/*
Copyright 2008-2010 Gephi
Authors : Mathieu Bastian <mathieu.bastian@gephi.org>
Website : http://www.gephi.org
This file is part of Gephi.
Gephi is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as
published by the Free Software Foundation, either version 3 of the
License, or (at your option) any later version.
Gephi is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Affero General Public License for more details.
You should have received a copy of the GNU Affero General Public License
along with Gephi. If not, see <http://www.gnu.org/licenses/>.
*/
package org.gephi.graph.dhns.core;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.locks.ReentrantReadWriteLock;
/**
*
* @author Mathieu Bastian
*/
public class SimpleLock {
private ThreadLocal<AtomicInteger> count = new ThreadLocal<AtomicInteger>();
private ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
public void readLock() {
if (get() == 0) {
lock.readLock().lock();
}
increment();
}
public void readUnlock() {
if (get() == 0) {
throw new IllegalMonitorStateException();
} else if (get() == 1) {
lock.readLock().unlock();
remove();
} else {
decrement();
}
}
public void writeLock() {
lock.writeLock().lock();
}
public void writeUnlock() {
lock.writeLock().unlock();
}
private void remove() {
count.remove();
}
private int get() {
AtomicInteger i = count.get();
if (i == null) {
return 0;
} else {
return i.intValue();
}
}
private void increment() {
AtomicInteger i = count.get();
if (i == null) {
i = new AtomicInteger(0);
count.set(i);
}
i.incrementAndGet();
}
private void decrement() {
AtomicInteger i = count.get();
if (i == null) {
// we should never get here...
throw new IllegalStateException();
}
i.decrementAndGet();
}
}