67 lines
1.8 KiB
PHP
67 lines
1.8 KiB
PHP
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<?php
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// $Id: bcpowmod.php,v 1.1 2007/07/02 04:19:55 terrafrost 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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* @license LGPL - http://www.gnu.org/licenses/lgpl.html
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* @copyright 2004-2007 Aidan Lister <aidan@php.net>, Arpad Ray <arpad@php.net>
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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: 1.1 $
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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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function php_compat_bcpowmod($x, $y, $modulus, $scale = 0)
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{
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// Sanity check
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if (!is_scalar($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 $t;
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}
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// Define
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if (!function_exists('bcpowmod')) {
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function bcpowmod($x, $y, $modulus, $scale = 0)
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{
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return php_compat_bcpowmod($x, $y, $modulus, $scale);
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}
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}
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?>
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