package org.apache.lucene.analysis.el;
/**
* Copyright 2005 The Apache Software Foundation
*
* Licensed 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.tokenattributes.CharTermAttribute;
import org.apache.lucene.util.CharacterUtils;
import org.apache.lucene.util.Version;
/**
* Normalizes token text to lower case, removes some Greek diacritics,
* and standardizes final sigma to sigma.
* <a name="version"/>
* <p>You must specify the required {@link Version}
* compatibility when creating GreekLowerCaseFilter:
* <ul>
* <li> As of 3.1, supplementary characters are properly lowercased.
* </ul>
*/
public final class GreekLowerCaseFilter extends TokenFilter {
private final CharTermAttribute termAtt = addAttribute(CharTermAttribute.class);
private final CharacterUtils charUtils;
/** @deprecated Use {@link #GreekLowerCaseFilter(Version, TokenStream)} instead. */
@Deprecated
public GreekLowerCaseFilter(TokenStream in) {
this(Version.LUCENE_30, in);
}
/**
* Create a GreekLowerCaseFilter that normalizes Greek token text.
*
* @param matchVersion Lucene compatibility version,
* See <a href="#version">above</a>
* @param in TokenStream to filter
*/
public GreekLowerCaseFilter(Version matchVersion, TokenStream in) {
super(in);
this.charUtils = CharacterUtils.getInstance(matchVersion);
}
@Override
public boolean incrementToken() throws IOException {
if (input.incrementToken()) {
char[] chArray = termAtt.buffer();
int chLen = termAtt.length();
for (int i = 0; i < chLen;) {
i += Character.toChars(
lowerCase(charUtils.codePointAt(chArray, i)), chArray, i);
}
return true;
} else {
return false;
}
}
private int lowerCase(int codepoint) {
switch(codepoint) {
/* There are two lowercase forms of sigma:
* U+03C2: small final sigma (end of word)
* U+03C3: small sigma (otherwise)
*
* Standardize both to U+03C3
*/
case '\u03C2': /* small final sigma */
return '\u03C3'; /* small sigma */
/* Some greek characters contain diacritics.
* This filter removes these, converting to the lowercase base form.
*/
case '\u0386': /* capital alpha with tonos */
case '\u03AC': /* small alpha with tonos */
return '\u03B1'; /* small alpha */
case '\u0388': /* capital epsilon with tonos */
case '\u03AD': /* small epsilon with tonos */
return '\u03B5'; /* small epsilon */
case '\u0389': /* capital eta with tonos */
case '\u03AE': /* small eta with tonos */
return '\u03B7'; /* small eta */
case '\u038A': /* capital iota with tonos */
case '\u03AA': /* capital iota with dialytika */
case '\u03AF': /* small iota with tonos */
case '\u03CA': /* small iota with dialytika */
case '\u0390': /* small iota with dialytika and tonos */
return '\u03B9'; /* small iota */
case '\u038E': /* capital upsilon with tonos */
case '\u03AB': /* capital upsilon with dialytika */
case '\u03CD': /* small upsilon with tonos */
case '\u03CB': /* small upsilon with dialytika */
case '\u03B0': /* small upsilon with dialytika and tonos */
return '\u03C5'; /* small upsilon */
case '\u038C': /* capital omicron with tonos */
case '\u03CC': /* small omicron with tonos */
return '\u03BF'; /* small omicron */
case '\u038F': /* capital omega with tonos */
case '\u03CE': /* small omega with tonos */
return '\u03C9'; /* small omega */
/* The previous implementation did the conversion below.
* Only implemented for backwards compatibility with old indexes.
*/
case '\u03A2': /* reserved */
return '\u03C2'; /* small final sigma */
default:
return Character.toLowerCase(codepoint);
}
}
}