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, 19 insertions, 6 deletions

diff --git a/src/corelib/tools/qset.h b/src/corelib/tools/qset.h
index ed89617cd6..3f4208e8b3 100644
--- a/src/corelib/tools/qset.h
+++ b/src/corelib/tools/qset.h
@@ -39,6 +39,8 @@
 #include <initializer_list>
 #endif
 
+#include <iterator>
+
 QT_BEGIN_NAMESPACE
 
 
@@ -161,14 +163,25 @@ public:
     };
 
     // STL style
+    typedef std::reverse_iterator<iterator> reverse_iterator;
+    typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
+
     inline iterator begin() { return q_hash.begin(); }
-    inline const_iterator begin() const { return q_hash.begin(); }
-    inline const_iterator cbegin() const { return q_hash.begin(); }
-    inline const_iterator constBegin() const { return q_hash.constBegin(); }
+    inline const_iterator begin() const Q_DECL_NOTHROW { return q_hash.begin(); }
+    inline const_iterator cbegin() const Q_DECL_NOTHROW { return q_hash.begin(); }
+    inline const_iterator constBegin() const Q_DECL_NOTHROW { return q_hash.constBegin(); }
     inline iterator end() { return q_hash.end(); }
-    inline const_iterator end() const { return q_hash.end(); }
-    inline const_iterator cend() const { return q_hash.end(); }
-    inline const_iterator constEnd() const { return q_hash.constEnd(); }
+    inline const_iterator end() const Q_DECL_NOTHROW { return q_hash.end(); }
+    inline const_iterator cend() const Q_DECL_NOTHROW { return q_hash.end(); }
+    inline const_iterator constEnd() const Q_DECL_NOTHROW { return q_hash.constEnd(); }
+
+    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 erase(iterator i)
     {
         Q_ASSERT_X(isValidIterator(i), "QSet::erase", "The specified const_iterator argument 'i' is invalid");