/*

 * Copyright (c) 2000, 2001, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 *

 */

package sun.jvm.hotspot.utilities;

/** This class abstracts the notion of a worker thread which is fed

    tasks in the form of Runnables. */

public class WorkerThread {

  private volatile boolean done = false;

  private MessageQueueBackend mqb;

  private MessageQueue mq;

  public WorkerThread() {

    mqb = new MessageQueueBackend();

    mq = mqb.getFirstQueue();

    // Enable to terminate this worker during runnning by daemonize.

    Thread mqthread = new Thread(new MainLoop());

    mqthread.setDaemon(true);

    mqthread.start();

  }

  /** Runs the given Runnable in the thread represented by this

      WorkerThread object at an unspecified later time. */

  public void invokeLater(Runnable runnable) {

    mq.writeMessage(runnable);

  }

  /** Can be used to dispose of the internal worker thread. Note that

      this method may return before the internal worker thread

      terminates. */

  public void shutdown() {

    done = true;

    mq.writeMessage(new Runnable() { public void run() {} });

  }

  class MainLoop implements Runnable {

    private MessageQueue myMq;

    public MainLoop() {

      myMq = mqb.getSecondQueue();

    }

    public void run() {

      while (!done) {

        Runnable runnable = (Runnable) myMq.readMessage();

        try {

          runnable.run();

        } catch (Exception e) {

          e.printStackTrace();

        }

      }

    }

  }

}