QVarLengthArray: add squeeze function

Add function to move back data to the stack.

Change-Id: Ic78a368459bce68629e29602e4eeae2e1afe398b
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/tools/qvarlengtharray.h

@@ -103,6 +103,7 @@ public:
     inline bool isEmpty() const { return (s == 0); }
     inline void resize(int size);
     inline void clear() { resize(0); }
+    inline void squeeze();
 
     inline int capacity() const { return a; }
     inline void reserve(int size);
@@ -243,6 +244,10 @@ Q_OUTOFLINE_TEMPLATE void QVarLengthArray<T, Prealloc>::append(const T *abuf, in
     }
 }
 
+template <class T, int Prealloc>
+Q_INLINE_TEMPLATE void QVarLengthArray<T, Prealloc>::squeeze()
+{ realloc(s, s); }
+
 template <class T, int Prealloc>
 Q_OUTOFLINE_TEMPLATE void QVarLengthArray<T, Prealloc>::realloc(int asize, int aalloc)
 {

src/corelib/tools/qvarlengtharray.qdoc

@@ -210,7 +210,7 @@
     initialized. For other types, the elements are initialized with a
     \l{default-constructed value}.
 
-    \sa size()
+    \sa size(), squeeze()
 */
 
 /*! \fn int QVarLengthArray::capacity() const
@@ -223,7 +223,7 @@
     need to call this function. If you want to know how many items are
     in the array, call size().
 
-    \sa reserve()
+    \sa reserve(), squeeze()
 */
 
 /*! \fn void QVarLengthArray::reserve(int size)
@@ -240,7 +240,21 @@
     rarely ever need to call this function. If you want to change the
     size of the array, call resize().
 
-    \sa capacity()
+    \sa capacity(), squeeze()
+*/
+
+/*! \fn void QVarLengthArray::squeeze()
+    \since 5.1
+
+    Releases any memory not required to store the items.
+    If the container can fit its storage on the stack allocation,
+    it will free the heap allocation and copy the elements back to the stack.
+
+    The sole purpose of this function is to provide a means of fine
+    tuning QVarLengthArray's memory usage. In general, you will rarely ever
+    need to call this function.
+
+    \sa reserve(), capacity(), resize()
 */
 
 /*! \fn T &QVarLengthArray::operator[](int i)

tests/auto/corelib/tools/qvarlengtharray/tst_qvarlengtharray.cpp

@@ -58,6 +58,7 @@ private slots:
     void count();
     void first();
     void last();
+    void squeeze();
 };
 
 int fooCtor = 0;
@@ -653,5 +654,28 @@ void tst_QVarLengthArray::last()
     QCOMPARE(list.length(), 1);
 }
 
+void tst_QVarLengthArray::squeeze()
+{
+    QVarLengthArray<int> list;
+    int sizeOnStack = list.capacity();
+    int sizeOnHeap = sizeOnStack * 2;
+    list.resize(0);
+    QCOMPARE(list.capacity(), sizeOnStack);
+    list.resize(sizeOnHeap);
+    QCOMPARE(list.capacity(), sizeOnHeap);
+    list.resize(sizeOnStack);
+    QCOMPARE(list.capacity(), sizeOnHeap);
+    list.resize(0);
+    QCOMPARE(list.capacity(), sizeOnHeap);
+    list.squeeze();
+    QCOMPARE(list.capacity(), sizeOnStack);
+    list.resize(sizeOnStack);
+    list.squeeze();
+    QCOMPARE(list.capacity(), sizeOnStack);
+    list.resize(sizeOnHeap);
+    list.squeeze();
+    QCOMPARE(list.capacity(), sizeOnHeap);
+}
+
 QTEST_APPLESS_MAIN(tst_QVarLengthArray)
 #include "tst_qvarlengtharray.moc"