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/*
* Copyright (C) 2008 Apple Inc. All rights reserved.
* Copyright (C) 2009 Google 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.
* 3. Neither the name of Apple Computer, Inc. ("Apple") nor the names of
* its contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "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 OR ITS 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.
*/
#ifndef MessageQueue_h
#define MessageQueue_h
#include <limits>
#include <wtf/Assertions.h>
#include <wtf/Deque.h>
#include <wtf/Noncopyable.h>
#include <wtf/Threading.h>
namespace WTF {
enum MessageQueueWaitResult {
MessageQueueTerminated, // Queue was destroyed while waiting for message.
MessageQueueTimeout, // Timeout was specified and it expired.
MessageQueueMessageReceived, // A message was successfully received and returned.
};
template<typename DataType>
class MessageQueue : Noncopyable {
public:
MessageQueue() : m_killed(false) { }
void append(const DataType&);
bool appendAndCheckEmpty(const DataType&);
void prepend(const DataType&);
bool waitForMessage(DataType&);
template<typename Predicate>
MessageQueueWaitResult waitForMessageFilteredWithTimeout(DataType&, Predicate&, double absoluteTime);
void kill();
bool tryGetMessage(DataType&);
bool killed() const;
// The result of isEmpty() is only valid if no other thread is manipulating the queue at the same time.
bool isEmpty();
static double infiniteTime() { return std::numeric_limits<double>::max(); }
private:
static bool alwaysTruePredicate(DataType&) { return true; }
mutable Mutex m_mutex;
ThreadCondition m_condition;
Deque<DataType> m_queue;
bool m_killed;
};
template<typename DataType>
inline void MessageQueue<DataType>::append(const DataType& message)
{
MutexLocker lock(m_mutex);
m_queue.append(message);
m_condition.signal();
}
// Returns true if the queue was empty before the item was added.
template<typename DataType>
inline bool MessageQueue<DataType>::appendAndCheckEmpty(const DataType& message)
{
MutexLocker lock(m_mutex);
bool wasEmpty = m_queue.isEmpty();
m_queue.append(message);
m_condition.signal();
return wasEmpty;
}
template<typename DataType>
inline void MessageQueue<DataType>::prepend(const DataType& message)
{
MutexLocker lock(m_mutex);
m_queue.prepend(message);
m_condition.signal();
}
template<typename DataType>
inline bool MessageQueue<DataType>::waitForMessage(DataType& result)
{
MessageQueueWaitResult exitReason = waitForMessageFilteredWithTimeout(result, MessageQueue<DataType>::alwaysTruePredicate, infiniteTime());
ASSERT(exitReason == MessageQueueTerminated || exitReason == MessageQueueMessageReceived);
return exitReason == MessageQueueMessageReceived;
}
template<typename DataType>
template<typename Predicate>
inline MessageQueueWaitResult MessageQueue<DataType>::waitForMessageFilteredWithTimeout(DataType& result, Predicate& predicate, double absoluteTime)
{
MutexLocker lock(m_mutex);
bool timedOut = false;
DequeConstIterator<DataType> found = m_queue.end();
while (!m_killed && !timedOut && (found = m_queue.findIf(predicate)) == m_queue.end())
timedOut = !m_condition.timedWait(m_mutex, absoluteTime);
ASSERT(!timedOut || absoluteTime != infiniteTime());
if (m_killed)
return MessageQueueTerminated;
if (timedOut)
return MessageQueueTimeout;
ASSERT(found != m_queue.end());
result = *found;
m_queue.remove(found);
return MessageQueueMessageReceived;
}
template<typename DataType>
inline bool MessageQueue<DataType>::tryGetMessage(DataType& result)
{
MutexLocker lock(m_mutex);
if (m_killed)
return false;
if (m_queue.isEmpty())
return false;
result = m_queue.first();
m_queue.removeFirst();
return true;
}
template<typename DataType>
inline bool MessageQueue<DataType>::isEmpty()
{
MutexLocker lock(m_mutex);
if (m_killed)
return true;
return m_queue.isEmpty();
}
template<typename DataType>
inline void MessageQueue<DataType>::kill()
{
MutexLocker lock(m_mutex);
m_killed = true;
m_condition.broadcast();
}
template<typename DataType>
inline bool MessageQueue<DataType>::killed() const
{
MutexLocker lock(m_mutex);
return m_killed;
}
} // namespace WTF
using WTF::MessageQueue;
// MessageQueueWaitResult enum and all its values.
using WTF::MessageQueueWaitResult;
using WTF::MessageQueueTerminated;
using WTF::MessageQueueTimeout;
using WTF::MessageQueueMessageReceived;
#endif // MessageQueue_h
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