QHash/QMultiHash: add range constructors

QMap and QMultiMap will go in a separate commit, due to QMap's
insertion behavior that "reverses" the inserted elements.

[ChangeLog][QtCore][QHash] Added range constructor.

[ChangeLog][QtCore][QMultiHash] Added range constructor.

Change-Id: Icfd0d0afde27792e8439ed6df3e8774696b134d3
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Sérgio Martins <sergio.martins@kdab.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/tools/qcontainertools_impl.h

@@ -84,6 +84,49 @@ void reserveIfForwardIterator(Container *c, ForwardIterator f, ForwardIterator l
 {
     c->reserve(static_cast<typename Container::size_type>(std::distance(f, l)));
 }
+
+// for detecting expression validity
+template <typename ... T>
+using void_t = void;
+
+template <typename Iterator, typename = void_t<>>
+struct AssociativeIteratorHasKeyAndValue : std::false_type
+{
+};
+
+template <typename Iterator>
+struct AssociativeIteratorHasKeyAndValue<
+        Iterator,
+        void_t<decltype(std::declval<Iterator &>().key()),
+               decltype(std::declval<Iterator &>().value())>
+    >
+    : std::true_type
+{
+};
+
+template <typename Iterator, typename = void_t<>, typename = void_t<>>
+struct AssociativeIteratorHasFirstAndSecond : std::false_type
+{
+};
+
+template <typename Iterator>
+struct AssociativeIteratorHasFirstAndSecond<
+        Iterator,
+        void_t<decltype(std::declval<Iterator &>()->first),
+               decltype(std::declval<Iterator &>()->second)>
+    >
+    : std::true_type
+{
+};
+
+template <typename Iterator>
+using IfAssociativeIteratorHasKeyAndValue =
+    typename std::enable_if<AssociativeIteratorHasKeyAndValue<Iterator>::value, bool>::type;
+
+template <typename Iterator>
+using IfAssociativeIteratorHasFirstAndSecond =
+    typename std::enable_if<AssociativeIteratorHasFirstAndSecond<Iterator>::value, bool>::type;
+
 } // namespace QtPrivate
 
 QT_END_NAMESPACE

src/corelib/tools/qhash.cpp

@@ -1251,6 +1251,17 @@ uint qHash(long double key, uint seed) noexcept
     compiled in C++11 mode.
 */
 
+/*! \fn template <class Key, class T> template <class InputIterator> QHash<Key, T>::QHash(InputIterator begin, InputIterator end)
+    \since 5.14
+
+    Constructs a hash with a copy of each of the elements in the iterator range
+    [\a begin, \a end). Either the elements iterated by the range must be
+    objects with \c{first} and \c{second} data members (like \c{QPair},
+    \c{std::pair}, etc.) convertible to \c Key and to \c T respectively; or the
+    iterators must have \c{key()} and \c{value()} member functions, returning a
+    key convertible to \c Key and a value convertible to \c T respectively.
+*/
+
 /*! \fn template <class Key, class T> QHash<Key, T>::QHash(const QHash &other)
 
     Constructs a copy of \a other.
@@ -2586,6 +2597,17 @@ uint qHash(long double key, uint seed) noexcept
     \sa operator=()
 */
 
+/*! \fn template <class Key, class T> template <class InputIterator> QMultiHash::QMultiHash(InputIterator begin, InputIterator end)
+    \since 5.14
+
+    Constructs a multi-hash with a copy of each of the elements in the iterator range
+    [\a begin, \a end). Either the elements iterated by the range must be
+    objects with \c{first} and \c{second} data members (like \c{QPair},
+    \c{std::pair}, etc.) convertible to \c Key and to \c T respectively; or the
+    iterators must have \c{key()} and \c{value()} member functions, returning a
+    key convertible to \c Key and a value convertible to \c T respectively.
+*/
+
 /*! \fn template <class Key, class T> QMultiHash<Key, T>::iterator QMultiHash<Key, T>::replace(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

@@ -46,6 +46,7 @@
 #include <QtCore/qlist.h>
 #include <QtCore/qrefcount.h>
 #include <QtCore/qhashfunctions.h>
+#include <QtCore/qcontainertools_impl.h>
 
 #ifdef Q_COMPILER_INITIALIZER_LISTS
 #include <initializer_list>
@@ -258,6 +259,28 @@ public:
     QHash(QHash &&other) noexcept : d(other.d) { other.d = const_cast<QHashData *>(&QHashData::shared_null); }
     QHash &operator=(QHash &&other) noexcept
     { QHash moved(std::move(other)); swap(moved); return *this; }
+#endif
+#ifdef Q_QDOC
+    template <typename InputIterator>
+    QHash(InputIterator f, InputIterator l);
+#else
+    template <typename InputIterator, QtPrivate::IfAssociativeIteratorHasKeyAndValue<InputIterator> = true>
+    QHash(InputIterator f, InputIterator l)
+        : QHash()
+    {
+        QtPrivate::reserveIfForwardIterator(this, f, l);
+        for (; f != l; ++f)
+            insert(f.key(), f.value());
+    }
+
+    template <typename InputIterator, QtPrivate::IfAssociativeIteratorHasFirstAndSecond<InputIterator> = true>
+    QHash(InputIterator f, InputIterator l)
+        : QHash()
+    {
+        QtPrivate::reserveIfForwardIterator(this, f, l);
+        for (; f != l; ++f)
+            insert(f->first, f->second);
+    }
 #endif
     void swap(QHash &other) noexcept { qSwap(d, other.d); }
 
@@ -1028,6 +1051,26 @@ public:
         for (typename std::initializer_list<std::pair<Key,T> >::const_iterator it = list.begin(); it != list.end(); ++it)
             insert(it->first, it->second);
     }
+#endif
+#ifdef Q_QDOC
+    template <typename InputIterator>
+    QMultiHash(InputIterator f, InputIterator l);
+#else
+    template <typename InputIterator, QtPrivate::IfAssociativeIteratorHasKeyAndValue<InputIterator> = true>
+    QMultiHash(InputIterator f, InputIterator l)
+    {
+        QtPrivate::reserveIfForwardIterator(this, f, l);
+        for (; f != l; ++f)
+            insert(f.key(), f.value());
+    }
+
+    template <typename InputIterator, QtPrivate::IfAssociativeIteratorHasFirstAndSecond<InputIterator> = true>
+    QMultiHash(InputIterator f, InputIterator l)
+    {
+        QtPrivate::reserveIfForwardIterator(this, f, l);
+        for (; f != l; ++f)
+            insert(f->first, f->second);
+    }
 #endif
     // compiler-generated copy/move ctors/assignment operators are fine!
     // compiler-generated destructor is fine!

tests/auto/corelib/tools/containerapisymmetry/tst_containerapisymmetry.cpp

@@ -34,6 +34,7 @@
 #include "qstring.h"
 #include "qvarlengtharray.h"
 #include "qvector.h"
+#include "qhash.h"
 #include "qdebug.h"
 
 #include <algorithm>
@@ -41,6 +42,7 @@
 #include <vector> // for reference
 #include <list>
 #include <set>
+#include <map>
 
 // MSVC has these containers from the Standard Library, but it lacks
 // a __has_include mechanism (that we need to use for other stdlibs).
@@ -58,6 +60,9 @@
 #if COMPILER_HAS_STDLIB_INCLUDE(<unordered_set>)
 #include <unordered_set>
 #endif
+#if COMPILER_HAS_STDLIB_INCLUDE(<unordered_map>)
+#include <unordered_map>
+#endif
 
 struct Movable
 {
@@ -255,6 +260,9 @@ private:
     template<template<typename ... T> class Container>
     void non_associative_container_duplicates_strategy() const;
 
+    template <typename Container>
+    void ranged_ctor_associative_impl() const;
+
 private Q_SLOTS:
     // non associative
     void ranged_ctor_std_vector_int() { ranged_ctor_non_associative_impl<std::vector<int>>(); }
@@ -403,6 +411,71 @@ private Q_SLOTS:
     void ranged_ctor_QSet_Complex() { ranged_ctor_non_associative_impl<QSet<Complex>>(); }
     void ranged_ctor_QSet_duplicates_strategy() { non_associative_container_duplicates_strategy<QSet>(); }
 
+    // associative
+    void ranged_ctor_std_map_int() { ranged_ctor_associative_impl<std::map<int, int>>(); }
+    void ranged_ctor_std_map_Movable() { ranged_ctor_associative_impl<std::map<Movable, int>>(); }
+    void ranged_ctor_std_map_Complex() { ranged_ctor_associative_impl<std::map<Complex, int>>(); }
+
+    void ranged_ctor_std_multimap_int() { ranged_ctor_associative_impl<std::multimap<int, int>>(); }
+    void ranged_ctor_std_multimap_Movable() { ranged_ctor_associative_impl<std::multimap<Movable, int>>(); }
+    void ranged_ctor_std_multimap_Complex() { ranged_ctor_associative_impl<std::multimap<Complex, int>>(); }
+
+    void ranged_ctor_unordered_map_int() {
+#if COMPILER_HAS_STDLIB_INCLUDE(<unordered_map>)
+        ranged_ctor_associative_impl<std::unordered_map<int, int>>();
+#else
+        QSKIP("<unordered_map> is needed for this test");
+#endif
+    }
+
+    void ranged_ctor_unordered_map_Movable() {
+#if COMPILER_HAS_STDLIB_INCLUDE(<unordered_map>)
+        ranged_ctor_associative_impl<std::unordered_map<Movable, Movable>>();
+#else
+        QSKIP("<unordered_map> is needed for this test");
+#endif
+    }
+
+    void ranged_ctor_unordered_map_Complex() {
+#if COMPILER_HAS_STDLIB_INCLUDE(<unordered_map>)
+        ranged_ctor_associative_impl<std::unordered_map<Complex, Complex>>();
+#else
+        QSKIP("<unordered_map> is needed for this test");
+#endif
+    }
+
+    void ranged_ctor_QHash_int() { ranged_ctor_associative_impl<QHash<int, int>>(); }
+    void ranged_ctor_QHash_Movable() { ranged_ctor_associative_impl<QHash<Movable, int>>(); }
+    void ranged_ctor_QHash_Complex() { ranged_ctor_associative_impl<QHash<Complex, int>>(); }
+
+    void ranged_ctor_unordered_multimap_int() {
+#if COMPILER_HAS_STDLIB_INCLUDE(<unordered_map>)
+        ranged_ctor_associative_impl<std::unordered_multimap<int, int>>();
+#else
+        QSKIP("<unordered_map> is needed for this test");
+#endif
+    }
+
+    void ranged_ctor_unordered_multimap_Movable() {
+#if COMPILER_HAS_STDLIB_INCLUDE(<unordered_map>)
+        ranged_ctor_associative_impl<std::unordered_multimap<Movable, Movable>>();
+#else
+        QSKIP("<unordered_map> is needed for this test");
+#endif
+    }
+
+    void ranged_ctor_unordered_multimap_Complex() {
+#if COMPILER_HAS_STDLIB_INCLUDE(<unordered_map>)
+        ranged_ctor_associative_impl<std::unordered_multimap<Complex, Complex>>();
+#else
+        QSKIP("<unordered_map> is needed for this test");
+#endif
+    }
+
+    void ranged_ctor_QMultiHash_int() { ranged_ctor_associative_impl<QMultiHash<int, int>>(); }
+    void ranged_ctor_QMultiHash_Movable() { ranged_ctor_associative_impl<QMultiHash<Movable, int>>(); }
+    void ranged_ctor_QMultiHash_Complex() { ranged_ctor_associative_impl<QMultiHash<Complex, int>>(); }
+
 private:
     template <typename Container>
     void front_back_impl() const;
@@ -651,6 +724,73 @@ void tst_ContainerApiSymmetry::non_associative_container_duplicates_strategy() c
 }
 #endif // Q_COMPILER_INITIALIZER_LISTS
 
+template <typename Container>
+void tst_ContainerApiSymmetry::ranged_ctor_associative_impl() const
+{
+    using K = typename Container::key_type;
+    using V = typename Container::mapped_type;
+
+    // The double K(0) is deliberate. The order of the elements matters:
+    // * for unique-key STL containers, the first one should be the one inserted (cf. LWG 2844)
+    // * for unique-key Qt containers, the last one should be the one inserted
+    // * for multi-key sorted containers, the order of insertion of identical keys is also the
+    //   iteration order (which establishes the equality of the containers)
+    // (although nothing of this is being tested here, that deserves its own testing)
+    const Container reference{
+        { K(0), V(1000) },
+        { K(1), V(1001) },
+        { K(2), V(1002) },
+        { K(0), V(1003) }
+    };
+
+    // Note that using anything not convertible to std::pair doesn't work for
+    // std containers. Their ranged construction is defined in terms of
+    // insert(value_type), which for std associative containers is
+    // std::pair<const K, T>.
+
+    // plain array
+    const std::pair<K, V> values1[] = {
+        std::make_pair(K(0), V(1000)),
+        std::make_pair(K(1), V(1001)),
+        std::make_pair(K(2), V(1002)),
+        std::make_pair(K(0), V(1003))
+    };
+
+    const Container c1(values1, values1 + sizeof(values1)/sizeof(values1[0]));
+
+    // from QList
+    QList<std::pair<K, V>> l2;
+    l2 << std::make_pair(K(0), V(1000))
+       << std::make_pair(K(1), V(1001))
+       << std::make_pair(K(2), V(1002))
+       << std::make_pair(K(0), V(1003));
+
+    const Container c2a(l2.begin(), l2.end());
+    const Container c2b(l2.cbegin(), l2.cend());
+
+    // from std::list
+    std::list<std::pair<K, V>> l3;
+    l3.push_back(std::make_pair(K(0), V(1000)));
+    l3.push_back(std::make_pair(K(1), V(1001)));
+    l3.push_back(std::make_pair(K(2), V(1002)));
+    l3.push_back(std::make_pair(K(0), V(1003)));
+    const Container c3a(l3.begin(), l3.end());
+
+    // from const std::list
+    const std::list<std::pair<K, V>> l3c = l3;
+    const Container c3b(l3c.begin(), l3c.end());
+
+    // from itself
+    const Container c4(reference.begin(), reference.end());
+
+    QCOMPARE(c1,  reference);
+    QCOMPARE(c2a, reference);
+    QCOMPARE(c2b, reference);
+    QCOMPARE(c3a, reference);
+    QCOMPARE(c3b, reference);
+    QCOMPARE(c4,  reference);
+}
+
 template <typename Container>
 Container make(int size)
 {