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

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

Task-number: QTBUG-25919
Change-Id: Icce870c22931e68cdcedd1519651bfa374ac44af
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/tools/qlist.cpp

@@ -1048,6 +1048,52 @@ void **QListData::erase(void **xi)
     \sa constBegin(), end()
 */
 
+/*! \fn QList::reverse_iterator QList::rbegin()
+    \since 5.6
+
+    Returns a \l{STL-style iterators}{STL-style} reverse iterator pointing to the first
+    item in the list, in reverse order.
+
+    \sa begin(), crbegin(), rend()
+*/
+
+/*! \fn QList::const_reverse_iterator QList::rbegin() const
+    \since 5.6
+    \overload
+*/
+
+/*! \fn QList::const_reverse_iterator QList::crbegin() const
+    \since 5.6
+
+    Returns a const \l{STL-style iterators}{STL-style} reverse iterator pointing to the first
+    item in the list, in reverse order.
+
+    \sa begin(), rbegin(), rend()
+*/
+
+/*! \fn QList::reverse_iterator QList::rend()
+    \since 5.6
+
+    Returns a \l{STL-style iterators}{STL-style} reverse iterator pointing to one past
+    the last item in the list, in reverse order.
+
+    \sa end(), crend(), rbegin()
+*/
+
+/*! \fn QList::const_reverse_iterator QList::rend() const
+    \since 5.6
+    \overload
+*/
+
+/*! \fn QList::const_reverse_iterator QList::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 list, in reverse order.
+
+    \sa end(), rend(), rbegin()
+*/
+
 /*! \fn QList::iterator QList::erase(iterator pos)
 
     Removes the item associated with the iterator \a pos from the
@@ -1118,6 +1164,38 @@ void **QListData::erase(void **xi)
     Typedef for const T &. Provided for STL compatibility.
 */
 
+/*! \typedef QList::reverse_iterator
+    \since 5.6
+
+    The QList::reverse_iterator typedef provides an STL-style non-const
+    reverse iterator for QList.
+
+    It is simply a typedef for \c{std::reverse_iterator<iterator>}.
+
+    \warning Iterators on implicitly shared containers do not work
+    exactly like STL-iterators. You should avoid copying a container
+    while iterators are active on that container. For more information,
+    read \l{Implicit sharing iterator problem}.
+
+    \sa QList::rbegin(), QList::rend(), QList::const_reverse_iterator, QList::iterator
+*/
+
+/*! \typedef QList::const_reverse_iterator
+    \since 5.6
+
+    The QList::const_reverse_iterator typedef provides an STL-style const
+    reverse iterator for QList.
+
+    It is simply a typedef for \c{std::reverse_iterator<const_iterator>}.
+
+    \warning Iterators on implicitly shared containers do not work
+    exactly like STL-iterators. You should avoid copying a container
+    while iterators are active on that container. For more information,
+    read \l{Implicit sharing iterator problem}.
+
+    \sa QList::rbegin(), QList::rend(), QList::reverse_iterator, QList::const_iterator
+*/
+
 /*! \fn int QList::count() const
 
     Returns the number of items in the list. This is effectively the

src/corelib/tools/qlist.h

@@ -291,6 +291,8 @@ public:
     friend class const_iterator;
 
     // stl style
+    typedef std::reverse_iterator<iterator> reverse_iterator;
+    typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
     inline iterator begin() { detach(); return reinterpret_cast<Node *>(p.begin()); }
     inline const_iterator begin() const { return reinterpret_cast<Node *>(p.begin()); }
     inline const_iterator cbegin() const { return reinterpret_cast<Node *>(p.begin()); }
@@ -299,6 +301,12 @@ public:
     inline const_iterator end() const { return reinterpret_cast<Node *>(p.end()); }
     inline const_iterator cend() const { return reinterpret_cast<Node *>(p.end()); }
     inline const_iterator constEnd() const { return reinterpret_cast<Node *>(p.end()); }
+    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(iterator before, const T &t);
     iterator erase(iterator pos);
     iterator erase(iterator first, iterator last);

tests/auto/corelib/tools/qlist/tst_qlist.cpp

@@ -349,6 +349,9 @@ private slots:
     void replaceOptimal() const;
     void replaceMovable() const;
     void replaceComplex() const;
+    void reverseIteratorsOptimal() const;
+    void reverseIteratorsMovable() const;
+    void reverseIteratorsComplex() const;
     void startsWithOptimal() const;
     void startsWithMovable() const;
     void startsWithComplex() const;
@@ -416,6 +419,7 @@ private:
     template<typename T> void removeAt() const;
     template<typename T> void removeOne() const;
     template<typename T> void replace() const;
+    template<typename T> void reverseIterators() const;
     template<typename T> void startsWith() const;
     template<typename T> void swap() const;
     template<typename T> void takeAt() const;
@@ -1239,6 +1243,43 @@ void tst_QList::replaceComplex() const
     QCOMPARE(liveCount, Complex::getLiveCount());
 }
 
+template<typename T>
+void tst_QList::reverseIterators() const
+{
+    QList<T> v;
+    v << T_CAT << T_DOG << T_BLAH << T_BAZ;
+    QList<T> vr = v;
+    std::reverse(vr.begin(), vr.end());
+    const QList<T> &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_QList::reverseIteratorsOptimal() const
+{
+    const int liveCount = Optimal::getLiveCount();
+    reverseIterators<Optimal>();
+    QCOMPARE(liveCount, Optimal::getLiveCount());
+}
+
+void tst_QList::reverseIteratorsMovable() const
+{
+    const int liveCount = Movable::getLiveCount();
+    reverseIterators<Movable>();
+    QCOMPARE(liveCount, Movable::getLiveCount());
+}
+
+void tst_QList::reverseIteratorsComplex() const
+{
+    const int liveCount = Complex::getLiveCount();
+    reverseIterators<Complex>();
+    QCOMPARE(liveCount, Complex::getLiveCount());
+}
+
 template<typename T>
 void tst_QList::startsWith() const
 {