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Abuse const_cast in QStringBuilder to get a little more performance

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Without this const_cast, the call to QString::data() or
QByteArray::data() will cause a call to detach(), which is totally
unnecessary since we've just allocated data a couple of lines before.
Since we know we're the owner of the only reference, we can skip the
detach attempt.

Change-Id: If40f66100f85cc9b405025f21c562828ead23475
Reviewed-by: hjk <hjk121@nokiamail.com>
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
This commit is contained in:
Thiago Macieira 2014-01-16 18:01:11 -08:00 committed by The Qt Project
parent 556c3209e2
commit 5fcee88097
1 changed files with 3 additions and 1 deletions
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4
src/corelib/tools/qstringbuilder.h
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@ -112,7 +112,9 @@ private:
const uint len = QConcatenable< QStringBuilder<A, B> >::size(*this); const uint len = QConcatenable< QStringBuilder<A, B> >::size(*this);
T s(len, Qt::Uninitialized); T s(len, Qt::Uninitialized);
typename T::iterator d = s.data(); // we abuse const_cast / constData here because we know we've just
// allocated the data and we're the only reference count
typename T::iterator d = const_cast<typename T::iterator>(s.constData());
typename T::const_iterator const start = d; typename T::const_iterator const start = d;
QConcatenable< QStringBuilder<A, B> >::appendTo(*this, d); QConcatenable< QStringBuilder<A, B> >::appendTo(*this, d);