format.OverlapLengthInputFormat.java Source code

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Here is the source code for format.OverlapLengthInputFormat.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 format;

import java.io.IOException;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.BytesWritable;
import org.apache.hadoop.io.LongWritable;
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.JobContext;
import org.apache.hadoop.mapreduce.RecordReader;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;

import format.OverlapLengthRecordReader;

/**
 * FixedLengthInputFormat is an input format used to read input files
 * which contain fixed length records.  The content of a record need not be
 * text.  It can be arbitrary binary data.  Users must configure the record
 * length property by calling:
 * OverlapLengthInputFormat.setRecordLength(conf, recordLength);<br><br> or
 * conf.setInt(OverlapLengthInputFormat.FIXED_RECORD_LENGTH, recordLength);
 * <br><br>
 * @see OverlapLengthRecordReader
 */
@InterfaceAudience.Public
@InterfaceStability.Stable
public class OverlapLengthInputFormat extends FileInputFormat<LongWritable, BytesWritable> {

    public static final String FIXED_RECORD_LENGTH = "overlaplengthinputformat.record.length";
    public static final String OVERLAP_LENGTH = "overlaplengthinputformat.overlap.length";

    /**
     * Set the length of each record
     * @param conf configuration
     * @param recordLength the length of a record
     */
    public static void setRecordLength(Configuration conf, int recordLength) {
        conf.setInt(FIXED_RECORD_LENGTH, recordLength);
    }

    /**
     * Get record length value
     * @param conf configuration
     * @return the record length, zero means none was set
     */
    public static int getRecordLength(Configuration conf) {
        return conf.getInt(FIXED_RECORD_LENGTH, 0);
    }

    /**
     * Set the overlapping portion of adjacent records
     * @param conf configuration
     * @param overlapLength the overlapping portion of adjacent records
     **/
    public static void setOverlapLength(Configuration conf, int recordLength) {
        conf.setInt(OVERLAP_LENGTH, recordLength);
    }

    /**
     * Get the overlapping portion of adjacent records
     * @param conf configuration
     * @return the overlapping length, zero means none was set
     **/
    public static int getOverlapLength(Configuration conf) {
        return conf.getInt(OVERLAP_LENGTH, 0);
    }

    @Override
    public RecordReader<LongWritable, BytesWritable> createRecordReader(InputSplit split,
            TaskAttemptContext context) throws IOException, InterruptedException {
        int recordLength = getRecordLength(context.getConfiguration());
        int overlapLength = getOverlapLength(context.getConfiguration());
        if (recordLength <= 0) {
            throw new IOException("Fixed record length " + recordLength
                    + " is invalid.  It should be set to a value greater than zero");
        }
        return new OverlapLengthRecordReader(recordLength, overlapLength);
    }

    @Override
    protected boolean isSplitable(JobContext context, Path file) {
        final CompressionCodec codec = new CompressionCodecFactory(context.getConfiguration()).getCodec(file);
        return (null == codec);
    }

}