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comparison agent/src/share/classes/sun/jvm/hotspot/utilities/MessageQueueBackend.java @ 0:a61af66fc99e jdk7-b24

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author duke
date Sat, 01 Dec 2007 00:00:00 +0000
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children c18cbe5936b8
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-1:000000000000 0:a61af66fc99e
1 /*
2 * Copyright 2000 Sun Microsystems, Inc. All Rights Reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any questions.
22 *
23 */
24
25 package sun.jvm.hotspot.utilities;
26
27 /** The backend for the message queue abstraction. This class is
28 instantiated first and queried to provide the two "sides" of the
29 message queue. */
30
31 import java.util.LinkedList;
32
33 public class MessageQueueBackend {
34 // The two queues
35 private MessageQueueImpl leftRightQueue;
36 private MessageQueueImpl rightLeftQueue;
37
38 public MessageQueueBackend() {
39 LinkedList leftRightPipe = new LinkedList();
40 LinkedList rightLeftPipe = new LinkedList();
41 leftRightQueue = new MessageQueueImpl(rightLeftPipe, leftRightPipe);
42 rightLeftQueue = new MessageQueueImpl(leftRightPipe, rightLeftPipe);
43 }
44
45 /** Get one of the two symmetric sides of this message queue. */
46 public MessageQueue getFirstQueue() {
47 return leftRightQueue;
48 }
49
50 /** Get second of the two symmetric sides of this message queue. */
51 public MessageQueue getSecondQueue() {
52 return rightLeftQueue;
53 }
54
55 private class MessageQueueImpl implements MessageQueue {
56 private LinkedList readList;
57 private LinkedList writeList;
58
59 public MessageQueueImpl(LinkedList listToReadFrom, LinkedList listToWriteTo) {
60 readList = listToReadFrom;
61 writeList = listToWriteTo;
62 }
63
64 public Object readMessage() {
65 synchronized(readList) {
66 while (readList.isEmpty()) {
67 try {
68 readList.wait();
69 }
70 catch (InterruptedException e) {
71 }
72 }
73 return readList.removeFirst();
74 }
75 }
76
77 public Object readMessageWithTimeout(long millis) {
78 synchronized(readList) {
79 if (readList.isEmpty()) {
80 if (millis == 0) {
81 return null;
82 }
83 try {
84 readList.wait(millis);
85 }
86 catch (InterruptedException e) {
87 }
88 }
89 // If list is still empty after wait, return null
90 if (readList.isEmpty()) {
91 return null;
92 }
93 return readList.removeFirst();
94 }
95 }
96
97 public void writeMessage(Object obj) {
98 synchronized(writeList) {
99 writeList.addLast(obj);
100 writeList.notify();
101 }
102 }
103 }
104 }