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

Had to mark {,c,const}{begin,end}() inline, since they are, and mingw
complains about inconsistent dllimport attributes.

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

Task-number: QTBUG-25919
Change-Id: I1d48729c76e510c1e49c0e5dc41691aa662fdf21
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/tools/qstring.cpp

@@ -1200,6 +1200,22 @@ const QString::Null QString::null = { };
     \sa QString::const_iterator
 */
 
+/*! \typedef QString::const_reverse_iterator
+    \since 5.6
+
+    This typedef provides an STL-style const reverse iterator for QString.
+
+    \sa QString::reverse_iterator, QString::const_iterator
+*/
+
+/*! \typedef QString::reverse_iterator
+    \since 5.6
+
+    This typedef provides an STL-style non-const reverse iterator for QString.
+
+    \sa QString::const_reverse_iterator, QString::iterator
+*/
+
 /*!
     \typedef QString::size_type
 
@@ -1303,6 +1319,52 @@ const QString::Null QString::null = { };
     \sa constBegin(), end()
 */
 
+/*! \fn QString::reverse_iterator QString::rbegin()
+    \since 5.6
+
+    Returns a \l{STL-style iterators}{STL-style} reverse iterator pointing to the first
+    character in the string, in reverse order.
+
+    \sa begin(), crbegin(), rend()
+*/
+
+/*! \fn QString::const_reverse_iterator QString::rbegin() const
+    \since 5.6
+    \overload
+*/
+
+/*! \fn QString::const_reverse_iterator QString::crbegin() const
+    \since 5.6
+
+    Returns a const \l{STL-style iterators}{STL-style} reverse iterator pointing to the first
+    character in the string, in reverse order.
+
+    \sa begin(), rbegin(), rend()
+*/
+
+/*! \fn QString::reverse_iterator QString::rend()
+    \since 5.6
+
+    Returns a \l{STL-style iterators}{STL-style} reverse iterator pointing to one past
+    the last character in the string, in reverse order.
+
+    \sa end(), crend(), rbegin()
+*/
+
+/*! \fn QString::const_reverse_iterator QString::rend() const
+    \since 5.6
+    \overload
+*/
+
+/*! \fn QString::const_reverse_iterator QString::crend() const
+    \since 5.6
+
+    Returns a const \l{STL-style iterators}{STL-style} reverse iterator pointing to one
+    past the last character in the string, in reverse order.
+
+    \sa end(), rend(), rbegin()
+*/
+
 /*!
     \fn QString::QString()
 

src/corelib/tools/qstring.h

@@ -44,6 +44,7 @@
 #include <QtCore/qnamespace.h>
 
 #include <string>
+#include <iterator>
 
 #if defined(Q_OS_ANDROID)
 // std::wstring is disabled on android's glibc, as bionic lacks certain features
@@ -715,14 +716,22 @@ public:
     typedef const QChar *const_iterator;
     typedef iterator Iterator;
     typedef const_iterator ConstIterator;
-    iterator begin();
-    const_iterator begin() const;
-    const_iterator cbegin() const;
-    const_iterator constBegin() const;
-    iterator end();
-    const_iterator end() const;
-    const_iterator cend() const;
-    const_iterator constEnd() const;
+    typedef std::reverse_iterator<iterator> reverse_iterator;
+    typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
+    inline iterator begin();
+    inline const_iterator begin() const;
+    inline const_iterator cbegin() const;
+    inline const_iterator constBegin() const;
+    inline iterator end();
+    inline const_iterator end() const;
+    inline const_iterator cend() const;
+    inline const_iterator constEnd() const;
+    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()); }
 
     // STL compatibility
     typedef int size_type;

tests/auto/corelib/tools/qstring/tst_qstring.cpp

@@ -534,6 +534,7 @@ private slots:
     void localeAwareCompare_data();
     void localeAwareCompare();
 #endif
+    void reverseIterators();
     void split_data();
     void split();
     void split_regexp_data();
@@ -5399,6 +5400,20 @@ void tst_QString::localeAwareCompare()
 }
 #endif //!defined(Q_OS_WIN) || defined(Q_OS_WIN_AND_WINCE)
 
+void tst_QString::reverseIterators()
+{
+    QString s = "1234";
+    QString sr = s;
+    std::reverse(sr.begin(), sr.end());
+    const QString &csr = sr;
+    QVERIFY(std::equal(s.begin(), s.end(), sr.rbegin()));
+    QVERIFY(std::equal(s.begin(), s.end(), sr.crbegin()));
+    QVERIFY(std::equal(s.begin(), s.end(), csr.rbegin()));
+    QVERIFY(std::equal(sr.rbegin(), sr.rend(), s.begin()));
+    QVERIFY(std::equal(sr.crbegin(), sr.crend(), s.begin()));
+    QVERIFY(std::equal(csr.rbegin(), csr.rend(), s.begin()));
+}
+
 void tst_QString::split_data()
 {
     QTest::addColumn<QString>("str");