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

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Here is the source code for org.apache.hadoop.io.compress.CompressionCodec.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 java.io.InputStream;
import java.io.OutputStream;

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

/**
 * This class encapsulates a streaming compression/decompression pair.
 */
@InterfaceAudience.Public
@InterfaceStability.Evolving
public interface CompressionCodec {

    /**
     * Create a {@link CompressionOutputStream} that will write to the given 
     * {@link OutputStream}.
     * 
     * @param out the location for the final output stream
     * @return a stream the user can write uncompressed data to have it compressed
     * @throws IOException
     */
    CompressionOutputStream createOutputStream(OutputStream out) throws IOException;

    /**
     * Create a {@link CompressionOutputStream} that will write to the given 
     * {@link OutputStream} with the given {@link Compressor}.
     * 
     * @param out the location for the final output stream
     * @param compressor compressor to use
     * @return a stream the user can write uncompressed data to have it compressed
     * @throws IOException
     */
    CompressionOutputStream createOutputStream(OutputStream out, Compressor compressor) throws IOException;

    /**
     * Get the type of {@link Compressor} needed by this {@link CompressionCodec}.
     * 
     * @return the type of compressor needed by this codec.
     */
    Class<? extends Compressor> getCompressorType();

    /**
     * Create a new {@link Compressor} for use by this {@link CompressionCodec}.
     * 
     * @return a new compressor for use by this codec
     */
    Compressor createCompressor();

    /**
     * Create a {@link CompressionInputStream} that will read from the given
     * input stream.
     * 
     * @param in the stream to read compressed bytes from
     * @return a stream to read uncompressed bytes from
     * @throws IOException
     */
    CompressionInputStream createInputStream(InputStream in) throws IOException;

    /**
     * Create a {@link CompressionInputStream} that will read from the given 
     * {@link InputStream} with the given {@link Decompressor}.
     * 
     * @param in the stream to read compressed bytes from
     * @param decompressor decompressor to use
     * @return a stream to read uncompressed bytes from
     * @throws IOException
     */
    CompressionInputStream createInputStream(InputStream in, Decompressor decompressor) throws IOException;

    /**
     * Get the type of {@link Decompressor} needed by this {@link CompressionCodec}.
     * 
     * @return the type of decompressor needed by this codec.
     */
    Class<? extends Decompressor> getDecompressorType();

    /**
     * Create a new {@link Decompressor} for use by this {@link CompressionCodec}.
     * 
     * @return a new decompressor for use by this codec
     */
    Decompressor createDecompressor();

    /**
     * Get the default filename extension for this kind of compression.
     * @return the extension including the '.'
     */
    String getDefaultExtension();

    static class Util {
        /**
         * Create an output stream with a codec taken from the global CodecPool.
         *
         * @param codec       The codec to use to create the output stream.
         * @param conf        The configuration to use if we need to create a new codec.
         * @param out         The output stream to wrap.
         * @return            The new output stream
         * @throws IOException
         */
        static CompressionOutputStream createOutputStreamWithCodecPool(CompressionCodec codec, Configuration conf,
                OutputStream out) throws IOException {
            Compressor compressor = CodecPool.getCompressor(codec, conf);
            CompressionOutputStream stream = null;
            try {
                stream = codec.createOutputStream(out, compressor);
            } finally {
                if (stream == null) {
                    CodecPool.returnCompressor(compressor);
                } else {
                    stream.setTrackedCompressor(compressor);
                }
            }
            return stream;
        }

        /**
         * Create an input stream with a codec taken from the global CodecPool.
         *
         * @param codec       The codec to use to create the input stream.
         * @param conf        The configuration to use if we need to create a new codec.
         * @param in          The input stream to wrap.
         * @return            The new input stream
         * @throws IOException
         */
        static CompressionInputStream createInputStreamWithCodecPool(CompressionCodec codec, Configuration conf,
                InputStream in) throws IOException {
            Decompressor decompressor = CodecPool.getDecompressor(codec);
            CompressionInputStream stream = null;
            try {
                stream = codec.createInputStream(in, decompressor);
            } finally {
                if (stream == null) {
                    CodecPool.returnDecompressor(decompressor);
                } else {
                    stream.setTrackedDecompressor(decompressor);
                }
            }
            return stream;
        }
    }
}