/*
* Copyright (c) 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017 David Berkman
*
* This file is part of the SmallMind Code Project.
*
* The SmallMind Code Project is free software, you can redistribute
* it and/or modify it under either, at your discretion...
*
* 1) The terms of GNU Affero General Public License as published by the
* Free Software Foundation, either version 3 of the License, or (at
* your option) any later version.
*
* ...or...
*
* 2) The terms of the Apache License, Version 2.0.
*
* The SmallMind Code Project 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
* General Public License or Apache License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* and the Apache License along with the SmallMind Code Project. If not, see
* <http://www.gnu.org/licenses/> or <http://www.apache.org/licenses/LICENSE-2.0>.
*
* Additional permission under the GNU Affero GPL version 3 section 7
* ------------------------------------------------------------------
* If you modify this Program, or any covered work, by linking or
* combining it with other code, such other code is not for that reason
* alone subject to any of the requirements of the GNU Affero GPL
* version 3.
*/
package org.smallmind.nutsnbolts.util;
import java.lang.ref.Reference;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.WeakReference;
import java.util.EventListener;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.atomic.AtomicBoolean;
public class WeakEventListenerList<E extends EventListener> implements Iterable<E> {
private static final Scrubber SCRUBBER;
static {
Thread scrubberThread;
SCRUBBER = new Scrubber();
scrubberThread = new Thread(SCRUBBER);
scrubberThread.setDaemon(true);
scrubberThread.start();
}
private final LinkedList<WeakReference<E>> referenceList;
public WeakEventListenerList () {
referenceList = new LinkedList<>();
}
public Iterator<E> getListeners () {
LinkedList<E> listenerList;
Iterator<WeakReference<E>> listenerReferenceIter;
E eventListener;
listenerList = new LinkedList<E>();
synchronized (referenceList) {
listenerReferenceIter = referenceList.iterator();
while (listenerReferenceIter.hasNext()) {
if ((eventListener = (listenerReferenceIter.next()).get()) != null) {
listenerList.add(eventListener);
}
}
}
return listenerList.iterator();
}
public void addListener (E eventListener) {
synchronized (referenceList) {
referenceList.add(SCRUBBER.createReference(this, eventListener));
}
}
public void removeAllListeners () {
synchronized (referenceList) {
referenceList.clear();
}
}
public void removeListener (E eventListener) {
Iterator<WeakReference<E>> referenceIter;
synchronized (referenceList) {
referenceIter = referenceList.iterator();
while (referenceIter.hasNext()) {
if ((referenceIter.next()).get().equals(eventListener)) {
referenceIter.remove();
}
}
}
}
private void removeListener (Reference<E> reference) {
synchronized (referenceList) {
referenceList.remove(reference);
}
}
public Iterator<E> iterator () {
return getListeners();
}
public static class Scrubber implements Runnable {
private CountDownLatch exitLatch;
private ReferenceQueue<EventListener> referenceQueue;
private HashMap<WeakReference<? extends EventListener>, WeakEventListenerList> parentMap;
private AtomicBoolean finished = new AtomicBoolean(false);
public Scrubber () {
referenceQueue = new ReferenceQueue<>();
parentMap = new HashMap<>();
exitLatch = new CountDownLatch(1);
}
public <E extends EventListener> WeakReference<E> createReference (WeakEventListenerList parent, E eventListener) {
WeakReference<E> reference;
reference = new WeakReference<>(eventListener, referenceQueue);
parentMap.put(reference, parent);
return reference;
}
public void finish ()
throws InterruptedException {
finished.set(true);
exitLatch.await();
}
public void run () {
Reference<? extends EventListener> reference;
while (!finished.get()) {
try {
if ((reference = referenceQueue.remove(1000)) != null) {
parentMap.remove(reference).removeListener(reference);
}
} catch (InterruptedException interruptedException) {
finished.set(true);
}
}
exitLatch.countDown();
}
}
}