01: /*
02: * HA-JDBC: High-Availability JDBC
03: * Copyright (c) 2004-2007 Paul Ferraro
04: *
05: * This library is free software; you can redistribute it and/or modify it
06: * under the terms of the GNU Lesser General Public License as published by the
07: * Free Software Foundation; either version 2.1 of the License, or (at your
08: * option) any later version.
09: *
10: * This library is distributed in the hope that it will be useful, but WITHOUT
11: * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12: * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
13: * for more details.
14: *
15: * You should have received a copy of the GNU Lesser General Public License
16: * along with this library; if not, write to the Free Software Foundation,
17: * Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
18: *
19: * Contact: ferraro@users.sourceforge.net
20: */
21: package net.sf.hajdbc.util.concurrent;
22:
23: import java.util.concurrent.Semaphore;
24: import java.util.concurrent.locks.Lock;
25: import java.util.concurrent.locks.ReadWriteLock;
26:
27: /**
28: * Simple {@link java.util.concurrent.lock.ReadWriteLock} implementation that uses a semaphore that grants up to {@link java.lang.Integer#MAX_VALUE} permits using a fair FIFO policy.
29: * A read lock requires 1 permit, while a write lock requires all the permits.
30: *
31: * @author Paul Ferraro
32: */
33: public class SemaphoreReadWriteLock implements ReadWriteLock {
34: private Semaphore semaphore = new Semaphore(Integer.MAX_VALUE, true);
35: private Lock readLock = new SemaphoreLock(this .semaphore, 1);
36: private Lock writeLock = new SemaphoreLock(this .semaphore,
37: Integer.MAX_VALUE);
38:
39: /**
40: * @see java.util.concurrent.locks.ReadWriteLock#readLock()
41: */
42: @Override
43: public Lock readLock() {
44: return this .readLock;
45: }
46:
47: /**
48: * @see java.util.concurrent.locks.ReadWriteLock#writeLock()
49: */
50: @Override
51: public Lock writeLock() {
52: return this.writeLock;
53: }
54: }
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