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.io.IOException;
  import java.nio.ByteBuffer;
  import java.nio.channels.ReadableByteChannel;
  import java.nio.channels.SeekableByteChannel;
  
  import com.google.common.base.Preconditions;
  
  import org.apache.cassandra.utils.memory.MemoryUtil;
  
  /**
   * Rough equivalent of BufferedInputStream and DataInputStream wrapping the input stream of a File or Socket
   * Created to work around the fact that when BIS + DIS delegate to NIO for socket IO they will allocate large
   * thread local direct byte buffers when a large array is used to read.
   *
   * There may also be some performance improvement due to using a DBB as the underlying buffer for IO and the removal
   * of some indirection and delegation when it comes to reading out individual values, but that is not the goal.
   *
   * Closing NIODataInputStream will invoke close on the ReadableByteChannel provided at construction.
   *
   * NIODataInputStream is not thread safe.
   */
  public class NIODataInputStream extends RebufferingInputStream
  {
      protected final ReadableByteChannel channel;
  
      private static ByteBuffer makeBuffer(int bufferSize)
      {
          ByteBuffer buffer = ByteBuffer.allocateDirect(bufferSize);
          buffer.position(0);
          buffer.limit(0);
  
          return buffer;
      }
  
      public NIODataInputStream(ReadableByteChannel channel, int bufferSize)
      {
          super(makeBuffer(bufferSize));
  
          Preconditions.checkNotNull(channel);
          this.channel = channel;
      }
  
      @Override
      protected void reBuffer() throws IOException
      {
          Preconditions.checkState(buffer.remaining() == 0);
          buffer.clear();
  
          while ((channel.read(buffer)) == 0) {}
  
          buffer.flip();
      }
  
      @Override
      public void close() throws IOException
      {
          channel.close();
          super.close();
          MemoryUtil.clean(buffer);
          buffer = null;
      }
  
      @Override
      public int available() throws IOException
      {
          if (channel instanceof SeekableByteChannel)
          {
              SeekableByteChannel sbc = (SeekableByteChannel) channel;
              long remainder = Math.max(0, sbc.size() - sbc.position());
              return (remainder > Integer.MAX_VALUE) ? Integer.MAX_VALUE : (int)(remainder + buffer.remaining());
          }
          return buffer.remaining();
      }
  }
  