Java tutorial
/** * 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 lennard; import java.io.IOException; import java.io.InputStream; 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.LongWritable; import org.apache.hadoop.io.Text; import org.apache.hadoop.io.compress.CompressionCodec; import org.apache.hadoop.io.compress.CompressionCodecFactory; import org.apache.hadoop.mapred.FileSplit; import org.apache.hadoop.mapred.RecordReader; import org.apache.commons.logging.LogFactory; import org.apache.commons.logging.Log; /** * Treats keys as offset in file and value as line. * @deprecated Use * {@link org.apache.hadoop.mapreduce.lib.input.LineRecordReader} instead. */ @Deprecated public class PiRecordReader implements RecordReader<LongWritable, LongWritable> { private static final Log LOG = LogFactory.getLog(PiRecordReader.class.getName()); private CompressionCodecFactory compressionCodecs = null; private long start; private long pos; private long end; private LineReader in; int maxLineLength; /** * A class that provides a line reader from an input stream. * @deprecated Use {@link org.apache.hadoop.util.LineReader} instead. */ @Deprecated public static class LineReader extends org.apache.hadoop.util.LineReader { LineReader(InputStream in) { super(in); } LineReader(InputStream in, int bufferSize) { super(in, bufferSize); } public LineReader(InputStream in, Configuration conf) throws IOException { super(in, conf); } } public PiRecordReader(Configuration job, FileSplit split) throws IOException { this.maxLineLength = job.getInt("mapred.linerecordreader.maxlength", Integer.MAX_VALUE); start = split.getStart(); end = start + split.getLength(); final Path file = split.getPath(); compressionCodecs = new CompressionCodecFactory(job); final CompressionCodec codec = compressionCodecs.getCodec(file); // open the file and seek to the start of the split FileSystem fs = file.getFileSystem(job); FSDataInputStream fileIn = fs.open(split.getPath()); boolean skipFirstLine = false; if (codec != null) { in = new LineReader(codec.createInputStream(fileIn), job); end = Long.MAX_VALUE; } else { if (start != 0) { skipFirstLine = true; --start; fileIn.seek(start); } in = new LineReader(fileIn, job); } if (skipFirstLine) { // skip first line and re-establish "start". start += in.readLine(new Text(), 0, (int) Math.min((long) Integer.MAX_VALUE, end - start)); } this.pos = start; } public PiRecordReader(InputStream in, long offset, long endOffset, int maxLineLength) { this.maxLineLength = maxLineLength; this.in = new LineReader(in); this.start = offset; this.pos = offset; this.end = endOffset; } public PiRecordReader(InputStream in, long offset, long endOffset, Configuration job) throws IOException { this.maxLineLength = job.getInt("mapred.linerecordreader.maxlength", Integer.MAX_VALUE); this.in = new LineReader(in, job); this.start = offset; this.pos = offset; this.end = endOffset; } public LongWritable createKey() { return new LongWritable(); } public LongWritable createValue() { return new LongWritable(); } /** Read a line. */ public synchronized boolean next(LongWritable key, LongWritable value) throws IOException { Text line = new Text(); while (pos < end) { int newSize = in.readLine(line, maxLineLength, Math.max((int) Math.min(Integer.MAX_VALUE, end - pos), maxLineLength)); String[] s = line.toString().split("\t"); key.set(Long.parseLong(s[0])); value.set(Long.parseLong(s[1])); if (newSize == 0) { return false; } pos += newSize; if (newSize < maxLineLength) { return true; } // line too long. try again LOG.info("Skipped line of size " + newSize + " at pos " + (pos - newSize)); } return false; } /** * 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 long getPos() throws IOException { return pos; } public synchronized void close() throws IOException { if (in != null) { in.close(); } } }