/**
* 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.reverse;
import org.apache.lucene.analysis.TokenFilter;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.tokenattributes.TermAttribute;
import java.io.IOException;
/**
* Reverse token string, for example "country" => "yrtnuoc".
* <p>
* If <code>marker</code> is supplied, then tokens will be also prepended by
* that character. For example, with a marker of \u0001, "country" =>
* "\u0001yrtnuoc". This is useful when implementing efficient leading
* wildcards search.
* </p>
*
* @version $Id: ReverseStringFilter.java 805769 2009-08-19 12:07:15Z rmuir $
*/
public final class ReverseStringFilter extends TokenFilter {
private TermAttribute termAtt;
private final char marker;
private static final char NOMARKER = '\uFFFF';
/**
* Example marker character: U+0001 (START OF HEADING)
*/
public static final char START_OF_HEADING_MARKER = '\u0001';
/**
* Example marker character: U+001F (INFORMATION SEPARATOR ONE)
*/
public static final char INFORMATION_SEPARATOR_MARKER = '\u001F';
/**
* Example marker character: U+EC00 (PRIVATE USE AREA: EC00)
*/
public static final char PUA_EC00_MARKER = '\uEC00';
/**
* Example marker character: U+200F (RIGHT-TO-LEFT MARK)
*/
public static final char RTL_DIRECTION_MARKER = '\u200F';
/**
* Create a new ReverseStringFilter that reverses all tokens in the
* supplied {@link TokenStream}.
* <p>
* The reversed tokens will not be marked.
* </p>
*
* @param in {@link TokenStream} to filter
*/
public ReverseStringFilter(TokenStream in) {
this(in, NOMARKER);
}
/**
* Create a new ReverseStringFilter that reverses and marks all tokens in the
* supplied {@link TokenStream}.
* <p>
* The reversed tokens will be prepended (marked) by the <code>marker</code>
* character.
* </p>
*
* @param in {@link TokenStream} to filter
* @param marker A character used to mark reversed tokens
*/
public ReverseStringFilter(TokenStream in, char marker) {
super(in);
this.marker = marker;
termAtt = (TermAttribute) addAttribute(TermAttribute.class);
}
public boolean incrementToken() throws IOException {
if (input.incrementToken()) {
int len = termAtt.termLength();
if (marker != NOMARKER) {
len++;
termAtt.resizeTermBuffer(len);
termAtt.termBuffer()[len - 1] = marker;
}
reverse( termAtt.termBuffer(), len );
termAtt.setTermLength(len);
return true;
} else {
return false;
}
}
public static String reverse( final String input ){
char[] charInput = input.toCharArray();
reverse( charInput );
return new String( charInput );
}
public static void reverse( char[] buffer ){
reverse( buffer, buffer.length );
}
public static void reverse( char[] buffer, int len ){
reverse( buffer, 0, len );
}
public static void reverse( char[] buffer, int start, int len ){
if( len <= 1 ) return;
int num = len>>1;
for( int i = start; i < ( start + num ); i++ ){
char c = buffer[i];
buffer[i] = buffer[start * 2 + len - i - 1];
buffer[start * 2 + len - i - 1] = c;
}
}
}