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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    *      http://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  package org.apache.commons.validator.routines.checkdigit;
18  
19  /**
20   * Modulus 10 <b>EAN-13</b> / <b>UPC</b> / <b>ISBN-13</b> Check Digit
21   * calculation/validation.
22   * <p>
23   * Check digit calculation is based on <i>modulus 10</i> with digits in
24   * an <i>odd</i> position (from right to left) being weighted 1 and <i>even</i>
25   * position digits being weighted 3.
26   * <p>
27   * For further information see:
28   * <ul>
29   *   <li>EAN-13 - see
30   *       <a href="http://en.wikipedia.org/wiki/European_Article_Number">Wikipedia -
31   *       European Article Number</a>.</li>
32   *   <li>UPC - see
33   *       <a href="http://en.wikipedia.org/wiki/Universal_Product_Code">Wikipedia -
34   *       Universal Product Code</a>.</li>
35   *   <li>ISBN-13 - see
36   *       <a href="http://en.wikipedia.org/wiki/ISBN">Wikipedia - International
37   *       Standard Book Number (ISBN)</a>.</li>
38   * </ul>
39   *
40   * @version $Revision: 1227719 $ $Date: 2012-01-05 18:45:51 +0100 (Do, 05 Jan 2012) $
41   * @since Validator 1.4
42   */
43  public final class EAN13CheckDigit extends ModulusCheckDigit {
44  
45      private static final long serialVersionUID = 1726347093230424107L;
46  
47      /** Singleton EAN-13 Check Digit instance */
48      public static final CheckDigit EAN13_CHECK_DIGIT = new EAN13CheckDigit();
49  
50      /** weighting given to digits depending on their right position */
51      private static final int[] POSITION_WEIGHT = new int[] {3, 1};
52  
53      /**
54       * Construct a modulus 10 Check Digit routine for EAN/UPC.
55       */
56      public EAN13CheckDigit() {
57          super(10);
58      }
59  
60      /**
61       * <p>Calculates the <i>weighted</i> value of a character in the
62       * code at a specified position.</p>
63       *
64       * <p>For EAN-13 (from right to left) <b>odd</b> digits are weighted
65       * with a factor of <b>one</b> and <b>even</b> digits with a factor
66       * of <b>three</b>.</p>
67       *
68       * @param charValue The numeric value of the character.
69       * @param leftPos The position of the character in the code, counting from left to right
70       * @param rightPos The positionof the character in the code, counting from right to left
71       * @return The weighted value of the character.
72       */
73      protected int weightedValue(int charValue, int leftPos, int rightPos) {
74          int weight = POSITION_WEIGHT[rightPos % 2];
75          return (charValue * weight);
76      }
77  }