/
XmlInputFormat.java
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/
XmlInputFormat.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 org.apache.mahout.classifier.bayes;
import java.io.IOException;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.DataOutputBuffer;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapred.FileSplit;
import org.apache.hadoop.mapred.InputSplit;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.RecordReader;
import org.apache.hadoop.mapred.Reporter;
import org.apache.hadoop.mapred.TextInputFormat;
/**
* Reads records that are delimited by a specifc begin/end tag.
*/
public class XmlInputFormat extends TextInputFormat {
public static final String START_TAG_KEY = "xmlinput.start";
public static final String END_TAG_KEY = "xmlinput.end";
@Override
public RecordReader<LongWritable,Text> getRecordReader(InputSplit inputSplit,
JobConf jobConf,
Reporter reporter) throws IOException {
return new XmlRecordReader((FileSplit) inputSplit, jobConf);
}
/**
* XMLRecordReader class to read through a given xml document to output xml
* blocks as records as specified by the start tag and end tag
*
*/
public static class XmlRecordReader implements
RecordReader<LongWritable,Text> {
private final byte[] startTag;
private final byte[] endTag;
private final long start;
private final long end;
private final FSDataInputStream fsin;
private final DataOutputBuffer buffer = new DataOutputBuffer();
public XmlRecordReader(FileSplit split, JobConf jobConf) throws IOException {
startTag = jobConf.get(START_TAG_KEY).getBytes("utf-8");
endTag = jobConf.get(END_TAG_KEY).getBytes("utf-8");
// open the file and seek to the start of the split
start = split.getStart();
end = start + split.getLength();
Path file = split.getPath();
FileSystem fs = file.getFileSystem(jobConf);
fsin = fs.open(split.getPath());
fsin.seek(start);
}
@Override
public boolean next(LongWritable key, Text value) throws IOException {
if (fsin.getPos() < end) {
if (readUntilMatch(startTag, false)) {
try {
buffer.write(startTag);
if (readUntilMatch(endTag, true)) {
key.set(fsin.getPos());
value.set(buffer.getData(), 0, buffer.getLength());
return true;
}
} finally {
buffer.reset();
}
}
}
return false;
}
@Override
public LongWritable createKey() {
return new LongWritable();
}
@Override
public Text createValue() {
return new Text();
}
@Override
public long getPos() throws IOException {
return fsin.getPos();
}
@Override
public void close() throws IOException {
fsin.close();
}
@Override
public float getProgress() throws IOException {
return (fsin.getPos() - start) / (float) (end - start);
}
private boolean readUntilMatch(byte[] match, boolean withinBlock) throws IOException {
int i = 0;
while (true) {
int b = fsin.read();
// end of file:
if (b == -1) return false;
// save to buffer:
if (withinBlock) buffer.write(b);
// check if we're matching:
if (b == match[i]) {
i++;
if (i >= match.length) return true;
} else i = 0;
// see if we've passed the stop point:
if (!withinBlock && i == 0 && fsin.getPos() >= end) return false;
}
}
}
}