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author | Oswald Buddenhagen <oswald.buddenhagen@nokia.com> | 2010-01-28 20:02:34 (GMT) |
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committer | Oswald Buddenhagen <oswald.buddenhagen@nokia.com> | 2010-02-16 18:10:38 (GMT) |
commit | 7134f8b25a7a69960767280f9c23981b08d8e68b (patch) | |
tree | 640eba8cf97d2906ed3befe718ca48dc6504a99f /src/corelib/tools/qlist.cpp | |
parent | d590fc729e3afaedf181da58f8b685d7597040da (diff) | |
download | Qt-7134f8b25a7a69960767280f9c23981b08d8e68b.zip Qt-7134f8b25a7a69960767280f9c23981b08d8e68b.tar.gz Qt-7134f8b25a7a69960767280f9c23981b08d8e68b.tar.bz2 |
add QList::reserve()
while this reserves memory "only" for the pointer list, this still
amounts to 100% of the re-allocs for small simple types. for
big/complex/static types the gain is lower, but still.
Reviewed-by: Denis
Reviewed-by: Joao
Diffstat (limited to 'src/corelib/tools/qlist.cpp')
-rw-r--r-- | src/corelib/tools/qlist.cpp | 39 |
1 files changed, 34 insertions, 5 deletions
diff --git a/src/corelib/tools/qlist.cpp b/src/corelib/tools/qlist.cpp index ce62016..ac0dc46 100644 --- a/src/corelib/tools/qlist.cpp +++ b/src/corelib/tools/qlist.cpp @@ -125,22 +125,23 @@ QListData::Data *QListData::detach2() } /*! - * Detaches the QListData by reallocating new memory. + * Detaches the QListData by allocating new memory for a list which possibly + * has a different size than the copied one. * Returns the old (shared) data, it is up to the caller to deref() and free() * For the new data node_copy needs to be called. * * \internal */ -QListData::Data *QListData::detach3() +QListData::Data *QListData::detach(int alloc) { Data *x = d; - Data* t = static_cast<Data *>(qMalloc(DataHeaderSize + x->alloc * sizeof(void *))); + Data* t = static_cast<Data *>(qMalloc(DataHeaderSize + alloc * sizeof(void *))); Q_CHECK_PTR(t); t->ref = 1; t->sharable = true; - t->alloc = x->alloc; - if (!t->alloc) { + t->alloc = alloc; + if (!alloc) { t->begin = 0; t->end = 0; } else { @@ -152,6 +153,21 @@ QListData::Data *QListData::detach3() return x; } +/*! + * Detaches the QListData by reallocating new memory. + * Returns the old (shared) data, it is up to the caller to deref() and free() + * For the new data node_copy needs to be called. + * + * \internal + */ +#if QT_VERSION >= 0x050000 +# error "Remove QListData::detach3(), it is only required for binary compatibility for 4.5.x to 4.6.x" +#endif +QListData::Data *QListData::detach3() +{ + return detach(d->alloc); +} + void QListData::realloc(int alloc) { Q_ASSERT(d->ref == 1); @@ -647,6 +663,19 @@ void **QListData::erase(void **xi) Same as at(). */ +/*! \fn QList::reserve(int alloc) + + Reserve space for \a alloc elements. + + If \a alloc is smaller than the current size of the list, nothing will happen. + + Use this function to avoid repetetive reallocation of QList's internal + data if you can predict how many elements will be appended. + Note that the reservation applies only to the internal pointer array. + + \since 4.7 +*/ + /*! \fn void QList::append(const T &value) Inserts \a value at the end of the list. |