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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