AuroraMiddleware/qt5base-lts
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Add an early-out to QVector::operator+= and QHash::unite for empty LHS

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If the container being added to is default constructed and has never
been modified, we don't have to do all the checking and iterating.
Instead we can just assign with operator=.

If the LHS is merely empty, we could lose reserve()d capacity, so only
do this for a shared-null LHS.

Change-Id: If1e3342662d10833babc7ab847ada0285073723b
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>
Reviewed-by: Milian Wolff <milian.wolff@kdab.com>
This commit is contained in:
Ulf Hermann 2016-04-25 14:43:43 +02:00
parent b393641888
commit 9366a8be1e
2 changed files with 30 additions and 22 deletions
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14
src/corelib/tools/qhash.h
View File

@ -554,11 +554,15 @@ QHash<Key, T>::createNode(uint ah, const Key &akey, const T &avalue, Node **anex
template <class Key, class T>
Q_INLINE_TEMPLATE QHash<Key, T> &QHash<Key, T>::unite(const QHash &other)
{
QHash copy(other);
const_iterator it = copy.constEnd();
while (it != copy.constBegin()) {
--it;
insertMulti(it.key(), it.value());
if (d == &QHashData::shared_null) {
*this = other;
} else {
QHash copy(other);
const_iterator it = copy.constEnd();
while (it != copy.constBegin()) {
--it;
insertMulti(it.key(), it.value());
}
}
return *this;
}

38
src/corelib/tools/qvector.h
View File

@ -793,24 +793,28 @@ QVector<T> &QVector<T>::fill(const T &from, int asize)
template <typename T>
QVector<T> &QVector<T>::operator+=(const QVector &l)
{
uint newSize = d->size + l.d->size;
const bool isTooSmall = newSize > d->alloc;
if (!isDetached() || isTooSmall) {
QArrayData::AllocationOptions opt(isTooSmall ? QArrayData::Grow : QArrayData::Default);
reallocData(d->size, isTooSmall ? newSize : d->alloc, opt);
}
if (d->alloc) {
T *w = d->begin() + newSize;
T *i = l.d->end();
T *b = l.d->begin();
while (i != b) {
if (QTypeInfo<T>::isComplex)
new (--w) T(*--i);
else
*--w = *--i;
if (d == Data::sharedNull()) {
*this = l;
} else {
uint newSize = d->size + l.d->size;
const bool isTooSmall = newSize > d->alloc;
if (!isDetached() || isTooSmall) {
QArrayData::AllocationOptions opt(isTooSmall ? QArrayData::Grow : QArrayData::Default);
reallocData(d->size, isTooSmall ? newSize : d->alloc, opt);
}
if (d->alloc) {
T *w = d->begin() + newSize;
T *i = l.d->end();
T *b = l.d->begin();
while (i != b) {
if (QTypeInfo<T>::isComplex)
new (--w) T(*--i);
else
*--w = *--i;
}
d->size = newSize;
}
d->size = newSize;
}
return *this;
}