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/*
* Copyright (C) 2016 Apple Inc. All rights reserved.
*
* 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/Deque.h>
#include <wtf/Lock.h>
#include <wtf/ThreadSafeRefCounted.h>
namespace WTF {
template<typename T, size_t BufferSize>
class SynchronizedFixedQueue final : public ThreadSafeRefCounted<SynchronizedFixedQueue<T, BufferSize>> {
public:
static Ref<SynchronizedFixedQueue> create()
{
return adoptRef(*new SynchronizedFixedQueue());
}
void open()
{
Locker locker { m_lock };
if (m_open)
return;
// Restore the queue to its original state.
m_open = true;
m_queue.clear();
}
void close()
{
Locker locker { m_lock };
if (!m_open)
return;
// Wake all the sleeping threads up with a closing state.
m_open = false;
m_condition.notifyAll();
}
bool isOpen()
{
Locker locker { m_lock };
return m_open;
}
bool enqueue(const T& value)
{
Locker locker { m_lock };
// Wait for an empty place to be available in the queue.
m_condition.wait(m_lock, [this] {
assertIsHeld(m_lock);
return !m_open || m_queue.size() < BufferSize;
});
// The queue is closing, exit immediately.
if (!m_open)
return false;
// Add the item in the queue.
m_queue.append(value);
// Notify the other threads that an item was added to the queue.
m_condition.notifyAll();
return true;
}
bool dequeue(T& value)
{
Locker locker { m_lock };
// Wait for an item to be added.
m_condition.wait(m_lock, [this] {
assertIsHeld(m_lock);
return !m_open || m_queue.size();
});
// The queue is closing, exit immediately.
if (!m_open)
return false;
// Get a copy from m_queue.first and then remove it.
value = m_queue.first();
m_queue.removeFirst();
// Notify the other threads that an item was removed from the queue.
m_condition.notifyAll();
return true;
}
private:
SynchronizedFixedQueue()
{
static_assert(!((BufferSize - 1) & BufferSize), "BufferSize must be power of 2.");
}
Lock m_lock;
Condition m_condition;
bool m_open WTF_GUARDED_BY_LOCK(m_lock) { true };
Deque<T, BufferSize> m_queue WTF_GUARDED_BY_LOCK(m_lock);
};
}
using WTF::SynchronizedFixedQueue;
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