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/*
* Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
* or more contributor license agreements. Licensed under the Elastic License
* 2.0 and the Server Side Public License, v 1; you may not use this file except
* in compliance with, at your election, the Elastic License 2.0 or the Server
* Side Public License, v 1.
*/
package org.elasticsearch.common.util.concurrent;
import java.util.concurrent.Semaphore;
public class AdjustableSemaphore extends Semaphore {
private final Object maxPermitsMutex = new Object();
private int maxPermits;
public AdjustableSemaphore(int maxPermits, boolean fair) {
super(maxPermits, fair);
this.maxPermits = maxPermits;
}
public void setMaxPermits(int permits) {
synchronized (maxPermitsMutex) {
final int diff = Math.subtractExact(permits, maxPermits);
if (diff > 0) {
// add permits
release(diff);
} else if (diff < 0) {
// remove permits
reducePermits(Math.negateExact(diff));
}
maxPermits = permits;
}
}
}