/*

 * Copyright (c) 1996, 2011, 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.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * 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.misc;

/**

 * The request processor allows functors (Request instances) to be created

 * in arbitrary threads, and to be posted for execution in a non-restricted

 * thread.

 *

 * @author      Steven B. Byrne

 */

public class RequestProcessor implements Runnable {

    private static Queue<Request> requestQueue;

    private static Thread dispatcher;

    /**

     * Queues a Request instance for execution by the request procesor

     * thread.

     */

    public static void postRequest(Request req) {

        lazyInitialize();

        requestQueue.enqueue(req);

    }

    /**

     * Process requests as they are queued.

     */

    public void run() {

        lazyInitialize();

        while (true) {

            try {

                Request req = requestQueue.dequeue();

                try {

                    req.execute();

                } catch (Throwable t) {

                    // do nothing at the moment...maybe report an error

                    // in the future

                }

            } catch (InterruptedException e) {

                // do nothing at the present time.

            }

        }

    }

    /**

     * This method initiates the request processor thread.  It is safe

     * to call it after the thread has been started.  It provides a way for

     * clients to deliberately control the context in which the request

     * processor thread is created

     */

    public static synchronized void startProcessing() {

        if (dispatcher == null) {

            dispatcher = new Thread(new RequestProcessor(), "Request Processor");

            dispatcher.setPriority(Thread.NORM_PRIORITY + 2);

            dispatcher.start();

        }

    }

    /**

     * This method performs lazy initialization.

     */

    private static synchronized void lazyInitialize() {

        if (requestQueue == null) {

            requestQueue = new Queue<Request>();

        }

    }

}