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 org.apache.commons.validator.GenericValidator; 20 import org.apache.commons.validator.routines.CodeValidator; 21 22 /** 23 * Modulus 10 <strong>CAS Registry Number</strong> (or <strong>Chemical Abstracts Service</strong> (CAS RN)) Check Digit 24 * calculation/validation. 25 * 26 * <p> 27 * CAS Numbers are unique identification numbers used 28 * to identify chemical substance described in the open scientific literature. 29 * </p> 30 * 31 * <p> 32 * Check digit calculation is based on <em>modulus 10</em> with digits being weighted 33 * based on their position (from right to left). 34 * </p> 35 * 36 * <p> 37 * The check digit is found by taking the last digit times 1, the preceding digit times 2, 38 * the preceding digit times 3 etc., adding all these up and computing the sum modulo 10. 39 * For example, the CAS number of water is {@code 7732-18-5}: 40 * the checksum 5 is calculated as (8×1 + 1×2 + 2×3 + 3×4 + 7×5 + 7×6) = 105; 105 mod 10 = 5. 41 * </p> 42 * 43 * <p> 44 * For further information see 45 * <a href="https://en.wikipedia.org/wiki/CAS_Registry_Number">Wikipedia - CAS Registry Number</a>. 46 * </p> 47 * 48 * @since 1.9.0 49 */ 50 public final class CASNumberCheckDigit extends ModulusCheckDigit { 51 52 private static final long serialVersionUID = -5387334603220786657L; 53 54 /** Singleton Check Digit instance */ 55 private static final CASNumberCheckDigit INSTANCE = new CASNumberCheckDigit(); 56 57 /** 58 * CAS number consists of 3 groups of numbers separated dashes (-). 59 * First group has 2 to 7 digits. 60 * Example: water is 7732-18-5 61 */ 62 private static final String GROUP1 = "(\\d{2,7})"; 63 64 private static final String DASH = "(?:\\-)"; 65 static final String CAS_REGEX = "^(?:" + GROUP1 + DASH + "(\\d{2})" + DASH + "(\\d))$"; 66 private static final int CAS_MIN_LEN = 4; // 9-99-9 LEN without SEP 67 68 /** maximum capacity of 1,000,000,000 == 9999999-99-9*/ 69 private static final int CAS_MAX_LEN = 10; 70 static final CodeValidator REGEX_VALIDATOR = new CodeValidator(CAS_REGEX, CAS_MIN_LEN, CAS_MAX_LEN, null); 71 /** Weighting given to digits depending on their right position */ 72 private static final int[] POSITION_WEIGHT = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 }; 73 74 /** 75 * Gets the singleton instance of this validator. 76 * @return A singleton instance of the CAS Number validator. 77 */ 78 public static CheckDigit getInstance() { 79 return INSTANCE; 80 } 81 82 /** 83 * Constructs a modulus 10 Check Digit routine for CAS Numbers. 84 */ 85 private CASNumberCheckDigit() { 86 } 87 88 /** 89 * {@inheritDoc} 90 */ 91 @Override 92 public String calculate(final String code) throws CheckDigitException { 93 if (GenericValidator.isBlankOrNull(code)) { 94 throw new CheckDigitException("Code is missing"); 95 } 96 final int modulusResult = INSTANCE.calculateModulus(code, false); 97 return toCheckDigit(modulusResult); 98 } 99 100 /** 101 * {@inheritDoc} 102 */ 103 @Override 104 public boolean isValid(final String code) { 105 if (GenericValidator.isBlankOrNull(code)) { 106 return false; 107 } 108 final Object cde = REGEX_VALIDATOR.validate(code); 109 if (!(cde instanceof String)) { 110 return false; 111 } 112 try { 113 final int modulusResult = INSTANCE.calculateModulus((String) cde, true); 114 return modulusResult == Character.getNumericValue(code.charAt(code.length() - 1)); 115 } catch (final CheckDigitException ex) { 116 return false; 117 } 118 } 119 120 /** 121 * Calculates the <em>weighted</em> value of a character in the code at a specified position. 122 * <p> 123 * CAS numbers are weighted in the following manner: 124 * </p> 125 * <pre>{@code 126 * right position: 1 2 3 4 5 6 7 8 9 10 127 * weight: 1 2 3 4 5 6 7 8 9 0 128 * }</pre> 129 * 130 * @param charValue The numeric value of the character. 131 * @param leftPos The position of the character in the code, counting from left to right 132 * @param rightPos The position of the character in the code, counting from right to left 133 * @return The weighted value of the character. 134 */ 135 @Override 136 protected int weightedValue(final int charValue, final int leftPos, final int rightPos) { 137 final int weight = POSITION_WEIGHT[(rightPos - 1) % MODULUS_10]; 138 return charValue * weight; 139 } 140 141 }