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 package org.apache.commons.validator.routines.checkdigit;
18
19 import java.io.Serializable;
20
21 import org.apache.commons.validator.GenericValidator;
22
23 /**
24 * <strong>Verhoeff</strong> (Dihedral) Check Digit calculation/validation.
25 * <p>
26 * Check digit calculation for numeric codes using a
27 * <a href="https://en.wikipedia.org/wiki/Dihedral_group">Dihedral Group</a>
28 * of order 10.
29 * <p>
30 * See <a href="https://en.wikipedia.org/wiki/Verhoeff_algorithm">Wikipedia
31 * - Verhoeff algorithm</a> for more details.
32 *
33 * @since 1.4
34 */
35 public final class VerhoeffCheckDigit extends AbstractCheckDigit implements Serializable {
36
37 private static final long serialVersionUID = 4138993995483695178L;
38
39 /** Singleton Verhoeff Check Digit instance */
40 public static final CheckDigit VERHOEFF_CHECK_DIGIT = new VerhoeffCheckDigit();
41
42 /** D - multiplication table */
43 private static final int[][] D_TABLE = {
44 {0, 1, 2, 3, 4, 5, 6, 7, 8, 9},
45 {1, 2, 3, 4, 0, 6, 7, 8, 9, 5},
46 {2, 3, 4, 0, 1, 7, 8, 9, 5, 6},
47 {3, 4, 0, 1, 2, 8, 9, 5, 6, 7},
48 {4, 0, 1, 2, 3, 9, 5, 6, 7, 8},
49 {5, 9, 8, 7, 6, 0, 4, 3, 2, 1},
50 {6, 5, 9, 8, 7, 1, 0, 4, 3, 2},
51 {7, 6, 5, 9, 8, 2, 1, 0, 4, 3},
52 {8, 7, 6, 5, 9, 3, 2, 1, 0, 4},
53 {9, 8, 7, 6, 5, 4, 3, 2, 1, 0}};
54
55 /** P - permutation table */
56 private static final int[][] P_TABLE = {
57 {0, 1, 2, 3, 4, 5, 6, 7, 8, 9},
58 {1, 5, 7, 6, 2, 8, 3, 0, 9, 4},
59 {5, 8, 0, 3, 7, 9, 6, 1, 4, 2},
60 {8, 9, 1, 6, 0, 4, 3, 5, 2, 7},
61 {9, 4, 5, 3, 1, 2, 6, 8, 7, 0},
62 {4, 2, 8, 6, 5, 7, 3, 9, 0, 1},
63 {2, 7, 9, 3, 8, 0, 6, 4, 1, 5},
64 {7, 0, 4, 6, 9, 1, 3, 2, 5, 8}};
65
66 /** Inverse table */
67 private static final int[] INV_TABLE = {0, 4, 3, 2, 1, 5, 6, 7, 8, 9};
68
69 /**
70 * Constructs a new instance.
71 */
72 public VerhoeffCheckDigit() {
73 // empty
74 }
75
76 /**
77 * Calculate a Verhoeff <em>Check Digit</em> for a code.
78 *
79 * @param code The code to calculate the Check Digit for
80 * @return The calculated Check Digit
81 * @throws CheckDigitException if an error occurs calculating
82 * the check digit for the specified code
83 */
84 @Override
85 public String calculate(final String code) throws CheckDigitException {
86 if (GenericValidator.isBlankOrNull(code)) {
87 throw new CheckDigitException("Code is missing");
88 }
89 final int checksum = calculateChecksum(code, false);
90 return Integer.toString(INV_TABLE[checksum]);
91 }
92
93 /**
94 * Calculate the checksum.
95 *
96 * @param code The code to calculate the checksum for.
97 * @param includesCheckDigit Whether the code includes the Check Digit or not.
98 * @return The checksum value
99 * @throws CheckDigitException if the code contains an invalid character (that is, a non-numeric character)
100 */
101 private int calculateChecksum(final String code, final boolean includesCheckDigit) throws CheckDigitException {
102 int checksum = 0;
103 for (int i = 0; i < code.length(); i++) {
104 final int idx = code.length() - (i + 1);
105 final int num = Character.getNumericValue(code.charAt(idx));
106 if (num < 0 || num > 9) { // CHECKSTYLE IGNORE MagicNumber
107 throw new CheckDigitException("Invalid Character[" +
108 i + "] = '" + (int) code.charAt(idx) + "'");
109 }
110 final int pos = includesCheckDigit ? i : i + 1;
111 checksum = D_TABLE[checksum][P_TABLE[pos % 8][num]]; // CHECKSTYLE IGNORE MagicNumber
112 }
113 return checksum;
114 }
115
116 /**
117 * Validate the Verhoeff <em>Check Digit</em> for a code.
118 *
119 * @param code The code to validate
120 * @return {@code true} if the check digit is valid,
121 * otherwise {@code false}
122 */
123 @Override
124 public boolean isValid(final String code) {
125 if (GenericValidator.isBlankOrNull(code)) {
126 return false;
127 }
128 try {
129 return calculateChecksum(code, true) == 0;
130 } catch (final CheckDigitException e) {
131 return false;
132 }
133 }
134
135 }