org.apache.solr.analysis.ReversedWildcardFilter Maven / Gradle / Ivy
package org.apache.solr.analysis;
/**
* 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.reverse.ReverseStringFilter;
import org.apache.lucene.analysis.tokenattributes.PositionIncrementAttribute;
import org.apache.lucene.analysis.tokenattributes.TermAttribute;
/**
* This class produces a special form of reversed tokens, suitable for
* better handling of leading wildcards. Tokens from the input TokenStream
* are reversed and prepended with a special "reversed" marker character.
* If withOriginal argument is true then first the
* original token is returned, and then the reversed token (with
* positionIncrement == 0) is returned. Otherwise only reversed
* tokens are returned.
* Note: this filter doubles the number of tokens in the input stream when
* withOriginal == true, which proportionally increases the size
* of postings and term dictionary in the index.
*/
public class ReversedWildcardFilter extends TokenFilter {
private boolean withOriginal;
private char markerChar;
private State save;
private TermAttribute termAtt;
private PositionIncrementAttribute posAtt;
protected ReversedWildcardFilter(TokenStream input, boolean withOriginal, char markerChar) {
super(input);
this.termAtt = (TermAttribute)addAttribute(TermAttribute.class);
this.posAtt = (PositionIncrementAttribute) addAttribute(PositionIncrementAttribute.class);
this.withOriginal = withOriginal;
this.markerChar = markerChar;
}
@Override
public boolean incrementToken() throws IOException {
if( save != null ) {
// clearAttributes(); // not currently necessary
restoreState(save);
save = null;
return true;
}
if (!input.incrementToken()) return false;
// pass through zero-length terms
int oldLen = termAtt.termLength();
if (oldLen ==0) return true;
int origOffset = posAtt.getPositionIncrement();
if (withOriginal == true){
posAtt.setPositionIncrement(0);
save = captureState();
}
char [] buffer = termAtt.resizeTermBuffer(oldLen + 1);
buffer[oldLen] = markerChar;
//String reversed = reverseAndMark(value, markerChar);
ReverseStringFilter.reverse(buffer, oldLen + 1);
posAtt.setPositionIncrement(origOffset);
termAtt.setTermBuffer(buffer, 0, oldLen +1);
return true;
}
}