org.apache.lucene.analysis.pattern.XPatternTokenizer Maven / Gradle / Ivy
/*
* Licensed to Elasticsearch under one or more contributor
* license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright
* ownership. Elasticsearch 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.
*/
/*
* 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.lucene.analysis.pattern;
import java.io.IOException;
import java.io.Reader;
import java.lang.Override;
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.lucene.util.AttributeFactory;
/**
* Note: This is forked from Lucene 4.10.4 org.apache.lucene.analysis.pattern.PatternTokenizer to
* apply LUCENE-6814.
*
* This tokenizer uses regex pattern matching to construct distinct tokens
* for the input stream. It takes two arguments: "pattern" and "group".
*
*
* - "pattern" is the regular expression.
* - "group" says which group to extract into tokens.
*
*
* 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)}
*
*
* Using group >= 0 selects the matching group as the token. For example, if you have:
*
* pattern = \'([^\']+)\'
* group = 0
* input = aaa 'bbb' 'ccc'
*
* 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)
*
* NOTE: This Tokenizer does not output tokens that are of zero length.
*
* @see Pattern
*/
public final class XPatternTokenizer extends Tokenizer {
private final CharTermAttribute termAtt = addAttribute(CharTermAttribute.class);
private final OffsetAttribute offsetAtt = addAttribute(OffsetAttribute.class);
private final StringBuilder str = new StringBuilder();
private int index;
private final int group;
private final Matcher matcher;
/** creates a new PatternTokenizer returning tokens from group (-1 for split functionality) */
public XPatternTokenizer(Pattern pattern, int group) {
this(DEFAULT_TOKEN_ATTRIBUTE_FACTORY, pattern, group);
}
/** creates a new PatternTokenizer returning tokens from group (-1 for split functionality) */
public XPatternTokenizer(AttributeFactory factory, Pattern pattern, int group) {
super(factory);
this.group = group;
// Use "" instead of str so don't consume chars
// (fillBuffer) from the input on throwing IAE below:
matcher = pattern.matcher("");
// confusingly group count depends ENTIRELY on the pattern but is only accessible via matcher
if (group >= 0 && group > matcher.groupCount()) {
throw new IllegalArgumentException("invalid group specified: pattern only has: " + matcher.groupCount() + " capturing groups");
}
}
@Override
public boolean incrementToken() {
if (index >= str.length()) return false;
clearAttributes();
if (group >= 0) {
// match a specific group
while (matcher.find()) {
index = matcher.start(group);
final int endIndex = matcher.end(group);
if (index == endIndex) continue;
termAtt.setEmpty().append(str, index, endIndex);
offsetAtt.setOffset(correctOffset(index), correctOffset(endIndex));
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 {
super.end();
final int ofs = correctOffset(str.length());
offsetAtt.setOffset(ofs, ofs);
}
@Override
public void close() throws IOException {
try {
super.close();
} finally {
str.setLength(0);
str.trimToSize();
}
}
@Override
public void reset() throws IOException {
super.reset();
fillBuffer(input);
matcher.reset(str);
index = 0;
}
// TODO: we should see if we can make this tokenizer work without reading
// the entire document into RAM, perhaps with Matcher.hitEnd/requireEnd ?
final char[] buffer = new char[8192];
private void fillBuffer(Reader input) throws IOException {
int len;
str.setLength(0);
while ((len = input.read(buffer)) > 0) {
str.append(buffer, 0, len);
}
}
}