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;
  
  /**
   * Special rebufferer that replaces the tail of the file (from the specified cutoff point) with the given buffer.
   * <p>
   * 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 BufferHolder can be active at a time. Calling {@link #rebuffer(long)} before the previously obtained
   * buffer holder is released will throw {@link AssertionError}.
   */
  @NotThreadSafe
  public class TailOverridingRebufferer extends WrappingRebufferer
  {
      private final long cutoff;
      private final ByteBuffer tail;
  
      public TailOverridingRebufferer(Rebufferer source, long cutoff, ByteBuffer tail)
      {
          super(source);
          this.cutoff = cutoff;
          this.tail = tail;
      }
  
      @Override
      public Rebufferer.BufferHolder rebuffer(long position)
      {
          assert buffer == null : "Buffer holder has been already acquired and has been not released yet";
          if (position < cutoff)
          {
              super.rebuffer(position);
              if (offset + buffer.limit() > cutoff)
                  buffer.limit((int) (cutoff - offset));
          }
          else
          {
              buffer = tail.duplicate();
              offset = cutoff;
          }
          return this;
      }
  
      @Override
      public long fileLength()
      {
          return cutoff + tail.limit();
      }
  
      @Override
      public String toString()
      {
          return String.format("%s[+%d@%d]:%s", getClass().getSimpleName(), tail.limit(), cutoff, wrapped.toString());
      }
  }
  