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* Copyright 2009 Red Hat Inc. and/or its affiliates and other
* contributors as indicated by the @author tags. All rights reserved.
* See the copyright.txt in the distribution for a full listing of
* individual contributors.
*
* This is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* This software 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this software; if not, write to the Free
* Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
* 02110-1301 USA, or see the FSF site: http://www.fsf.org.
*/
package org.infinispan.util.concurrent;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.AbstractQueuedSynchronizer;
/**
* A thread gat, that uses an {@link java.util.concurrent.locks.AbstractQueuedSynchronizer}.
* <p/>
* This implementation allows you to create a latch with a default state (open or closed), and repeatedly open or close
* the latch.
*
* @author Manik Surtani (<a href="mailto:manik@jboss.org">manik@jboss.org</a>)
* @since 4.0
*/
public class ReclosableLatch extends AbstractQueuedSynchronizer {
private static final long serialVersionUID = 1744280161777661090l;
// the following states are used in the AQS.
private static final int OPEN_STATE = 0, CLOSED_STATE = 1;
public ReclosableLatch() {
setState(CLOSED_STATE);
}
public ReclosableLatch(boolean defaultOpen) {
setState(defaultOpen ? OPEN_STATE : CLOSED_STATE);
}
@Override
public final int tryAcquireShared(int ignored) {
// return 1 if we allow the requestor to proceed, -1 if we want the requestor to block.
return getState() == OPEN_STATE ? 1 : -1;
}
@Override
public final boolean tryReleaseShared(int state) {
// used as a mechanism to set the state of the Sync.
setState(state);
return true;
}
public final void open() {
// do not use setState() directly since this won't notify parked threads.
releaseShared(OPEN_STATE);
}
public final void close() {
// do not use setState() directly since this won't notify parked threads.
releaseShared(CLOSED_STATE);
}
public boolean isOpened() {
return getState() == OPEN_STATE;
}
public final void await() throws InterruptedException {
acquireSharedInterruptibly(1); // the 1 is a dummy value that is not used.
}
public final boolean await(long time, TimeUnit unit) throws InterruptedException {
return tryAcquireSharedNanos(1, unit.toNanos(time)); // the 1 is a dummy value that is not used.
}
@Override
public String toString() {
int s = getState();
String q = hasQueuedThreads() ? "non" : "";
return "ReclosableLatch [State = " + s + ", " + q + "empty queue]";
}
}