/*
 * 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.geode.distributed.internal;

import java.util.concurrent.atomic.AtomicLong;

/**
 * An atomic integer with update methods that check to see if the value is equal to a special flag.
 * Care should be taken to ensure that the value can never become the special value accidentally.
 * For example, a long that can never go negative with normal use could have a terminal state of
 * Long.MIN_VALUE
 * 
 * @since GemFire 6.0
 */
public class AtomicLongWithTerminalState extends AtomicLong {

  private static final long serialVersionUID = -6130409343386576390L;



  public AtomicLongWithTerminalState() {
    super();
  }



  public AtomicLongWithTerminalState(long initialValue) {
    super(initialValue);
  }

  /**
   * Add and the the given delta to the long, unless the long has been set to the terminal state.
   * 
   * @param terminalState
   * @param delta
   * @return the new value of the field, or the terminalState if the field is already set to the
   *         terminal state.
   */
  public long compareAddAndGet(long terminalState, long delta) {
    while (true) {
      long current = get();
      if (current == terminalState) {
        return terminalState;
      }
      long newValue = current + delta;
      if (compareAndSet(current, newValue)) {
        return newValue;
      }
    }
  }
}