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
019/**
020 * Modulus 11 <b>ISBN-10</b> Check Digit calculation/validation.
021 * <p>
022 * ISBN-10 Numbers are a numeric code except for the last (check) digit
023 * which can have a value of "X".
024 * <p>
025 * Check digit calculation is based on <i>modulus 11</i> with digits being weighted
026 * based by their position, from right to left  with the first digit being weighted
027 * 1, the second 2 and so on. If the check digit is calculated as "10" it is converted
028 * to "X".
029 * <p>
030 * <b>N.B.</b> From 1st January 2007 the book industry will start to use a new 13 digit
031 * ISBN number (rather than this 10 digit ISBN number) which uses the EAN-13 / UPC
032 * (see {@link EAN13CheckDigit}) standard.
033 * <p>
034 * For further information see:
035 * <ul>
036 *   <li><a href="http://en.wikipedia.org/wiki/ISBN">Wikipedia - International
037 *       Standard Book Number (ISBN)</a>.</li>
038 *   <li><a href="http://www.isbn.org/standards/home/isbn/transition.asp">ISBN-13
039 *       Transition details</a>.</li>
040 * </ul>
041 *
042 * @version $Revision: 1227719 $ $Date: 2012-01-05 18:45:51 +0100 (Do, 05 Jan 2012) $
043 * @since Validator 1.4
044 */
045public final class ISBN10CheckDigit extends ModulusCheckDigit {
046
047    private static final long serialVersionUID = 8000855044504864964L;
048
049    /** Singleton ISBN-10 Check Digit instance */
050    public static final CheckDigit ISBN10_CHECK_DIGIT = new ISBN10CheckDigit();
051
052    /**
053     * Construct a modulus 11 Check Digit routine for ISBN-10.
054     */
055    public ISBN10CheckDigit() {
056        super(11);
057    }
058
059    /**
060     * Calculates the <i>weighted</i> value of a charcter in the
061     * code at a specified position.
062     *
063     * <p>For ISBN-10 (from right to left) digits are weighted
064     * by their position.</p>
065     *
066     * @param charValue The numeric value of the character.
067     * @param leftPos The position of the character in the code, counting from left to right
068     * @param rightPos The positionof the character in the code, counting from right to left
069     * @return The weighted value of the character.
070     */
071    protected int weightedValue(int charValue, int leftPos, int rightPos) {
072        return (charValue * rightPos);
073    }
074
075    /**
076     * <p>Convert a character at a specified position to an
077     * integer value.</p>
078     *
079     * <p>Character 'X' check digit converted to 10.</p>
080     *
081     * @param character The character to convert.
082     * @param leftPos The position of the character in the code, counting from left to right
083     * @param rightPos The positionof the character in the code, counting from right to left
084     * @return The integer value of the character.
085     * @throws CheckDigitException if an error occurs.
086     */
087    protected int toInt(char character, int leftPos, int rightPos)
088            throws CheckDigitException {
089        if (rightPos == 1 && character == 'X') {
090            return 10;
091        } else {
092            return super.toInt(character, leftPos, rightPos);
093        }
094    }
095
096    /**
097     * <p>Convert an integer value to a character at a specified position.</p>
098     *
099     * <p>Value '10' for position 1 (check digit) converted to 'X'.</p>
100     *
101     * @param charValue The integer value of the character.
102     * @return The converted character.
103     * @throws CheckDigitException if an error occurs.
104     */
105    protected String toCheckDigit(int charValue)
106            throws CheckDigitException {
107        if (charValue == 10) {
108            return "X";
109        } else {
110            return super.toCheckDigit(charValue);
111        }
112    }
113
114}