org.apache.lucene.util.RefCount Maven / Gradle / Ivy
/*
* 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.
*/
package org.apache.lucene.util;
import java.io.IOException;
import java.util.concurrent.atomic.AtomicInteger;
/**
* Manages reference counting for a given object. Extensions can override
* {@link #release()} to do custom logic when reference counting hits 0.
*/
public class RefCount {
private final AtomicInteger refCount = new AtomicInteger(1);
protected final T object;
public RefCount(T object) {
this.object = object;
}
/**
* Called when reference counting hits 0. By default this method does nothing,
* but extensions can override to e.g. release resources attached to object
* that is managed by this class.
*/
protected void release() throws IOException {}
/**
* Decrements the reference counting of this object. When reference counting
* hits 0, calls {@link #release()}.
*/
public final void decRef() throws IOException {
final int rc = refCount.decrementAndGet();
if (rc == 0) {
boolean success = false;
try {
release();
success = true;
} finally {
if (!success) {
// Put reference back on failure
refCount.incrementAndGet();
}
}
} else if (rc < 0) {
throw new IllegalStateException("too many decRef calls: refCount is " + rc + " after decrement");
}
}
public final T get() {
return object;
}
/** Returns the current reference count. */
public final int getRefCount() {
return refCount.get();
}
/**
* Increments the reference count. Calls to this method must be matched with
* calls to {@link #decRef()}.
*/
public final void incRef() {
refCount.incrementAndGet();
}
}