hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/compress/DirectDecompressor.java

/*
 * 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.hadoop.io.compress;

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

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;

/**
 * Specification of a direct ByteBuffer 'de-compressor'. 
 */
@InterfaceAudience.Public
@InterfaceStability.Evolving
public interface DirectDecompressor {
  /*
   * This exposes a direct interface for record decompression with direct byte
   * buffers.
   * 
   * The decompress() function need not always consume the buffers provided,
   * it will need to be called multiple times to decompress an entire buffer 
   * and the object will hold the compression context internally.
   * 
   * Codecs such as {@link SnappyCodec} may or may not support partial
   * decompression of buffers and will need enough space in the destination
   * buffer to decompress an entire block.
   * 
   * The operation is modelled around dst.put(src);
   * 
   * The end result will move src.position() by the bytes-read and
   * dst.position() by the bytes-written. It should not modify the src.limit()
   * or dst.limit() to maintain consistency of operation between codecs.
   * 
   * @param src Source direct {@link ByteBuffer} for reading from. Requires src
   * != null and src.remaining() > 0
   * 
   * @param dst Destination direct {@link ByteBuffer} for storing the results
   * into. Requires dst != null and dst.remaining() to be > 0
   * 
   * @throws IOException if compression fails
   */
  public void decompress(ByteBuffer src, ByteBuffer dst) throws IOException;
}