QVarLengthArray: add {const_,reverse_iterator}, {c,}r{begin,end}()

[ChangeLog][QtCore][QVarLengthArray] Added rbegin(), crbegin(), rend(), crend(),
and reverse_iterator and const_reverse_iterator typedefs.

Task-number: QTBUG-25919
Change-Id: Ifda5d420802a3594c3181f54036279f16a7da16e
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/tools/qvarlengtharray.h

@@ -45,6 +45,7 @@
 #ifdef Q_COMPILER_INITIALIZER_LISTS
 #include <initializer_list>
 #endif
+#include <iterator>
 
 QT_BEGIN_NAMESPACE
 
@@ -165,6 +166,8 @@ public:
 
     typedef T* iterator;
     typedef const T* const_iterator;
+    typedef std::reverse_iterator<iterator> reverse_iterator;
+    typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
 
     inline iterator begin() { return ptr; }
     inline const_iterator begin() const { return ptr; }
@@ -174,6 +177,12 @@ public:
     inline const_iterator end() const { return ptr + s; }
     inline const_iterator cend() const { return ptr + s; }
     inline const_iterator constEnd() const { return ptr + s; }
+    reverse_iterator rbegin() { return reverse_iterator(end()); }
+    reverse_iterator rend() { return reverse_iterator(begin()); }
+    const_reverse_iterator rbegin() const { return const_reverse_iterator(end()); }
+    const_reverse_iterator rend() const { return const_reverse_iterator(begin()); }
+    const_reverse_iterator crbegin() const { return const_reverse_iterator(end()); }
+    const_reverse_iterator crend() const { return const_reverse_iterator(begin()); }
     iterator insert(const_iterator before, int n, const T &x);
     inline iterator insert(const_iterator before, const T &x) { return insert(before, 1, x); }
     iterator erase(const_iterator begin, const_iterator end);

src/corelib/tools/qvarlengtharray.qdoc

@@ -459,6 +459,20 @@
     Typedef for T *. Provided for STL compatibility.
 */
 
+/*!
+    \typedef QVarLengthArray::const_reverse_iterator
+    \since 5.6
+
+    Typedef for \c{std::reverse_iterator<const T*>}. Provided for STL compatibility.
+*/
+
+/*!
+    \typedef QVarLengthArray::reverse_iterator
+    \since 5.6
+
+    Typedef for \c{std::reverse_iterator<T*>}. Provided for STL compatibility.
+*/
+
 /*! \fn void QVarLengthArray::prepend(const T &value)
 
     \since 4.8
@@ -573,6 +587,52 @@
     \sa constBegin(), end()
 */
 
+/*! \fn QVarLengthArray::reverse_iterator QVarLengthArray::rbegin()
+    \since 5.6
+
+    Returns a \l{STL-style iterators}{STL-style} reverse iterator pointing to the first
+    item in the variable length array, in reverse order.
+
+    \sa begin(), crbegin(), rend()
+*/
+
+/*! \fn QVarLengthArray::const_reverse_iterator QVarLengthArray::rbegin() const
+    \since 5.6
+    \overload
+*/
+
+/*! \fn QVarLengthArray::const_reverse_iterator QVarLengthArray::crbegin() const
+    \since 5.6
+
+    Returns a const \l{STL-style iterators}{STL-style} reverse iterator pointing to the first
+    item in the variable length array, in reverse order.
+
+    \sa begin(), rbegin(), rend()
+*/
+
+/*! \fn QVarLengthArray::reverse_iterator QVarLengthArray::rend()
+    \since 5.6
+
+    Returns a \l{STL-style iterators}{STL-style} reverse iterator pointing to one past
+    the last item in the variable length array, in reverse order.
+
+    \sa end(), crend(), rbegin()
+*/
+
+/*! \fn QVarLengthArray::const_reverse_iterator QVarLengthArray::rend() const
+    \since 5.6
+    \overload
+*/
+
+/*! \fn QVarLengthArray::const_reverse_iterator QVarLengthArray::crend() const
+    \since 5.6
+
+    Returns a const \l{STL-style iterators}{STL-style} reverse iterator pointing to one
+    past the last item in the variable length array, in reverse order.
+
+    \sa end(), rend(), rbegin()
+*/
+
 /*! \fn QVarLengthArray::iterator QVarLengthArray::erase(const_iterator pos)
     \since 4.8
 

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

@@ -47,6 +47,7 @@ private slots:
     void appendCausingRealloc();
     void resize();
     void realloc();
+    void reverseIterators();
     void count();
     void first();
     void last();
@@ -563,6 +564,21 @@ void tst_QVarLengthArray::realloc()
     QVERIFY(reallocTestProceed);
 }
 
+void tst_QVarLengthArray::reverseIterators()
+{
+    QVarLengthArray<int> v;
+    v << 1 << 2 << 3 << 4;
+    QVarLengthArray<int> vr = v;
+    std::reverse(vr.begin(), vr.end());
+    const QVarLengthArray<int> &cvr = vr;
+    QVERIFY(std::equal(v.begin(), v.end(), vr.rbegin()));
+    QVERIFY(std::equal(v.begin(), v.end(), vr.crbegin()));
+    QVERIFY(std::equal(v.begin(), v.end(), cvr.rbegin()));
+    QVERIFY(std::equal(vr.rbegin(), vr.rend(), v.begin()));
+    QVERIFY(std::equal(vr.crbegin(), vr.crend(), v.begin()));
+    QVERIFY(std::equal(cvr.rbegin(), cvr.rend(), v.begin()));
+}
+
 void tst_QVarLengthArray::count()
 {
     // tests size(), count() and length(), since they're the same thing