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

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Here is the source code for org.apache.hadoop.io.compress.Compressor.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;
import org.apache.hadoop.conf.Configuration;

/**
 * Specification of a stream-based 'compressor' which can be  
 * plugged into a {@link CompressionOutputStream} to compress data.
 * This is modelled after {@link java.util.zip.Deflater}
 * 
 */
@InterfaceAudience.Public
@InterfaceStability.Evolving
public interface Compressor {
    /**
     * Sets input data for compression. 
     * This should be called whenever #needsInput() returns 
     * <code>true</code> indicating that more input data is required.
     * 
     * @param b Input data
     * @param off Start offset
     * @param len Length
     */
    public void setInput(byte[] b, int off, int len);

    /**
     * Returns true if the input data buffer is empty and 
     * #setInput() should be called to provide more input. 
     * 
     * @return <code>true</code> if the input data buffer is empty and 
     * #setInput() 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);

    /**
     * Return number of uncompressed bytes input so far.
     */
    public long getBytesRead();

    /**
     * Return number of compressed bytes output so far.
     */
    public long getBytesWritten();

    /**
     * When called, indicates that compression should end
     * with the current contents of the input buffer.
     */
    public void finish();

    /**
     * Returns true if the end of the compressed 
     * data output stream has been reached.
     * @return <code>true</code> if the end of the compressed
     * data output stream has been reached.
     */
    public boolean finished();

    /**
     * Fills specified buffer with compressed data. Returns actual number
     * of bytes of compressed data. A return value of 0 indicates that
     * 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 compressed data.
     */
    public int compress(byte[] b, int off, int len) throws IOException;

    /**
     * Resets compressor so that a new set of input data can be processed.
     */
    public void reset();

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

    /**
     * Prepare the compressor to be used in a new stream with settings defined in
     * the given Configuration
     * 
     * @param conf Configuration from which new setting are fetched
     */
    public void reinit(Configuration conf);
}