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.io.util;
  
  import java.nio.ByteBuffer;
  import javax.annotation.concurrent.NotThreadSafe;
  
  /**
   * Instantiated once per RandomAccessReader, thread-unsafe.
   * The instances reuse themselves as the BufferHolder to avoid having to return a new object for each rebuffer call.
   * Only one buffer holder can be active at a time. Calling {@link #rebuffer(long)} before the previously obtained
   * buffer holder is released will throw {@link AssertionError}. We will get that exception also in case we try to close
   * the rebufferer without closing the recently obtained buffer holder.
   * <p>
   * Calling methods of {@link BufferHolder} will also produce {@link AssertionError} if buffer holder is not acquired.
   * <p>
   * The overriding classes must conform to the aforementioned rules.
   */
  @NotThreadSafe
  public abstract class WrappingRebufferer implements Rebufferer, Rebufferer.BufferHolder
  {
      protected final Rebufferer wrapped;
  
      protected BufferHolder bufferHolder;
      protected ByteBuffer buffer;
      protected long offset;
  
      public WrappingRebufferer(Rebufferer wrapped)
      {
          this.wrapped = wrapped;
      }
  
      @Override
      public BufferHolder rebuffer(long position)
      {
          assert buffer == null;
          bufferHolder = wrapped.rebuffer(position);
          buffer = bufferHolder.buffer();
          offset = bufferHolder.offset();
  
          return this;
      }
  
      @Override
      public ChannelProxy channel()
      {
          return wrapped.channel();
      }
  
      @Override
      public long fileLength()
      {
          return wrapped.fileLength();
      }
  
      @Override
      public double getCrcCheckChance()
      {
          return wrapped.getCrcCheckChance();
      }
  
      @Override
      public void close()
      {
          assert buffer == null : "Rebufferer is attempted to be closed but the buffer holder has not been released";
          wrapped.close();
      }
  
      @Override
      public void closeReader()
      {
          wrapped.closeReader();
      }
  
      @Override
      public String toString()
      {
          return String.format("%s[]:%s", getClass().getSimpleName(), wrapped.toString());
      }
  
      @Override
      public ByteBuffer buffer()
      {
          assert buffer != null : "Buffer holder has not been acquired";
          return buffer;
      }
  
      @Override
      public long offset()
      {
          assert buffer != null : "Buffer holder has not been acquired";
          return offset;
      }
  
      @Override
      public void release()
      {
          assert buffer != null;
          if (bufferHolder != null)
          {
              bufferHolder.release();
              bufferHolder = null;
          }
          buffer = null;
      }
  }