org.apache.activemq.artemis.utils.ReferenceCounterUtil Maven / Gradle / Ivy

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This artifact provides a single jar that contains all classes required to use remote Jakarta Enterprise Beans and Jakarta Messaging, including all dependencies. It is intended for use by those not using maven, maven users should just import the Jakarta Enterprise Beans and Jakarta Messaging BOM's instead (shaded JAR's cause lots of problems with maven, as it is very easy to inadvertently end up with different versions on classes on the class path).

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/*
 * 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.activemq.artemis.utils;

import java.util.concurrent.Executor;
import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;

public class ReferenceCounterUtil implements ReferenceCounter, AutoCloseable {

   private Runnable task;

   /**
    * If executor is null the runnable will be called within the same thread, otherwise the executor will be used
    */
   private final Executor executor;

   private volatile int use = 0;

   private static final AtomicIntegerFieldUpdater useUpdater = AtomicIntegerFieldUpdater.newUpdater(ReferenceCounterUtil.class, "use");

   public ReferenceCounterUtil() {
      this.executor = null;
      this.task = null;
   }

   public ReferenceCounterUtil(Executor executor) {
      this.executor = executor;
   }

   public ReferenceCounterUtil(Runnable runnable, Executor executor) {
      this.setTask(runnable);
      this.executor = executor;
   }

   public ReferenceCounterUtil(Runnable runnable) {
      this.setTask(runnable);
      this.executor = null;
   }

   @Override
   public void setTask(Runnable task) {
      this.task = task;
   }

   @Override
   public Runnable getTask() {
      return task;
   }

   @Override
   public int increment() {
      return useUpdater.incrementAndGet(this);
   }

   @Override
   public int decrement() {
      int value = useUpdater.decrementAndGet(this);
      if (value == 0) {
         execute();
      }

      return value;
   }

   /** it will set the value all the way to 0, and execute the task meant for when the value was 0. */
   public void exhaust() {
      execute();
      useUpdater.set(this, 0);
   }

   private void execute() {
      if (task != null) {
         if (executor != null) {
            executor.execute(task);
         } else {
            task.run();
         }
      }
   }

   @Override
   public void check() {
      if (getCount() <= 0) {
         execute();
      }
   }

   @Override
   public int getCount() {
      return useUpdater.get(this);
   }

   @Override
   public void close() {
      decrement();
   }
}