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 019package org.apache.hadoop.mapreduce.lib.input; 020 021import java.io.IOException; 022import java.io.DataInput; 023import java.io.DataOutput; 024 025import org.apache.hadoop.mapreduce.InputFormat; 026import org.apache.hadoop.mapreduce.InputSplit; 027import org.apache.hadoop.mapreduce.TaskAttemptContext; 028import org.apache.hadoop.classification.InterfaceAudience; 029import org.apache.hadoop.classification.InterfaceStability; 030import org.apache.hadoop.fs.Path; 031import org.apache.hadoop.io.Text; 032import org.apache.hadoop.io.Writable; 033 034/** A section of an input file. Returned by {@link 035 * InputFormat#getSplits(JobContext)} and passed to 036 * {@link InputFormat#createRecordReader(InputSplit,TaskAttemptContext)}. */ 037@InterfaceAudience.Public 038@InterfaceStability.Stable 039public class FileSplit extends InputSplit implements Writable { 040 private Path file; 041 private long start; 042 private long length; 043 private String[] hosts; 044 045 public FileSplit() {} 046 047 /** Constructs a split with host information 048 * 049 * @param file the file name 050 * @param start the position of the first byte in the file to process 051 * @param length the number of bytes in the file to process 052 * @param hosts the list of hosts containing the block, possibly null 053 */ 054 public FileSplit(Path file, long start, long length, String[] hosts) { 055 this.file = file; 056 this.start = start; 057 this.length = length; 058 this.hosts = hosts; 059 } 060 061 /** The file containing this split's data. */ 062 public Path getPath() { return file; } 063 064 /** The position of the first byte in the file to process. */ 065 public long getStart() { return start; } 066 067 /** The number of bytes in the file to process. */ 068 @Override 069 public long getLength() { return length; } 070 071 @Override 072 public String toString() { return file + ":" + start + "+" + length; } 073 074 //////////////////////////////////////////// 075 // Writable methods 076 //////////////////////////////////////////// 077 078 @Override 079 public void write(DataOutput out) throws IOException { 080 Text.writeString(out, file.toString()); 081 out.writeLong(start); 082 out.writeLong(length); 083 } 084 085 @Override 086 public void readFields(DataInput in) throws IOException { 087 file = new Path(Text.readString(in)); 088 start = in.readLong(); 089 length = in.readLong(); 090 hosts = null; 091 } 092 093 @Override 094 public String[] getLocations() throws IOException { 095 if (this.hosts == null) { 096 return new String[]{}; 097 } else { 098 return this.hosts; 099 } 100 } 101}