| /* |
| * 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.ar; |
| |
| 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; |
| } |
| } |
| } |