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