content: /*
   * 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.bifromq.util.index;
  
  import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
  
  public class INode<V> {
      private static final AtomicReferenceFieldUpdater<INode, MainNode>
          MAIN_UPDATER = AtomicReferenceFieldUpdater.newUpdater(INode.class, MainNode.class, "main");
  
      private volatile MainNode<V> main = null;
  
      INode(MainNode<V> main) {
          cas(null, main);
      }
  
      @SuppressWarnings("unchecked")
      public MainNode<V> main() {
          return MAIN_UPDATER.get(this);
      }
  
      public boolean cas(MainNode<V> expect, MainNode<V> update) {
          return MAIN_UPDATER.compareAndSet(this, expect, update);
      }
  }
  