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/*
* Copyright 2002-2005 The Apache Software Foundation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*/
package org.apache.tools.ant.util;
import java.util.Enumeration;
import java.util.Vector;
/**
* Generalization of <code>ExecuteWatchdog</code>
*
* @since Ant 1.5
*
* @see org.apache.tools.ant.taskdefs.ExecuteWatchdog
*
*/
public class Watchdog implements Runnable {
private Vector observers = new Vector(1);
private long timeout = -1;
private boolean stopped = false;
/**
* Constructor for Watchdog.
* @param timeout the timeout to use in milliseconds (must be >= 1).
*/
public Watchdog(long timeout) {
if (timeout < 1) {
throw new IllegalArgumentException("timeout less than 1.");
}
this.timeout = timeout;
}
/**
* Add a timeout observer.
* @param to the timeout observer to add.
*/
public void addTimeoutObserver(TimeoutObserver to) {
observers.addElement(to);
}
/**
* Remove a timeout observer.
* @param to the timeout observer to remove.
*/
public void removeTimeoutObserver(TimeoutObserver to) {
observers.removeElement(to);
}
/**
* Inform the observers that a timeout has occurred.
*/
protected final void fireTimeoutOccured() {
Enumeration e = observers.elements();
while (e.hasMoreElements()) {
((TimeoutObserver) e.nextElement()).timeoutOccured(this);
}
}
/**
* Start the watch dog.
*/
public synchronized void start() {
stopped = false;
Thread t = new Thread(this, "WATCHDOG");
t.setDaemon(true);
t.start();
}
/**
* Stop the watch dog.
*/
public synchronized void stop() {
stopped = true;
notifyAll();
}
/**
* The run method of the watch dog thread.
* This simply does a wait for the timeout time, and
* if the stop flag has not been set when the wait has returned or
* has been interrupted, the watch dog listeners are informed.
*/
public synchronized void run() {
final long until = System.currentTimeMillis() + timeout;
long now;
while (!stopped && until > (now = System.currentTimeMillis())) {
try {
wait(until - now);
} catch (InterruptedException e) {
// Ignore exception
}
}
if (!stopped) {
fireTimeoutOccured();
}
}
}
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