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>ISIN</b> (International Securities Identifying Number)
21 * Check Digit calculation/validation.
22 * <p>
23 * ISIN Numbers are 12 character alphanumeric codes used
24 * to identify Securities.
25 * <p>
26 * Check digit calculation uses the <i>Modulus 10 Double Add Double</i> technique
27 * with every second digit being weighted by 2. Alphabetic characters are
28 * converted to numbers by their position in the alphabet starting with A being 10.
29 * Weighted numbers greater than ten are treated as two separate numbers.
30 * <p>
31 * See <a href="http://en.wikipedia.org/wiki/ISIN">Wikipedia - ISIN</a>
32 * for more details.
33 *
34 * @version $Revision: 1227719 $ $Date: 2012-01-05 12:45:51 -0500 (Thu, 05 Jan 2012) $
35 * @since Validator 1.4
36 */
37 public final class ISINCheckDigit extends ModulusCheckDigit {
38
39 private static final long serialVersionUID = -1239211208101323599L;
40
41 /** Singleton ISIN Check Digit instance */
42 public static final CheckDigit ISIN_CHECK_DIGIT = new ISINCheckDigit();
43
44 /** weighting given to digits depending on their right position */
45 private static final int[] POSITION_WEIGHT = new int[] {2, 1};
46
47 /**
48 * Construct an ISIN Indetifier Check Digit routine.
49 */
50 public ISINCheckDigit() {
51 super(10);
52 }
53
54 /**
55 * Calculate the modulus for an ISIN code.
56 *
57 * @param code The code to calculate the modulus for.
58 * @param includesCheckDigit Whether the code includes the Check Digit or not.
59 * @return The modulus value
60 * @throws CheckDigitException if an error occurs calculating the modulus
61 * for the specified code
62 */
63 protected int calculateModulus(String code, boolean includesCheckDigit) throws CheckDigitException {
64 StringBuffer transformed = new StringBuffer(code.length() * 2);
65 for (int i = 0; i < code.length(); i++) {
66 int charValue = Character.getNumericValue(code.charAt(i));
67 if (charValue < 0 || charValue > 35) {
68 throw new CheckDigitException("Invalid Character[" +
69 (i + 1) + "] = '" + charValue + "'");
70 }
71 transformed.append(charValue);
72 }
73 return super.calculateModulus(transformed.toString(), includesCheckDigit);
74 }
75
76 /**
77 * <p>Calculates the <i>weighted</i> value of a charcter in the
78 * code at a specified position.</p>
79 *
80 * <p>For Luhn (from right to left) <b>odd</b> digits are weighted
81 * with a factor of <b>one</b> and <b>even</b> digits with a factor
82 * of <b>two</b>. Weighted values > 9, have 9 subtracted</p>
83 *
84 * @param charValue The numeric value of the character.
85 * @param leftPos The position of the character in the code, counting from left to right
86 * @param rightPos The positionof the character in the code, counting from right to left
87 * @return The weighted value of the character.
88 */
89 protected int weightedValue(int charValue, int leftPos, int rightPos) {
90 int weight = POSITION_WEIGHT[rightPos % 2];
91 int weightedValue = (charValue * weight);
92 return ModulusCheckDigit.sumDigits(weightedValue);
93 }
94 }