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QCommonArrayOps: append when inserting into empty container

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Ensured append is chosen instead of prepend for corner cases when
inserting into an empty container

Mirrored the logic in shouldGrowBeforeInsert function

Task-number: QTBUG-84320
Change-Id: I1c963a2588c331029e450fe55001bbf324f65fb4
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
This commit is contained in:
Andrei Golubev 2020-09-02 15:35:07 +02:00
parent 08c70ca0cc
commit 6239246ea8
1 changed files with 3 additions and 3 deletions
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6
src/corelib/tools/qarraydataops.h
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@ -1320,7 +1320,7 @@ public:
const qsizetype freeAtEnd = this->freeSpaceAtEnd();
const qsizetype capacity = this->constAllocatedCapacity();
if (where == this->begin()) { // prepend
if (this->size > 0 && where == this->begin()) { // prepend
// Qt5 QList in prepend: not enough space at begin && 33% full
// Now (below):
return freeAtBegin < n && (this->size >= (capacity / 3));
@ -1420,7 +1420,7 @@ public:
Q_ASSERT(e <= where || b > this->end() || where == this->end()); // No overlap or append
Q_ASSERT(size_t(e - b) <= this->allocatedCapacity() - this->size);
if (where == this->begin()) { // prepend case - special space arrangement
if (this->size > 0 && where == this->begin()) { // prepend case - special space arrangement
prepareSpaceForPrepend(b, e, e - b); // ### perf. loss
Base::insert(GrowsBackwardsTag{}, this->begin(), b, e);
return;
@ -1445,7 +1445,7 @@ public:
Q_ASSERT(where >= this->begin() && where <= this->end());
Q_ASSERT(this->allocatedCapacity() - size_t(this->size) >= n);
if (where == this->begin()) { // prepend case - special space arrangement
if (this->size > 0 && where == this->begin()) { // prepend case - special space arrangement
// Preserve the value, because it might be a reference to some part of the moved chunk
T tmp(t);
prepareSpaceForPrepend(n); // ### perf. loss