FSByteBufferInputStream.java

/**
 * Copyright 2008 - CommonCrawl Foundation
 * 
 *    This program is free software: you can redistribute it and/or modify
 *    it under the terms of the GNU General Public License as published by
 *    the Free Software Foundation, either version 3 of the License, or
 *    (at your option) any later version.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU General Public License for more details.
 *
 *    You should have received a copy of the GNU General Public License
 *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 **/

package org.commoncrawl.util;

import java.io.IOException;
import java.io.InputStream;
import java.nio.ByteBuffer;

import org.apache.hadoop.fs.PositionedReadable;
import org.apache.hadoop.fs.Seekable;

/**
 * ByteBuffer based input stream that also implements Seekable and Positionable,
 * thus allowing it to emulate FSDataInputStream
 * 
 * @author rana
 * 
 */
public class FSByteBufferInputStream extends InputStream implements Seekable, PositionedReadable {

  ByteBuffer _source;
  ByteBufferInputStream _sourceStream;
  public FSByteBufferInputStream(ByteBuffer in) {
    _sourceStream = new ByteBufferInputStream(in);
    _source = in;

  }

  public long getPos() throws IOException {
    return _source.position();
  }

  public long skip(long n) throws IOException {
    if (n <= 0) {
      return 0;
    }
    _source.position(_source.position() + (int) n);
    return n;
  }

  public void seek(long pos) throws IOException {
    _source.position((int) pos);
  }

  public boolean seekToNewSource(long targetPos) throws IOException {
    _source.position((int) targetPos);
    return true;
  }

  public int read(long position, byte[] buffer, int offset, int length)
      throws IOException {
    _source.mark();
    _source.position((int) position);
    int bytesToRead = Math.min(length, _source.remaining());
    _source.get(buffer, offset, bytesToRead);
    _source.reset();
    return bytesToRead;
  }

  public void readFully(long position, byte[] buffer, int offset, int length)
      throws IOException {
    _source.mark();
    _source.position((int) position);
    _source.get(buffer, offset, length);
    _source.reset();
  }

  public void readFully(long position, byte[] buffer) throws IOException {
    _source.mark();
    _source.position((int) position);
    _source.get(buffer);
    _source.reset();
  }

  @Override
  public int read() throws IOException {
    if (_source.remaining() == 0) 
      return -1;
    else 
      return _source.get();
  }
  
  @Override
  public int read(byte[] b, int off, int len) throws IOException {
    int amtToRead = Math.min(_source.remaining(),len);
    if (amtToRead == 0) { 
      return -1;
    }
    else {
      _source.get(b, off, amtToRead);
      return amtToRead;
    }
  }
}