org.apache.commons.validator.routines.checkdigit.VerhoeffCheckDigit Maven / Gradle / Ivy
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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.validator.routines.checkdigit;
import java.io.Serializable;
/**
* Verhoeff (Dihedral) Check Digit calculation/validation.
*
* Check digit calculation for numeric codes using a
* Dihedral Group
* of order 10.
*
* See Wikipedia
* - Verhoeff algorithm for more details.
*
* @version $Revision: 1739357 $
* @since Validator 1.4
*/
public final class VerhoeffCheckDigit implements CheckDigit, Serializable {
private static final long serialVersionUID = 4138993995483695178L;
/** Singleton Verhoeff Check Digit instance */
public static final CheckDigit VERHOEFF_CHECK_DIGIT = new VerhoeffCheckDigit();
/** D - multiplication table */
private static final int[][] D_TABLE = new int[][] {
{0, 1, 2, 3, 4, 5, 6, 7, 8, 9},
{1, 2, 3, 4, 0, 6, 7, 8, 9, 5},
{2, 3, 4, 0, 1, 7, 8, 9, 5, 6},
{3, 4, 0, 1, 2, 8, 9, 5, 6, 7},
{4, 0, 1, 2, 3, 9, 5, 6, 7, 8},
{5, 9, 8, 7, 6, 0, 4, 3, 2, 1},
{6, 5, 9, 8, 7, 1, 0, 4, 3, 2},
{7, 6, 5, 9, 8, 2, 1, 0, 4, 3},
{8, 7, 6, 5, 9, 3, 2, 1, 0, 4},
{9, 8, 7, 6, 5, 4, 3, 2, 1, 0}};
/** P - permutation table */
private static final int[][] P_TABLE = new int[][] {
{0, 1, 2, 3, 4, 5, 6, 7, 8, 9},
{1, 5, 7, 6, 2, 8, 3, 0, 9, 4},
{5, 8, 0, 3, 7, 9, 6, 1, 4, 2},
{8, 9, 1, 6, 0, 4, 3, 5, 2, 7},
{9, 4, 5, 3, 1, 2, 6, 8, 7, 0},
{4, 2, 8, 6, 5, 7, 3, 9, 0, 1},
{2, 7, 9, 3, 8, 0, 6, 4, 1, 5},
{7, 0, 4, 6, 9, 1, 3, 2, 5, 8}};
/** inv: inverse table */
private static final int[] INV_TABLE = new int[]
{0, 4, 3, 2, 1, 5, 6, 7, 8, 9};
/**
* Validate the Verhoeff Check Digit for a code.
*
* @param code The code to validate
* @return true if the check digit is valid,
* otherwise false
*/
@Override
public boolean isValid(String code) {
if (code == null || code.length() == 0) {
return false;
}
try {
return (calculateChecksum(code, true) == 0);
} catch (CheckDigitException e) {
return false;
}
}
/**
* Calculate a Verhoeff Check Digit for a code.
*
* @param code The code to calculate the Check Digit for
* @return The calculated Check Digit
* @throws CheckDigitException if an error occurs calculating
* the check digit for the specified code
*/
@Override
public String calculate(String code) throws CheckDigitException {
if (code == null || code.length() == 0) {
throw new CheckDigitException("Code is missing");
}
int checksum = calculateChecksum(code, false);
return Integer.toString(INV_TABLE[checksum]);
}
/**
* Calculate the checksum.
*
* @param code The code to calculate the checksum for.
* @param includesCheckDigit Whether the code includes the Check Digit or not.
* @return The checksum value
* @throws CheckDigitException if the code contains an invalid character (i.e. not numeric)
*/
private int calculateChecksum(String code, boolean includesCheckDigit) throws CheckDigitException {
int checksum = 0;
for (int i = 0; i < code.length(); i++) {
int idx = code.length() - (i + 1);
int num = Character.getNumericValue(code.charAt(idx));
if (num < 0 || num > 9) { // CHECKSTYLE IGNORE MagicNumber
throw new CheckDigitException("Invalid Character[" +
i + "] = '" + ((int)code.charAt(idx)) + "'");
}
int pos = includesCheckDigit ? i : i + 1;
checksum = D_TABLE[checksum][P_TABLE[pos % 8][num]]; // CHECKSTYLE IGNORE MagicNumber
}
return checksum;
}
}