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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *      https://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  
18  package org.apache.commons.codec.language;
19  
20  import org.apache.commons.codec.EncoderException;
21  import org.apache.commons.codec.StringEncoder;
22  
23  /**
24   * Encodes a string into a Soundex value. Soundex is an encoding used to relate similar names, but can also be used as a
25   * general purpose scheme to find word with similar phonemes.
26   *
27   * <p>This class is thread-safe.
28   * Although not strictly immutable, the mutable fields are not actually used.</p>
29   */
30  public class Soundex implements StringEncoder {
31  
32      /**
33       * The marker character used to indicate a silent (ignored) character.
34       * These are ignored except when they appear as the first character.
35       * <p>
36       * Note: The {@link #US_ENGLISH_MAPPING_STRING} does not use this mechanism
37       * because changing it might break existing code. Mappings that don't contain
38       * a silent marker code are treated as though H and W are silent.
39       * </p>
40       * <p>
41       * To override this, use the {@link #Soundex(String, boolean)} constructor.
42       * </p>
43       *
44       * @since 1.11
45       */
46      public static final char SILENT_MARKER = '-';
47  
48      /**
49       * This is a default mapping of the 26 letters used in US English. A value of {@code 0} for a letter position
50       * means do not encode, but treat as a separator when it occurs between consonants with the same code.
51       * <p>
52       * (This constant is provided as both an implementation convenience and to allow Javadoc to pick
53       * up the value for the constant values page.)
54       * </p>
55       * <p>
56       * <strong>Note that letters H and W are treated specially.</strong>
57       * They are ignored (after the first letter) and don't act as separators
58       * between consonants with the same code.
59       * </p>
60       */
61      public static final String US_ENGLISH_MAPPING_STRING = "01230120022455012623010202";
62  
63      /**
64       * This is a default mapping of the 26 letters used in US English. A value of {@code 0} for a letter position
65       * means do not encode.
66       *
67       * @see Soundex#Soundex(char[])
68       */
69      private static final char[] US_ENGLISH_MAPPING = US_ENGLISH_MAPPING_STRING.toCharArray();
70  
71      /**
72       * An instance of Soundex using the US_ENGLISH_MAPPING mapping.
73       * This treats H and W as silent letters.
74       * Apart from when they appear as the first letter, they are ignored.
75       * They don't act as separators between duplicate codes.
76       *
77       * @see #US_ENGLISH_MAPPING_STRING
78       */
79      public static final Soundex US_ENGLISH = new Soundex();
80  
81      /**
82       * An instance of Soundex using the Simplified Soundex mapping, as described here:
83       * http://west-penwith.org.uk/misc/soundex.htm
84       * <p>
85       * This treats H and W the same as vowels (AEIOUY).
86       * Such letters aren't encoded (after the first), but they do
87       * act as separators when dropping duplicate codes.
88       * The mapping is otherwise the same as for {@link #US_ENGLISH}
89       * </p>
90       *
91       * @since 1.11
92       */
93      public static final Soundex US_ENGLISH_SIMPLIFIED = new Soundex(US_ENGLISH_MAPPING_STRING, false);
94  
95      /**
96       * An instance of Soundex using the mapping as per the Genealogy site:
97       * http://www.genealogy.com/articles/research/00000060.html
98       * <p>
99       * This treats vowels (AEIOUY), H and W as silent letters.
100      * Such letters are ignored (after the first) and do not
101      * act as separators when dropping duplicate codes.
102      * </p>
103      * <p>
104      * The codes for consonants are otherwise the same as for
105      * {@link #US_ENGLISH_MAPPING_STRING} and {@link #US_ENGLISH_SIMPLIFIED}
106      * </p>
107      *
108      * @since 1.11
109      */
110     public static final Soundex US_ENGLISH_GENEALOGY = new Soundex("-123-12--22455-12623-1-2-2");
111     //                                                              ABCDEFGHIJKLMNOPQRSTUVWXYZ
112 
113     /**
114      * The maximum length of a Soundex code - Soundex codes are only four characters by definition.
115      *
116      * @deprecated This feature is not needed since the encoding size must be constant. Will be removed in 2.0.
117      */
118     @Deprecated
119     private int maxLength = 4;
120 
121     /**
122      * Every letter of the alphabet is "mapped" to a numerical value. This char array holds the values to which each
123      * letter is mapped. This implementation contains a default map for US_ENGLISH
124      */
125     private final char[] soundexMapping;
126 
127     /**
128      * Should H and W be treated specially?
129      * <p>
130      * In versions of the code prior to 1.11,
131      * the code always treated H and W as silent (ignored) letters.
132      * If this field is false, H and W are no longer special-cased.
133      * </p>
134      */
135     private final boolean specialCaseHW;
136 
137     /**
138      * Creates an instance using US_ENGLISH_MAPPING.
139      *
140      * @see Soundex#Soundex(char[])
141      * @see Soundex#US_ENGLISH_MAPPING_STRING
142      */
143     public Soundex() {
144         this.soundexMapping = US_ENGLISH_MAPPING;
145         this.specialCaseHW = true;
146     }
147 
148     /**
149      * Creates a Soundex instance using the given mapping. This constructor can be used to provide an internationalized
150      * mapping for a non-Western character set.
151      * <p>
152      * Every letter of the alphabet is "mapped" to a numerical value. This char array holds the values to which each
153      * letter is mapped. This implementation contains a default map for US_ENGLISH
154      * </p>
155      * <p>
156      * If the mapping contains an instance of {@link #SILENT_MARKER} then H and W are not given special treatment.
157      * </p>
158      *
159      * @param mapping
160      *                  Mapping array to use when finding the corresponding code for a given character.
161      */
162     public Soundex(final char[] mapping) {
163         this.soundexMapping = mapping.clone();
164         this.specialCaseHW = !hasMarker(this.soundexMapping);
165     }
166 
167     /**
168      * Creates a refined Soundex instance using a custom mapping. This constructor can be used to customize the mapping,
169      * and/or possibly provide an internationalized mapping for a non-Western character set.
170      * <p>
171      * If the mapping contains an instance of {@link #SILENT_MARKER} then H and W are not given special treatment.
172      * </p>
173      *
174      * @param mapping
175      *            Mapping string to use when finding the corresponding code for a given character.
176      * @since 1.4
177      */
178     public Soundex(final String mapping) {
179         this.soundexMapping = mapping.toCharArray();
180         this.specialCaseHW = !hasMarker(this.soundexMapping);
181     }
182 
183     /**
184      * Creates a refined Soundex instance using a custom mapping. This constructor can be used to customize the mapping,
185      * and/or possibly provide an internationalized mapping for a non-Western character set.
186      *
187      * @param mapping
188      *            Mapping string to use when finding the corresponding code for a given character.
189      * @param specialCaseHW if true, then
190      * @since 1.11
191      */
192     public Soundex(final String mapping, final boolean specialCaseHW) {
193         this.soundexMapping = mapping.toCharArray();
194         this.specialCaseHW = specialCaseHW;
195     }
196 
197     /**
198      * Encodes the Strings and returns the number of characters in the two encoded Strings that are the same. This return value ranges from 0 through 4: 0
199      * indicates little or no similarity, and 4 indicates strong similarity or identical values.
200      *
201      * @param s1 A String that will be encoded and compared.
202      * @param s2 A String that will be encoded and compared.
203      * @return The number of characters in the two encoded Strings that are the same from 0 to 4.
204      * @see SoundexUtils#difference(StringEncoder,String,String)
205      * @see <a href="https://msdn.microsoft.com/library/default.asp?url=/library/en-us/tsqlref/ts_de-dz_8co5.asp"> MS T-SQL DIFFERENCE</a>
206      *
207      * @throws EncoderException if an error occurs encoding one of the strings.
208      * @since 1.3
209      */
210     public int difference(final String s1, final String s2) throws EncoderException {
211         return SoundexUtils.difference(this, s1, s2);
212     }
213 
214     /**
215      * Encodes an Object using the Soundex algorithm. This method is provided in order to satisfy the requirements of the Encoder interface, and will throw an
216      * EncoderException if the supplied object is not of type {@link String}.
217      *
218      * @param obj Object to encode.
219      * @return An object (or type {@link String}) containing the Soundex code which corresponds to the String supplied.
220      * @throws EncoderException         if the parameter supplied is not of type {@link String}.
221      * @throws IllegalArgumentException if a character is not mapped.
222      */
223     @Override
224     public Object encode(final Object obj) throws EncoderException {
225         if (!(obj instanceof String)) {
226             throw new EncoderException("Parameter supplied to Soundex encode is not of type java.lang.String");
227         }
228         return soundex((String) obj);
229     }
230 
231     /**
232      * Encodes a String using the Soundex algorithm.
233      *
234      * @param str A String object to encode.
235      * @return A Soundex code corresponding to the String supplied.
236      * @throws IllegalArgumentException if a character is not mapped.
237      */
238     @Override
239     public String encode(final String str) {
240         return soundex(str);
241     }
242 
243     /**
244      * Returns the maxLength. Standard Soundex
245      *
246      * @deprecated This feature is not needed since the encoding size must be constant. Will be removed in 2.0.
247      * @return the maxLength.
248      */
249     @Deprecated
250     public int getMaxLength() {
251         return this.maxLength;
252     }
253 
254     private boolean hasMarker(final char[] mapping) {
255         for (final char ch : mapping) {
256             if (ch == SILENT_MARKER) {
257                 return true;
258             }
259         }
260         return false;
261     }
262 
263     /**
264      * Maps the given upper-case character to its Soundex code.
265      *
266      * @param ch
267      *                  An upper-case character.
268      * @return A Soundex code.
269      * @throws IllegalArgumentException
270      *                  Thrown if {@code ch} is not mapped.
271      */
272     private char map(final char ch) {
273         final int index = ch - 'A';
274         if (index < 0 || index >= this.soundexMapping.length) {
275             throw new IllegalArgumentException("The character is not mapped: " + ch + " (index=" + index + ")");
276         }
277         return this.soundexMapping[index];
278     }
279 
280     /**
281      * Sets the maxLength.
282      *
283      * @deprecated This feature is not needed since the encoding size must be constant. Will be removed in 2.0.
284      * @param maxLength
285      *                  The maxLength to set.
286      */
287     @Deprecated
288     public void setMaxLength(final int maxLength) {
289         this.maxLength = maxLength;
290     }
291 
292     /**
293      * Retrieves the Soundex code for a given String object.
294      *
295      * @param str String to encode using the Soundex algorithm.
296      * @return A Soundex code for the String supplied.
297      * @throws IllegalArgumentException if a character is not mapped.
298      */
299     public String soundex(String str) {
300         if (str == null) {
301             return null;
302         }
303         str = SoundexUtils.clean(str);
304         if (str.isEmpty()) {
305             return str;
306         }
307         final char[] out = { '0', '0', '0', '0' };
308         int count = 0;
309         final char first = str.charAt(0);
310         out[count++] = first;
311         char lastDigit = map(first); // previous digit
312         for (int i = 1; i < str.length() && count < out.length; i++) {
313             final char ch = str.charAt(i);
314             if (this.specialCaseHW && (ch == 'H' || ch == 'W')) { // these are ignored completely
315                 continue;
316             }
317             final char digit = map(ch);
318             if (digit == SILENT_MARKER) {
319                 continue;
320             }
321             if (digit != '0' && digit != lastDigit) { // don't store vowels or repeats
322                 out[count++] = digit;
323             }
324             lastDigit = digit;
325         }
326         return new String(out);
327     }
328 
329 }