001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package org.apache.hadoop.io.compress;
019
020import java.io.IOException;
021import java.nio.ByteBuffer;
022
023import org.apache.hadoop.classification.InterfaceAudience;
024import org.apache.hadoop.classification.InterfaceStability;
025
026/**
027 * Specification of a direct ByteBuffer 'de-compressor'. 
028 */
029@InterfaceAudience.Public
030@InterfaceStability.Evolving
031public interface DirectDecompressor {
032  /*
033   * This exposes a direct interface for record decompression with direct byte
034   * buffers.
035   * 
036   * The decompress() function need not always consume the buffers provided,
037   * it will need to be called multiple times to decompress an entire buffer 
038   * and the object will hold the compression context internally.
039   * 
040   * Codecs such as {@link SnappyCodec} may or may not support partial
041   * decompression of buffers and will need enough space in the destination
042   * buffer to decompress an entire block.
043   * 
044   * The operation is modelled around dst.put(src);
045   * 
046   * The end result will move src.position() by the bytes-read and
047   * dst.position() by the bytes-written. It should not modify the src.limit()
048   * or dst.limit() to maintain consistency of operation between codecs.
049   * 
050   * @param src Source direct {@link ByteBuffer} for reading from. Requires src
051   * != null and src.remaining() > 0
052   * 
053   * @param dst Destination direct {@link ByteBuffer} for storing the results
054   * into. Requires dst != null and dst.remaining() to be > 0
055   * 
056   * @throws IOException if compression fails
057   */
058  public void decompress(ByteBuffer src, ByteBuffer dst) throws IOException;
059}