Non-associative containers: add range constructors

Something nice we'd like to detect for array-backed containers
is if the iterator passed is a Contiguous one; if the type is also
trivially copyable / Q_PRIMITIVE_TYPE, we could memcpy() the whole
range.

However, there's no trait in the Standard to detect contiguous
iterators (the best approximation would be detecting if the iterator
is actually a pointer). Also, it's probably not smart to do the work
now for QVector since QVector needs refactoring anyhow, and this work
will be lost.

QString and QByteArray are left in another commit.

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

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

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

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

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

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

Change-Id: I220edb796053c9c4d31a6dbdc7efc5fc0f6678f9
Reviewed-by: Milian Wolff <milian.wolff@kdab.com>

1 files changed, 14 insertions, 2 deletions

diff --git a/src/corelib/tools/qlist.h b/src/corelib/tools/qlist.h
index 77d8df4a88..dfb8a8a4ab 100644
--- a/src/corelib/tools/qlist.h
+++ b/src/corelib/tools/qlist.h
@@ -46,6 +46,7 @@
 #include <QtCore/qarraydata.h>
 #include <QtCore/qhashfunctions.h>
 #include <QtCore/qvector.h>
+#include <QtCore/qcontainertools_impl.h>
 
 #include <iterator>
 #include <list>
@@ -169,9 +170,11 @@ public:
     inline void swap(QList<T> &other) noexcept { qSwap(d, other.d); }
 #ifdef Q_COMPILER_INITIALIZER_LISTS
     inline QList(std::initializer_list<T> args)
-        : d(const_cast<QListData::Data *>(&QListData::shared_null))
-    { reserve(int(args.size())); std::copy(args.begin(), args.end(), std::back_inserter(*this)); }
+        : QList(args.begin(), args.end()) {}
 #endif
+    template <typename InputIterator, QtPrivate::IfIsInputIterator<InputIterator> = true>
+    QList(InputIterator first, InputIterator last);
+
     bool operator==(const QList<T> &l) const;
     inline bool operator!=(const QList<T> &l) const { return !(*this == l); }
 
@@ -843,6 +846,15 @@ Q_OUTOFLINE_TEMPLATE QList<T>::~QList()
 }
 
 template <typename T>
+template <typename InputIterator, QtPrivate::IfIsInputIterator<InputIterator>>
+QList<T>::QList(InputIterator first, InputIterator last)
+    : QList()
+{
+    QtPrivate::reserveIfForwardIterator(this, first, last);
+    std::copy(first, last, std::back_inserter(*this));
+}
+
+template <typename T>
 Q_OUTOFLINE_TEMPLATE bool QList<T>::operator==(const QList<T> &l) const
 {
     if (d == l.d)