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/* ------------------------------------------------------------------------
* $Id: ThreadQueue.hh,v 1.6 2001/07/18 07:47:49 elm Exp $
*
* This file is part of 3Dwm: The Three-Dimensional User Environment.
*
* 3Dwm: The Three-Dimensional User Environment:
* <http://www.3dwm.org>
*
* Chalmers Medialab
* <http://www.medialab.chalmers.se>
*
* ------------------------------------------------------------------------
* File created 2000-06-19 by Niklas Elmqvist.
*
* Copyright (c) 2000 Niklas Elmqvist <elm@3dwm.org>.
* ------------------------------------------------------------------------
* 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; either
* version 2.1 of the License, or (at your option) any later version.
*
* 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307
* USA
* ------------------------------------------------------------------------
*/
#ifndef _ThreadQueue_hh_
#define _ThreadQueue_hh_
// -- System Includes
#include <queue>
// -- Celsius Includes
#include "Mutex.hh"
#include "Semaphore.hh"
#include "Exception.hh"
#include "Guard.hh"
// -- Template Definitions
/**
* Simple thread queue implemented using POSIX mutexes and semaphores.
* This is the basic building-block of any producer-consumer scheme
* for making two threads talk to each other.
**/
template <class T>
class ThreadQueue : private std::queue<T> {
private:
typedef std::queue<T> rep_type;
public:
/**
* Constructor.
*
* @param capacity the maximum number of items in the queue.
**/
ThreadQueue(size_t capacity) : _allowWrite(capacity), _allowRead(0) { }
/**
* Push an element to the end of the queue.
*
* @param t element to push.
**/
void push(const T &t) {
_allowWrite.lock();
rep_type::push(t);
_allowRead.unlock();
}
/**
* Erase the element at the front of the queue.
**/
T pop() {
_allowRead.lock();
Guard<Mutex> guard(_mutex);
T t = rep_type::front();
rep_type::pop();
_allowWrite.unlock();
return t;
}
/**
* Try to retrieve (and remove) the element at the front of the
* queue. If there is nothing to retrieve (i.e. the queue is
* empty), signal this to the caller.
*
* @param t element at the top of the queue.
* @return true if the operation was successful, false if not.
**/
bool try_top_pop(T &t) {
if (_allowRead.tryLock() == true) {
Guard<Mutex> guard(_mutex);
t = rep_type::top();
rep_type::pop();
_allowWrite.unlock();
return true;
}
else
return false;
}
/**
* Retrieve the size of the queue.
*
* @return the queue size.
**/
size_t size() const {
Guard<Mutex> guard(_mutex);
return rep_type::size();
}
private:
Semaphore _allowWrite;
Semaphore _allowRead;
Mutex _mutex;
};
#endif /* ThreadQueue.hh */
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