82 lines
2.4 KiB
C++
82 lines
2.4 KiB
C++
/*
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* Copyright (C) 2018 Yusuke Suzuki <utatane.tea@gmail.com>.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
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* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
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* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#pragma once
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#include <wtf/Condition.h>
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#include <wtf/Lock.h>
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#include <wtf/Noncopyable.h>
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namespace WTF {
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class Semaphore final {
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WTF_MAKE_NONCOPYABLE(Semaphore);
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WTF_MAKE_FAST_ALLOCATED;
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public:
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constexpr Semaphore(unsigned value)
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: m_value(value)
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{
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}
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void signal()
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{
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Locker locker { m_lock };
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m_value++;
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m_condition.notifyOne();
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}
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bool waitUntil(const TimeWithDynamicClockType& timeout)
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{
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Locker locker { m_lock };
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bool satisfied = m_condition.waitUntil(m_lock, timeout, [&] {
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assertIsHeld(m_lock);
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return m_value;
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});
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if (satisfied)
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--m_value;
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return satisfied;
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}
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bool waitFor(Seconds relativeTimeout)
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{
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return waitUntil(MonotonicTime::now() + relativeTimeout);
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}
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void wait()
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{
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waitUntil(ParkingLot::Time::infinity());
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}
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private:
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unsigned m_value WTF_GUARDED_BY_LOCK(m_lock) { 0 };
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Lock m_lock;
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Condition m_condition;
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};
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} // namespace WTF
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using WTF::Semaphore;
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