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 java.nio.ByteOrder;
  
  import org.apache.cassandra.utils.memory.BufferPools;
  
  /**
   * Buffer manager used for reading from a ChunkReader when cache is not in use. Instances of this class are
   * reader-specific and thus do not need to be thread-safe since the reader itself isn't.
   *
   * The instances reuse themselves as the BufferHolder to avoid having to return a new object for each rebuffer call.
   */
  public abstract class BufferManagingRebufferer implements Rebufferer, Rebufferer.BufferHolder
  {
      protected final ChunkReader source;
      protected final ByteBuffer buffer;
      protected long offset = 0;
  
      abstract long alignedPosition(long position);
  
      protected BufferManagingRebufferer(ChunkReader wrapped)
      {
          this.source = wrapped;
          buffer = BufferPools.forChunkCache().get(wrapped.chunkSize(), wrapped.preferredBufferType()).order(ByteOrder.BIG_ENDIAN);
          buffer.limit(0);
      }
  
      @Override
      public void closeReader()
      {
          BufferPools.forChunkCache().put(buffer);
          source.releaseUnderlyingResources();
          offset = -1;
      }
  
      @Override
      public void close()
      {
          assert offset == -1;    // reader must be closed at this point.
          source.close();
      }
  
      @Override
      public ChannelProxy channel()
      {
          return source.channel();
      }
  
      @Override
      public long fileLength()
      {
          return source.fileLength();
      }
  
      @Override
      public BufferHolder rebuffer(long position)
      {
          offset = alignedPosition(position);
          source.readChunk(offset, buffer);
          return this;
      }
  
      @Override
      public double getCrcCheckChance()
      {
          return source.getCrcCheckChance();
      }
  
      @Override
      public String toString()
      {
          return "BufferManagingRebufferer." + getClass().getSimpleName() + ":" + source;
      }
  
      // BufferHolder methods
  
      public ByteBuffer buffer()
      {
          return buffer;
      }
  
      public long offset()
      {
          return offset;
      }
  
      @Override
      public void release()
      {
          // nothing to do, we don't delete buffers before we're closed.
      }
  
      public static class Unaligned extends BufferManagingRebufferer
      {
          public Unaligned(ChunkReader wrapped)
          {
              super(wrapped);
          }
  
          @Override
          long alignedPosition(long position)
          {
              return position;
          }
      }
  
      public static class Aligned extends BufferManagingRebufferer
      {
          public Aligned(ChunkReader wrapped)
          {
              super(wrapped);
              assert Integer.bitCount(wrapped.chunkSize()) == 1;
          }
  
          @Override
          long alignedPosition(long position)
          {
              return position & -buffer.capacity();
          }
      }
  }
  