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comparison src/org/tmatesoft/hg/repo/HgRepositoryLock.java @ 487:db48a77ec8ff

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Access to reposiotry lock mechanism via HgRepositoryLock
author Artem Tikhomirov <tikhomirov.artem@gmail.com>
date Mon, 13 Aug 2012 18:11:47 +0200
parents src/org/tmatesoft/hg/internal/Lock.java@d740edfff563
children 45b3b6ca046f
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486:d740edfff563 487:db48a77ec8ff
1 /*
2 * Copyright (c) 2012 TMate Software Ltd
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; version 2 of the License.
7 *
8 * This program is distributed in the hope that it will be useful,
9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
11 * GNU General Public License for more details.
12 *
13 * For information on how to redistribute this software under
14 * the terms of a license other than GNU General Public License
15 * contact TMate Software at support@hg4j.com
16 */
17 package org.tmatesoft.hg.repo;
18
19 import java.io.File;
20 import java.io.FileInputStream;
21 import java.io.FileOutputStream;
22 import java.io.IOException;
23 import java.lang.management.ManagementFactory;
24 import java.net.InetAddress;
25 import java.nio.ByteBuffer;
26 import java.nio.channels.FileChannel;
27
28 import org.tmatesoft.hg.internal.Internals;
29
30 /**
31 * NOT SAFE FOR MULTITHREAD USE!
32 *
33 * Unlike original mechanism, we don't use symlinks, rather files, as it's easier to implement
34 *
35 * @author Artem Tikhomirov
36 * @author TMate Software Ltd.
37 */
38 public class HgRepositoryLock {
39 /*
40 * Lock .hg/ except .hg/store/ .hg/wlock (HgRepository.repoPathHelper("wlock"))
41 * Lock .hg/store/ .hg/store/lock (HgRepository.repoPathHelper("store/lock") ???)
42 */
43
44 private final File lockFile;
45 private int use = 0;
46 private final int timeoutSeconds;
47
48 HgRepositoryLock(File lock, int timeoutInSeconds) {
49 lockFile = lock;
50 timeoutSeconds = timeoutInSeconds;
51 }
52
53 /**
54 * Tries to read lock file and supplies hostname:pid (or just pid) information from there
55 * @return <code>null</code> if no lock file available at the moment
56 */
57 public String readLockInfo() {
58 if (lockFile.exists()) {
59 try {
60 byte[] bytes = read(lockFile);
61 if (bytes != null && bytes.length > 0) {
62 return new String(bytes);
63 }
64 } catch (Exception ex) {
65 // deliberately ignored
66 }
67 }
68 return null;
69 }
70
71 public boolean isLocked() {
72 return use > 0;
73 }
74
75 public void acquire() {
76 if (use > 0) {
77 use++;
78 return;
79 }
80 StringBuilder lockDescription = new StringBuilder();
81 lockDescription.append(getHostname());
82 lockDescription.append(':');
83 lockDescription.append(getPid());
84 byte[] bytes = lockDescription.toString().getBytes();
85 long stopTime = timeoutSeconds < 0 ? -1 : (System.currentTimeMillis() + timeoutSeconds*1000);
86 do {
87 synchronized(this) {
88 try {
89 if (!lockFile.exists()) {
90 write(lockFile, bytes);
91 use++;
92 return;
93 }
94 } catch (IOException ex) {
95 // deliberately ignored
96 }
97 try {
98 wait(1000);
99 } catch (InterruptedException ex) {
100 // deliberately ignored
101 }
102 }
103
104 } while (stopTime == -1/*no timeout*/ || System.currentTimeMillis() <= stopTime);
105 String msg = String.format("Failed to aquire lock, waited for %d seconds, present owner: '%s'", timeoutSeconds, readLockInfo());
106 throw new HgInvalidStateException(msg);
107 }
108
109 public void release() {
110 if (use == 0) {
111 throw new HgInvalidStateException("");
112 }
113 use--;
114 if (use > 0) {
115 return;
116 }
117 // do release
118 lockFile.delete();
119 }
120
121 protected String getHostname() {
122 try {
123 return InetAddress.getLocalHost().getHostName();
124 } catch (Exception ex) {
125 return "localhost";
126 }
127 }
128
129 protected int getPid() {
130 try {
131 // @see http://blog.igorminar.com/2007/03/how-java-application-can-discover-its.html
132 if (!Internals.runningOnWindows()) {
133 File f = new File("/proc/self");
134 if (f.exists()) {
135 // /proc/self is a symlink to /proc/pid/ directory
136 return Integer.parseInt(f.getCanonicalFile().getName());
137 }
138 }
139 String rtBean = ManagementFactory.getRuntimeMXBean().getName();
140 int x;
141 if ((x = rtBean.indexOf('@')) != -1) {
142 return Integer.parseInt(rtBean.substring(0, x));
143 }
144 return -1;
145 } catch (Exception ex) {
146 return -1;
147 }
148 }
149
150 private static void write(File f, byte[] content) throws IOException {
151 FileOutputStream fos = new FileOutputStream(f);
152 fos.write(content);
153 fos.close();
154 }
155
156 private static byte[] read(File f) throws IOException {
157 FileChannel fc = new FileInputStream(f).getChannel();
158 ByteBuffer bb = ByteBuffer.allocate(Internals.ltoi(fc.size()));
159 fc.read(bb);
160 fc.close();
161 return bb.array();
162 }
163 }