| /** |
| * 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.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; |
| |
| /** |
| * 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> |
| * |
| * @see Pattern |
| */ |
| public final class PatternTokenizer 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 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; |
| |
| // 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"); |
| } |
| fillBuffer(str, input); |
| matcher.reset(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()) { |
| 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 { |
| final int ofs = correctOffset(str.length()); |
| offsetAtt.setOffset(ofs, ofs); |
| } |
| |
| @Override |
| public void reset(Reader input) throws IOException { |
| super.reset(input); |
| fillBuffer(str, 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(StringBuilder sb, Reader input) throws IOException { |
| int len; |
| sb.setLength(0); |
| while ((len = input.read(buffer)) > 0) { |
| sb.append(buffer, 0, len); |
| } |
| } |
| } |