QStringRef: add missing {c,}r{begin,end}()

Most containers have them in Qt 5.7, so add them
to QStringRef, too.

Brush up the docs, use the const_iterator typedef
in the API, for consistency with QString's docs.

[ChangeLog][QtCore][QStringRef] Added reverse iterators,
rbegin(), rend(), crbegin(), crend().

Change-Id: I3d2884a1b2faae02c610ab3871552b65bc6e2521
Reviewed-by: Lars Knoll <lars.knoll@theqtcompany.com>

2 files changed, 83 insertions, 18 deletions

diff --git a/src/corelib/tools/qstring.cpp b/src/corelib/tools/qstring.cpp
index c7cd1a7751..5cbad2554c 100644
--- a/src/corelib/tools/qstring.cpp
+++ b/src/corelib/tools/qstring.cpp
@@ -8759,7 +8759,20 @@ QDataStream &operator>>(QDataStream &in, QString &str)
 
 /*!
     \typedef QStringRef::const_iterator
-    \internal
+    \since 5.4
+
+    This typedef provides an STL-style const iterator for QStringRef.
+
+    \sa QStringRef::const_reverse_iterator
+*/
+
+/*!
+    \typedef QStringRef::const_reverse_iterator
+    \since 5.7
+
+    This typedef provides an STL-style const reverse iterator for QStringRef.
+
+    \sa QStringRef::const_iterator
 */
 
 /*!
@@ -8883,39 +8896,85 @@ ownership of it, no memory is freed when instances are destroyed.
 */
 
 /*!
-    \fn const QChar *QStringRef::begin() const
-    \since 5.4
+    \fn const QChar *QStringRef::constData() const
 
     Same as unicode().
 */
 
 /*!
-    \fn const QChar *QStringRef::cbegin() const
+    \fn QStringRef::const_iterator QStringRef::begin() const
     \since 5.4
 
-    Same as unicode().
+    Returns a const \l{STL-style iterators}{STL-style iterator} pointing to the first character in
+    the string.
+
+    \sa cbegin(), end(), rbegin(), rend()
 */
 
 /*!
-    \fn const QChar *QStringRef::end() const
+    \fn QStringRef::const_iterator QStringRef::cbegin() const
     \since 5.4
 
-    Returns a pointer to one character past the last one in this string.
-    (It is the same as \c {unicode() + size()}.)
+    Same as begin().
+
+    \sa begin(), cend(), rbegin(), rend()
 */
 
 /*!
-    \fn const QChar *QStringRef::cend() const
+    \fn QStringRef::const_iterator QStringRef::end() const
+    \since 5.4
+
+    Returns a const \l{STL-style iterators}{STL-style iterator} pointing to the imaginary
+    character after the last character in the list.
+
+    \sa cbegin(), end(), rbegin(), rend()
+*/
+
+/*! \fn QStringRef::const_iterator QStringRef::cend() const
     \since 5.4
 
-    Returns a pointer to one character past the last one in this string.
-    (It is the same as \c {unicode() + size()}.)
+    Same as end().
+
+    \sa end(), cbegin(), rbegin(), rend()
 */
 
 /*!
-    \fn const QChar *QStringRef::constData() const
+    \fn QStringRef::const_reverse_iterator QStringRef::rbegin() const
+    \since 5.7
 
-    Same as unicode().
+    Returns a const \l{STL-style iterators}{STL-style} reverse iterator pointing to the first
+    character in the string, in reverse order.
+
+    \sa begin(), crbegin(), rend()
+*/
+
+/*!
+    \fn QStringRef::const_reverse_iterator QStringRef::crbegin() const
+    \since 5.7
+
+    Same as rbegin().
+
+    \sa begin(), rbegin(), rend()
+*/
+
+/*!
+    \fn QStringRef::const_reverse_iterator QStringRef::rend() const
+    \since 5.7
+
+    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 QStringRef::const_reverse_iterator QStringRef::crend() const
+    \since 5.7
+
+    Same as rend().
+
+    \sa end(), rend(), rbegin()
 */
 
 /*!
diff --git a/src/corelib/tools/qstring.h b/src/corelib/tools/qstring.h
index 6676efab41..793a859228 100644
--- a/src/corelib/tools/qstring.h
+++ b/src/corelib/tools/qstring.h
@@ -1360,7 +1360,8 @@ class Q_CORE_EXPORT QStringRef {
 public:
     typedef QString::size_type size_type;
     typedef QString::value_type value_type;
-    typedef QString::const_iterator const_iterator;
+    typedef const QChar *const_iterator;
+    typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
     typedef QString::const_pointer const_pointer;
     typedef QString::const_reference const_reference;
 
@@ -1439,10 +1440,15 @@ public:
     }
     inline const QChar *data() const { return unicode(); }
     inline const QChar *constData() const {  return unicode(); }
-    inline const QChar *begin() const { return unicode(); }
-    inline const QChar *cbegin() const { return unicode(); }
-    inline const QChar *end() const { return unicode() + size(); }
-    inline const QChar *cend() const { return unicode() + size(); }
+
+    inline const_iterator begin() const { return unicode(); }
+    inline const_iterator cbegin() const { return unicode(); }
+    inline const_iterator end() const { return unicode() + size(); }
+    inline const_iterator cend() const { return unicode() + size(); }
+    inline const_reverse_iterator rbegin() const { return const_reverse_iterator(end()); }
+    inline const_reverse_iterator crbegin() const { return rbegin(); }
+    inline const_reverse_iterator rend() const { return const_reverse_iterator(begin()); }
+    inline const_reverse_iterator crend() const { return rend(); }
 
 #if QT_DEPRECATED_SINCE(5, 0)
     QT_DEPRECATED QByteArray toAscii() const Q_REQUIRED_RESULT