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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.
};
// The queue takes ownership of messages and transfer it to the new owner
// when messages are fetched from the queue.
// Essentially, MessageQueue acts as a queue of OwnPtr<DataType>.
template<typename DataType>
class MessageQueue : public Noncopyable {
public:
MessageQueue() : m_killed(false) { }
~MessageQueue();
void append(PassOwnPtr<DataType>);
bool appendAndCheckEmpty(PassOwnPtr<DataType>);
void prepend(PassOwnPtr<DataType>);
PassOwnPtr<DataType> waitForMessage();
PassOwnPtr<DataType> tryGetMessage();
template<typename Predicate>
PassOwnPtr<DataType> waitForMessageFilteredWithTimeout(MessageQueueWaitResult&, Predicate&, double absoluteTime);
template<typename Predicate>
void removeIf(Predicate&);
void kill();
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>
MessageQueue<DataType>::~MessageQueue()
{
deleteAllValues(m_queue);
}
template<typename DataType>
inline void MessageQueue<DataType>::append(PassOwnPtr<DataType> message)
{
MutexLocker lock(m_mutex);
m_queue.append(message.leakPtr());
m_condition.signal();
}
// Returns true if the queue was empty before the item was added.
template<typename DataType>
inline bool MessageQueue<DataType>::appendAndCheckEmpty(PassOwnPtr<DataType> message)
{
MutexLocker lock(m_mutex);
bool wasEmpty = m_queue.isEmpty();
m_queue.append(message.leakPtr());
m_condition.signal();
return wasEmpty;
}
template<typename DataType>
inline void MessageQueue<DataType>::prepend(PassOwnPtr<DataType> message)
{
MutexLocker lock(m_mutex);
m_queue.prepend(message.leakPtr());
m_condition.signal();
}
template<typename DataType>
inline PassOwnPtr<DataType> MessageQueue<DataType>::waitForMessage()
{
MessageQueueWaitResult exitReason;
PassOwnPtr<DataType> result = waitForMessageFilteredWithTimeout(exitReason, MessageQueue<DataType>::alwaysTruePredicate, infiniteTime());
ASSERT(exitReason == MessageQueueTerminated || exitReason == MessageQueueMessageReceived);
return result;
}
template<typename DataType>
template<typename Predicate>
inline PassOwnPtr<DataType> MessageQueue<DataType>::waitForMessageFilteredWithTimeout(MessageQueueWaitResult& 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) {
result = MessageQueueTerminated;
return 0;
}
if (timedOut) {
result = MessageQueueTimeout;
return 0;
}
ASSERT(found != m_queue.end());
DataType* message = *found;
m_queue.remove(found);
result = MessageQueueMessageReceived;
return message;
}
template<typename DataType>
inline PassOwnPtr<DataType> MessageQueue<DataType>::tryGetMessage()
{
MutexLocker lock(m_mutex);
if (m_killed)
return 0;
if (m_queue.isEmpty())
return 0;
return m_queue.takeFirst();
}
template<typename DataType>
template<typename Predicate>
inline void MessageQueue<DataType>::removeIf(Predicate& predicate)
{
MutexLocker lock(m_mutex);
// See bug 31657 for why this loop looks so weird
while (true) {
DequeConstIterator<DataType*> found = m_queue.findIf(predicate);
if (found == m_queue.end())
break;
DataType* message = *found;
m_queue.remove(found);
delete message;
}
}
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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