_stream *strm, int verbosity, int small );
-
- -

-Prepares for decompression. As with BZ2_bzCompressInit, a -bz_stream record should be allocated and initialised before the -call. Fields bzalloc, bzfree and opaque should be -set if a custom memory allocator is required, or made NULL for -the normal malloc/free routines. Upon return, the internal -state will have been initialised, and total_in and -total_out will be zero. - -

-

-For the meaning of parameter verbosity, see BZ2_bzCompressInit. - -

-

-If small is nonzero, the library will use an alternative -decompression algorithm which uses less memory but at the cost of -decompressing more slowly (roughly speaking, half the speed, but the -maximum memory requirement drops to around 2300k). See Chapter 2 for -more information on memory management. - -

-

-Note that the amount of memory needed to decompress -a stream cannot be determined until the stream's header has been read, -so even if BZ2_bzDecompressInit succeeds, a subsequent -BZ2_bzDecompress could fail with BZ_MEM_ERROR. - -

-

-Possible return values: - -

-      BZ_CONFIG_ERROR
-         if the library has been mis-compiled
-      BZ_PARAM_ERROR
-         if (small != 0 && small != 1)
-         or (verbosity < 0 || verbosity > 4)
-      BZ_MEM_ERROR
-         if insufficient memory is available
-
- -

-Allowable next actions: - -

-      BZ2_bzDecompress
-         if BZ_OK was returned
-      no specific action required in case of error
-
- -

- - -

- - -

BZ2_bzDecompress

- -
-int BZ2_bzDecompress ( bz_stream *strm );
-
- -

-Provides more input and/out output buffer space for the library. The -caller maintains input and output buffers, and uses BZ2_bzDecompress -to transfer data between them. - -

-

-Before each call to BZ2_bzDecompress, next_in -should point at the compressed data, -and avail_in should indicate how many bytes the library -may read. BZ2_bzDecompress updates next_in, avail_in -and total_in -to reflect the number of bytes it has read. - -

-

-Similarly, next_out should point to a buffer in which the uncompressed -output is to be placed, with avail_out indicating how much output space -is available. BZ2_bzCompress updates next_out, -avail_out and total_out to reflect -the number of bytes output. - -

-

-You may provide and remove as little or as much data as you like on -each call of BZ2_bzDecompress. -In the limit, it is acceptable to -supply and remove data one byte at a time, although this would be -terribly inefficient. You should always ensure that at least one -byte of output space is available at each call. - -

-

-Use of BZ2_bzDecompress is simpler than BZ2_bzCompress. - -

-

-You should provide input and remove output as described above, and -repeatedly call BZ2_bzDecompress until BZ_STREAM_END is -returned. Appearance of BZ_STREAM_END denotes that -BZ2_bzDecompress has detected the logical end of the compressed -stream. BZ2_bzDecompress will not produce BZ_STREAM_END until -all output data has been placed into the output buffer, so once -BZ_STREAM_END appears, you are guaranteed to have available all -the decompressed output, and BZ2_bzDecompressEnd can safely be -called. - -

-

-If case of an error return value, you should call BZ2_bzDecompressEnd -to clean up and release memory. - -

-

-Possible return values: - -

-      BZ_PARAM_ERROR
-         if strm is NULL or strm->s is NULL
-         or strm->avail_out < 1
-      BZ_DATA_ERROR
-         if a data integrity error is detected in the compressed stream
-      BZ_DATA_ERROR_MAGIC
-         if the compressed stream doesn't begin with the right magic bytes
-      BZ_MEM_ERROR
-         if there wasn't enough memory available
-      BZ_STREAM_END
-         if the logical end of the data stream was detected and all
-         output in has been consumed, eg s->avail_out > 0
-      BZ_OK
-         otherwise
-
- -

-Allowable next actions: - -

-      BZ2_bzDecompress
-         if BZ_OK was returned
-      BZ2_bzDecompressEnd
-         otherwise
-
- - - -

BZ2_bzDecompressEnd

- -
-int BZ2_bzDecompressEnd ( bz_stream *strm );
-
- -

-Releases all memory associated with a decompression stream. - -

-

-Possible return values: - -

-      BZ_PARAM_ERROR
-         if strm is NULL or strm->s is NULL
-      BZ_OK
-         otherwise
-
- -

-Allowable next actions: - -

-      None.
-
- - - -

High-level interface

- -

-This interface provides functions for reading and writing -bzip2 format files. First, some general points. - -

- -
    -
  • All of the functions take an int* first argument, - - bzerror. - After each call, bzerror should be consulted first to determine - the outcome of the call. If bzerror is BZ_OK, - the call completed - successfully, and only then should the return value of the function - (if any) be consulted. If bzerror is BZ_IO_ERROR, - there was an error - reading/writing the underlying compressed file, and you should - then consult errno/perror to determine the - cause of the difficulty. - bzerror may also be set to various other values; precise details are - given on a per-function basis below. -
  • If bzerror indicates an error - - (ie, anything except BZ_OK and BZ_STREAM_END), - you should immediately call BZ2_bzReadClose (or BZ2_bzWriteClose, - depending on whether you are attempting to read or to write) - to free up all resources associated - with the stream. Once an error has been indicated, behaviour of all calls - except BZ2_bzReadClose (BZ2_bzWriteClose) is undefined. - The implication is that (1) bzerror should - be checked after each call, and (2) if bzerror indicates an error, - BZ2_bzReadClose (BZ2_bzWriteClose) should then be called to clean up. -
  • The FILE* arguments passed to - - BZ2_bzReadOpen/BZ2_bzWriteOpen - should be set to binary mode. - Most Unix systems will do this by default, but other platforms, - including Windows and Mac, will not. If you omit this, you may - encounter problems when moving code to new platforms. -
  • Memory allocation requests are handled by - - malloc/free. - At present - there is no facility for user-defined memory allocators in the file I/O - functions (could easily be added, though). -
- - - -

BZ2_bzReadOpen

- -
-   typedef void BZFILE;
-
-   BZFILE *BZ2_bzReadOpen ( int *bzerror, FILE *f, 
-                            int small, int verbosity,
-                            void *unused, int nUnused );
-
- -

-Prepare to read compressed data from file handle f. f -should refer to a file which has been opened for reading, and for which -the error indicator (ferror(f))is not set. If small is 1, -the library will try to decompress using less memory, at the expense of -speed. - -

-

-For reasons explained below, BZ2_bzRead will decompress the -nUnused bytes starting at unused, before starting to read -from the file f. At most BZ_MAX_UNUSED bytes may be -supplied like this. If this facility is not required, you should pass -NULL and 0 for unused and nUnused -respectively. - -

-

-For the meaning of parameters small and verbosity, -see BZ2_bzDecompressInit. - -

-

-The amount of memory needed to decompress a file cannot be determined -until the file's header has been read. So it is possible that -BZ2_bzReadOpen returns BZ_OK but a subsequent call of -BZ2_bzRead will return BZ_MEM_ERROR. - -

-

-Possible assignments to bzerror: - -

-      BZ_CONFIG_ERROR
-         if the library has been mis-compiled
-      BZ_PARAM_ERROR
-         if f is NULL 
-         or small is neither 0 nor 1                 
-         or (unused == NULL && nUnused != 0)
-         or (unused != NULL && !(0 <= nUnused <= BZ_MAX_UNUSED))
-      BZ_IO_ERROR    
-         if ferror(f) is nonzero
-      BZ_MEM_ERROR   
-         if insufficient memory is available
-      BZ_OK
-         otherwise.
-
- -

-Possible return values: - -

-      Pointer to an abstract BZFILE        
-         if bzerror is BZ_OK   
-      NULL
-         otherwise
-
- -

-Allowable next actions: - -

-      BZ2_bzRead
-         if bzerror is BZ_OK   
-      BZ2_bzClose 
-         otherwise
-
- - - -

BZ2_bzRead

- -
-   int BZ2_bzRead ( int *bzerror, BZFILE *b, void *buf, int len );
-
- -

-Reads up to len (uncompressed) bytes from the compressed file -b into -the buffer buf. If the read was successful, -bzerror is set to BZ_OK -and the number of bytes read is returned. If the logical end-of-stream -was detected, bzerror will be set to BZ_STREAM_END, -and the number -of bytes read is returned. All other bzerror values denote an error. - -

-

-BZ2_bzRead will supply len bytes, -unless the logical stream end is detected -or an error occurs. Because of this, it is possible to detect the -stream end by observing when the number of bytes returned is -less than the number -requested. Nevertheless, this is regarded as inadvisable; you should -instead check bzerror after every call and watch out for -BZ_STREAM_END. - -

-

-Internally, BZ2_bzRead copies data from the compressed file in chunks -of size BZ_MAX_UNUSED bytes -before decompressing it. If the file contains more bytes than strictly -needed to reach the logical end-of-stream, BZ2_bzRead will almost certainly -read some of the trailing data before signalling BZ_SEQUENCE_END. -To collect the read but unused data once BZ_SEQUENCE_END has -appeared, call BZ2_bzReadGetUnused immediately before BZ2_bzReadClose. - -

-

-Possible assignments to bzerror: - -

-      BZ_PARAM_ERROR
-         if b is NULL or buf is NULL or len < 0
-      BZ_SEQUENCE_ERROR 
-         if b was opened with BZ2_bzWriteOpen
-      BZ_IO_ERROR 
-         if there is an error reading from the compressed file
-      BZ_UNEXPECTED_EOF 
-         if the compressed file ended before the logical end-of-stream was detected
-      BZ_DATA_ERROR 
-         if a data integrity error was detected in the compressed stream
-      BZ_DATA_ERROR_MAGIC
-         if the stream does not begin with the requisite header bytes (ie, is not 
-         a bzip2 data file).  This is really a special case of BZ_DATA_ERROR.
-      BZ_MEM_ERROR 
-         if insufficient memory was available
-      BZ_STREAM_END 
-         if the logical end of stream was detected.
-      BZ_OK
-         otherwise.
-
- -

-Possible return values: - -

-      number of bytes read
-         if bzerror is BZ_OK or BZ_STREAM_END
-      undefined
-         otherwise
-
- -

-Allowable next actions: - -

-      collect data from buf, then BZ2_bzRead or BZ2_bzReadClose
-         if bzerror is BZ_OK 
-      collect data from buf, then BZ2_bzReadClose or BZ2_bzReadGetUnused 
-         if bzerror is BZ_SEQUENCE_END   
-      BZ2_bzReadClose 
-         otherwise
-
- - - -

BZ2_bzReadGetUnused

- -
-   void BZ2_bzReadGetUnused ( int* bzerror, BZFILE *b, 
-                              void** unused, int* nUnused );
-
- -

-Returns data which was read from the compressed file but was not needed -to get to the logical end-of-stream. *unused is set to the address -of the data, and *nUnused to the number of bytes. *nUnused will -be set to a value between 0 and BZ_MAX_UNUSED inclusive. - -

-

-This function may only be called once BZ2_bzRead has signalled -BZ_STREAM_END but before BZ2_bzReadClose. - -

-

-Possible assignments to bzerror: - -

-      BZ_PARAM_ERROR 
-         if b is NULL 
-         or unused is NULL or nUnused is NULL
-      BZ_SEQUENCE_ERROR 
-         if BZ_STREAM_END has not been signalled
-         or if b was opened with BZ2_bzWriteOpen
-     BZ_OK
-         otherwise
-
- -

-Allowable next actions: - -

-      BZ2_bzReadClose
-
- - - -

BZ2_bzReadClose

- -
-   void BZ2_bzReadClose ( int *bzerror, BZFILE *b );
-
- -

-Releases all memory pertaining to the compressed file b. -BZ2_bzReadClose does not call fclose on the underlying file -handle, so you should do that yourself if appropriate. -BZ2_bzReadClose should be called to clean up after all error -situations. - -

-

-Possible assignments to bzerror: - -

-      BZ_SEQUENCE_ERROR 
-         if b was opened with BZ2_bzOpenWrite 
-      BZ_OK 
-         otherwise
-
- -

-Allowable next actions: - -

-      none
-
- - - -

BZ2_bzWriteOpen

- -
-   BZFILE *BZ2_bzWriteOpen ( int *bzerror, FILE *f, 
-                             int blockSize100k, int verbosity,
-                             int workFactor );
-
- -

-Prepare to write compressed data to file handle f. -f should refer to -a file which has been opened for writing, and for which the error -indicator (ferror(f))is not set. - -

-

-For the meaning of parameters blockSize100k, -verbosity and workFactor, see -
BZ2_bzCompressInit. - -

-

-All required memory is allocated at this stage, so if the call -completes successfully, BZ_MEM_ERROR cannot be signalled by a -subsequent call to BZ2_bzWrite. - -

-

-Possible assignments to bzerror: - -

-      BZ_CONFIG_ERROR
-         if the library has been mis-compiled
-      BZ_PARAM_ERROR 
-         if f is NULL 
-         or blockSize100k < 1 or blockSize100k > 9
-      BZ_IO_ERROR 
-         if ferror(f) is nonzero
-      BZ_MEM_ERROR 
-         if insufficient memory is available
-      BZ_OK 
-         otherwise
-
- -

-Possible return values: - -

-      Pointer to an abstract BZFILE  
-         if bzerror is BZ_OK   
-      NULL 
-         otherwise
-
- -

-Allowable next actions: - -

-      BZ2_bzWrite 
-         if bzerror is BZ_OK 
-         (you could go directly to BZ2_bzWriteClose, but this would be pretty pointless)
-      BZ2_bzWriteClose 
-         otherwise
-
- - - -

BZ2_bzWrite

- -
-   void BZ2_bzWrite ( int *bzerror, BZFILE *b, void *buf, int len );
-
- -

-Absorbs len bytes from the buffer buf, eventually to be -compressed and written to the file. - -

-

-Possible assignments to bzerror: - -

-      BZ_PARAM_ERROR 
-         if b is NULL or buf is NULL or len < 0
-      BZ_SEQUENCE_ERROR 
-         if b was opened with BZ2_bzReadOpen
-      BZ_IO_ERROR 
-         if there is an error writing the compressed file.
-      BZ_OK 
-         otherwise
-
- - - -

BZ2_bzWriteClose

- -
-   void BZ2_bzWriteClose ( int *bzerror, BZFILE* f,
-                           int abandon,
-                           unsigned int* nbytes_in,
-                           unsigned int* nbytes_out );
-
-   void BZ2_bzWriteClose64 ( int *bzerror, BZFILE* f,
-                             int abandon,
-                             unsigned int* nbytes_in_lo32,
-                             unsigned int* nbytes_in_hi32,
-                             unsigned int* nbytes_out_lo32,
-                             unsigned int* nbytes_out_hi32 );
-
- -

-Compresses and flushes to the compressed file all data so far supplied -by BZ2_bzWrite. The logical end-of-stream markers are also written, so -subsequent calls to BZ2_bzWrite are illegal. All memory associated -with the compressed file b is released. -fflush is called on the -compressed file, but it is not fclose'd. - -

-

-If BZ2_bzWriteClose is called to clean up after an error, the only -action is to release the memory. The library records the error codes -issued by previous calls, so this situation will be detected -automatically. There is no attempt to complete the compression -operation, nor to fflush the compressed file. You can force this -behaviour to happen even in the case of no error, by passing a nonzero -value to abandon. - -

-

-If nbytes_in is non-null, *nbytes_in will be set to be the -total volume of uncompressed data handled. Similarly, nbytes_out -will be set to the total volume of compressed data written. For -compatibility with older versions of the library, BZ2_bzWriteClose -only yields the lower 32 bits of these counts. Use -BZ2_bzWriteClose64 if you want the full 64 bit counts. These -two functions are otherwise absolutely identical. - -

- -

-Possible assignments to bzerror: - -

-      BZ_SEQUENCE_ERROR 
-         if b was opened with BZ2_bzReadOpen
-      BZ_IO_ERROR 
-         if there is an error writing the compressed file
-      BZ_OK 
-         otherwise
-
- - - -

Handling embedded compressed data streams

- -

-The high-level library facilitates use of -bzip2 data streams which form some part of a surrounding, larger -data stream. - -

    -
  • For writing, the library takes an open file handle, writes - -compressed data to it, fflushes it but does not fclose it. -The calling application can write its own data before and after the -compressed data stream, using that same file handle. -
  • Reading is more complex, and the facilities are not as general - -as they could be since generality is hard to reconcile with efficiency. -BZ2_bzRead reads from the compressed file in blocks of size -BZ_MAX_UNUSED bytes, and in doing so probably will overshoot -the logical end of compressed stream. -To recover this data once decompression has -ended, call BZ2_bzReadGetUnused after the last call of BZ2_bzRead -(the one returning BZ_STREAM_END) but before calling -BZ2_bzReadClose. -
- -

-This mechanism makes it easy to decompress multiple bzip2 -streams placed end-to-end. As the end of one stream, when BZ2_bzRead -returns BZ_STREAM_END, call BZ2_bzReadGetUnused to collect the -unused data (copy it into your own buffer somewhere). -That data forms the start of the next compressed stream. -To start uncompressing that next stream, call BZ2_bzReadOpen again, -feeding in the unused data via the unused/nUnused -parameters. -Keep doing this until BZ_STREAM_END return coincides with the -physical end of file (feof(f)). In this situation -BZ2_bzReadGetUnused -will of course return no data. - -

-

-This should give some feel for how the high-level interface can be used. -If you require extra flexibility, you'll have to bite the bullet and get -to grips with the low-level interface. - -

- - -

Standard file-reading/writing code

-

-Here's how you'd write data to a compressed file: - -

-FILE*   f;
-BZFILE* b;
-int     nBuf;
-char    buf[ /* whatever size you like */ ];
-int     bzerror;
-int     nWritten;
-
-f = fopen ( "myfile.bz2", "w" );
-if (!f) {
-   /* handle error */
-}
-b = BZ2_bzWriteOpen ( &bzerror, f, 9 );
-if (bzerror != BZ_OK) {
-   BZ2_bzWriteClose ( b );
-   /* handle error */
-}
-
-while ( /* condition */ ) {
-   /* get data to write into buf, and set nBuf appropriately */
-   nWritten = BZ2_bzWrite ( &bzerror, b, buf, nBuf );
-   if (bzerror == BZ_IO_ERROR) { 
-      BZ2_bzWriteClose ( &bzerror, b );
-      /* handle error */
-   }
-}
-
-BZ2_bzWriteClose ( &bzerror, b );
-if (bzerror == BZ_IO_ERROR) {
-   /* handle error */
-}
-
- -

-And to read from a compressed file: - -

-FILE*   f;
-BZFILE* b;
-int     nBuf;
-char    buf[ /* whatever size you like */ ];
-int     bzerror;
-int     nWritten;
-
-f = fopen ( "myfile.bz2", "r" );
-if (!f) {
-   /* handle error */
-}
-b = BZ2_bzReadOpen ( &bzerror, f, 0, NULL, 0 );
-if (bzerror != BZ_OK) {
-   BZ2_bzReadClose ( &bzerror, b );
-   /* handle error */
-}
-
-bzerror = BZ_OK;
-while (bzerror == BZ_OK && /* arbitrary other conditions */) {
-   nBuf = BZ2_bzRead ( &bzerror, b, buf, /* size of buf */ );
-   if (bzerror == BZ_OK) {
-      /* do something with buf[0 .. nBuf-1] */
-   }
-}
-if (bzerror != BZ_STREAM_END) {
-   BZ2_bzReadClose ( &bzerror, b );
-   /* handle error */
-} else {
-   BZ2_bzReadClose ( &bzerror );
-}
-
- - - -

Utility functions

- - -

BZ2_bzBuffToBuffCompress

- -
-   int BZ2_bzBuffToBuffCompress( char*         dest,
-                                 unsigned int* destLen,
-                                 char*         source,
-                                 unsigned int  sourceLen,
-                                 int           blockSize100k,
-                                 int           verbosity,
-                                 int           workFactor );
-
- -

-Attempts to compress the data in source[0 .. sourceLen-1] -into the destination buffer, dest[0 .. *destLen-1]. -If the destination buffer is big enough, *destLen is -set to the size of the compressed data, and BZ_OK is -returned. If the compressed data won't fit, *destLen -is unchanged, and BZ_OUTBUFF_FULL is returned. - -

-

-Compression in this manner is a one-shot event, done with a single call -to this function. The resulting compressed data is a complete -bzip2 format data stream. There is no mechanism for making -additional calls to provide extra input data. If you want that kind of -mechanism, use the low-level interface. - -

-

-For the meaning of parameters blockSize100k, verbosity -and workFactor,
see BZ2_bzCompressInit. - -

-

-To guarantee that the compressed data will fit in its buffer, allocate -an output buffer of size 1% larger than the uncompressed data, plus -six hundred extra bytes. - -

-

-BZ2_bzBuffToBuffDecompress will not write data at or -beyond dest[*destLen], even in case of buffer overflow. - -

-

-Possible return values: - -

-      BZ_CONFIG_ERROR
-         if the library has been mis-compiled
-      BZ_PARAM_ERROR 
-         if dest is NULL or destLen is NULL
-         or blockSize100k < 1 or blockSize100k > 9
-         or verbosity < 0 or verbosity > 4 
-         or workFactor < 0 or workFactor > 250
-      BZ_MEM_ERROR
-         if insufficient memory is available 
-      BZ_OUTBUFF_FULL
-         if the size of the compressed data exceeds *destLen
-      BZ_OK 
-         otherwise
-
- - - -

BZ2_bzBuffToBuffDecompress

- -
-   int BZ2_bzBuffToBuffDecompress ( char*         dest,
-                                    unsigned int* destLen,
-                                    char*         source,
-                                    unsigned int  sourceLen,
-                                    int           small,
-                                    int           verbosity );
-
- -

-Attempts to decompress the data in source[0 .. sourceLen-1] -into the destination buffer, dest[0 .. *destLen-1]. -If the destination buffer is big enough, *destLen is -set to the size of the uncompressed data, and BZ_OK is -returned. If the compressed data won't fit, *destLen -is unchanged, and BZ_OUTBUFF_FULL is returned. - -

-

-source is assumed to hold a complete bzip2 format -data stream.
BZ2_bzBuffToBuffDecompress tries to decompress -the entirety of the stream into the output buffer. - -

-

-For the meaning of parameters small and verbosity, -see BZ2_bzDecompressInit. - -

-

-Because the compression ratio of the compressed data cannot be known in -advance, there is no easy way to guarantee that the output buffer will -be big enough. You may of course make arrangements in your code to -record the size of the uncompressed data, but such a mechanism is beyond -the scope of this library. - -

-

-BZ2_bzBuffToBuffDecompress will not write data at or -beyond dest[*destLen], even in case of buffer overflow. - -

-

-Possible return values: - -

-      BZ_CONFIG_ERROR
-         if the library has been mis-compiled
-      BZ_PARAM_ERROR 
-         if dest is NULL or destLen is NULL
-         or small != 0 && small != 1
-         or verbosity < 0 or verbosity > 4 
-      BZ_MEM_ERROR
-         if insufficient memory is available 
-      BZ_OUTBUFF_FULL
-         if the size of the compressed data exceeds *destLen
-      BZ_DATA_ERROR
-         if a data integrity error was detected in the compressed data
-      BZ_DATA_ERROR_MAGIC
-         if the compressed data doesn't begin with the right magic bytes
-      BZ_UNEXPECTED_EOF
-         if the compressed data ends unexpectedly
-      BZ_OK 
-         otherwise
-
- - - -

zlib compatibility functions

-

-Yoshioka Tsuneo has contributed some functions to -give better zlib compatibility. These functions are -BZ2_bzopen, BZ2_bzread, BZ2_bzwrite, BZ2_bzflush, -BZ2_bzclose, -BZ2_bzerror and BZ2_bzlibVersion. -These functions are not (yet) officially part of -the library. If they break, you get to keep all the pieces. -Nevertheless, I think they work ok. - -

-typedef void BZFILE;
-
-const char * BZ2_bzlibVersion ( void );
-
- -

-Returns a string indicating the library version. - -

-BZFILE * BZ2_bzopen  ( const char *path, const char *mode );
-BZFILE * BZ2_bzdopen ( int        fd,    const char *mode );
-
- -

-Opens a .bz2 file for reading or writing, using either its name -or a pre-existing file descriptor. -Analogous to fopen and fdopen. - -

-int BZ2_bzread  ( BZFILE* b, void* buf, int len );
-int BZ2_bzwrite ( BZFILE* b, void* buf, int len );
-
- -

-Reads/writes data from/to a previously opened BZFILE. -Analogous to fread and fwrite. - -

-int  BZ2_bzflush ( BZFILE* b );
-void BZ2_bzclose ( BZFILE* b );
-
- -

-Flushes/closes a BZFILE. BZ2_bzflush doesn't actually do -anything. Analogous to fflush and fclose. - -

- -
-const char * BZ2_bzerror ( BZFILE *b, int *errnum )
-
- -

-Returns a string describing the more recent error status of -b, and also sets *errnum to its numerical value. - -

- - - -

Using the library in a stdio-free environment

- - - -

Getting rid of stdio

- -

-In a deeply embedded application, you might want to use just -the memory-to-memory functions. You can do this conveniently -by compiling the library with preprocessor symbol BZ_NO_STDIO -defined. Doing this gives you a library containing only the following -eight functions: - -

-

-BZ2_bzCompressInit, BZ2_bzCompress, BZ2_bzCompressEnd
-BZ2_bzDecompressInit, BZ2_bzDecompress, BZ2_bzDecompressEnd
-BZ2_bzBuffToBuffCompress, BZ2_bzBuffToBuffDecompress - -

-

-When compiled like this, all functions will ignore verbosity -settings. - -

- - -

Critical error handling

-

-libbzip2 contains a number of internal assertion checks which -should, needless to say, never be activated. Nevertheless, if an -assertion should fail, behaviour depends on whether or not the library -was compiled with BZ_NO_STDIO set. - -

-

-For a normal compile, an assertion failure yields the message - -

-   bzip2/libbzip2: internal error number N.
-   This is a bug in bzip2/libbzip2, 1.0 of 21-Mar-2000.
-   Please report it to me at: jseward@acm.org.  If this happened
-   when you were using some program which uses libbzip2 as a
-   component, you should also report this bug to the author(s)
-   of that program.  Please make an effort to report this bug;
-   timely and accurate bug reports eventually lead to higher
-   quality software.  Thanks.  Julian Seward, 21 March 2000.
-
- -

-where N is some error code number. exit(3) -is then called. - -

-

-For a stdio-free library, assertion failures result -in a call to a function declared as: - -

-   extern void bz_internal_error ( int errcode );
-
- -

-The relevant code is passed as a parameter. You should supply -such a function. - -

-

-In either case, once an assertion failure has occurred, any -bz_stream records involved can be regarded as invalid. -You should not attempt to resume normal operation with them. - -

-

-You may, of course, change critical error handling to suit -your needs. As I said above, critical errors indicate bugs -in the library and should not occur. All "normal" error -situations are indicated via error return codes from functions, -and can be recovered from. - -

- - - -

Making a Windows DLL

-

-Everything related to Windows has been contributed by Yoshioka Tsuneo -
(QWF00133@niftyserve.or.jp / -tsuneo-y@is.aist-nara.ac.jp), so you should send your queries to -him (but perhaps Cc: me, jseward@acm.org). - -

-

-My vague understanding of what to do is: using Visual C++ 5.0, -open the project file libbz2.dsp, and build. That's all. - -

-

-If you can't -open the project file for some reason, make a new one, naming these files: -blocksort.c, bzlib.c, compress.c, -crctable.c, decompress.c, huffman.c,
-randtable.c and libbz2.def. You will also need -to name the header files bzlib.h and bzlib_private.h. - -

-

-If you don't use VC++, you may need to define the proprocessor symbol -_WIN32. - -

-

-Finally, dlltest.c is a sample program using the DLL. It has a -project file, dlltest.dsp. - -

-

-If you just want a makefile for Visual C, have a look at -makefile.msc. - -

-

-Be aware that if you compile bzip2 itself on Win32, you must set -BZ_UNIX to 0 and BZ_LCCWIN32 to 1, in the file -bzip2.c, before compiling. Otherwise the resulting binary won't -work correctly. - -

-

-I haven't tried any of this stuff myself, but it all looks plausible. - -

- -

-

Go to the first, previous, next, last section, table of contents. - - diff -Nru bzip2-1.0.1/manual_4.html bzip2-1.0.1.new/manual_4.html --- bzip2-1.0.1/manual_4.html Sat Jun 24 20:13:27 2000 +++ bzip2-1.0.1.new/manual_4.html Thu Jan 1 01:00:00 1970 @@ -1,528 +0,0 @@ - - - - -bzip2 and libbzip2 - Miscellanea - - - - - -

Go to the first, previous, next, last section, table of contents. -

- - -

Miscellanea

- -

-These are just some random thoughts of mine. Your mileage may -vary. - -

- - -

Limitations of the compressed file format

-

-bzip2-1.0, 0.9.5 and 0.9.0 -use exactly the same file format as the previous -version, bzip2-0.1. This decision was made in the interests of -stability. Creating yet another incompatible compressed file format -would create further confusion and disruption for users. - -

-

-Nevertheless, this is not a painless decision. Development -work since the release of bzip2-0.1 in August 1997 -has shown complexities in the file format which slow down -decompression and, in retrospect, are unnecessary. These are: - -

    -
  • The run-length encoder, which is the first of the - - compression transformations, is entirely irrelevant. - The original purpose was to protect the sorting algorithm - from the very worst case input: a string of repeated - symbols. But algorithm steps Q6a and Q6b in the original - Burrows-Wheeler technical report (SRC-124) show how - repeats can be handled without difficulty in block - sorting. -
  • The randomisation mechanism doesn't really need to be - - there. Udi Manber and Gene Myers published a suffix - array construction algorithm a few years back, which - can be employed to sort any block, no matter how - repetitive, in O(N log N) time. Subsequent work by - Kunihiko Sadakane has produced a derivative O(N (log N)^2) - algorithm which usually outperforms the Manber-Myers - algorithm. - - I could have changed to Sadakane's algorithm, but I find - it to be slower than bzip2's existing algorithm for - most inputs, and the randomisation mechanism protects - adequately against bad cases. I didn't think it was - a good tradeoff to make. Partly this is due to the fact - that I was not flooded with email complaints about - bzip2-0.1's performance on repetitive data, so - perhaps it isn't a problem for real inputs. - - Probably the best long-term solution, - and the one I have incorporated into 0.9.5 and above, - is to use the existing sorting - algorithm initially, and fall back to a O(N (log N)^2) - algorithm if the standard algorithm gets into difficulties. -
  • The compressed file format was never designed to be - - handled by a library, and I have had to jump though - some hoops to produce an efficient implementation of - decompression. It's a bit hairy. Try passing - decompress.c through the C preprocessor - and you'll see what I mean. Much of this complexity - could have been avoided if the compressed size of - each block of data was recorded in the data stream. -
  • An Adler-32 checksum, rather than a CRC32 checksum, - - would be faster to compute. -
- -

-It would be fair to say that the bzip2 format was frozen -before I properly and fully understood the performance -consequences of doing so. - -

-

-Improvements which I was able to incorporate into -0.9.0, despite using the same file format, are: - -

    -
  • Single array implementation of the inverse BWT. This - - significantly speeds up decompression, presumably - because it reduces the number of cache misses. -
  • Faster inverse MTF transform for large MTF values. The - - new implementation is based on the notion of sliding blocks - of values. -
  • bzip2-0.9.0 now reads and writes files with fread - - and fwrite; version 0.1 used putc and getc. - Duh! Well, you live and learn. - -
- -

-Further ahead, it would be nice -to be able to do random access into files. This will -require some careful design of compressed file formats. - -

- - - -

Portability issues

-

-After some consideration, I have decided not to use -GNU autoconf to configure 0.9.5 or 1.0. - -

-

-autoconf, admirable and wonderful though it is, -mainly assists with portability problems between Unix-like -platforms. But bzip2 doesn't have much in the way -of portability problems on Unix; most of the difficulties appear -when porting to the Mac, or to Microsoft's operating systems. -autoconf doesn't help in those cases, and brings in a -whole load of new complexity. - -

-

-Most people should be able to compile the library and program -under Unix straight out-of-the-box, so to speak, especially -if you have a version of GNU C available. - -

-

-There are a couple of __inline__ directives in the code. GNU C -(gcc) should be able to handle them. If you're not using -GNU C, your C compiler shouldn't see them at all. -If your compiler does, for some reason, see them and doesn't -like them, just #define __inline__ to be /* */. One -easy way to do this is to compile with the flag -D__inline__=, -which should be understood by most Unix compilers. - -

-

-If you still have difficulties, try compiling with the macro -BZ_STRICT_ANSI defined. This should enable you to build the -library in a strictly ANSI compliant environment. Building the program -itself like this is dangerous and not supported, since you remove -bzip2's checks against compressing directories, symbolic links, -devices, and other not-really-a-file entities. This could cause -filesystem corruption! - -

-

-One other thing: if you create a bzip2 binary for public -distribution, please try and link it statically (gcc -s). This -avoids all sorts of library-version issues that others may encounter -later on. - -

-

-If you build bzip2 on Win32, you must set BZ_UNIX to 0 and -BZ_LCCWIN32 to 1, in the file bzip2.c, before compiling. -Otherwise the resulting binary won't work correctly. - -

- - - -

Reporting bugs

-

-I tried pretty hard to make sure bzip2 is -bug free, both by design and by testing. Hopefully -you'll never need to read this section for real. - -

-

-Nevertheless, if bzip2 dies with a segmentation -fault, a bus error or an internal assertion failure, it -will ask you to email me a bug report. Experience with -version 0.1 shows that almost all these problems can -be traced to either compiler bugs or hardware problems. - -

    -
  • - -Recompile the program with no optimisation, and see if it -works. And/or try a different compiler. -I heard all sorts of stories about various flavours -of GNU C (and other compilers) generating bad code for -bzip2, and I've run across two such examples myself. - -2.7.X versions of GNU C are known to generate bad code from -time to time, at high optimisation levels. -If you get problems, try using the flags --O2 -fomit-frame-pointer -fno-strength-reduce. -You should specifically not use -funroll-loops. - -You may notice that the Makefile runs six tests as part of -the build process. If the program passes all of these, it's -a pretty good (but not 100%) indication that the compiler has -done its job correctly. -
  • - -If bzip2 crashes randomly, and the crashes are not -repeatable, you may have a flaky memory subsystem. bzip2 -really hammers your memory hierarchy, and if it's a bit marginal, -you may get these problems. Ditto if your disk or I/O subsystem -is slowly failing. Yup, this really does happen. - -Try using a different machine of the same type, and see if -you can repeat the problem. -
  • This isn't really a bug, but ... If bzip2 tells - -you your file is corrupted on decompression, and you -obtained the file via FTP, there is a possibility that you -forgot to tell FTP to do a binary mode transfer. That absolutely -will cause the file to be non-decompressible. You'll have to transfer -it again. -
- -

-If you've incorporated libbzip2 into your own program -and are getting problems, please, please, please, check that the -parameters you are passing in calls to the library, are -correct, and in accordance with what the documentation says -is allowable. I have tried to make the library robust against -such problems, but I'm sure I haven't succeeded. - -

-

-Finally, if the above comments don't help, you'll have to send -me a bug report. Now, it's just amazing how many people will -send me a bug report saying something like - -

-   bzip2 crashed with segmentation fault on my machine
-
- -

-and absolutely nothing else. Needless to say, a such a report -is totally, utterly, completely and comprehensively 100% useless; -a waste of your time, my time, and net bandwidth. -With no details at all, there's no way I can possibly begin -to figure out what the problem is. - -

-

-The rules of the game are: facts, facts, facts. Don't omit -them because "oh, they won't be relevant". At the bare -minimum: - -

-   Machine type.  Operating system version.  
-   Exact version of bzip2 (do bzip2 -V).  
-   Exact version of the compiler used.  
-   Flags passed to the compiler.
-
- -

-However, the most important single thing that will help me is -the file that you were trying to compress or decompress at the -time the problem happened. Without that, my ability to do anything -more than speculate about the cause, is limited. - -

-

-Please remember that I connect to the Internet with a modem, so -you should contact me before mailing me huge files. - -

- - - -

Did you get the right package?

- -

-bzip2 is a resource hog. It soaks up large amounts of CPU cycles -and memory. Also, it gives very large latencies. In the worst case, you -can feed many megabytes of uncompressed data into the library before -getting any compressed output, so this probably rules out applications -requiring interactive behaviour. - -

-

-These aren't faults of my implementation, I hope, but more -an intrinsic property of the Burrows-Wheeler transform (unfortunately). -Maybe this isn't what you want. - -

-

-If you want a compressor and/or library which is faster, uses less -memory but gets pretty good compression, and has minimal latency, -consider Jean-loup -Gailly's and Mark Adler's work, zlib-1.1.2 and -gzip-1.2.4. Look for them at - -

-

-http://www.cdrom.com/pub/infozip/zlib and -http://www.gzip.org respectively. - -

-

-For something faster and lighter still, you might try Markus F X J -Oberhumer's LZO real-time compression/decompression library, at -
http://wildsau.idv.uni-linz.ac.at/mfx/lzo.html. - -

-

-If you want to use the bzip2 algorithms to compress small blocks -of data, 64k bytes or smaller, for example on an on-the-fly disk -compressor, you'd be well advised not to use this library. Instead, -I've made a special library tuned for that kind of use. It's part of -e2compr-0.40, an on-the-fly disk compressor for the Linux -ext2 filesystem. Look at -http://www.netspace.net.au/~reiter/e2compr. - -

- - - -

Testing

- -

-A record of the tests I've done. - -

-

-First, some data sets: - -

    -
  • B: a directory containing 6001 files, one for every length in the - - range 0 to 6000 bytes. The files contain random lowercase - letters. 18.7 megabytes. -
  • H: my home directory tree. Documents, source code, mail files, - - compressed data. H contains B, and also a directory of - files designed as boundary cases for the sorting; mostly very - repetitive, nasty files. 565 megabytes. -
  • A: directory tree holding various applications built from source: - - egcs, gcc-2.8.1, KDE, GTK, Octave, etc. - 2200 megabytes. -
- -

-The tests conducted are as follows. Each test means compressing -(a copy of) each file in the data set, decompressing it and -comparing it against the original. - -

-

-First, a bunch of tests with block sizes and internal buffer -sizes set very small, -to detect any problems with the -blocking and buffering mechanisms. -This required modifying the source code so as to try to -break it. - -

    -
  1. Data set H, with - - buffer size of 1 byte, and block size of 23 bytes. -
  2. Data set B, buffer sizes 1 byte, block size 1 byte. - -
  3. As (2) but small-mode decompression. - -
  4. As (2) with block size 2 bytes. - -
  5. As (2) with block size 3 bytes. - -
  6. As (2) with block size 4 bytes. - -
  7. As (2) with block size 5 bytes. - -
  8. As (2) with block size 6 bytes and small-mode decompression. - -
  9. H with buffer size of 1 byte, but normal block - - size (up to 900000 bytes). -
- -

-Then some tests with unmodified source code. - -

    -
  1. H, all settings normal. - -
  2. As (1), with small-mode decompress. - -
  3. H, compress with flag -1. - -
  4. H, compress with flag -s, decompress with flag -s. - -
  5. Forwards compatibility: H, bzip2-0.1pl2 compressing, - - bzip2-0.9.5 decompressing, all settings normal. -
  6. Backwards compatibility: H, bzip2-0.9.5 compressing, - - bzip2-0.1pl2 decompressing, all settings normal. -
  7. Bigger tests: A, all settings normal. - -
  8. As (7), using the fallback (Sadakane-like) sorting algorithm. - -
  9. As (8), compress with flag -1, decompress with flag - - -s. -
  10. H, using the fallback sorting algorithm. - -
  11. Forwards compatibility: A, bzip2-0.1pl2 compressing, - - bzip2-0.9.5 decompressing, all settings normal. -
  12. Backwards compatibility: A, bzip2-0.9.5 compressing, - - bzip2-0.1pl2 decompressing, all settings normal. -
  13. Misc test: about 400 megabytes of .tar files with - - bzip2 compiled with Checker (a memory access error - detector, like Purify). -
  14. Misc tests to make sure it builds and runs ok on non-Linux/x86 - - platforms. -
- -

-These tests were conducted on a 225 MHz IDT WinChip machine, running -Linux 2.0.36. They represent nearly a week of continuous computation. -All tests completed successfully. - -

- - - -

Further reading

-

-bzip2 is not research work, in the sense that it doesn't present -any new ideas. Rather, it's an engineering exercise based on existing -ideas. - -

-

-Four documents describe essentially all the ideas behind bzip2: - -

-Michael Burrows and D. J. Wheeler:
-  "A block-sorting lossless data compression algorithm"
-   10th May 1994. 
-   Digital SRC Research Report 124.
-   ftp://ftp.digital.com/pub/DEC/SRC/research-reports/SRC-124.ps.gz
-   If you have trouble finding it, try searching at the
-   New Zealand Digital Library, http://www.nzdl.org.
-
-Daniel S. Hirschberg and Debra A. LeLewer
-  "Efficient Decoding of Prefix Codes"
-   Communications of the ACM, April 1990, Vol 33, Number 4.
-   You might be able to get an electronic copy of this
-      from the ACM Digital Library.
-
-David J. Wheeler
-   Program bred3.c and accompanying document bred3.ps.
-   This contains the idea behind the multi-table Huffman
-   coding scheme.
-   ftp://ftp.cl.cam.ac.uk/users/djw3/
-
-Jon L. Bentley and Robert Sedgewick
-  "Fast Algorithms for Sorting and Searching Strings"
-   Available from Sedgewick's web page,
-   www.cs.princeton.edu/~rs
-
- -

-The following paper gives valuable additional insights into the -algorithm, but is not immediately the basis of any code -used in bzip2. - -

-Peter Fenwick:
-   Block Sorting Text Compression
-   Proceedings of the 19th Australasian Computer Science Conference,
-     Melbourne, Australia.  Jan 31 - Feb 2, 1996.
-   ftp://ftp.cs.auckland.ac.nz/pub/peter-f/ACSC96paper.ps
-
- -

-Kunihiko Sadakane's sorting algorithm, mentioned above, -is available from: - -

-http://naomi.is.s.u-tokyo.ac.jp/~sada/papers/Sada98b.ps.gz
-
- -

-The Manber-Myers suffix array construction -algorithm is described in a paper -available from: - -

-http://www.cs.arizona.edu/people/gene/PAPERS/suffix.ps
-
- -

-Finally, the following paper documents some recent investigations -I made into the performance of sorting algorithms: - -

-Julian Seward:
-   On the Performance of BWT Sorting Algorithms
-   Proceedings of the IEEE Data Compression Conference 2000
-     Snowbird, Utah.  28-30 March 2000.
-
- -

-

Go to the first, previous, next, last section, table of contents. - - diff -Nru bzip2-1.0.1/manual_toc.html bzip2-1.0.1.new/manual_toc.html --- bzip2-1.0.1/manual_toc.html Sat Jun 24 20:13:27 2000 +++ bzip2-1.0.1.new/manual_toc.html Thu Jan 1 01:00:00 1970 @@ -1,173 +0,0 @@ - - - - -bzip2 and libbzip2 - Table of Contents - - - -

bzip2 and libbzip2

-

a program and library for data compression

-

copyright (C) 1996-2000 Julian Seward

-

version 1.0 of 21 March 2000

-
Julian Seward
-

-

- -

-This program, bzip2, -and associated library libbzip2, are -Copyright (C) 1996-2000 Julian R Seward. All rights reserved. - -

-

-Redistribution and use in source and binary forms, with or without -modification, are permitted provided that the following conditions -are met: - -

    -
  • - - Redistributions of source code must retain the above copyright - notice, this list of conditions and the following disclaimer. -
  • - - The origin of this software must not be misrepresented; you must - not claim that you wrote the original software. If you use this - software in a product, an acknowledgment in the product - documentation would be appreciated but is not required. -
  • - - Altered source versions must be plainly marked as such, and must - not be misrepresented as being the original software. -
  • - - The name of the author may not be used to endorse or promote - products derived from this software without specific prior written - permission. -
- -

-THIS SOFTWARE IS PROVIDED BY THE AUTHOR "AS IS" AND ANY EXPRESS -OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED -WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE -ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY -DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL -DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE -GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS -INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, -WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING -NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS -SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. - -

-

-Julian Seward, Cambridge, UK. - -

-

-jseward@acm.org - -

-

-http://sourceware.cygnus.com/bzip2 - -

-

-http://www.cacheprof.org - -

-

-http://www.muraroa.demon.co.uk - -

-

-bzip2/libbzip2 version 1.0 of 21 March 2000. - -

-

-PATENTS: To the best of my knowledge, bzip2 does not use any patented -algorithms. However, I do not have the resources available to carry out -a full patent search. Therefore I cannot give any guarantee of the -above statement. - -

- - -

-This document was generated on 23 March 2000 using the -texi2html -translator version 1.51a.

- - diff -Nru bzip2-1.0.1/randtable.c bzip2-1.0.1.new/randtable.c --- bzip2-1.0.1/randtable.c Sat Jun 24 20:13:27 2000 +++ bzip2-1.0.1.new/randtable.c Sat Jun 24 20:13:06 2000 @@ -58,6 +58,10 @@ For more information on these sources, see the manual. --*/ +#ifdef HAVE_CONFIG_H +#include +#endif + #include "bzlib_private.h" diff -Nru bzip2-1.0.1/spewG.c bzip2-1.0.1.new/spewG.c --- bzip2-1.0.1/spewG.c Sat Jun 24 20:13:27 2000 +++ bzip2-1.0.1.new/spewG.c Sat Jun 24 20:13:06 2000 @@ -9,7 +9,10 @@ (but is otherwise harmless). */ -#define _FILE_OFFSET_BITS 64 +#ifdef HAVE_CONFIG_H +#include +#endif + #include #include diff -Nru bzip2-1.0.1/stamp-h.in bzip2-1.0.1.new/stamp-h.in --- bzip2-1.0.1/stamp-h.in Thu Jan 1 01:00:00 1970 +++ bzip2-1.0.1.new/stamp-h.in Sat Jun 24 20:13:06 2000 @@ -0,0 +1 @@ +timestamp diff -Nru bzip2-1.0.1/unzcrash.c bzip2-1.0.1.new/unzcrash.c --- bzip2-1.0.1/unzcrash.c Sat Jun 24 20:13:27 2000 +++ bzip2-1.0.1.new/unzcrash.c Sat Jun 24 20:13:06 2000 @@ -13,6 +13,12 @@ many hours. */ +#ifdef HAVE_CONFIG_H +#include +#endif + + + #include #include #include "bzlib.h"