/**
* 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.solr.analysis;
import java.io.IOException;
import java.io.Reader;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import org.apache.lucene.analysis.Tokenizer;
import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
import org.apache.lucene.analysis.tokenattributes.OffsetAttribute;
import org.apache.commons.io.IOUtils;
/**
* This tokenizer uses regex pattern matching to construct distinct tokens
* for the input stream. It takes two arguments: "pattern" and "group".
* <p/>
* <ul>
* <li>"pattern" is the regular expression.</li>
* <li>"group" says which group to extract into tokens.</li>
* </ul>
* <p>
* group=-1 (the default) is equivalent to "split". In this case, the tokens will
* be equivalent to the output from (without empty tokens):
* {@link String#split(java.lang.String)}
* </p>
* <p>
* Using group >= 0 selects the matching group as the token. For example, if you have:<br/>
* <pre>
* pattern = \'([^\']+)\'
* group = 0
* input = aaa 'bbb' 'ccc'
*</pre>
* the output will be two tokens: 'bbb' and 'ccc' (including the ' marks). With the same input
* but using group=1, the output would be: bbb and ccc (no ' marks)
* </p>
* <p>NOTE: This Tokenizer does not output tokens that are of zero length.</p>
*
* @version $Id: PatternTokenizer.java 940806 2010-05-04 11:18:46Z uschindler $
* @see Pattern
*/
public final class PatternTokenizer extends Tokenizer {
private final CharTermAttribute termAtt = addAttribute(CharTermAttribute.class);
private final OffsetAttribute offsetAtt = addAttribute(OffsetAttribute.class);
private String str;
private int index;
private final Pattern pattern;
private final int group;
private final Matcher matcher;
/** creates a new PatternTokenizer returning tokens from group (-1 for split functionality) */
public PatternTokenizer(Reader input, Pattern pattern, int group) throws IOException {
super(input);
this.pattern = pattern;
this.group = group;
str = IOUtils.toString(input);
matcher = pattern.matcher(str);
index = 0;
}
@Override
public boolean incrementToken() throws IOException {
if (index >= str.length()) return false;
clearAttributes();
if (group >= 0) {
// match a specific group
while (matcher.find()) {
final String match = matcher.group(group);
if (match.length() == 0) continue;
termAtt.setEmpty().append(match);
index = matcher.start(group);
offsetAtt.setOffset(correctOffset(index), correctOffset(matcher.end(group)));
return true;
}
index = Integer.MAX_VALUE; // mark exhausted
return false;
} else {
// String.split() functionality
while (matcher.find()) {
if (matcher.start() - index > 0) {
// found a non-zero-length token
termAtt.setEmpty().append(str, index, matcher.start());
offsetAtt.setOffset(correctOffset(index), correctOffset(matcher.start()));
index = matcher.end();
return true;
}
index = matcher.end();
}
if (str.length() - index == 0) {
index = Integer.MAX_VALUE; // mark exhausted
return false;
}
termAtt.setEmpty().append(str, index, str.length());
offsetAtt.setOffset(correctOffset(index), correctOffset(str.length()));
index = Integer.MAX_VALUE; // mark exhausted
return true;
}
}
@Override
public void end() throws IOException {
final int ofs = correctOffset(str.length());
offsetAtt.setOffset(ofs, ofs);
}
@Override
public void reset(Reader input) throws IOException {
super.reset(input);
str = IOUtils.toString(input);
matcher.reset(str);
index = 0;
}
}