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QRegularExpression: add an option to prevent automatic optimization

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If a user doesn't like that QRegularExpression might do an
uncontrolled CPU/memory spike when it decides to optimize a pattern,
offer a way to disable the automatic optimization.

Change-Id: I38a98a3bfb239cfad9f977b0eeb75903268e747f
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
This commit is contained in:
Giuseppe D'Angelo 2014-04-29 20:45:45 +02:00 committed by The Qt Project
parent 260f24228b
commit 5b300a1526
2 changed files with 27 additions and 8 deletions
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32
src/corelib/tools/qregularexpression.cpp
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@ -705,6 +705,17 @@ QT_BEGIN_NAMESPACE
JIT-compiled) on its first usage, instead of after a certain (undefined)
number of usages. See also \l{QRegularExpression::}{optimize()}.
This enum value has been introduced in Qt 5.4.
\value DontAutomaticallyOptimizeOption
Regular expressions are automatically optimized after a
certain number of usages; setting this option prevents such
optimizations, therefore avoiding possible unpredictable spikes in
CPU and memory usage. If both this option and the
\c{OptimizeOnFirstUsageOption} option are set, then this option takes
precedence. Note: this option will still let the regular expression
to be optimized by manually calling
\l{QRegularExpression::}{optimize()}. This enum value has been
introduced in Qt 5.4.
*/
/*!
@ -1108,7 +1119,10 @@ static bool isJitEnabled()
setting the studyData member variable to the result of the study. It gets
called by doMatch() every time a match is performed. As of now, the
optimizations on the pattern are performed after a certain number of usages
(i.e. the qt_qregularexpression_optimize_after_use_count constant).
(i.e. the qt_qregularexpression_optimize_after_use_count constant) unless
the DontAutomaticallyOptimizeOption option is set on the QRegularExpression
object, or anyhow by calling optimize() (which will pass
ImmediateOptimizeOption).
Notice that although the method is protected by a mutex, one thread may
invoke this function and return immediately (i.e. not study the pattern,
@ -1248,13 +1262,15 @@ QRegularExpressionMatchPrivate *QRegularExpressionPrivate::doMatch(const QString
matchType, matchOptions,
capturingCount + 1);
const OptimizePatternOption optimizePatternOption =
(patternOptions & QRegularExpression::OptimizeOnFirstUsageOption)
? ImmediateOptimizeOption
: LazyOptimizeOption;
if (!(patternOptions & QRegularExpression::DontAutomaticallyOptimizeOption)) {
const OptimizePatternOption optimizePatternOption =
(patternOptions & QRegularExpression::OptimizeOnFirstUsageOption)
? ImmediateOptimizeOption
: LazyOptimizeOption;
// this is mutex protected
const_cast<QRegularExpressionPrivate *>(this)->optimizePattern(optimizePatternOption);
// this is mutex protected
const_cast<QRegularExpressionPrivate *>(this)->optimizePattern(optimizePatternOption);
}
// work with a local copy of the study data, as we are running pcre_exec
// potentially more than once, and we don't want to run call it
@ -2370,6 +2386,8 @@ QDebug operator<<(QDebug debug, QRegularExpression::PatternOptions patternOption
flags.append("UseUnicodePropertiesOption|");
if (patternOptions & QRegularExpression::OptimizeOnFirstUsageOption)
flags.append("OptimizeOnFirstUsageOption|");
if (patternOptions & QRegularExpression::DontAutomaticallyOptimizeOption)
flags.append("DontAutomaticallyOptimizeOption|");
flags.chop(1);
}

3
src/corelib/tools/qregularexpression.h
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@ -70,7 +70,8 @@ public:
InvertedGreedinessOption = 0x0010,
DontCaptureOption = 0x0020,
UseUnicodePropertiesOption = 0x0040,
OptimizeOnFirstUsageOption = 0x0080
OptimizeOnFirstUsageOption = 0x0080,
DontAutomaticallyOptimizeOption = 0x0100
};
Q_DECLARE_FLAGS(PatternOptions, PatternOption)