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/*******************************************************************************
* Copyright (c) 2012 IBM Corporation and others.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* IBM Corporation - initial API and implementation
*******************************************************************************/
package org.eclipse.osgi.internal.container;
import java.util.Map;
import java.util.WeakHashMap;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.ReentrantLock;
public class LockSet<T> {
private final Map<T, ReentrantLock> locks = new WeakHashMap<T, ReentrantLock>();
private final Object monitor = new Object();
private final boolean reentrant;
public LockSet(boolean reentrant) {
this.reentrant = reentrant;
}
public boolean lock(T t) {
ReentrantLock lock = getLock(t);
lock.lock();
if (reentrant)
return true;
if (lock.getHoldCount() > 1) {
lock.unlock();
return false;
}
return true;
}
public boolean tryLock(T t) {
ReentrantLock lock = getLock(t);
boolean obtained = lock.tryLock();
if (obtained) {
if (reentrant)
return true;
if (lock.getHoldCount() > 1) {
lock.unlock();
return false;
}
}
return obtained;
}
public boolean tryLock(T t, long time, TimeUnit unit) throws InterruptedException {
ReentrantLock lock = getLock(t);
boolean obtained = lock.tryLock(time, unit);
if (obtained) {
if (reentrant)
return true;
if (lock.getHoldCount() > 1) {
lock.unlock();
return false;
}
}
return obtained;
}
public void unlock(T t) {
synchronized (monitor) {
ReentrantLock lock = locks.get(t);
if (lock == null)
throw new IllegalStateException("No lock found."); //$NON-NLS-1$
lock.unlock();
}
}
private ReentrantLock getLock(T t) {
synchronized (monitor) {
ReentrantLock lock = locks.get(t);
if (lock == null) {
lock = new ReentrantLock();
locks.put(t, lock);
}
return lock;
}
}
}
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