| /* |
| * Copyright (c) 2000, 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; |
| |
| /** The backend for the message queue abstraction. This class is |
| instantiated first and queried to provide the two "sides" of the |
| message queue. */ |
| |
| import java.util.LinkedList; |
| |
| public class MessageQueueBackend { |
| // The two queues |
| private MessageQueueImpl leftRightQueue; |
| private MessageQueueImpl rightLeftQueue; |
| |
| public MessageQueueBackend() { |
| LinkedList leftRightPipe = new LinkedList(); |
| LinkedList rightLeftPipe = new LinkedList(); |
| leftRightQueue = new MessageQueueImpl(rightLeftPipe, leftRightPipe); |
| rightLeftQueue = new MessageQueueImpl(leftRightPipe, rightLeftPipe); |
| } |
| |
| /** Get one of the two symmetric sides of this message queue. */ |
| public MessageQueue getFirstQueue() { |
| return leftRightQueue; |
| } |
| |
| /** Get second of the two symmetric sides of this message queue. */ |
| public MessageQueue getSecondQueue() { |
| return rightLeftQueue; |
| } |
| |
| private class MessageQueueImpl implements MessageQueue { |
| private LinkedList readList; |
| private LinkedList writeList; |
| |
| public MessageQueueImpl(LinkedList listToReadFrom, LinkedList listToWriteTo) { |
| readList = listToReadFrom; |
| writeList = listToWriteTo; |
| } |
| |
| public Object readMessage() { |
| synchronized(readList) { |
| while (readList.isEmpty()) { |
| try { |
| readList.wait(); |
| } |
| catch (InterruptedException e) { |
| } |
| } |
| return readList.removeFirst(); |
| } |
| } |
| |
| public Object readMessageWithTimeout(long millis) { |
| synchronized(readList) { |
| if (readList.isEmpty()) { |
| if (millis == 0) { |
| return null; |
| } |
| try { |
| readList.wait(millis); |
| } |
| catch (InterruptedException e) { |
| } |
| } |
| // If list is still empty after wait, return null |
| if (readList.isEmpty()) { |
| return null; |
| } |
| return readList.removeFirst(); |
| } |
| } |
| |
| public void writeMessage(Object obj) { |
| synchronized(writeList) { |
| writeList.addLast(obj); |
| writeList.notify(); |
| } |
| } |
| } |
| } |