EventListenerList.java

/*******************************************************************************
 * Copyright (c) 2000, 2005 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.draw2d;

import java.util.Iterator;

/**
 * This class is intended for internal use only.
 * TODO: If this is for internal use only, we should move it to the internal package.
 */
public final class EventListenerList {

private volatile Object array[];

/**
 * Adds a listener of type <i>c</i> to the list.
 * @param c the class
 * @param listener the listener
 */
public synchronized void addListener(Class c, Object listener) {
	if (listener == null || c == null)
		throw new IllegalArgumentException();

	int oldSize = (array == null) ? 0 : array.length;
	Object[] newArray = new Object[oldSize + 2];
	if (oldSize != 0)
		System.arraycopy(array, 0, newArray, 0, oldSize);
	newArray[oldSize++] = c;
	newArray[oldSize] = listener;
	array = newArray;
}

/**
 * Returns <code>true</code> if this list of listeners contains a listener of type 
 * <i>c</i>.
 * @param c the type
 * @return whether this list contains a listener of type <i>c</i>
 */
public synchronized boolean containsListener(Class c) {
	if (array == null)
		return false;
	for (int i = 0; i < array.length; i += 2)
		if (array[i] == c)
			return true;
	return false;
}

static class TypeIterator implements Iterator {
	private final Object[] items;
	private final Class type;
	private int index;
	TypeIterator(Object items[], Class type) {
		this.items = items;
		this.type = type;
	}
	public Object next() {
		Object result = items[index + 1];
		index += 2;
		return result;
	}

	public boolean hasNext() {
		if (items == null)
			return false;
		while (index < items.length && items[index] != type)
			index += 2;
		return index < items.length;
	}

	public void remove() {
		throw new UnsupportedOperationException("Iterator removal not supported"); //$NON-NLS-1$
	}
}

/**
 * Returns an Iterator of all the listeners of type <i>c</i>.
 * @param listenerType the type
 * @return an Iterator of all the listeners of type <i>c</i>
 */
public synchronized Iterator getListeners(final Class listenerType) {
	return new TypeIterator(array, listenerType);
}

/**
 * Removes the first <i>listener</i> of the specified type by identity.
 * @param c the type
 * @param listener the listener
 */
public synchronized void removeListener(Class c, Object listener) {
	if (array == null || array.length == 0)
		return;
	if (listener == null || c == null)
		throw new IllegalArgumentException();
	
	int index = 0;
	while (index < array.length) {
		if (array[index] == c && array[index + 1] == listener)
			break;
		index += 2;
	}
	if (index == array.length)
		return; //listener was not found
	
	Object newArray[] = new Object[array.length - 2];
	System.arraycopy(array, 0, newArray, 0, index);
	System.arraycopy(array, index + 2, newArray, index, array.length - index - 2);
	array = newArray;
}

}