Add QHash::insert(const QHash &other)

As opposed to unite(), this inserts one hash into the other
without duplicating elements.

Change-Id: Ifc786c48f5dc3ab18c29782e73eac3c1a3ef8981
Reviewed-by: Anton Kudryavtsev <antkudr@mail.ru>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

src/corelib/tools/qhash.cpp

@@ -1807,6 +1807,18 @@ uint qHash(long double key, uint seed) noexcept
     \sa insertMulti()
 */
 
+/*! \fn template <class Key, class T> void QHash<Key, T>::insert(const QHash &other)
+    \since 5.15
+
+    Inserts all the items in the \a other hash into this hash.
+
+    If a key is common to both hashes, its value will be replaced with the
+    value stored in \a other.
+
+    \note If \a other contains multiple entries with the same key then the
+    final value of the key is undefined.
+*/
+
 /*! \fn template <class Key, class T> QHash<Key, T>::iterator QHash<Key, T>::insertMulti(const Key &key, const T &value)
 
     Inserts a new item with the \a key and a value of \a value.

src/corelib/tools/qhash.h

@@ -526,6 +526,7 @@ public:
     const_iterator find(const Key &key) const;
     const_iterator constFind(const Key &key) const;
     iterator insert(const Key &key, const T &value);
+    void insert(const QHash &hash);
     iterator insertMulti(const Key &key, const T &value);
     QHash &unite(const QHash &other);
 
@@ -840,6 +841,31 @@ Q_INLINE_TEMPLATE typename QHash<Key, T>::iterator QHash<Key, T>::insert(const K
     return iterator(*node);
 }
 
+template <class Key, class T>
+Q_INLINE_TEMPLATE void QHash<Key, T>::insert(const QHash &hash)
+{
+    if (d == hash.d)
+        return;
+
+    detach();
+
+    QHashData::Node *i = hash.d->firstNode();
+    QHashData::Node *end = reinterpret_cast<QHashData::Node *>(hash.e);
+    while (i != end) {
+        Node *n = concrete(i);
+        Node **node = findNode(n->key, n->h);
+        if (*node == e) {
+            if (d->willGrow())
+                node = findNode(n->key, n->h);
+            createNode(n->h, n->key, n->value, node);
+        } else {
+            if (!std::is_same<T, QHashDummyValue>::value)
+                (*node)->value = n->value;
+        }
+        i = QHashData::nextNode(i);
+    }
+}
+
 template <class Key, class T>
 Q_INLINE_TEMPLATE typename QHash<Key, T>::iterator QHash<Key, T>::insertMulti(const Key &akey,
                                                                               const T &avalue)

tests/auto/corelib/tools/qhash/tst_qhash.cpp

@@ -69,6 +69,7 @@ private slots:
     void initializerList();
     void eraseValidIteratorOnSharedHash();
     void equal_range();
+    void insert_hash();
 };
 
 struct IdentityTracker {
@@ -1643,5 +1644,77 @@ void tst_QHash::equal_range()
     }
 }
 
+void tst_QHash::insert_hash()
+{
+    {
+        QHash<int, int> hash;
+        hash.insert(1, 1);
+        hash.insert(2, 2);
+        hash.insert(0, -1);
+
+        QHash<int, int> hash2;
+        hash2.insert(0, 0);
+        hash2.insert(3, 3);
+        hash2.insert(4, 4);
+
+        hash.insert(hash2);
+
+        QCOMPARE(hash.count(), 5);
+        for (int i = 0; i < 5; ++i)
+            QCOMPARE(hash[i], i);
+    }
+    {
+        QHash<int, int> hash;
+        hash.insert(0, 5);
+
+        QHash<int, int> hash2;
+
+        hash.insert(hash2);
+
+        QCOMPARE(hash.count(), 1);
+        QCOMPARE(hash[0], 5);
+    }
+    {
+        QHash<int, int> hash;
+        QHash<int, int> hash2;
+        hash2.insert(0, 5);
+
+        hash.insert(hash2);
+
+        QCOMPARE(hash.count(), 1);
+        QCOMPARE(hash[0], 5);
+        QCOMPARE(hash, hash2);
+    }
+    {
+        QHash<int, int> hash;
+        hash.insert(0, 7);
+        hash.insert(2, 5);
+        hash.insert(7, 55);
+
+        // insert into ourself, nothing should happen
+        hash.insert(hash);
+
+        QCOMPARE(hash.count(), 3);
+        QCOMPARE(hash[0], 7);
+        QCOMPARE(hash[2], 5);
+        QCOMPARE(hash[7], 55);
+    }
+    {
+        // This will use a QMultiHash and then insert that into QHash,
+        // the ordering is undefined so we won't test that but make
+        // sure this isn't adding multiple entries with the same key
+        // to the QHash.
+        QHash<int, int> hash;
+        QMultiHash<int, int> hash2;
+        hash2.insert(0, 5);
+        hash2.insert(0, 6);
+        hash2.insert(0, 7);
+
+        hash.insert(hash2);
+
+        QCOMPARE(hash.count(), 1);
+    }
+}
+
 QTEST_APPLESS_MAIN(tst_QHash)
 #include "tst_qhash.moc"