85 lines
2.1 KiB
C++
85 lines
2.1 KiB
C++
// Copyright 2014 Dolphin Emulator Project
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// SPDX-License-Identifier: GPL-2.0-or-later
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// Multithreaded event class. This allows waiting in a thread for an event to
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// be triggered in another thread. While waiting, the CPU will be available for
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// other tasks.
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// * Set(): triggers the event and wakes up the waiting thread.
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// * Wait(): waits for the event to be triggered.
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// * Reset(): tries to reset the event before the waiting thread sees it was
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// triggered. Usually a bad idea.
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#pragma once
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#ifdef _WIN32
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#include <concrt.h>
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#endif
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#include <chrono>
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#include <condition_variable>
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#include <mutex>
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#include "Common/Flag.h"
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namespace Common
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{
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class Event final
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{
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public:
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void Set()
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{
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if (m_flag.TestAndSet())
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{
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// Lock and immediately unlock m_mutex.
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{
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// Holding the lock at any time between the change of our flag and notify call
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// is sufficient to prevent a race where both of these actions
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// happen between the other thread's predicate test and wait call
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// which would cause wait to block until the next spurious wakeup or timeout.
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// Unlocking before notification is a micro-optimization to prevent
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// the notified thread from immediately blocking on the mutex.
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std::lock_guard<std::mutex> lk(m_mutex);
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}
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m_condvar.notify_one();
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}
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}
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void Wait()
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{
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if (m_flag.TestAndClear())
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return;
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std::unique_lock<std::mutex> lk(m_mutex);
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m_condvar.wait(lk, [&] { return m_flag.TestAndClear(); });
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}
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template <class Rep, class Period>
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bool WaitFor(const std::chrono::duration<Rep, Period>& rel_time)
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{
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if (m_flag.TestAndClear())
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return true;
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std::unique_lock<std::mutex> lk(m_mutex);
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bool signaled = m_condvar.wait_for(lk, rel_time, [&] { return m_flag.TestAndClear(); });
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return signaled;
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}
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void Reset()
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{
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// no other action required, since wait loops on
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// the predicate and any lingering signal will get
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// cleared on the first iteration
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m_flag.Clear();
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}
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private:
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Flag m_flag;
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std::condition_variable m_condvar;
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std::mutex m_mutex;
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};
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} // namespace Common
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