| 1 | // Copyright (C) 2019 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Marc Mutz <marc.mutz@kdab.com> |
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| 2 | // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only |
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| 3 | |
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| 4 | #ifndef QLOCKING_P_H |
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| 5 | #define QLOCKING_P_H |
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| 6 | |
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| 7 | // |
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| 8 | // W A R N I N G |
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| 9 | // ------------- |
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| 10 | // |
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| 11 | // This file is not part of the Qt API. It exists for the convenience of |
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| 12 | // qmutex.cpp and qmutex_unix.cpp. This header file may change from version to |
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| 13 | // version without notice, or even be removed. |
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| 14 | // |
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| 15 | // We mean it. |
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| 16 | // |
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| 17 | |
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| 18 | #include <QtCore/qmutex.h> |
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| 19 | #include <QtCore/private/qglobal_p.h> |
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| 20 | |
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| 21 | #include <mutex> |
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| 22 | |
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| 23 | QT_BEGIN_NAMESPACE |
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| 24 | |
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| 25 | // |
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| 26 | // This API is bridging the time until we can depend on C++17: |
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| 27 | // |
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| 28 | // - qt_scoped_lock returns a lock that cannot be unlocked again before the end of the scope |
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| 29 | // - qt_unique_lock returns a lock that can be unlock()ed and moved around |
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| 30 | // - for compat with QMutexLocker, qt_unique_lock supports passing by pointer. |
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| 31 | // Do NOT use this overload lightly; it's only for cases such as where a Q_GLOBAL_STATIC |
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| 32 | // may have already been deleted. In particular, do NOT port from |
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| 33 | // QMutexLocker locker(&mutex); |
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| 34 | // to |
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| 35 | // auto locker = qt_unique_lock(&mutex); |
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| 36 | // as this will not port automatically to std::unique_lock come C++17! |
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| 37 | // |
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| 38 | // The intent, come C++17, is to replace |
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| 39 | // qt_scoped_lock(mutex); |
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| 40 | // qt_unique_lock(mutex); // except qt_unique_lock(&mutex) |
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| 41 | // with |
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| 42 | // std::scoped_lock(mutex); |
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| 43 | // std::unique_lock(mutex); |
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| 44 | // resp. (C++17 meaning CTAD, guaranteed copy elision + scoped_lock available on all platforms), |
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| 45 | // so please use these functions only in ways which don't break this mechanical search & replace. |
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| 46 | // |
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| 47 | |
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| 48 | namespace { |
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| 49 | |
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| 50 | template <typename Mutex, typename Lock = |
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| 51 | # if defined(__cpp_lib_scoped_lock) && __cpp_lib_scoped_lock >= 201703L |
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| 52 | std::scoped_lock |
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| 53 | # else |
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| 54 | std::lock_guard |
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| 55 | # endif |
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| 56 | <typename std::decay<Mutex>::type> |
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| 57 | > |
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| 58 | Lock qt_scoped_lock(Mutex &mutex) |
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| 59 | { |
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| 60 | return Lock(mutex); |
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| 61 | } |
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| 62 | |
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| 63 | template <typename Mutex, typename Lock = std::unique_lock<typename std::decay<Mutex>::type>> |
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| 64 | Lock qt_unique_lock(Mutex &mutex) |
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| 65 | { |
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| 66 | return Lock(mutex); |
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| 67 | } |
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| 68 | |
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| 69 | template <typename Mutex, typename Lock = std::unique_lock<typename std::decay<Mutex>::type>> |
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| 70 | Lock qt_unique_lock(Mutex *mutex) |
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| 71 | { |
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| 72 | return mutex ? Lock(*mutex) : Lock() ; |
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| 73 | } |
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| 74 | |
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| 75 | } // unnamed namespace |
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| 76 | |
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| 77 | QT_END_NAMESPACE |
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| 78 | |
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| 79 | #endif // QLOCKING_P_H |
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| 80 | |
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