org.apache.pig.impl.io.BinStorageRecordReader.java Source code

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Here is the source code for org.apache.pig.impl.io.BinStorageRecordReader.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.pig.impl.io;

import java.io.DataInputStream;
import java.io.IOException;

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.Text;
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.pig.backend.executionengine.ExecException;
import org.apache.pig.data.DataReaderWriter;
import org.apache.pig.data.DataType;
import org.apache.pig.data.Tuple;

/**
 * Treats keys as offset in file and value as line. 
 */
public class BinStorageRecordReader extends RecordReader<Text, Tuple> {

    private long start;
    private long pos;
    private long end;
    private BufferedPositionedInputStream in;
    private Tuple value = null;
    public static final int RECORD_1 = 0x01;
    public static final int RECORD_2 = 0x02;
    public static final int RECORD_3 = 0x03;
    private DataInputStream inData = null;

    public void initialize(InputSplit genericSplit, TaskAttemptContext context) throws IOException {
        FileSplit split = (FileSplit) genericSplit;
        Configuration job = context.getConfiguration();
        start = split.getStart();
        end = start + split.getLength();
        final Path file = split.getPath();

        // open the file and seek to the start of the split
        FileSystem fs = file.getFileSystem(job);
        FSDataInputStream fileIn = fs.open(split.getPath());
        if (start != 0) {
            fileIn.seek(start);
        }
        in = new BufferedPositionedInputStream(fileIn, start);
        inData = new DataInputStream(in);
    }

    public boolean nextKeyValue() throws IOException {
        int b = 0;
        //    skip to next record
        while (true) {
            if (in == null || in.getPosition() >= end) {
                return false;
            }
            // check if we saw RECORD_1 in our last attempt
            // this can happen if we have the following 
            // sequence RECORD_1-RECORD_1-RECORD_2-RECORD_3
            // After reading the second RECORD_1 in the above
            // sequence, we should not look for RECORD_1 again
            if (b != RECORD_1) {
                b = in.read();
                if (b != RECORD_1 && b != -1) {
                    continue;
                }
                if (b == -1)
                    return false;
            }
            b = in.read();
            if (b != RECORD_2 && b != -1) {
                continue;
            }
            if (b == -1)
                return false;
            b = in.read();
            if (b != RECORD_3 && b != -1) {
                continue;
            }
            if (b == -1)
                return false;
            b = in.read();
            if (b != DataType.TUPLE && b != -1) {
                continue;
            }
            if (b == -1)
                return false;
            break;
        }
        try {
            // if we got here, we have seen RECORD_1-RECORD_2-RECORD_3-TUPLE_MARKER
            // sequence - lets now read the contents of the tuple 
            value = (Tuple) DataReaderWriter.readDatum(inData, DataType.TUPLE);
            pos = in.getPosition();
            return true;
        } catch (ExecException ee) {
            throw ee;
        }

    }

    @Override
    public Text getCurrentKey() {
        // the key is always null since we don't really have a key for each
        // input record
        return null;
    }

    @Override
    public Tuple getCurrentValue() {
        return value;
    }

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

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