Implement emplace() for QHash and QMultiHash

At the same time use the opportunity to refactor the
insertion code inside the implementation of QHash to
avoid copy and move constructors as much as possible
and always construct nodes in place.

Change-Id: I951b4cf2c77a17f7db825c6a776aae38c2662d23
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>

1 files changed, 47 insertions, 0 deletions

diff --git a/src/corelib/tools/qhash.cpp b/src/corelib/tools/qhash.cpp
index ab699a7f94..4b3996d432 100644
--- a/src/corelib/tools/qhash.cpp
+++ b/src/corelib/tools/qhash.cpp
@@ -1422,6 +1422,18 @@ size_t qHash(long double key, size_t seed) noexcept
     is replaced with \a value.
 */
 
+/*!
+    \fn template <typename T> template <typename ...Args> QHash<Key, T>::iterator QHash<Key, T>::emplace(const Key &key, Args&&... args)
+    \fn template <typename T> template <typename ...Args> QHash<Key, T>::iterator QHash<Key, T>::emplace(Key &&key, Args&&... args)
+
+    Inserts a new element into the container. This new element
+    is constructed in-place using \a args as the arguments for its
+    construction.
+
+    Returns an iterator pointing to the new element.
+*/
+
+
 /*! \fn template <class Key, class T> void QHash<Key, T>::insert(const QHash &other)
     \since 5.15
 
@@ -2099,6 +2111,41 @@ size_t qHash(long double key, size_t seed) noexcept
     \sa replace()
 */
 
+/*!
+    \fn template <typename T> template <typename ...Args> QMultiHash<Key, T>::iterator QMultiHash<Key, T>::emplace(const Key &key, Args&&... args)
+    \fn template <typename T> template <typename ...Args> QMultiHash<Key, T>::iterator QMultiHash<Key, T>::emplace(Key &&key, Args&&... args)
+
+    Inserts a new element into the container. This new element
+    is constructed in-place using \a args as the arguments for its
+    construction.
+
+    If there is already an item with the same key in the hash, this
+    function will simply create a new one. (This behavior is
+    different from replace(), which overwrites the value of an
+    existing item.)
+
+    Returns an iterator pointing to the new element.
+
+    \sa insert
+*/
+
+/*!
+    \fn template <typename T> template <typename ...Args> QMultiHash<Key, T>::iterator QMultiHash<Key, T>::emplaceReplace(const Key &key, Args&&... args)
+    \fn template <typename T> template <typename ...Args> QMultiHash<Key, T>::iterator QMultiHash<Key, T>::emplaceReplace(Key &&key, Args&&... args)
+
+    Inserts a new element into the container. This new element
+    is constructed in-place using \a args as the arguments for its
+    construction.
+
+    If there is already an item with the same key in the hash, that item's
+    value is replaced with a value constructed from \a args.
+
+    Returns an iterator pointing to the new element.
+
+    \sa replace, emplace
+*/
+
+
 /*! \fn template <class Key, class T> QMultiHash &QMultiHash<Key, T>::unite(const QMultiHash &other)
     \since 5.13