63 lines
1.2 KiB
PHP
63 lines
1.2 KiB
PHP
<?php
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/**
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* Zend Framework (http://framework.zend.com/)
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*
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* @link http://github.com/zendframework/zend-validator for the canonical source repository
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* @copyright Copyright (c) 2005-2016 Zend Technologies USA Inc. (http://www.zend.com)
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* @license http://framework.zend.com/license/new-bsd New BSD License
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*/
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namespace Zend\Validator\Isbn;
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class Isbn13
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{
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/**
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* @param int|string $value
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* @return int|string
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*/
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public function getChecksum($value)
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{
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$sum = $this->sum($value);
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return $this->checksum($sum);
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}
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/**
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* Calculate the value sum.
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*
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* @param int|string $value
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* @return int
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*/
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private function sum($value)
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{
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$sum = 0;
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for ($i = 0; $i < 12; $i++) {
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if ($i % 2 == 0) {
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$sum += $value{$i};
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continue;
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}
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$sum += 3 * $value{$i};
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}
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return $sum;
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}
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/**
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* Calculate the checksum for the value's sum.
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*
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* @param int $sum
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* @return int|string
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*/
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private function checksum($sum)
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{
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$checksum = 10 - ($sum % 10);
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if ($checksum == 10) {
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return '0';
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}
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return $checksum;
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}
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}
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