0029-Reduce-the-amount-of-allocations-by-preallocating-a-.patch

   1 From 89357c7b0fc5e76091510af504058c036fa1b2f9 Mon Sep 17 00:00:00 2001
   2 From: Milian Wolff <mail@milianw.de>
   3 Date: Wed, 10 Dec 2014 21:04:24 +0100
   4 Subject: [PATCH 29/30] Reduce the amount of allocations by preallocating a
   5  buffer.
   6
   7 Sadly, QByteArray cannot be cleared without destroying the buffer.
   8 But we can guesstimate the target size of the buffer and thus
   9 reduce the amount of allocations.
  10
  11 This also adds a benchmark for ImapParser::parseString.
  12 ---
  13  libs/imapparser.cpp                |  1 +
  14  libs/tests/imapparserbenchmark.cpp | 19 +++++++++++++++++++
  15  2 files changed, 20 insertions(+)
  16
  17 diff --git a/libs/imapparser.cpp b/libs/imapparser.cpp
  18 index 6f9f592..f3301e7 100644
  19 --- a/libs/imapparser.cpp
  20 +++ b/libs/imapparser.cpp
  21 @@ -186,6 +186,7 @@ int ImapParser::parseQuotedString( const QByteArray &data, QByteArray &result, i
  22    // quoted string
  23    if ( data[begin] == '"' ) {
  24      ++begin;
  25 +    result.reserve(qMin(32, data.size() - begin));
  26      for ( int i = begin; i < data.length(); ++i ) {
  27        const char ch = data.at( i );
  28        if ( foundSlash ) {
  29 diff --git a/libs/tests/imapparserbenchmark.cpp b/libs/tests/imapparserbenchmark.cpp
  30 index fd4335c..ee861a0 100644
  31 --- a/libs/tests/imapparserbenchmark.cpp
  32 +++ b/libs/tests/imapparserbenchmark.cpp
  33 @@ -95,6 +95,25 @@ class ImapParserBenchmark : public QObject
  34        }
  35      }
  36
  37 +    void parseString_data()
  38 +    {
  39 +      QTest::addColumn<QByteArray>( "data" );
  40 +      QTest::newRow("plain") << QByteArray("fooobarasdf something more lalala");
  41 +      QTest::newRow("quoted") << QByteArray("\"fooobarasdf\" something more lalala");
  42 +    }
  43 +
  44 +    void parseString()
  45 +    {
  46 +      QFETCH(QByteArray, data);
  47 +      QByteArray result;
  48 +      qint64 sum = 0;
  49 +      QBENCHMARK {
  50 +        sum += ImapParser::parseString( data, result );
  51 +      }
  52 +      QVERIFY(!result.isEmpty());
  53 +      QVERIFY(sum > 0);
  54 +    }
  55 +
  56      void parseNumber()
  57      {
  58        QByteArray data( "123456" );
  59 --
  60 2.1.0
  61