| package org.apache.lucene.analysis.ngram; |
| |
| /* |
| * 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. |
| */ |
| |
| import java.io.IOException; |
| |
| import org.apache.lucene.analysis.TokenFilter; |
| import org.apache.lucene.analysis.TokenStream; |
| import org.apache.lucene.analysis.miscellaneous.CodepointCountFilter; |
| import org.apache.lucene.analysis.tokenattributes.CharTermAttribute; |
| import org.apache.lucene.analysis.tokenattributes.OffsetAttribute; |
| import org.apache.lucene.analysis.tokenattributes.PositionIncrementAttribute; |
| import org.apache.lucene.analysis.tokenattributes.PositionLengthAttribute; |
| import org.apache.lucene.analysis.util.CharacterUtils; |
| import org.apache.lucene.util.Version; |
| |
| /** |
| * Tokenizes the input into n-grams of the given size(s). |
| * As of Lucene 4.4, this token filter:<ul> |
| * <li>handles supplementary characters correctly,</li> |
| * <li>emits all n-grams for the same token at the same position,</li> |
| * <li>does not modify offsets,</li> |
| * <li>sorts n-grams by their offset in the original token first, then |
| * increasing length (meaning that "abc" will give "a", "ab", "abc", "b", "bc", |
| * "c").</li></ul> |
| * <p>You can make this filter use the old behavior by using |
| * {@link org.apache.lucene.analysis.ngram.Lucene43NGramTokenFilter} but this is not recommended as |
| * it will lead to broken {@link TokenStream}s that will cause highlighting |
| * bugs. |
| * <p>If you were using this {@link TokenFilter} to perform partial highlighting, |
| * this won't work anymore since this filter doesn't update offsets. You should |
| * modify your analysis chain to use {@link NGramTokenizer}, and potentially |
| * override {@link NGramTokenizer#isTokenChar(int)} to perform pre-tokenization. |
| */ |
| public final class NGramTokenFilter extends TokenFilter { |
| public static final int DEFAULT_MIN_NGRAM_SIZE = 1; |
| public static final int DEFAULT_MAX_NGRAM_SIZE = 2; |
| |
| private final int minGram, maxGram; |
| |
| private char[] curTermBuffer; |
| private int curTermLength; |
| private int curCodePointCount; |
| private int curGramSize; |
| private int curPos; |
| private int curPosInc, curPosLen; |
| private int tokStart; |
| private int tokEnd; |
| private boolean hasIllegalOffsets; // only if the length changed before this filter |
| |
| private final Version version; |
| private final CharacterUtils charUtils; |
| private final CharTermAttribute termAtt = addAttribute(CharTermAttribute.class); |
| private final PositionIncrementAttribute posIncAtt; |
| private final PositionLengthAttribute posLenAtt; |
| private final OffsetAttribute offsetAtt = addAttribute(OffsetAttribute.class); |
| |
| /** |
| * Creates NGramTokenFilter with given min and max n-grams. |
| * @param input {@link TokenStream} holding the input to be tokenized |
| * @param minGram the smallest n-gram to generate |
| * @param maxGram the largest n-gram to generate |
| */ |
| public NGramTokenFilter(TokenStream input, int minGram, int maxGram) { |
| this(Version.LATEST, input, minGram, maxGram); |
| } |
| |
| /** |
| * @deprecated Use {@link #NGramTokenFilter(TokenStream, int, int)} |
| */ |
| @Deprecated |
| public NGramTokenFilter(Version version, TokenStream input, int minGram, int maxGram) { |
| super(new CodepointCountFilter(version, input, minGram, Integer.MAX_VALUE)); |
| this.version = version; |
| this.charUtils = version.onOrAfter(Version.LUCENE_4_4) |
| ? CharacterUtils.getInstance(version) |
| : CharacterUtils.getJava4Instance(); |
| if (minGram < 1) { |
| throw new IllegalArgumentException("minGram must be greater than zero"); |
| } |
| if (minGram > maxGram) { |
| throw new IllegalArgumentException("minGram must not be greater than maxGram"); |
| } |
| this.minGram = minGram; |
| this.maxGram = maxGram; |
| if (version.onOrAfter(Version.LUCENE_4_4)) { |
| posIncAtt = addAttribute(PositionIncrementAttribute.class); |
| posLenAtt = addAttribute(PositionLengthAttribute.class); |
| } else { |
| posIncAtt = new PositionIncrementAttribute() { |
| @Override |
| public void setPositionIncrement(int positionIncrement) {} |
| @Override |
| public int getPositionIncrement() { |
| return 0; |
| } |
| }; |
| posLenAtt = new PositionLengthAttribute() { |
| @Override |
| public void setPositionLength(int positionLength) {} |
| @Override |
| public int getPositionLength() { |
| return 0; |
| } |
| }; |
| } |
| } |
| |
| /** |
| * Creates NGramTokenFilter with default min and max n-grams. |
| * @param input {@link TokenStream} holding the input to be tokenized |
| */ |
| public NGramTokenFilter(TokenStream input) { |
| this(Version.LATEST, input, DEFAULT_MIN_NGRAM_SIZE, DEFAULT_MAX_NGRAM_SIZE); |
| } |
| |
| /** |
| * @deprecated Use {@link #NGramTokenFilter(TokenStream)} |
| */ |
| @Deprecated |
| public NGramTokenFilter(Version version, TokenStream input) { |
| this(version, input, DEFAULT_MIN_NGRAM_SIZE, DEFAULT_MAX_NGRAM_SIZE); |
| } |
| |
| /** Returns the next token in the stream, or null at EOS. */ |
| @Override |
| public final boolean incrementToken() throws IOException { |
| while (true) { |
| if (curTermBuffer == null) { |
| if (!input.incrementToken()) { |
| return false; |
| } else { |
| curTermBuffer = termAtt.buffer().clone(); |
| curTermLength = termAtt.length(); |
| curCodePointCount = charUtils.codePointCount(termAtt); |
| curGramSize = minGram; |
| curPos = 0; |
| curPosInc = posIncAtt.getPositionIncrement(); |
| curPosLen = posLenAtt.getPositionLength(); |
| tokStart = offsetAtt.startOffset(); |
| tokEnd = offsetAtt.endOffset(); |
| // if length by start + end offsets doesn't match the term text then assume |
| // this is a synonym and don't adjust the offsets. |
| hasIllegalOffsets = (tokStart + curTermLength) != tokEnd; |
| } |
| } |
| if (version.onOrAfter(Version.LUCENE_4_4_0)) { |
| if (curGramSize > maxGram || (curPos + curGramSize) > curCodePointCount) { |
| ++curPos; |
| curGramSize = minGram; |
| } |
| if ((curPos + curGramSize) <= curCodePointCount) { |
| clearAttributes(); |
| final int start = charUtils.offsetByCodePoints(curTermBuffer, 0, curTermLength, 0, curPos); |
| final int end = charUtils.offsetByCodePoints(curTermBuffer, 0, curTermLength, start, curGramSize); |
| termAtt.copyBuffer(curTermBuffer, start, end - start); |
| posIncAtt.setPositionIncrement(curPosInc); |
| curPosInc = 0; |
| posLenAtt.setPositionLength(curPosLen); |
| offsetAtt.setOffset(tokStart, tokEnd); |
| curGramSize++; |
| return true; |
| } |
| } else { |
| while (curGramSize <= maxGram) { |
| while (curPos+curGramSize <= curTermLength) { // while there is input |
| clearAttributes(); |
| termAtt.copyBuffer(curTermBuffer, curPos, curGramSize); |
| if (hasIllegalOffsets) { |
| offsetAtt.setOffset(tokStart, tokEnd); |
| } else { |
| offsetAtt.setOffset(tokStart + curPos, tokStart + curPos + curGramSize); |
| } |
| curPos++; |
| return true; |
| } |
| curGramSize++; // increase n-gram size |
| curPos = 0; |
| } |
| } |
| curTermBuffer = null; |
| } |
| } |
| |
| @Override |
| public void reset() throws IOException { |
| super.reset(); |
| curTermBuffer = null; |
| } |
| } |
