lucene/analysis/common/src/java/org/apache/lucene/analysis/ar/ArabicNormalizer.java

/*
 * 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.*;

/**
 *  Normalizer for Arabic.
 *  <p>
 *  Normalization is done in-place for efficiency, operating on a termbuffer.
 *  <p>
 *  Normalization is defined as:
 *  <ul>
 *  <li> Normalization of hamza with alef seat to a bare alef.
 *  <li> Normalization of teh marbuta to heh
 *  <li> Normalization of dotless yeh (alef maksura) to yeh.
 *  <li> Removal of Arabic diacritics (the harakat)
 *  <li> Removal of tatweel (stretching character).
 * </ul>
 *
 */
public class ArabicNormalizer {
  public static final char ALEF = '\u0627';
  public static final char ALEF_MADDA = '\u0622';
  public static final char ALEF_HAMZA_ABOVE = '\u0623';
  public static final char ALEF_HAMZA_BELOW = '\u0625';

  public static final char YEH = '\u064A';
  public static final char DOTLESS_YEH = '\u0649';

  public static final char TEH_MARBUTA = '\u0629';
  public static final char HEH = '\u0647';

  public static final char TATWEEL = '\u0640';

  public static final char FATHATAN = '\u064B';
  public static final char DAMMATAN = '\u064C';
  public static final char KASRATAN = '\u064D';
  public static final char FATHA = '\u064E';
  public static final char DAMMA = '\u064F';
  public static final char KASRA = '\u0650';
  public static final char SHADDA = '\u0651';
  public static final char SUKUN = '\u0652';

  /**
   * Normalize 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 normalize(char s[], int len) {

    for (int i = 0; i < len; i++) {
      switch (s[i]) {
      case ALEF_MADDA:
      case ALEF_HAMZA_ABOVE:
      case ALEF_HAMZA_BELOW:
        s[i] = ALEF;
        break;
      case DOTLESS_YEH:
        s[i] = YEH;
        break;
      case TEH_MARBUTA:
        s[i] = HEH;
        break;
      case TATWEEL:
      case KASRATAN:
      case DAMMATAN:
      case FATHATAN:
      case FATHA:
      case DAMMA:
      case KASRA:
      case SHADDA:
      case SUKUN:
        len = delete(s, i, len);
        i--;
        break;
      default:
        break;
      }
    }

    return len;
  }
}