0
|
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 }
|