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.cassandra.utils;
  
  import java.util.concurrent.locks.ReadWriteLock;
  import java.util.concurrent.locks.ReentrantReadWriteLock;
  
  // simple thread-unsafe skiplist that permits indexing/removal by position, insertion at the end
  // (though easily extended to insertion at any position, not necessary here)
  // we use it for sampling items by position for visiting writes in the pool of pending writes
  public class LockedDynamicList<E> extends DynamicList<E>
  {
  
      private final ReadWriteLock lock = new ReentrantReadWriteLock();
  
      public LockedDynamicList(int maxExpectedSize)
      {
          super(maxExpectedSize);
      }
  
      // add the value to the end of the list, and return the associated Node that permits efficient removal
      // regardless of its future position in the list from other modifications
      public Node<E> append(E value, int maxSize)
      {
          lock.writeLock().lock();
          try
          {
              return super.append(value, maxSize);
          }
          finally
          {
              lock.writeLock().unlock();
          }
      }
  
      // remove the provided node and its associated value from the list
      public void remove(Node<E> node)
      {
          lock.writeLock().lock();
          try
          {
              super.remove(node);
          }
          finally
          {
              lock.writeLock().unlock();
          }
      }
  
      // retrieve the item at the provided index, or return null if the index is past the end of the list
      public E get(int index)
      {
          lock.readLock().lock();
          try
          {
              return super.get(index);
          }
          finally
          {
              lock.readLock().unlock();
          }
      }
  
      public int size()
      {
          lock.readLock().lock();
          try
          {
              return super.size();
          }
          finally
          {
              lock.readLock().unlock();
          }
      }
  }
  