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

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Here is the source code for org.apache.hadoop.io.compress.BlockDecompressorStream.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.EOFException;
import java.io.IOException;
import java.io.InputStream;

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

/**
 * A {@link org.apache.hadoop.io.compress.DecompressorStream} which works
 * with 'block-based' based compression algorithms, as opposed to 
 * 'stream-based' compression algorithms.
 *  
 */
@InterfaceAudience.Public
@InterfaceStability.Evolving
public class BlockDecompressorStream extends DecompressorStream {
    private int originalBlockSize = 0;
    private int noUncompressedBytes = 0;

    /**
     * Create a {@link BlockDecompressorStream}.
     * 
     * @param in input stream
     * @param decompressor decompressor to use
     * @param bufferSize size of buffer
     * @throws IOException
     */
    public BlockDecompressorStream(InputStream in, Decompressor decompressor, int bufferSize) throws IOException {
        super(in, decompressor, bufferSize);
    }

    /**
     * Create a {@link BlockDecompressorStream}.
     * 
     * @param in input stream
     * @param decompressor decompressor to use
     * @throws IOException
     */
    public BlockDecompressorStream(InputStream in, Decompressor decompressor) throws IOException {
        super(in, decompressor);
    }

    protected BlockDecompressorStream(InputStream in) throws IOException {
        super(in);
    }

    @Override
    protected int decompress(byte[] b, int off, int len) throws IOException {
        // Check if we are the beginning of a block
        if (noUncompressedBytes == originalBlockSize) {
            // Get original data size
            try {
                originalBlockSize = rawReadInt();
            } catch (IOException ioe) {
                return -1;
            }
            noUncompressedBytes = 0;
            // EOF if originalBlockSize is 0
            // This will occur only when decompressing previous compressed empty file
            if (originalBlockSize == 0) {
                eof = true;
                return -1;
            }
        }

        int n = 0;
        while ((n = decompressor.decompress(b, off, len)) == 0) {
            if (decompressor.finished() || decompressor.needsDictionary()) {
                if (noUncompressedBytes >= originalBlockSize) {
                    eof = true;
                    return -1;
                }
            }
            if (decompressor.needsInput()) {
                int m;
                try {
                    m = getCompressedData();
                } catch (EOFException e) {
                    eof = true;
                    return -1;
                }
                // Send the read data to the decompressor
                decompressor.setInput(buffer, 0, m);
            }
        }

        // Note the no. of decompressed bytes read from 'current' block
        noUncompressedBytes += n;

        return n;
    }

    @Override
    protected int getCompressedData() throws IOException {
        checkStream();

        // Get the size of the compressed chunk (always non-negative)
        int len = rawReadInt();

        // Read len bytes from underlying stream 
        if (len > buffer.length) {
            buffer = new byte[len];
        }
        int n = 0, off = 0;
        while (n < len) {
            int count = in.read(buffer, off + n, len - n);
            if (count < 0) {
                throw new EOFException("Unexpected end of block in input stream");
            }
            n += count;
        }

        return len;
    }

    @Override
    public void resetState() throws IOException {
        originalBlockSize = 0;
        noUncompressedBytes = 0;
        super.resetState();
    }

    private int rawReadInt() throws IOException {
        int b1 = in.read();
        int b2 = in.read();
        int b3 = in.read();
        int b4 = in.read();
        if ((b1 | b2 | b3 | b4) < 0)
            throw new EOFException();
        return ((b1 << 24) + (b2 << 16) + (b3 << 8) + (b4 << 0));
    }
}