QMultiMap: add range erase

Also remove duplication by centralizing the main code for
erase(), and implement erase(pos) in terms of erase(first, last).

Change-Id: Ie0272ebac92fd7da48c31f9d68e69a2faa583bbc
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/tools/qmap.h

@@ -65,6 +65,8 @@ public:
     using T = typename Map::mapped_type;
     using value_type = typename Map::value_type;
     using size_type = typename Map::size_type;
+    using iterator = typename Map::iterator;
+    using const_iterator = typename Map::const_iterator;
 
     Map m;
 
@@ -165,6 +167,47 @@ public:
     {
         return m.count(key);
     }
+
+    // Used in erase. Allocates a new QMapData and copies, from this->m,
+    // the elements not in the [first, last) range. The return contains
+    // the new QMapData and an iterator in its map pointing at the first
+    // element after the erase.
+    struct EraseResult {
+        QMapData *data;
+        iterator it;
+    };
+
+    EraseResult erase(const_iterator first, const_iterator last) const
+    {
+        EraseResult result;
+        result.data = new QMapData;
+        result.it = result.data->m.end();
+        const auto newDataEnd = result.it;
+
+        auto i = m.begin();
+        const auto e = m.end();
+
+        // copy over all the elements before first
+        while (i != first) {
+            result.it = result.data->m.insert(newDataEnd, *i);
+            ++i;
+        }
+
+        // skip until last
+        while (i != last)
+            ++i;
+
+        // copy from last to the end
+        while (i != e) {
+            result.data->m.insert(newDataEnd, *i);
+            ++i;
+        }
+
+        if (result.it != newDataEnd)
+            ++result.it;
+
+        return result;
+    }
 };
 
 //
@@ -531,36 +574,21 @@ public:
     const_key_value_iterator constKeyValueEnd() const { return const_key_value_iterator(end()); }
 
     iterator erase(const_iterator it)
+    {
+        return erase(it, std::next(it));
+    }
+
+    iterator erase(const_iterator afirst, const_iterator alast)
     {
         if (!d)
             return iterator();
 
         if (!d.isShared())
-            return iterator(d->m.erase(it.i));
+            return iterator(d->m.erase(afirst.i, alast.i));
 
-        MapData *newData = new MapData;
+        auto result = d->erase(afirst.i, alast.i);
-        const auto newDataEnd = newData->m.end();
+        d.reset(result.data);
-
+        return iterator(result.it);
-        auto i = d->m.begin();
-        auto e = d->m.end();
-        size_type steps = 0;
-
-        while (i != it.i) {
-            newData->m.insert(newDataEnd, *i);
-            ++i;
-            ++steps;
-        }
-
-        if (i != e)
-            ++i;
-
-        while (i != e)
-            newData->m.insert(newDataEnd, *i);
-
-        d.reset(newData);
-
-        auto result = std::next(d->m.begin(), steps);
-        return iterator(result);
     }
 
     // more Qt
@@ -1138,36 +1166,21 @@ public:
     const_key_value_iterator constKeyValueEnd() const { return const_key_value_iterator(end()); }
 
     iterator erase(const_iterator it)
+    {
+        return erase(it, std::next(it));
+    }
+
+    iterator erase(const_iterator afirst, const_iterator alast)
     {
         if (!d)
             return iterator();
 
         if (!d.isShared())
-            return iterator(d->m.erase(it.i));
+            return iterator(d->m.erase(afirst.i, alast.i));
 
-        auto newData = new MapData;
+        auto result = d->erase(afirst.i, alast.i);
-        const auto newDataEnd = newData->m.end();
+        d.reset(result.data);
-
+        return iterator(result.it);
-        auto i = d->m.begin();
-        auto e = d->m.end();
-        size_type steps = 0;
-
-        while (i != it.i) {
-            newData->m.insert(newDataEnd, *i);
-            ++i;
-            ++steps;
-        }
-
-        if (i != e)
-            ++i;
-
-        while (i != e)
-            newData->m.insert(newDataEnd, *i++);
-
-        d.reset(newData);
-
-        auto result = std::next(d->m.begin(), steps);
-        return iterator(result);
     }
 
     // more Qt

src/corelib/tools/qmap.qdoc

@@ -660,6 +660,16 @@
     \sa remove()
 */
 
+/*! \fn template <class Key, class T> QMap<Key, T>::iterator QMap<Key, T>::erase(const_iterator first, const_iterator last)
+    \since 6.0
+
+    Removes the (key, value) pairs pointed to by the iterator range
+    [\a first, \a last) from the map.
+    Returns an iterator to the item in the map following the last removed element.
+
+    \sa remove()
+*/
+
 /*! \fn template <class Key, class T> QMap<Key, T>::iterator QMap<Key, T>::find(const Key &key)
 
     Returns an iterator pointing to the item with key \a key in the

src/corelib/tools/qmultimap.qdoc

@@ -664,6 +664,17 @@
     \sa remove()
 */
 
+/*! \fn template <class Key, class T> QMultiMap<Key, T>::iterator QMultiMap<Key, T>::erase(const_iterator first, const_iterator last)
+    \since 6.0
+
+    Removes the (key, value) pairs pointed to by the iterator range
+    [\a first, \a last) from the multi map.
+    Returns an iterator to the item in the multi map following the last
+    removed element.
+
+    \sa remove()
+*/
+
 /*! \fn template <class Key, class T> QMultiMap<Key, T>::iterator QMultiMap<Key, T>::find(const Key &key)
 
     Returns an iterator pointing to the item with key \a key in the