/**
* UpDownLatch
* Copyright 2011 by Michael Peter Christen, mc@yacy.net, Frankfurt a. M., Germany
* First released 16.07.2011 at http://yacy.net
*
* $LastChangedDate: 2011-05-30 10:53:58 +0200 (Mo, 30 Mai 2011) $
* $LastChangedRevision: 7759 $
* $LastChangedBy: orbiter $
*
* This library 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 library 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 program in the file lgpl21.txt
* If not, see <http://www.gnu.org/licenses/>.
*/
package net.yacy.cora.sorting;
import java.util.concurrent.locks.AbstractQueuedSynchronizer;
public class UpDownLatch extends AbstractQueuedSynchronizer {
private static final long serialVersionUID = 1L;
public UpDownLatch(final int count) {
setState(count);
}
public int getCount() {
return getState();
}
@Override
public int tryAcquireShared(final int acquires) {
return getState() == 0? 1 : -1;
}
@Override
public boolean tryReleaseShared(final int releases) {
// Decrement count; signal when transition to zero
for (;;) {
final int c = getState();
if (c == 0) return false;
final int nextc = c-1;
if (compareAndSetState(c, nextc)) return nextc == 0;
}
}
public void countUp() {
for (;;) {
final int c = getState();
if (compareAndSetState(c, c + 1)) return;
}
}
public void countDown() {
releaseShared(1);
}
public void await() throws InterruptedException {
acquireSharedInterruptibly(1);
}
}