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.mapreduce.lib.input;
020
021 import java.io.IOException;
022 import java.io.DataInput;
023 import java.io.DataOutput;
024
025 import org.apache.hadoop.mapreduce.InputFormat;
026 import org.apache.hadoop.mapreduce.InputSplit;
027 import org.apache.hadoop.mapreduce.TaskAttemptContext;
028 import org.apache.hadoop.classification.InterfaceAudience;
029 import org.apache.hadoop.classification.InterfaceStability;
030 import org.apache.hadoop.fs.Path;
031 import org.apache.hadoop.io.Text;
032 import 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
039 public 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 }