Queue.h

/*
 * Copyright (C) 2010 Tommi Maekitalo
 * 
 * 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.
 * 
 * As a special exception, you may use this file as part of a free
 * software library without restriction. Specifically, if other files
 * instantiate templates or use macros or inline functions from this
 * file, or you compile this file and link it with other files to
 * produce an executable, this file does not by itself cause the
 * resulting executable to be covered by the GNU General Public
 * License. This exception does not however invalidate any other
 * reasons why the executable file might be covered by the GNU Library
 * General Public License.
 * 
 * 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
 */

#ifndef PT_SYSTEM_QUEUE_H
#define PT_SYSTEM_QUEUE_H

#include <Pt/System/Api.h>
#include <Pt/System/Mutex.h>
#include <Pt/System/Condition.h>
#include <deque>

namespace Pt {

namespace System {

template <typename T>
class Queue
{
    public:
        typedef T value_type;
        typedef typename std::deque<T>::size_type size_type;
        typedef typename std::deque<T>::const_reference const_reference;

    private:
        mutable Mutex _mutex;
        Condition _notEmpty;
        Condition _notFull;
        std::deque<value_type> _queue;
        size_type _maxSize;
        size_type _numWaiting;

    public:
        Queue()
        : _maxSize(0)
        , _numWaiting(0)
        { }

        value_type get();

        void put(const_reference element);

        bool empty() const
        {
            MutexLock lock(_mutex);
            return _queue.empty();
        }

        size_type size() const
        {
            MutexLock lock(_mutex);
            return _queue.size();
        }

        void maxSize(size_type m);

        size_type maxSize() const
        {
            MutexLock lock(_mutex);
            return _maxSize;
        }

        size_type numWaiting() const
        {
            MutexLock lock(_mutex);
            return _numWaiting;
        }
};

template <typename T>
typename Queue<T>::value_type Queue<T>::get()
{
    MutexLock lock(_mutex);

    ++_numWaiting;
    while (_queue.empty())
        _notEmpty.wait(lock);
    --_numWaiting;

    value_type element = _queue.front();
    _queue.pop_front();

    if (!_queue.empty())
        _notEmpty.signal();

    _notFull.signal();

    return element;
}

template <typename T>
void Queue<T>::put(typename Queue<T>::const_reference element)
{
    MutexLock lock(_mutex);

    while (_maxSize > 0 && _queue.size() >= _maxSize)
        _notFull.wait(lock);

    _queue.push_back(element);
    _notEmpty.signal();

    if (_maxSize > 0 && _queue.size() < _maxSize)
        _notFull.signal();
}

template <typename T>
void Queue<T>::maxSize(size_type m)
{
    _maxSize = m;
    MutexLock lock(_mutex);
    if (_queue.size() < _maxSize)
        _notFull.signal();
}

} // namespace System

} // namespace Pt

#endif // PT_SYSTEM_QUEUE_H