org.apache.lucene.analysis.ngram.XEdgeNGramTokenFilter Maven / Gradle / Ivy
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 org.elasticsearch.common.lucene.Lucene;
import org.apache.lucene.analysis.TokenFilter;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.reverse.ReverseStringFilter;
import org.apache.lucene.analysis.tokenattributes.OffsetAttribute;
import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
import org.apache.lucene.analysis.tokenattributes.PositionIncrementAttribute;
import org.apache.lucene.analysis.tokenattributes.PositionLengthAttribute;
import org.apache.lucene.analysis.util.XCharacterUtils;
import org.apache.lucene.util.Version;
import java.io.IOException;
/**
* Tokenizes the given token into n-grams of given size(s).
*
* This {@link TokenFilter} create n-grams from the beginning edge or ending edge of a input token.
*
As of Lucene 4.4, this filter does not support
* {@link Side#BACK} (you can use {@link ReverseStringFilter} up-front and
* afterward to get the same behavior), handles supplementary characters
* correctly and does not update offsets anymore.
*/
public final class XEdgeNGramTokenFilter extends TokenFilter {
static {
// LUCENE MONITOR: this should be in Lucene 4.4 copied from Revision: 1492640.
assert Lucene.VERSION == Version.LUCENE_43 : "Elasticsearch has upgraded to Lucene Version: [" + Lucene.VERSION + "] this class should be removed";
}
public static final Side DEFAULT_SIDE = Side.FRONT;
public static final int DEFAULT_MAX_GRAM_SIZE = 1;
public static final int DEFAULT_MIN_GRAM_SIZE = 1;
/** Specifies which side of the input the n-gram should be generated from */
public static enum Side {
/** Get the n-gram from the front of the input */
FRONT {
@Override
public String getLabel() { return "front"; }
},
/** Get the n-gram from the end of the input */
@Deprecated
BACK {
@Override
public String getLabel() { return "back"; }
};
public abstract String getLabel();
// Get the appropriate Side from a string
public static Side getSide(String sideName) {
if (FRONT.getLabel().equals(sideName)) {
return FRONT;
}
if (BACK.getLabel().equals(sideName)) {
return BACK;
}
return null;
}
}
private final XCharacterUtils charUtils;
private final int minGram;
private final int maxGram;
private Side side;
private char[] curTermBuffer;
private int curTermLength;
private int curCodePointCount;
private int curGramSize;
private int tokStart;
private int tokEnd;
private int savePosIncr;
private int savePosLen;
private final CharTermAttribute termAtt = addAttribute(CharTermAttribute.class);
private final OffsetAttribute offsetAtt = addAttribute(OffsetAttribute.class);
private final PositionIncrementAttribute posIncrAtt = addAttribute(PositionIncrementAttribute.class);
private final PositionLengthAttribute posLenAtt = addAttribute(PositionLengthAttribute.class);
/**
* Creates XEdgeNGramTokenFilter that can generate n-grams in the sizes of the given range
*
* @param version the Lucene match version
* @param input {@link TokenStream} holding the input to be tokenized
* @param side the {@link Side} from which to chop off an n-gram
* @param minGram the smallest n-gram to generate
* @param maxGram the largest n-gram to generate
*/
@Deprecated
public XEdgeNGramTokenFilter(Version version, TokenStream input, Side side, int minGram, int maxGram) {
super(input);
if (version == null) {
throw new IllegalArgumentException("version must not be null");
}
if (side == Side.BACK) {
throw new IllegalArgumentException("Side.BACK is not supported anymore as of Lucene 4.4, use ReverseStringFilter up-front and afterward");
}
if (side == null) {
throw new IllegalArgumentException("sideLabel must be either front or back");
}
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.charUtils = XCharacterUtils.getInstance(version);
this.minGram = minGram;
this.maxGram = maxGram;
this.side = side;
}
/**
* Creates XEdgeNGramTokenFilter that can generate n-grams in the sizes of the given range
*
* @param version the Lucene match version
* @param input {@link TokenStream} holding the input to be tokenized
* @param sideLabel the name of the {@link Side} from which to chop off an n-gram
* @param minGram the smallest n-gram to generate
* @param maxGram the largest n-gram to generate
*/
@Deprecated
public XEdgeNGramTokenFilter(Version version, TokenStream input, String sideLabel, int minGram, int maxGram) {
this(version, input, Side.getSide(sideLabel), minGram, maxGram);
}
/**
* Creates XEdgeNGramTokenFilter that can generate n-grams in the sizes of the given range
*
* @param version the Lucene match version
* @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 XEdgeNGramTokenFilter(Version version, TokenStream input, int minGram, int maxGram) {
this(version, input, Side.FRONT, minGram, maxGram);
}
@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;
tokStart = offsetAtt.startOffset();
tokEnd = offsetAtt.endOffset();
savePosIncr += posIncrAtt.getPositionIncrement();
savePosLen = posLenAtt.getPositionLength();
}
}
if (curGramSize <= maxGram) { // if we have hit the end of our n-gram size range, quit
if (curGramSize <= curCodePointCount) { // if the remaining input is too short, we can't generate any n-grams
// grab gramSize chars from front or back
final int start = side == Side.FRONT ? 0 : charUtils.offsetByCodePoints(curTermBuffer, 0, curTermLength, curTermLength, -curGramSize);
final int end = charUtils.offsetByCodePoints(curTermBuffer, 0, curTermLength, start, curGramSize);
clearAttributes();
offsetAtt.setOffset(tokStart, tokEnd);
// first ngram gets increment, others don't
if (curGramSize == minGram) {
posIncrAtt.setPositionIncrement(savePosIncr);
savePosIncr = 0;
} else {
posIncrAtt.setPositionIncrement(0);
}
posLenAtt.setPositionLength(savePosLen);
termAtt.copyBuffer(curTermBuffer, start, end - start);
curGramSize++;
return true;
}
}
curTermBuffer = null;
}
}
@Override
public void reset() throws IOException {
super.reset();
curTermBuffer = null;
savePosIncr = 0;
}
}