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.concurrent;
  
  /**
   * A simple extension of AutoCloseable, that represents a resource that can be utilised in multiple locations,
   * each managing their own closure of the resource, so that when the last such instance is closed all are.
   *
   */
  public interface SharedCloseable extends AutoCloseable
  {
      /**
       * @return a new instance of the object representing the same state and backed by the same underlying resources.
       * Coordinates with the original (and other instances) when the underlying resource should be closed.
       * Throws an exception if the shared resource has already been closed.
       */
      public SharedCloseable sharedCopy();
      public Throwable close(Throwable accumulate);
  
      public void addTo(Ref.IdentityCollection identities);
  
      static <T extends SharedCloseable> T sharedCopyOrNull(T sharedCloseable)
      {
          if (sharedCloseable != null)
              return (T) sharedCloseable.sharedCopy();
  
          return null;
      }
  }