QLinkedList/QSet: add {const_,}reverse_iterator, {c,}r{begin,end}()

Now all Qt sequential containers consistently provide reverse iterators.

The associative ones, by way of not returning std::pair from op*, can't
just use std::reverse_iterator. They would miss .key() and .value() methods.
So that has to wait for 5.7.

The reverse versions of the new key_iterators can also just use
std::reverse_iterator, but I'm afraid that after bikeshedding over
keyRBegin() vs. rKeyBegin() vs. reverseKeyBegin() vs. rkbegin()
vs. krbegin() (<-- of course, what else?), it would anyway be too
late for 5.6, so defer, too.

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

Task-number: QTBUG-25919
Change-Id: I58316fffade469e9a42c61d7aa1455ae3443fd94
Reviewed-by: Sérgio Martins <sergio.martins@kdab.com>
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>

1 files changed, 17 insertions, 6 deletions

diff --git a/src/corelib/tools/qlinkedlist.h b/src/corelib/tools/qlinkedlist.h
index 2854885d60..110529d843 100644
--- a/src/corelib/tools/qlinkedlist.h
+++ b/src/corelib/tools/qlinkedlist.h
@@ -183,14 +183,25 @@ 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 e->n; }
-    inline const_iterator begin() const { return e->n; }
-    inline const_iterator cbegin() const { return e->n; }
-    inline const_iterator constBegin() const { return e->n; }
+    inline const_iterator begin() const Q_DECL_NOTHROW { return e->n; }
+    inline const_iterator cbegin() const Q_DECL_NOTHROW { return e->n; }
+    inline const_iterator constBegin() const Q_DECL_NOTHROW { return e->n; }
     inline iterator end() { detach(); return e; }
-    inline const_iterator end() const { return e; }
-    inline const_iterator cend() const { return e; }
-    inline const_iterator constEnd() const { return e; }
+    inline const_iterator end() const Q_DECL_NOTHROW { return e; }
+    inline const_iterator cend() const Q_DECL_NOTHROW { return e; }
+    inline const_iterator constEnd() const Q_DECL_NOTHROW { return e; }
+
+    reverse_iterator rbegin() { return reverse_iterator(end()); }
+    reverse_iterator rend() { return reverse_iterator(begin()); }
+    const_reverse_iterator rbegin() const Q_DECL_NOTHROW { return const_reverse_iterator(end()); }
+    const_reverse_iterator rend() const Q_DECL_NOTHROW { return const_reverse_iterator(begin()); }
+    const_reverse_iterator crbegin() const Q_DECL_NOTHROW { return const_reverse_iterator(end()); }
+    const_reverse_iterator crend() const Q_DECL_NOTHROW { return const_reverse_iterator(begin()); }
+
     iterator insert(iterator before, const T &t);
     iterator erase(iterator pos);
     iterator erase(iterator first, iterator last);