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/**
* @file llthreadsafequeue.h
* @brief Base classes for thread, mutex and condition handling.
*
* $LicenseInfo:firstyear=2004&license=viewerlgpl$
* Second Life Viewer Source Code
* Copyright (C) 2010, Linden Research, Inc.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation;
* version 2.1 of the License only.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*
* Linden Research, Inc., 945 Battery Street, San Francisco, CA 94111 USA
* $/LicenseInfo$
*/
#ifndef LL_LLTHREADSAFEQUEUE_H
#define LL_LLTHREADSAFEQUEUE_H
#include "llexception.h"
#include <deque>
#include <string>
#if LL_WINDOWS
#pragma warning (push)
#pragma warning (disable:4265)
#endif
// 'std::_Pad' : class has virtual functions, but destructor is not virtual
#include <mutex>
#include <condition_variable>
#if LL_WINDOWS
#pragma warning (pop)
#endif
//
// A general queue exception.
//
class LL_COMMON_API LLThreadSafeQueueError:
public LLException
{
public:
LLThreadSafeQueueError(std::string const & message):
LLException(message)
{
; // No op.
}
};
//
// An exception raised when blocking operations are interrupted.
//
class LL_COMMON_API LLThreadSafeQueueInterrupt:
public LLThreadSafeQueueError
{
public:
LLThreadSafeQueueInterrupt(void):
LLThreadSafeQueueError("queue operation interrupted")
{
; // No op.
}
};
//
// Implements a thread safe FIFO.
//
template<typename ElementT>
class LLThreadSafeQueue
{
public:
typedef ElementT value_type;
// If the pool is set to NULL one will be allocated and managed by this
// queue.
LLThreadSafeQueue(U32 capacity = 1024);
// Add an element to the front of queue (will block if the queue has
// reached capacity).
//
// This call will raise an interrupt error if the queue is deleted while
// the caller is blocked.
void pushFront(ElementT const & element);
// Try to add an element to the front ofqueue without blocking. Returns
// true only if the element was actually added.
bool tryPushFront(ElementT const & element);
// Pop the element at the end of the queue (will block if the queue is
// empty).
//
// This call will raise an interrupt error if the queue is deleted while
// the caller is blocked.
ElementT popBack(void);
// Pop an element from the end of the queue if there is one available.
// Returns true only if an element was popped.
bool tryPopBack(ElementT & element);
// Returns the size of the queue.
size_t size();
private:
std::deque< ElementT > mStorage;
U32 mCapacity;
std::mutex mLock;
std::condition_variable mCapacityCond;
std::condition_variable mEmptyCond;
};
// LLThreadSafeQueue
//-----------------------------------------------------------------------------
template<typename ElementT>
LLThreadSafeQueue<ElementT>::LLThreadSafeQueue(U32 capacity) :
mCapacity(capacity)
{
}
template<typename ElementT>
void LLThreadSafeQueue<ElementT>::pushFront(ElementT const & element)
{
while (true)
{
std::unique_lock<std::mutex> lock1(mLock);
if (mStorage.size() < mCapacity)
{
mStorage.push_front(element);
mEmptyCond.notify_one();
return;
}
// Storage Full. Wait for signal.
mCapacityCond.wait(lock1);
}
}
template<typename ElementT>
bool LLThreadSafeQueue<ElementT>::tryPushFront(ElementT const & element)
{
std::unique_lock<std::mutex> lock1(mLock, std::defer_lock);
if (!lock1.try_lock())
return false;
if (mStorage.size() >= mCapacity)
return false;
mStorage.push_front(element);
mEmptyCond.notify_one();
return true;
}
template<typename ElementT>
ElementT LLThreadSafeQueue<ElementT>::popBack(void)
{
while (true)
{
std::unique_lock<std::mutex> lock1(mLock);
if (!mStorage.empty())
{
ElementT value = mStorage.back();
mStorage.pop_back();
mCapacityCond.notify_one();
return value;
}
// Storage empty. Wait for signal.
mEmptyCond.wait(lock1);
}
}
template<typename ElementT>
bool LLThreadSafeQueue<ElementT>::tryPopBack(ElementT & element)
{
std::unique_lock<std::mutex> lock1(mLock, std::defer_lock);
if (!lock1.try_lock())
return false;
if (mStorage.empty())
return false;
element = mStorage.back();
mStorage.pop_back();
mCapacityCond.notify_one();
return true;
}
template<typename ElementT>
size_t LLThreadSafeQueue<ElementT>::size(void)
{
std::lock_guard<std::mutex> lock(mLock);
return mStorage.size();
}
#endif
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