org.apache.solr.util.AdjustableSemaphore Maven / Gradle / Ivy
package org.apache.solr.util;
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import java.util.concurrent.Semaphore;
final public class AdjustableSemaphore {
private final ResizeableSemaphore semaphore;
private int maxPermits = 0;
public AdjustableSemaphore(int size) {
semaphore = new ResizeableSemaphore(size);
}
public synchronized void setMaxPermits(int newMax) {
if (newMax < 1) {
throw new IllegalArgumentException("Semaphore size must be at least 1,"
+ " was " + newMax);
}
int delta = newMax - this.maxPermits;
if (delta == 0) {
return;
} else if (delta > 0) {
this.semaphore.release(delta);
} else {
delta *= -1;
this.semaphore.reducePermits(delta);
}
this.maxPermits = newMax;
}
public void release() {
this.semaphore.release();
}
public void release(int numPermits) {
this.semaphore.release(numPermits);
}
public void acquire() throws InterruptedException {
this.semaphore.acquire();
}
public synchronized int getMaxPermits() {
return maxPermits;
}
private static final class ResizeableSemaphore extends Semaphore {
ResizeableSemaphore(int size) {
super(size);
}
@Override
protected void reducePermits(int reduction) {
super.reducePermits(reduction);
}
}
}