1/****************************************************************************
2**
3** Copyright (C) 2019 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Marc Mutz <marc.mutz@kdab.com>
4** Contact: https://www.qt.io/licensing/
5**
6** This file is part of the QtCore module of the Qt Toolkit.
7**
8** $QT_BEGIN_LICENSE:LGPL$
9** Commercial License Usage
10** Licensees holding valid commercial Qt licenses may use this file in
11** accordance with the commercial license agreement provided with the
12** Software or, alternatively, in accordance with the terms contained in
13** a written agreement between you and The Qt Company. For licensing terms
14** and conditions see https://www.qt.io/terms-conditions. For further
15** information use the contact form at https://www.qt.io/contact-us.
16**
17** GNU Lesser General Public License Usage
18** Alternatively, this file may be used under the terms of the GNU Lesser
19** General Public License version 3 as published by the Free Software
20** Foundation and appearing in the file LICENSE.LGPL3 included in the
21** packaging of this file. Please review the following information to
22** ensure the GNU Lesser General Public License version 3 requirements
23** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
24**
25** GNU General Public License Usage
26** Alternatively, this file may be used under the terms of the GNU
27** General Public License version 2.0 or (at your option) the GNU General
28** Public license version 3 or any later version approved by the KDE Free
29** Qt Foundation. The licenses are as published by the Free Software
30** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
31** included in the packaging of this file. Please review the following
32** information to ensure the GNU General Public License requirements will
33** be met: https://www.gnu.org/licenses/gpl-2.0.html and
34** https://www.gnu.org/licenses/gpl-3.0.html.
35**
36** $QT_END_LICENSE$
37**
38****************************************************************************/
39
40#ifndef QLOCKING_P_H
41#define QLOCKING_P_H
42
43//
44// W A R N I N G
45// -------------
46//
47// This file is not part of the Qt API. It exists for the convenience
48// of qmutex.cpp, qmutex_unix.cpp, and qmutex_win.cpp. This header
49// file may change from version to version without notice, or even be
50// removed.
51//
52// We mean it.
53//
54
55#include <QtCore/qmutex.h>
56
57#include <mutex>
58
59QT_BEGIN_NAMESPACE
60
61//
62// This API is bridging the time until we can depend on C++17:
63//
64// - qt_scoped_lock returns a lock that cannot be unlocked again before the end of the scope
65// - qt_unique_lock returns a lock that can be unlock()ed and moved around
66// - for compat with QMutexLocker, qt_unique_lock supports passing by pointer.
67// Do NOT use this overload lightly; it's only for cases such as where a Q_GLOBAL_STATIC
68// may have already been deleted. In particular, do NOT port from
69// QMutexLocker locker(&mutex);
70// to
71// auto locker = qt_unique_lock(&mutex);
72// as this will not port automatically to std::unique_lock come C++17!
73//
74// The intent, come C++17, is to replace
75// qt_scoped_lock(mutex);
76// qt_unique_lock(mutex); // except qt_unique_lock(&mutex)
77// with
78// std::scoped_lock(mutex);
79// std::unique_lock(mutex);
80// resp. (C++17 meaning CTAD, guaranteed copy elision + scoped_lock available on all platforms),
81// so please use these functions only in ways which don't break this mechanical search & replace.
82//
83
84namespace {
85
86template <typename Mutex, typename Lock =
87#if defined(__cpp_guaranteed_copy_elision) && __cpp_guaranteed_copy_elision >= 201606L
88# if defined(__cpp_lib_scoped_lock) && __cpp_lib_scoped_lock >= 201703L
89 std::scoped_lock
90# else
91 std::lock_guard
92# endif
93#else
94 std::unique_lock
95#endif
96 <typename std::decay<Mutex>::type>
97>
98Lock qt_scoped_lock(Mutex &mutex)
99{
100 return Lock(mutex);
101}
102
103template <typename Mutex, typename Lock = std::unique_lock<typename std::decay<Mutex>::type>>
104Lock qt_unique_lock(Mutex &mutex)
105{
106 return Lock(mutex);
107}
108
109template <typename Mutex, typename Lock = std::unique_lock<typename std::decay<Mutex>::type>>
110Lock qt_unique_lock(Mutex *mutex)
111{
112 return mutex ? Lock(*mutex) : Lock() ;
113}
114
115} // unnamed namespace
116
117QT_END_NAMESPACE
118
119#endif // QLOCKING_P_H
120

source code of qtbase/src/corelib/thread/qlocking_p.h