Support GrowsBackwards flag in QArrayDataPointer

Introduced allocation function in QArrayDataPointer with
interface similar to QArrayData::allocate that supports growing
strategies. This func is used instead of the original in cases
when prepend-aware storage is needed. Tried to follow Qt5 QList
policy in terms of space reservation

Updated QPodArrayOps::reallocate to be aware of growing
shenanigans. It doesn't look like a perfect solution but it is
rather close and similar to what Qt6 QList is doing when not
growing (e.g. reserve/squeeze)

Added initial QCommonArrayOps with helper function that tells
when reallocation is preferable over just using the insert-like
operation. This comes up later on when GrowsBackwards policy is
properly supported in operations

Essentially, 2/3 main data management blocks for prepend optimization
are introduced here. The last one being a generalized data move that
is done instead of reallocation when existing free space is not enough

Task-number: QTBUG-84320
Change-Id: I9a2bac62ad600613a6d7c5348325e0e54aadb73d
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/src/corelib/tools/qarraydata.cpp b/src/corelib/tools/qarraydata.cpp
index cea41dbaff..03465238b8 100644
--- a/src/corelib/tools/qarraydata.cpp
+++ b/src/corelib/tools/qarraydata.cpp
@@ -145,7 +145,7 @@ static inline qsizetype calculateBlockSize(qsizetype &capacity, qsizetype object
     // Calculate the byte size
     // allocSize = objectSize * capacity + headerSize, but checked for overflow
     // plus padded to grow in size
-    if (options & QArrayData::GrowsForward) {
+    if (options & (QArrayData::GrowsForward | QArrayData::GrowsBackwards)) {
         auto r = qCalculateGrowingBlockSize(capacity, objectSize, headerSize);
         capacity = r.elementCount;
         return r.size;