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