75 lines
2.7 KiB
PHP
75 lines
2.7 KiB
PHP
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<?php
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// +----------------------------------------------------------------------+
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// | PHP Version 4 |
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// +----------------------------------------------------------------------+
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// | Copyright (c) 1997-2004 The PHP Group |
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// +----------------------------------------------------------------------+
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// | This source file is subject to version 3.0 of the PHP license, |
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// | that is bundled with this package in the file LICENSE, and is |
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// | available at through the world-wide-web at |
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// | http://www.php.net/license/3_0.txt. |
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// | If you did not receive a copy of the PHP license and are unable to |
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// | obtain it through the world-wide-web, please send a note to |
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// | license@php.net so we can mail you a copy immediately. |
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// +----------------------------------------------------------------------+
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// | Authors: Aidan Lister <aidan@php.net> |
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// +----------------------------------------------------------------------+
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//
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// $Id: bcpowmod.php,v 1.2 2005/11/22 20:24:45 aidan Exp $
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/**
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* Replace bcpowmod()
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*
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* @category PHP
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* @package PHP_Compat
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* @link http://php.net/function.bcpowmod
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* @author Sara Golemon <pollita@php.net>
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* @version $Revision: 1.2 $
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* @since PHP 5.0.0
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* @require PHP 4.0.0 (user_error)
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*/
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if (!function_exists('bcpowmod')) {
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function bcpowmod($x, $y, $modulus, $scale)
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{
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// Sanity check
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if (!is_scalar($x)) {
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user_error('bcpowmod() expects parameter 1 to be string, ' .
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gettype($x) . ' given', E_USER_WARNING);
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return false;
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}
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if (!is_scalar($y)) {
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user_error('bcpowmod() expects parameter 2 to be string, ' .
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gettype($y) . ' given', E_USER_WARNING);
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return false;
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}
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if (!is_scalar($modulus)) {
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user_error('bcpowmod() expects parameter 3 to be string, ' .
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gettype($modulus) . ' given', E_USER_WARNING);
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return false;
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}
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if (!is_scalar($scale)) {
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user_error('bcpowmod() expects parameter 4 to be integer, ' .
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gettype($scale) . ' given', E_USER_WARNING);
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return false;
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}
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$t = '1';
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while (bccomp($y, '0')) {
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if (bccomp(bcmod($y, '2'), '0')) {
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$t = bcmod(bcmul($t, $x), $modulus);
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$y = bcsub($y, '1');
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}
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$x = bcmod(bcmul($x, $x), $modulus);
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$y = bcdiv($y, '2');
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}
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return $t;
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}
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}
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?>
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