org/objectweb/proactive/benchmarks/timit/util/observing/RealEventObservable.java

/* 
 * ################################################################
 * 
 * ProActive: The Java(TM) library for Parallel, Distributed, 
 *            Concurrent computing with Security and Mobility
 * 
 * Copyright (C) 1997-2007 INRIA/University of Nice-Sophia Antipolis
 * Contact: proactive@objectweb.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 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
 *  
 *  Initial developer(s):               The ProActive Team
 *                        http://www.inria.fr/oasis/ProActive/contacts.html
 *  Contributor(s): 
 * 
 * ################################################################
 */ 
package org.objectweb.proactive.benchmarks.timit.util.observing;

import java.util.Vector;

public class RealEventObservable implements EventObservable {
    private boolean changed = false;

    private Vector<EventObserver> eventDataObservers;

    public RealEventObservable() {
        this.eventDataObservers = new Vector<EventObserver>();
    }

    public synchronized void addObserver(EventObserver o) {
        if (o == null) {
            throw new NullPointerException();
        }
        if (!this.eventDataObservers.contains(o)) {
            this.eventDataObservers.addElement(o);
        }
    }

    public synchronized void deleteObserver(EventObserver o) {
        this.eventDataObservers.removeElement(o);
    }

    public void notifyObservers() {
        this.notifyObservers(null);
    }

    public void notifyObservers(Object arg) {
        /*
         * a temporary array buffer, used as a snapshot of the state of current
         * Observers.
         */
        Object[] arrLocal;
        this.setChanged();
        synchronized (this) {
            /*
             * We don't want the Observer doing callbacks into arbitrary code
             * while holding its own Monitor. The code where we extract each
             * Observable from the Vector and store the state of the Observer
             * needs synchronization, but notifying observers does not (should
             * not). The worst result of any potential race-condition here is
             * that: 1) a newly-added Observer will miss a notification in
             * progress 2) a recently unregistered Observer will be wrongly
             * notified when it doesn't care
             */
            if (!this.changed) {
                return;
            }
            arrLocal = this.eventDataObservers.toArray();
            this.clearChanged();
        }

        for (int i = arrLocal.length - 1; i >= 0; i--) {
            ((EventObserver) arrLocal[i]).update(this, arg);
        }
    }

    public synchronized void deleteObservers() {
        this.eventDataObservers.removeAllElements();
    }

    public synchronized void setChanged() {
        this.changed = true;
    }

    public synchronized void clearChanged() {
        this.changed = false;
    }

    public synchronized boolean hasChanged() {
        return this.changed;
    }

    public synchronized int countObservers() {
        return this.eventDataObservers.size();
    }

    public synchronized EventDataBag getEventDataBag(int subjectRank) {
        EventDataBag result = new EventDataBag(subjectRank);
        Vector<EventData> v = new Vector<EventData>();
        EventObserver eventDataObserver = null;
        EventData eventData = null;
        for (int i = 0; i < this.eventDataObservers.size(); i++) {
            eventDataObserver = this.eventDataObservers.get(i);
            if (eventDataObserver == null) {
                throw new NullPointerException();
            } else {
                eventData = eventDataObserver.getEventData();
                if (eventData == null) {
                    throw new NullPointerException();
                } else {
                    v.add(eventData);
                }
            }
        }
        result.setBag(v);
        return result;
    }
}

---