001    /**
002     * Licensed to the Apache Software Foundation (ASF) under one
003     * or more contributor license agreements.  See the NOTICE file
004     * distributed with this work for additional information
005     * regarding copyright ownership.  The ASF licenses this file
006     * to you under the Apache License, Version 2.0 (the
007     * "License"); you may not use this file except in compliance
008     * with the License.  You may obtain a copy of the License at
009     *
010     *     http://www.apache.org/licenses/LICENSE-2.0
011     *
012     * Unless required by applicable law or agreed to in writing, software
013     * distributed under the License is distributed on an "AS IS" BASIS,
014     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015     * See the License for the specific language governing permissions and
016     * limitations under the License.
017     */
018    
019    package org.apache.hadoop.mapred;
020    
021    import java.io.IOException;
022    
023    import org.apache.hadoop.classification.InterfaceAudience;
024    import org.apache.hadoop.classification.InterfaceStability;
025    import org.apache.hadoop.conf.Configuration;
026    import org.apache.hadoop.fs.FileSystem;
027    import org.apache.hadoop.fs.Path;
028    import org.apache.hadoop.io.BytesWritable;
029    import org.apache.hadoop.io.LongWritable;
030    import org.apache.hadoop.io.compress.CompressionCodec;
031    import org.apache.hadoop.io.compress.CompressionCodecFactory;
032    
033    /**
034     * FixedLengthInputFormat is an input format used to read input files
035     * which contain fixed length records.  The content of a record need not be
036     * text.  It can be arbitrary binary data.  Users must configure the record
037     * length property by calling:
038     * FixedLengthInputFormat.setRecordLength(conf, recordLength);<br><br> or
039     * conf.setInt(FixedLengthInputFormat.FIXED_RECORD_LENGTH, recordLength);
040     * <br><br>
041     * @see FixedLengthRecordReader
042     */
043    @InterfaceAudience.Public
044    @InterfaceStability.Stable
045    public class FixedLengthInputFormat
046        extends FileInputFormat<LongWritable, BytesWritable>
047        implements JobConfigurable {
048    
049      private CompressionCodecFactory compressionCodecs = null;
050      
051      public static final String FIXED_RECORD_LENGTH =
052          "fixedlengthinputformat.record.length"; 
053    
054      /**
055       * Set the length of each record
056       * @param conf configuration
057       * @param recordLength the length of a record
058       */
059      public static void setRecordLength(Configuration conf, int recordLength) {
060        conf.setInt(FIXED_RECORD_LENGTH, recordLength);
061      }
062    
063      /**
064       * Get record length value
065       * @param conf configuration
066       * @return the record length, zero means none was set
067       */
068      public static int getRecordLength(Configuration conf) {
069        return conf.getInt(FIXED_RECORD_LENGTH, 0);
070      }
071    
072      @Override
073      public void configure(JobConf conf) {
074        compressionCodecs = new CompressionCodecFactory(conf);
075      }
076    
077      @Override
078      public RecordReader<LongWritable, BytesWritable>
079          getRecordReader(InputSplit genericSplit, JobConf job, Reporter reporter)
080          throws IOException {
081        reporter.setStatus(genericSplit.toString());
082        int recordLength = getRecordLength(job);
083        if (recordLength <= 0) {
084          throw new IOException("Fixed record length " + recordLength
085              + " is invalid.  It should be set to a value greater than zero");
086        }
087        return new FixedLengthRecordReader(job, (FileSplit)genericSplit,
088                                           recordLength);
089      }
090    
091      @Override
092      protected boolean isSplitable(FileSystem fs, Path file) {
093        final CompressionCodec codec = compressionCodecs.getCodec(file);
094        return(null == codec);
095      }
096    
097    }