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 */ 017package org.apache.commons.validator.routines.checkdigit; 018 019import 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 $Revision$ 032 * @since Validator 1.4 033 */ 034public 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 @Override 078 public boolean isValid(String code) { 079 if (code == null || code.length() == 0) { 080 return false; 081 } 082 try { 083 return (calculateChecksum(code, true) == 0); 084 } catch (CheckDigitException e) { 085 return false; 086 } 087 } 088 089 /** 090 * Calculate a Verhoeff <i>Check Digit</i> for a code. 091 * 092 * @param code The code to calculate the Check Digit for 093 * @return The calculated Check Digit 094 * @throws CheckDigitException if an error occurs calculating 095 * the check digit for the specified code 096 */ 097 @Override 098 public String calculate(String code) throws CheckDigitException { 099 if (code == null || code.length() == 0) { 100 throw new CheckDigitException("Code is missing"); 101 } 102 int checksum = calculateChecksum(code, false); 103 return Integer.toString(INV_TABLE[checksum]); 104 } 105 106 /** 107 * Calculate the checksum. 108 * 109 * @param code The code to calculate the checksum for. 110 * @param includesCheckDigit Whether the code includes the Check Digit or not. 111 * @return The checksum value 112 * @throws CheckDigitException if the code contains an invalid character (i.e. not numeric) 113 */ 114 private int calculateChecksum(String code, boolean includesCheckDigit) throws CheckDigitException { 115 int checksum = 0; 116 for (int i = 0; i < code.length(); i++) { 117 int idx = code.length() - (i + 1); 118 int num = Character.getNumericValue(code.charAt(idx)); 119 if (num < 0 || num > 9) { // CHECKSTYLE IGNORE MagicNumber 120 throw new CheckDigitException("Invalid Character[" + 121 i + "] = '" + ((int)code.charAt(idx)) + "'"); 122 } 123 int pos = includesCheckDigit ? i : i + 1; 124 checksum = D_TABLE[checksum][P_TABLE[pos % 8][num]]; // CHECKSTYLE IGNORE MagicNumber 125 } 126 return checksum; 127 } 128 129}