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QString: optimize case conversion code

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Handle special case mapping of length 1 explicitly;
Skip calculating of high surrogate for the same plane;
Optimize branch prediction with Q_LIKELY/Q_UNLIKELY;
Replace peekNext() + advance() with just next() in the caller function.

Change-Id: I0d37969749bd8ca855321242e6a0e72c405c5f8d
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
This commit is contained in:
Konstantin Ritt 2015-11-24 10:23:23 +04:00
parent 7edd488a5f
commit c3850dd636
1 changed files with 28 additions and 22 deletions
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50
src/corelib/tools/qstring.cpp
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@ -5709,37 +5709,42 @@ static QString detachAndConvertCase(T &str, QStringIterator it)
Q_ASSERT(!str.isEmpty());
QString s = qMove(str); // will copy if T is const QString
QChar *pp = s.begin() + it.index(); // will detach if necessary
uint uc = it.nextUnchecked();
forever {
do {
uint uc = it.nextUnchecked();
const QUnicodeTables::Properties *prop = qGetProp(uc);
signed short caseDiff = Traits::caseDiff(prop);
if (Q_UNLIKELY(Traits::caseSpecial(prop))) {
// slow path: the string is growing
const ushort *specialCase = specialCaseMap + caseDiff;
ushort length = *specialCase++;
int inpos = it.index() - 1;
int outpos = pp - s.constBegin();
s.replace(outpos, 1, reinterpret_cast<const QChar *>(specialCase), length);
pp = const_cast<QChar *>(s.constBegin()) + outpos + length;
if (Q_LIKELY(length == 1)) {
*pp++ = QChar(*specialCase);
} else {
// slow path: the string is growing
int inpos = it.index() - 1;
int outpos = pp - s.constBegin();
// do we need to adjust the input iterator too?
// if it is pointing to s's data, str is empty
if (str.isEmpty())
it = QStringIterator(s.constBegin(), inpos + length, s.constEnd());
} else if (QChar::requiresSurrogates(uc)) {
*pp++ = QChar::highSurrogate(uc + caseDiff);
s.replace(outpos, 1, reinterpret_cast<const QChar *>(specialCase), length);
pp = const_cast<QChar *>(s.constBegin()) + outpos + length;
// do we need to adjust the input iterator too?
// if it is pointing to s's data, str is empty
if (str.isEmpty())
it = QStringIterator(s.constBegin(), inpos + length, s.constEnd());
}
} else if (Q_UNLIKELY(QChar::requiresSurrogates(uc))) {
// so far, case convertion never changes planes (guaranteed by the qunicodetables generator)
pp++;
*pp++ = QChar::lowSurrogate(uc + caseDiff);
} else {
*pp++ = QChar(uc + caseDiff);
}
} while (it.hasNext());
if (!it.hasNext())
return s;
uc = it.nextUnchecked();
}
return s;
}
template <typename Traits, typename T>
@ -5752,12 +5757,13 @@ static QString convertCase(T &str)
while (e != p && e[-1].isHighSurrogate())
--e;
const QUnicodeTables::Properties *prop;
QStringIterator it(p, e);
for ( ; it.hasNext(); it.advanceUnchecked()) {
prop = qGetProp(it.peekNextUnchecked());
if (Traits::caseDiff(prop))
while (it.hasNext()) {
uint uc = it.nextUnchecked();
if (Traits::caseDiff(qGetProp(uc))) {
it.recedeUnchecked();
return detachAndConvertCase<Traits>(str, it);
}
}
return qMove(str);
}