1 | <?php |
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2 | // +----------------------------------------------------------------------+ |
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3 | // | PHP Version 4 | |
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4 | // +----------------------------------------------------------------------+ |
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5 | // | Copyright (c) 1997-2004 The PHP Group | |
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6 | // +----------------------------------------------------------------------+ |
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7 | // | This source file is subject to version 3.0 of the PHP license, | |
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8 | // | that is bundled with this package in the file LICENSE, and is | |
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9 | // | available at through the world-wide-web at | |
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10 | // | http://www.php.net/license/3_0.txt. | |
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11 | // | If you did not receive a copy of the PHP license and are unable to | |
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12 | // | obtain it through the world-wide-web, please send a note to | |
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13 | // | license@php.net so we can mail you a copy immediately. | |
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14 | // +----------------------------------------------------------------------+ |
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15 | // | Authors: Aidan Lister <aidan@php.net> | |
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16 | // +----------------------------------------------------------------------+ |
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17 | // |
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18 | // $Id: bcpowmod.php,v 1.2 2005/11/22 20:24:45 aidan Exp $ |
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19 | |
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20 | |
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21 | /** |
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22 | * Replace bcpowmod() |
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23 | * |
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24 | * @category PHP |
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25 | * @package PHP_Compat |
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26 | * @link http://php.net/function.bcpowmod |
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27 | * @author Sara Golemon <pollita@php.net> |
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28 | * @version $Revision: 1.2 $ |
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29 | * @since PHP 5.0.0 |
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30 | * @require PHP 4.0.0 (user_error) |
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31 | */ |
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32 | if (!function_exists('bcpowmod')) { |
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33 | function bcpowmod($x, $y, $modulus, $scale) |
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34 | { |
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35 | // Sanity check |
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36 | if (!is_scalar($x)) { |
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37 | user_error('bcpowmod() expects parameter 1 to be string, ' . |
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38 | gettype($x) . ' given', E_USER_WARNING); |
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39 | return false; |
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40 | } |
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41 | |
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42 | if (!is_scalar($y)) { |
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43 | user_error('bcpowmod() expects parameter 2 to be string, ' . |
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44 | gettype($y) . ' given', E_USER_WARNING); |
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45 | return false; |
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46 | } |
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47 | |
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48 | if (!is_scalar($modulus)) { |
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49 | user_error('bcpowmod() expects parameter 3 to be string, ' . |
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50 | gettype($modulus) . ' given', E_USER_WARNING); |
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51 | return false; |
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52 | } |
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53 | |
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54 | if (!is_scalar($scale)) { |
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55 | user_error('bcpowmod() expects parameter 4 to be integer, ' . |
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56 | gettype($scale) . ' given', E_USER_WARNING); |
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57 | return false; |
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58 | } |
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59 | |
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60 | $t = '1'; |
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61 | while (bccomp($y, '0')) { |
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62 | if (bccomp(bcmod($y, '2'), '0')) { |
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63 | $t = bcmod(bcmul($t, $x), $modulus); |
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64 | $y = bcsub($y, '1'); |
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65 | } |
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66 | |
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67 | $x = bcmod(bcmul($x, $x), $modulus); |
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68 | $y = bcdiv($y, '2'); |
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69 | } |
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70 | |
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71 | return $t; |
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72 | } |
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73 | } |
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74 | |
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75 | ?> |
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