1 /*
2 * Licensed under the GPL License. You may not use this file except in compliance with the License.
3 * You may obtain a copy of the License at
4 *
5 * https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
6 *
7 * THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING,
8 * WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR
9 * PURPOSE.
10 */
11 package psiprobe.tools;
12
13 /**
14 * Simple update-commit lock. This implementation assumes that unlimited number of updates can
15 * happen concurrently. However if commit is in progress any update must wait for it to end.
16 * Likewise commits must wait for any updates to finish before acquiring the lock.
17 *
18 * <p>
19 * Commits themselves are not synchronized. It is allowed for two commits to run concurrently.
20 * </p>
21 */
22 public class UpdateCommitLock {
23
24 /** The update count. */
25 private int updateCount;
26
27 /** The commit count. */
28 private int commitCount;
29
30 /** The commit requests. */
31 private int commitRequests;
32
33 /**
34 * Lock for update.
35 *
36 * @throws InterruptedException the interrupted exception
37 */
38 public synchronized void lockForUpdate() throws InterruptedException {
39 while (commitCount > 0 || commitRequests > 0) {
40 wait();
41 }
42 updateCount++;
43 }
44
45 /**
46 * Release update lock.
47 */
48 public synchronized void releaseUpdateLock() {
49 updateCount--;
50 notifyAll();
51 }
52
53 /**
54 * Lock for commit.
55 *
56 * @throws InterruptedException the interrupted exception
57 */
58 public synchronized void lockForCommit() throws InterruptedException {
59 commitRequests++;
60 while (updateCount > 0 || commitCount > 0) {
61 wait();
62 }
63 commitRequests--;
64 commitCount++;
65 }
66
67 /**
68 * Release commit lock.
69 */
70 public synchronized void releaseCommitLock() {
71 commitCount--;
72 notifyAll();
73 }
74
75 }