From 7ee9551b62b050f7e9aefdc19e19bac5ba263507 Mon Sep 17 00:00:00 2001
From: Thiago Macieira <thiago.macieira@intel.com>
Date: Wed, 23 May 2012 21:10:31 +0200
Subject: Add support for multiple arguments to QSharedPointer::create()

Requires C++11 rvalue references and variadic templates so we can
implement perfect forwarding.

Change-Id: I62e47d1ffd0c61e8386f9f246aa79031b7430b46
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
---
 src/corelib/tools/qsharedpointer.cpp    | 31 +++++++++++++++++++++++++++++++
 src/corelib/tools/qsharedpointer.h      |  3 +++
 src/corelib/tools/qsharedpointer_impl.h | 27 +++++++++++++++++++++++++++
 3 files changed, 61 insertions(+)

(limited to 'src/corelib')

diff --git a/src/corelib/tools/qsharedpointer.cpp b/src/corelib/tools/qsharedpointer.cpp
index 167771027e..c9456c44c2 100644
--- a/src/corelib/tools/qsharedpointer.cpp
+++ b/src/corelib/tools/qsharedpointer.cpp
@@ -604,6 +604,37 @@
     \sa qSharedPointerObjectCast()
 */
 
+/*!
+    \fn QSharedPointer<T> QSharedPointer::create()
+    \since 4.6
+
+    Creates a QSharedPointer object and allocates a new item of type \tt T. The
+    QSharedPointer internals and the object are allocated in one single memory
+    allocation, which could help reduce memory fragmentation in a long-running
+    application.
+
+    This function calls the default constructor for type \tt T.
+*/
+
+/*!
+    \fn QSharedPointer<T> QSharedPointer::create(...)
+    \overload
+    \since 5.1
+
+    Creates a QSharedPointer object and allocates a new item of type \tt T. The
+    QSharedPointer internals and the object are allocated in one single memory
+    allocation, which could help reduce memory fragmentation in a long-running
+    application.
+
+    This function will attempt to call a constructor for type \tt T that can
+    accept all the arguments passed. Arguments will be perfectly-forwarded.
+
+    \note This function is only available with a C++11 compiler that supports
+    perfect forwarding of an arbitrary number of arguments. If the compiler
+    does not support the necessary C++11 features, you must use the overload
+    that calls the default constructor.
+*/
+
 /*!
     \fn QWeakPointer<T> QSharedPointer::toWeakRef() const
 
diff --git a/src/corelib/tools/qsharedpointer.h b/src/corelib/tools/qsharedpointer.h
index cfc5cadbb0..a430153bca 100644
--- a/src/corelib/tools/qsharedpointer.h
+++ b/src/corelib/tools/qsharedpointer.h
@@ -95,6 +95,9 @@ public:
     template <class X> QSharedPointer<X> dynamicCast() const;
     template <class X> QSharedPointer<X> constCast() const;
     template <class X> QSharedPointer<X> objectCast() const;
+
+    static inline QSharedPointer<T> create();
+    static inline QSharedPointer<T> create(...);
 };
 
 template <class T>
diff --git a/src/corelib/tools/qsharedpointer_impl.h b/src/corelib/tools/qsharedpointer_impl.h
index 6f3e577e55..6393cc3970 100644
--- a/src/corelib/tools/qsharedpointer_impl.h
+++ b/src/corelib/tools/qsharedpointer_impl.h
@@ -62,6 +62,10 @@ QT_END_HEADER
 #include <QtCore/qobject.h>    // for qobject_cast
 #include <QtCore/qhash.h>    // for qHash
 
+#if defined(Q_COMPILER_RVALUE_REFS) && defined(Q_COMPILER_VARIADIC_TEMPLATES)
+#  include <utility>           // for std::forward
+#endif
+
 QT_BEGIN_HEADER
 
 QT_BEGIN_NAMESPACE
@@ -389,6 +393,28 @@ public:
 
     QWeakPointer<T> toWeakRef() const;
 
+#if defined(Q_COMPILER_RVALUE_REFS) && defined(Q_COMPILER_VARIADIC_TEMPLATES)
+    template <typename... Args>
+    static QSharedPointer<T> create(Args && ...arguments)
+    {
+        typedef QtSharedPointer::ExternalRefCountWithContiguousData<T> Private;
+# ifdef QT_SHAREDPOINTER_TRACK_POINTERS
+        typename Private::DestroyerFn destroy = &Private::safetyCheckDeleter;
+# else
+        typename Private::DestroyerFn destroy = &Private::deleter;
+# endif
+        QSharedPointer<T> result(Qt::Uninitialized);
+        result.d = Private::create(&result.value, destroy);
+
+        // now initialize the data
+        new (result.data()) T(std::forward<Args>(arguments)...);
+        result.d->setQObjectShared(result.value, true);
+# ifdef QT_SHAREDPOINTER_TRACK_POINTERS
+        internalSafetyCheckAdd(result.d, result.value);
+# endif
+        return result;
+    }
+#else
     static inline QSharedPointer<T> create()
     {
         typedef QtSharedPointer::ExternalRefCountWithContiguousData<T> Private;
@@ -408,6 +434,7 @@ public:
         result.d->setQObjectShared(result.value, true);
         return result;
     }
+#endif
 
 private:
     explicit QSharedPointer(Qt::Initialization) {}
-- 
cgit v1.2.3