com.hadoop.mapreduce.FourMcLineRecordReader.java Source code

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Here is the source code for com.hadoop.mapreduce.FourMcLineRecordReader.java

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/**
4MC
Copyright (c) 2014, Carlo Medas
BSD 2-Clause License (http://www.opensource.org/licenses/bsd-license.php)
    
Redistribution and use in source and binary forms, with or without modification,
are permitted provided that the following conditions are met:
    
* Redistributions of source code must retain the above copyright notice, this
  list of conditions and the following disclaimer.
    
* Redistributions in binary form must reproduce the above copyright notice, this
  list of conditions and the following disclaimer in the documentation and/or
  other materials provided with the distribution.
    
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
    
  You can contact 4MC author at :
  - 4MC source repository : https://github.com/carlomedas/4mc
    
  LZ4 - Copyright (C) 2011-2014, Yann Collet - BSD 2-Clause License.
  You can contact LZ4 lib author at :
  - LZ4 source repository : http://code.google.com/p/lz4/
**/
package com.hadoop.mapreduce;

import com.hadoop.compression.fourmc.util.HadoopUtils;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.compress.CompressionCodec;
import org.apache.hadoop.io.compress.CompressionCodecFactory;
import org.apache.hadoop.mapreduce.InputSplit;
import org.apache.hadoop.mapreduce.RecordReader;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.hadoop.mapreduce.lib.input.FileSplit;
import org.apache.hadoop.util.LineReader;

import java.io.IOException;

/**
 * Reads line from a 4mc compressed text file.
 * Treats keys as offset in file and value as line.
 */
public class FourMcLineRecordReader extends RecordReader<LongWritable, Text> {

    public static final String MAX_LINE_LEN_CONF = "com.hadoop.mapreduce.fourmc.line.recordreader.max.line.length";

    private long start;
    private long pos;
    private long end;
    private LineReader in;
    private FSDataInputStream fileIn;

    private int maxLineLen = Integer.MAX_VALUE;

    private final LongWritable key = new LongWritable();
    private final Text value = new Text();

    public String getName() {
        return "fourmc";
    }

    public String getFilePattern() {
        return "\\.4mc&";
    }

    /**
     * Get the progress within the split.
     */
    @Override
    public float getProgress() {
        if (start == end) {
            return 0.0f;
        } else {
            return Math.min(1.0f, (pos - start) / (float) (end - start));
        }
    }

    public synchronized long getPos() throws IOException {
        return pos;
    }

    @Override
    public synchronized void close() throws IOException {
        if (in != null) {
            in.close();
        }
    }

    @Override
    public LongWritable getCurrentKey() throws IOException, InterruptedException {
        return key;
    }

    @Override
    public Text getCurrentValue() throws IOException, InterruptedException {
        return value;
    }

    @Override
    public void initialize(InputSplit genericSplit, TaskAttemptContext context)
            throws IOException, InterruptedException {
        FileSplit split = (FileSplit) genericSplit;
        start = split.getStart();
        end = start + split.getLength();
        final Path file = split.getPath();
        Configuration job = HadoopUtils.getConfiguration(context);
        maxLineLen = job.getInt(MAX_LINE_LEN_CONF, Integer.MAX_VALUE);

        FileSystem fs = file.getFileSystem(job);
        CompressionCodecFactory compressionCodecs = new CompressionCodecFactory(job);
        final CompressionCodec codec = compressionCodecs.getCodec(file);
        if (codec == null) {
            throw new IOException("Codec for file " + file + " not found, cannot run");
        }

        // open the file and seek to the start of the split
        fileIn = fs.open(split.getPath());

        // creates input stream and also reads the file header
        in = new LineReader(codec.createInputStream(fileIn), job);

        if (start != 0) {
            fileIn.seek(start);

            // read and ignore the first line
            in.readLine(new Text());
            start = fileIn.getPos();
        }

        this.pos = start;
    }

    @Override
    public boolean nextKeyValue() throws IOException, InterruptedException {
        // exactly same as EB one
        if (pos <= end) {
            key.set(pos);

            int newSize = in.readLine(value, maxLineLen);
            if (newSize == 0) {
                return false;
            }
            pos = fileIn.getPos();

            return true;
        }
        return false;
    }
}