src/core/org/apache/hadoop/io/compress/CompressionInputStream.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.io.InputStream;

/**
 * A compression input stream.
 *
 * <p>Implementations are assumed to be buffered.  This permits clients to
 * reposition the underlying input stream then call {@link #resetState()},
 * without having to also synchronize client buffers.
 */
public abstract class CompressionInputStream extends InputStream {
  /**
   * The input stream to be compressed. 
   */
  protected final InputStream in;

  /**
   * Create a compression input stream that reads
   * the decompressed bytes from the given stream.
   * 
   * @param in The input stream to be compressed.
   */
  protected CompressionInputStream(InputStream in) {
    this.in = in;
  }

  public void close() throws IOException {
    in.close();
  }
  
  /**
   * Read bytes from the stream.
   * Made abstract to prevent leakage to underlying stream.
   */
  public abstract int read(byte[] b, int off, int len) throws IOException;

  /**
   * Reset the decompressor to its initial state and discard any buffered data,
   * as the underlying stream may have been repositioned.
   */
  public abstract void resetState() throws IOException;
  
}