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/*******************************************************************************
* Copyright (c) 2003, 2004 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.osgi.framework.eventmgr;
/**
* This package private class is used for asynchronously dispatching events.
*/
class EventThread extends Thread {
/**
* Queued is a nested top-level (non-member) class. This class
* represents the items which are placed on the asynch dispatch queue.
* This class is private.
*/
private static class Queued {
/** listener list for this event */
final ListElement[] listeners;
/** dispatcher of this event */
final EventDispatcher dispatcher;
/** action for this event */
final int action;
/** object for this event */
final Object object;
/** next item in event queue */
Queued next;
/**
* Constructor for event queue item
*
* @param l Listener list for this event
* @param d Dispatcher for this event
* @param a Action for this event
* @param o Object for this event
*/
Queued(ListElement[] l, EventDispatcher d, int a, Object o) {
listeners = l;
dispatcher = d;
action = a;
object = o;
next = null;
}
}
/** item at the head of the event queue */
private Queued head;
/** item at the tail of the event queue */
private Queued tail;
/** if false the thread must terminate */
private volatile boolean running;
/**
* Constructor for the event thread.
* @param threadName Name of the EventThread
*/
EventThread(String threadName) {
super(threadName);
init();
}
/**
* Constructor for the event thread.
*/
EventThread() {
super();
init();
}
private void init() {
running = true;
head = null;
tail = null;
setDaemon(true); /* Mark thread as daemon thread */
}
/**
* Stop thread.
*/
void close() {
running = false;
interrupt();
}
/**
* This method pulls events from
* the queue and dispatches them.
*/
public void run() {
try {
while (true) {
Queued item = getNextEvent();
if (item == null) {
return;
}
EventManager.dispatchEvent(item.listeners, item.dispatcher, item.action, item.object);
}
}
catch (RuntimeException e) {
if (EventManager.DEBUG) {
e.printStackTrace();
}
throw e;
}
catch (Error e) {
if (EventManager.DEBUG) {
e.printStackTrace();
}
throw e;
}
}
/**
* This methods takes the input parameters and creates a Queued
* object and queues it.
* The thread is notified.
*
* @param l Listener list for this event
* @param d Dispatcher for this event
* @param a Action for this event
* @param o Object for this event
*/
synchronized void postEvent(ListElement[] l, EventDispatcher d, int a, Object o) {
if (!isAlive()) { /* If the thread is not alive, throw an exception */
throw new IllegalStateException();
}
Queued item = new Queued(l, d, a, o);
if (head == null) /* if the queue was empty */
{
head = item;
tail = item;
} else /* else add to end of queue */
{
tail.next = item;
tail = item;
}
notify();
}
/**
* This method is called by the thread to remove
* items from the queue so that they can be dispatched to their listeners.
* If the queue is empty, the thread waits.
*
* @return The Queued removed from the top of the queue or null
* if the thread has been requested to stop.
*/
private synchronized Queued getNextEvent() {
while (running && (head == null)) {
try {
wait();
}
catch (InterruptedException e) {
}
}
if (!running) { /* if we are stopping */
return null;
}
Queued item = head;
head = item.next;
if (head == null) {
tail = null;
}
return item;
}
}
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