/*
* 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.flink.runtime.util;
/**
* Atomic reference counter, which enters a "disposed" state after it reaches a configurable
* reference count (default 0).
*/
public class AtomicDisposableReferenceCounter {
private final Object lock = new Object();
private int referenceCount;
private boolean isDisposed;
/** Enter the disposed state when the reference count reaches this number. */
private final int disposeOnReferenceCount;
public AtomicDisposableReferenceCounter() {
this.disposeOnReferenceCount = 0;
}
public AtomicDisposableReferenceCounter(int disposeOnReferenceCount) {
this.disposeOnReferenceCount = disposeOnReferenceCount;
}
/**
* Increments the reference count and returns whether it was successful.
* <p>
* If the method returns <code>false</code>, the counter has already been disposed. Otherwise it
* returns <code>true</code>.
*/
public boolean increment() {
synchronized (lock) {
if (isDisposed) {
return false;
}
referenceCount++;
return true;
}
}
/**
* Decrements the reference count and returns whether the reference counter entered the disposed
* state.
* <p>
* If the method returns <code>true</code>, the decrement operation disposed the counter.
* Otherwise it returns <code>false</code>.
*/
public boolean decrement() {
synchronized (lock) {
if (isDisposed) {
return false;
}
referenceCount--;
if (referenceCount <= disposeOnReferenceCount) {
isDisposed = true;
}
return isDisposed;
}
}
public int get() {
synchronized (lock) {
return referenceCount;
}
}
/**
* Returns whether the reference count has reached the disposed state.
*/
public boolean isDisposed() {
synchronized (lock) {
return isDisposed;
}
}
public boolean disposeIfNotUsed() {
synchronized (lock) {
if (referenceCount <= disposeOnReferenceCount) {
isDisposed = true;
}
return isDisposed;
}
}
}