SharedQueue.cc

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/*
 * SharedQueue.cc
 *
 * Smalltalk like class library for C++
 * Data queue with reader-writer synchronization.
 *
 * Copyright (c) 2005 Milan Cermak
 */
/*
 * 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
 */
#include <stlib/os/SharedQueue.h>
#include <stlib/OrderedCollection.h>
#include <stlib/String.h>
#include <stlib/os/Semaphore.h>

namespace OS {

SharedQueue::SharedQueue(long size)
{
    content = new OrderedCollection(size);
    accessLock = Semaphore::forMutualExclusion();
    emptySemaphore = new Semaphore;
}

/* Class-accessing protocol */
String *SharedQueue::className(void) const
{
    return new String("SharedQueue");
}

/* Accessing protocol */
Object *SharedQueue::next(void)
{
    Object *data;

    emptySemaphore->wait();
    accessLock->wait();
    data = content->removeFirst();
    accessLock->signal();
    return data;
}

void SharedQueue::nextPut(Object *object)
{
    accessLock->wait();
    content->addLast(object);
    emptySemaphore->signal();
    accessLock->signal();
}

Object *SharedQueue::peek(void)
{
    Object *data;

    accessLock->wait();
    if (isEmpty()) data = nil;
              else data = content->first();
    accessLock->signal();
    return data;
}

long SharedQueue::size(void)
{
    return content->size();
}

/* Testing protocol */
bool SharedQueue::isEmpty(void)
{
    return content->isEmpty();
}

}; /* namespace OS */

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