Introduce QArrayDataOps::appendInitialize

Adds given number of default-initialized elements at end of array. For
POD types, initialization is reduced to a single memset call. Other
types get default constructed in place.

As part of adding a test for the new functionality the arrayOps test was
extended to verify objects are being constructed and assigned as
desired.

Change-Id: I9fb2afe0d92667e76993313fcd370fe129d72b90
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 23 insertions, 0 deletions

diff --git a/src/corelib/tools/qarraydataops.h b/src/corelib/tools/qarraydataops.h
index 1b8ed3372d..785a26c3a8 100644
--- a/src/corelib/tools/qarraydataops.h
+++ b/src/corelib/tools/qarraydataops.h
@@ -57,6 +57,16 @@ template <class T>
 struct QPodArrayOps
     : QTypedArrayData<T>
 {
+    void appendInitialize(size_t newSize)
+    {
+        Q_ASSERT(!this->ref.isShared());
+        Q_ASSERT(newSize > uint(this->size));
+        Q_ASSERT(newSize <= this->alloc);
+
+        ::memset(this->end(), 0, (newSize - this->size) * sizeof(T));
+        this->size = newSize;
+    }
+
     void copyAppend(const T *b, const T *e)
     {
         Q_ASSERT(!this->ref.isShared());
@@ -105,6 +115,18 @@ template <class T>
 struct QGenericArrayOps
     : QTypedArrayData<T>
 {
+    void appendInitialize(size_t newSize)
+    {
+        Q_ASSERT(!this->ref.isShared());
+        Q_ASSERT(newSize > uint(this->size));
+        Q_ASSERT(newSize <= this->alloc);
+
+        T *const begin = this->begin();
+        do {
+            new (begin + this->size) T();
+        } while (uint(++this->size) != newSize);
+    }
+
     void copyAppend(const T *b, const T *e)
     {
         Q_ASSERT(!this->ref.isShared());
@@ -215,6 +237,7 @@ template <class T>
 struct QMovableArrayOps
     : QGenericArrayOps<T>
 {
+    // using QGenericArrayOps<T>::appendInitialize;
     // using QGenericArrayOps<T>::copyAppend;
     // using QGenericArrayOps<T>::destroyAll;