include/QtCore/qsemaphore.h

0001 // Copyright (C) 2016 The Qt Company Ltd.
0002 // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
0003
0004 #ifndef QSEMAPHORE_H
0005 #define QSEMAPHORE_H
0006
0007 #include <QtCore/qglobal.h>
0008 #include <QtCore/qdeadlinetimer.h>
0009
0010 #include <chrono>
0011
0012 QT_REQUIRE_CONFIG(thread);
0013
0014 QT_BEGIN_NAMESPACE
0015
0016 class QSemaphorePrivate;
0017 class Q_CORE_EXPORT QSemaphore
0018 {
0019 public:
0020     explicit QSemaphore(int n = 0);
0021     ~QSemaphore();
0022
0023     void acquire(int n = 1);
0024     bool tryAcquire(int n = 1);
0025     QT_CORE_INLINE_SINCE(6, 6)
0026     bool tryAcquire(int n, int timeout);
0027     bool tryAcquire(int n, QDeadlineTimer timeout);
0028 #if QT_VERSION < QT_VERSION_CHECK(7, 0, 0)
0029     template <typename Rep, typename Period>
0030     bool tryAcquire(int n, std::chrono::duration<Rep, Period> timeout)
0031     { return tryAcquire(n, QDeadlineTimer(timeout)); }
0032 #endif
0033
0034     void release(int n = 1);
0035
0036     int available() const;
0037
0038     // std::counting_semaphore compatibility:
0039     bool try_acquire() noexcept { return tryAcquire(); }
0040     template <typename Rep, typename Period>
0041     bool try_acquire_for(const std::chrono::duration<Rep, Period> &timeout)
0042     { return tryAcquire(1, timeout); }
0043     template <typename Clock, typename Duration>
0044     bool try_acquire_until(const std::chrono::time_point<Clock, Duration> &tp)
0045     {
0046         return try_acquire_for(tp - Clock::now());
0047     }
0048 private:
0049     Q_DISABLE_COPY(QSemaphore)
0050
0051     union {
0052         QSemaphorePrivate *d;
0053         QBasicAtomicInteger<quintptr> u;
0054         QBasicAtomicInteger<quint32> u32[2];
0055         QBasicAtomicInteger<quint64> u64;
0056     };
0057 };
0058
0059 #if QT_CORE_INLINE_IMPL_SINCE(6, 6)
0060 bool QSemaphore::tryAcquire(int n, int timeout)
0061 {
0062     return tryAcquire(n, QDeadlineTimer(timeout));
0063 }
0064 #endif
0065
0066 class QSemaphoreReleaser
0067 {
0068 public:
0069     Q_NODISCARD_CTOR
0070     QSemaphoreReleaser() = default;
0071     Q_NODISCARD_CTOR
0072     explicit QSemaphoreReleaser(QSemaphore &sem, int n = 1) noexcept
0073         : m_sem(&sem), m_n(n) {}
0074     Q_NODISCARD_CTOR
0075     explicit QSemaphoreReleaser(QSemaphore *sem, int n = 1) noexcept
0076         : m_sem(sem), m_n(n) {}
0077     Q_NODISCARD_CTOR
0078     QSemaphoreReleaser(QSemaphoreReleaser &&other) noexcept
0079         : m_sem(other.cancel()), m_n(other.m_n) {}
0080     QT_MOVE_ASSIGNMENT_OPERATOR_IMPL_VIA_MOVE_AND_SWAP(QSemaphoreReleaser)
0081
0082     ~QSemaphoreReleaser()
0083     {
0084         if (m_sem)
0085             m_sem->release(m_n);
0086     }
0087
0088     void swap(QSemaphoreReleaser &other) noexcept
0089     {
0090         qt_ptr_swap(m_sem, other.m_sem);
0091         std::swap(m_n, other.m_n);
0092     }
0093
0094     QSemaphore *semaphore() const noexcept
0095     { return m_sem; }
0096
0097     QSemaphore *cancel() noexcept
0098     {
0099         return std::exchange(m_sem, nullptr);
0100     }
0101
0102 private:
0103     QSemaphore *m_sem = nullptr;
0104     int m_n;
0105 };
0106
0107 QT_END_NAMESPACE
0108
0109 #endif // QSEMAPHORE_H