com.hazelcast.dataconnection.impl.ReferenceCounter Maven / Gradle / Ivy
/*
* Copyright (c) 2008-2024, Hazelcast, Inc. All Rights Reserved.
*
* Licensed 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.
*/
package com.hazelcast.dataconnection.impl;
import com.hazelcast.core.HazelcastException;
import java.util.concurrent.atomic.AtomicInteger;
/**
* A closeable reference counter to handle closing of a resource after all
* references are released. The initial refCount is 1. It is incremented by
* calling {@link #retain()} and decremented by calling {@link #release()},
* which must be paired. When the refCount gets to 0, the {@link #destroyAction}
* is run, and it is not possible to call {@link #retain()} afterwards.
*
* It is useful to delay closing of a resource provider itself until all
* resources it provided are closed too. The initial refCount of 1 is for the
* resource provider itself, other retain/release calls are for other resources.
* The resource then has a `close` method which releases the initial reference,
* but the destroy action is called only after all other resources are released
* too.
*/
public class ReferenceCounter {
private final AtomicInteger referenceCount = new AtomicInteger(1);
private final Runnable destroyAction;
public ReferenceCounter(Runnable destroyAction) {
this.destroyAction = destroyAction;
}
/**
* Increments the reference count
*
* @throws IllegalStateException when called after the reference count reached 0
*/
public void retain() {
referenceCount.updateAndGet(cnt -> {
if (cnt <= 0) {
throw new IllegalStateException("Resurrected a dead object");
}
return cnt + 1;
});
}
/**
* Decrements the reference count
*
* @return true if the counter reached 0, false otherwise
*/
public boolean release() {
long newCount = referenceCount.decrementAndGet();
if (newCount < 0) {
throw new IllegalStateException("release without retain");
}
if (newCount == 0) {
try {
destroyAction.run();
} catch (Exception e) {
throw new HazelcastException("Could not destroy reference counted object: " + e, e);
}
return true;
} else {
return false;
}
}
}