001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017 package org.apache.commons.validator.routines.checkdigit;
018
019 import java.io.Serializable;
020
021 /**
022 * <b>Verhoeff</b> (Dihedral) Check Digit calculation/validation.
023 * <p>
024 * Check digit calculation for numeric codes using a
025 * <a href="http://en.wikipedia.org/wiki/Dihedral_group">Dihedral Group</a>
026 * of order 10.
027 * <p>
028 * See <a href="http://en.wikipedia.org/wiki/Verhoeff_algorithm">Wikipedia
029 * - Verhoeff algorithm</a> for more details.
030 *
031 * @version $Revision: 1227719 $ $Date: 2012-01-05 18:45:51 +0100 (Thu, 05 Jan 2012) $
032 * @since Validator 1.4
033 */
034 public final class VerhoeffCheckDigit implements CheckDigit, Serializable {
035
036 private static final long serialVersionUID = 4138993995483695178L;
037
038 /** Singleton Verhoeff Check Digit instance */
039 public static final CheckDigit VERHOEFF_CHECK_DIGIT = new VerhoeffCheckDigit();
040
041 /** D - multiplication table */
042 private static final int[][] D_TABLE = new int[][] {
043 {0, 1, 2, 3, 4, 5, 6, 7, 8, 9},
044 {1, 2, 3, 4, 0, 6, 7, 8, 9, 5},
045 {2, 3, 4, 0, 1, 7, 8, 9, 5, 6},
046 {3, 4, 0, 1, 2, 8, 9, 5, 6, 7},
047 {4, 0, 1, 2, 3, 9, 5, 6, 7, 8},
048 {5, 9, 8, 7, 6, 0, 4, 3, 2, 1},
049 {6, 5, 9, 8, 7, 1, 0, 4, 3, 2},
050 {7, 6, 5, 9, 8, 2, 1, 0, 4, 3},
051 {8, 7, 6, 5, 9, 3, 2, 1, 0, 4},
052 {9, 8, 7, 6, 5, 4, 3, 2, 1, 0}};
053
054 /** P - permutation table */
055 private static final int[][] P_TABLE = new int[][] {
056 {0, 1, 2, 3, 4, 5, 6, 7, 8, 9},
057 {1, 5, 7, 6, 2, 8, 3, 0, 9, 4},
058 {5, 8, 0, 3, 7, 9, 6, 1, 4, 2},
059 {8, 9, 1, 6, 0, 4, 3, 5, 2, 7},
060 {9, 4, 5, 3, 1, 2, 6, 8, 7, 0},
061 {4, 2, 8, 6, 5, 7, 3, 9, 0, 1},
062 {2, 7, 9, 3, 8, 0, 6, 4, 1, 5},
063 {7, 0, 4, 6, 9, 1, 3, 2, 5, 8}};
064
065 /** inv: inverse table */
066 private static final int[] INV_TABLE = new int[]
067 {0, 4, 3, 2, 1, 5, 6, 7, 8, 9};
068
069
070 /**
071 * Validate the Verhoeff <i>Check Digit</i> for a code.
072 *
073 * @param code The code to validate
074 * @return <code>true</code> if the check digit is valid,
075 * otherwise <code>false</code>
076 */
077 public boolean isValid(String code) {
078 if (code == null || code.length() == 0) {
079 return false;
080 }
081 try {
082 return (calculateChecksum(code, true) == 0);
083 } catch (CheckDigitException e) {
084 return false;
085 }
086 }
087
088 /**
089 * Calculate a Verhoeff <i>Check Digit</i> for a code.
090 *
091 * @param code The code to calculate the Check Digit for
092 * @return The calculated Check Digit
093 * @throws CheckDigitException if an error occurs calculating
094 * the check digit for the specified code
095 */
096 public String calculate(String code) throws CheckDigitException {
097 if (code == null || code.length() == 0) {
098 throw new CheckDigitException("Code is missing");
099 }
100 int checksum = calculateChecksum(code, false);
101 return Integer.toString(INV_TABLE[checksum]);
102 }
103
104 /**
105 * Calculate the checksum.
106 *
107 * @param code The code to calculate the checksum for.
108 * @param includesCheckDigit Whether the code includes the Check Digit or not.
109 * @return The checksum value
110 * @throws CheckDigitException if the code contains an invalid character (i.e. not numeric)
111 */
112 private int calculateChecksum(String code, boolean includesCheckDigit) throws CheckDigitException {
113 int checksum = 0;
114 for (int i = 0; i < code.length(); i++) {
115 int idx = code.length() - (i + 1);
116 int num = Character.getNumericValue(code.charAt(idx));
117 if (num < 0 || num > 9) {
118 throw new CheckDigitException("Invalid Character[" +
119 i + "] = '" + ((int)code.charAt(idx)) + "'");
120 }
121 int pos = includesCheckDigit ? i : i + 1;
122 checksum = D_TABLE[checksum][P_TABLE[pos % 8][num]];
123 }
124 return checksum;
125 }
126
127 }