org.apache.hadoop.io.compress.Decompressor.java Source code

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Here is the source code for org.apache.hadoop.io.compress.Decompressor.java

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

/**
 * Specification of a stream-based 'de-compressor' which can be  
 * plugged into a {@link CompressionInputStream} to compress data.
 * This is modelled after {@link java.util.zip.Inflater}
 * 
 */
@InterfaceAudience.Public
@InterfaceStability.Evolving
public interface Decompressor {
    /**
     * Sets input data for decompression. 
     * This should be called if and only if {@link #needsInput()} returns 
     * <code>true</code> indicating that more input data is required.
     * (Both native and non-native versions of various Decompressors require
     * that the data passed in via <code>b[]</code> remain unmodified until
     * the caller is explicitly notified--via {@link #needsInput()}--that the
     * buffer may be safely modified.  With this requirement, an extra
     * buffer-copy can be avoided.)
     * 
     * @param b Input data
     * @param off Start offset
     * @param len Length
     */
    public void setInput(byte[] b, int off, int len);

    /**
     * Returns <code>true</code> if the input data buffer is empty and 
     * {@link #setInput(byte[], int, int)} should be called to
     * provide more input. 
     * 
     * @return <code>true</code> if the input data buffer is empty and 
     * {@link #setInput(byte[], int, int)} should be called in
     * order to provide more input.
     */
    public boolean needsInput();

    /**
     * Sets preset dictionary for compression. A preset dictionary
     * is used when the history buffer can be predetermined. 
     *
     * @param b Dictionary data bytes
     * @param off Start offset
     * @param len Length
     */
    public void setDictionary(byte[] b, int off, int len);

    /**
     * Returns <code>true</code> if a preset dictionary is needed for decompression.
     * @return <code>true</code> if a preset dictionary is needed for decompression
     */
    public boolean needsDictionary();

    /**
     * Returns <code>true</code> if the end of the decompressed 
     * data output stream has been reached. Indicates a concatenated data stream
     * when finished() returns <code>true</code> and {@link #getRemaining()}
     * returns a positive value. finished() will be reset with the
     * {@link #reset()} method.
     * @return <code>true</code> if the end of the decompressed
     * data output stream has been reached.
     */
    public boolean finished();

    /**
     * Fills specified buffer with uncompressed data. Returns actual number
     * of bytes of uncompressed data. A return value of 0 indicates that
     * {@link #needsInput()} should be called in order to determine if more
     * input data is required.
     * 
     * @param b Buffer for the compressed data
     * @param off Start offset of the data
     * @param len Size of the buffer
     * @return The actual number of bytes of uncompressed data.
     * @throws IOException
     */
    public int decompress(byte[] b, int off, int len) throws IOException;

    /**
     * Returns the number of bytes remaining in the compressed data buffer.
     * Indicates a concatenated data stream if {@link #finished()} returns
     * <code>true</code> and getRemaining() returns a positive value. If
     * {@link #finished()} returns <code>true</code> and getRemaining() returns
     * a zero value, indicates that the end of data stream has been reached and
     * is not a concatenated data stream. 
     * @return The number of bytes remaining in the compressed data buffer.
     */
    public int getRemaining();

    /**
     * Resets decompressor and input and output buffers so that a new set of
     * input data can be processed. If {@link #finished()}} returns
     * <code>true</code> and {@link #getRemaining()} returns a positive value,
     * reset() is called before processing of the next data stream in the
     * concatenated data stream. {@link #finished()} will be reset and will
     * return <code>false</code> when reset() is called.
     */
    public void reset();

    /**
     * Closes the decompressor and discards any unprocessed input.
     */
    public void end();
}