80 lines
2.3 KiB
C++
80 lines
2.3 KiB
C++
// Copyright (C) 2019 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Marc Mutz <marc.mutz@kdab.com>
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// 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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#ifndef QLOCKING_P_H
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#define QLOCKING_P_H
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//
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// W A R N I N G
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// -------------
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//
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// This file is not part of the Qt API. It exists for the convenience of
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// qmutex.cpp and qmutex_unix.cpp. This header file may change from version to
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// version without notice, or even be removed.
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//
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// We mean it.
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//
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#include <QtCore/qmutex.h>
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#include <QtCore/private/qglobal_p.h>
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#include <mutex>
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QT_BEGIN_NAMESPACE
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//
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// This API is bridging the time until we can depend on C++17:
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//
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// - qt_scoped_lock returns a lock that cannot be unlocked again before the end of the scope
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// - qt_unique_lock returns a lock that can be unlock()ed and moved around
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// - for compat with QMutexLocker, qt_unique_lock supports passing by pointer.
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// Do NOT use this overload lightly; it's only for cases such as where a Q_GLOBAL_STATIC
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// may have already been deleted. In particular, do NOT port from
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// QMutexLocker locker(&mutex);
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// to
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// auto locker = qt_unique_lock(&mutex);
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// as this will not port automatically to std::unique_lock come C++17!
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//
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// The intent, come C++17, is to replace
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// qt_scoped_lock(mutex);
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// qt_unique_lock(mutex); // except qt_unique_lock(&mutex)
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// with
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// std::scoped_lock(mutex);
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// std::unique_lock(mutex);
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// resp. (C++17 meaning CTAD, guaranteed copy elision + scoped_lock available on all platforms),
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// so please use these functions only in ways which don't break this mechanical search & replace.
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//
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namespace {
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template <typename Mutex, typename Lock =
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# if defined(__cpp_lib_scoped_lock) && __cpp_lib_scoped_lock >= 201703L
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std::scoped_lock
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# else
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std::lock_guard
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# endif
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<typename std::decay<Mutex>::type>
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>
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Lock qt_scoped_lock(Mutex &mutex)
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{
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return Lock(mutex);
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}
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template <typename Mutex, typename Lock = std::unique_lock<typename std::decay<Mutex>::type>>
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Lock qt_unique_lock(Mutex &mutex)
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{
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return Lock(mutex);
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}
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template <typename Mutex, typename Lock = std::unique_lock<typename std::decay<Mutex>::type>>
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Lock qt_unique_lock(Mutex *mutex)
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{
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return mutex ? Lock(*mutex) : Lock() ;
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}
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} // unnamed namespace
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QT_END_NAMESPACE
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#endif // QLOCKING_P_H
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