package org.apache.lucene.analysis.ar;
/**
* 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 static org.apache.lucene.analysis.util.StemmerUtil.*;
/**
* Stemmer for Arabic.
* <p>
* Stemming is done in-place for efficiency, operating on a termbuffer.
* <p>
* Stemming is defined as:
* <ul>
* <li> Removal of attached definite article, conjunction, and prepositions.
* <li> Stemming of common suffixes.
* </ul>
*
*/
public class ArabicStemmer {
public static final char ALEF = '\u0627';
public static final char BEH = '\u0628';
public static final char TEH_MARBUTA = '\u0629';
public static final char TEH = '\u062A';
public static final char FEH = '\u0641';
public static final char KAF = '\u0643';
public static final char LAM = '\u0644';
public static final char NOON = '\u0646';
public static final char HEH = '\u0647';
public static final char WAW = '\u0648';
public static final char YEH = '\u064A';
public static final char prefixes[][] = {
("" + ALEF + LAM).toCharArray(),
("" + WAW + ALEF + LAM).toCharArray(),
("" + BEH + ALEF + LAM).toCharArray(),
("" + KAF + ALEF + LAM).toCharArray(),
("" + FEH + ALEF + LAM).toCharArray(),
("" + LAM + LAM).toCharArray(),
("" + WAW).toCharArray(),
};
public static final char suffixes[][] = {
("" + HEH + ALEF).toCharArray(),
("" + ALEF + NOON).toCharArray(),
("" + ALEF + TEH).toCharArray(),
("" + WAW + NOON).toCharArray(),
("" + YEH + NOON).toCharArray(),
("" + YEH + HEH).toCharArray(),
("" + YEH + TEH_MARBUTA).toCharArray(),
("" + HEH).toCharArray(),
("" + TEH_MARBUTA).toCharArray(),
("" + YEH).toCharArray(),
};
/**
* Stem an input buffer of Arabic text.
*
* @param s input buffer
* @param len length of input buffer
* @return length of input buffer after normalization
*/
public int stem(char s[], int len) {
len = stemPrefix(s, len);
len = stemSuffix(s, len);
return len;
}
/**
* Stem a prefix off an Arabic word.
* @param s input buffer
* @param len length of input buffer
* @return new length of input buffer after stemming.
*/
public int stemPrefix(char s[], int len) {
for (int i = 0; i < prefixes.length; i++)
if (startsWithCheckLength(s, len, prefixes[i]))
return deleteN(s, 0, len, prefixes[i].length);
return len;
}
/**
* Stem suffix(es) off an Arabic word.
* @param s input buffer
* @param len length of input buffer
* @return new length of input buffer after stemming
*/
public int stemSuffix(char s[], int len) {
for (int i = 0; i < suffixes.length; i++)
if (endsWithCheckLength(s, len, suffixes[i]))
len = deleteN(s, len - suffixes[i].length, len, suffixes[i].length);
return len;
}
/**
* Returns true if the prefix matches and can be stemmed
* @param s input buffer
* @param len length of input buffer
* @param prefix prefix to check
* @return true if the prefix matches and can be stemmed
*/
boolean startsWithCheckLength(char s[], int len, char prefix[]) {
if (prefix.length == 1 && len < 4) { // wa- prefix requires at least 3 characters
return false;
} else if (len < prefix.length + 2) { // other prefixes require only 2.
return false;
} else {
for (int i = 0; i < prefix.length; i++)
if (s[i] != prefix[i])
return false;
return true;
}
}
/**
* Returns true if the suffix matches and can be stemmed
* @param s input buffer
* @param len length of input buffer
* @param suffix suffix to check
* @return true if the suffix matches and can be stemmed
*/
boolean endsWithCheckLength(char s[], int len, char suffix[]) {
if (len < suffix.length + 2) { // all suffixes require at least 2 characters after stemming
return false;
} else {
for (int i = 0; i < suffix.length; i++)
if (s[len - suffix.length + i] != suffix[i])
return false;
return true;
}
}
}