diff options
| author | Andrei Golubev <andrei.golubev@qt.io> | 2020-09-04 11:27:44 +0200 |
|---|---|---|
| committer | Andrei Golubev <andrei.golubev@qt.io> | 2020-09-07 15:50:03 +0200 |
| commit | 08c70ca0ccd70af5442330db62f5bcffaeb89aad (patch) | |
| tree | 6d534f388cacb5e7291513acfa07a6ea84e5d23a /src/corelib/text | |
| parent | c9e419e026fec8a98ec2648e3645d5f066882521 (diff) | |
QList/QString/QByteArray: no prepend optimized allocation when empty
Scoped prepend optimized allocation to only work when prepending into
a non-empty container. Otherwise, even appends would be considered
prepends since d.size == 0 when container is empty
This is, of course, not good for prepend cases but we prefer appends
over prepends. My proposal is to figure out what's the best strategy
based on use cases and performance measurements. For now, let's just
make sure appends are not additionally pessimized
Anyhow, this is an implementation detail and should not be considered
behavior change (at least not the one that is user noticeable)
Task-number: QTBUG-84320
Change-Id: Ibed616a2afa9bc24f78252f15a617bf92e2c6ea3
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
Diffstat (limited to 'src/corelib/text')
| -rw-r--r-- | src/corelib/text/qbytearray.cpp | 2 | ||||
| -rw-r--r-- | src/corelib/text/qstring.cpp | 4 |
2 files changed, 3 insertions, 3 deletions
diff --git a/src/corelib/text/qbytearray.cpp b/src/corelib/text/qbytearray.cpp index 8cc45d4500..1eb5162fb1 100644 --- a/src/corelib/text/qbytearray.cpp +++ b/src/corelib/text/qbytearray.cpp @@ -1942,7 +1942,7 @@ QByteArray &QByteArray::insert(qsizetype i, qsizetype count, char ch) // ### optimize me if (d->needsDetach() || newSize > capacity() || shouldGrow) { auto flags = d->detachFlags() | Data::GrowsForward; - if (i <= oldSize / 4) // using QList's policy + if (oldSize != 0 && i <= oldSize / 4) // using QList's policy flags |= Data::GrowsBackwards; reallocGrowData(newSize + 1, flags); } diff --git a/src/corelib/text/qstring.cpp b/src/corelib/text/qstring.cpp index e00b45f3f2..dd1b57dbf3 100644 --- a/src/corelib/text/qstring.cpp +++ b/src/corelib/text/qstring.cpp @@ -2690,7 +2690,7 @@ QString& QString::insert(qsizetype i, const QChar *unicode, qsizetype size) const bool shouldGrow = d->shouldGrowBeforeInsert(d.begin() + qMin(i, oldSize), size); auto flags = d->detachFlags() | Data::GrowsForward; - if (i <= oldSize / 4) + if (oldSize != 0 && i <= oldSize / 4) flags |= Data::GrowsBackwards; // ### optimize me @@ -2724,7 +2724,7 @@ QString& QString::insert(qsizetype i, QChar ch) const bool shouldGrow = d->shouldGrowBeforeInsert(d.begin() + qMin(i, oldSize), 1); auto flags = d->detachFlags() | Data::GrowsForward; - if (i <= oldSize / 4) + if (oldSize != 0 && i <= oldSize / 4) flags |= Data::GrowsBackwards; // ### optimize me |