| 1 | <?php |
| 2 | /** |
| 3 | * A class for arbitrary precision math functions implemented in PHP |
| 4 | * |
| 5 | * PHP version 5.3 |
| 6 | * |
| 7 | * @category PHPCryptLib |
| 8 | * @package Core |
| 9 | * @subpackage BigMath |
| 10 | * @author Anthony Ferrara <ircmaxell@ircmaxell.com> |
| 11 | * @copyright 2011 The Authors |
| 12 | * @license http://www.opensource.org/licenses/mit-license.html MIT License |
| 13 | * @version Build @@version@@ |
| 14 | */ |
| 15 | namespace CryptLib\Core\BigMath; |
| 16 | |
| 17 | use CryptLib\Core\BaseConverter; |
| 18 | |
| 19 | /** |
| 20 | * A class for arbitrary precision math functions implemented in PHP |
| 21 | * |
| 22 | * @category PHPCryptLib |
| 23 | * @package Core |
| 24 | * @subpackage BigMath |
| 25 | */ |
| 26 | class PHPMath extends \CryptLib\Core\BigMath { |
| 27 | |
| 28 | /** |
| 29 | * Add two numbers together |
| 30 | * |
| 31 | * @param string $left The left argument |
| 32 | * @param string $right The right argument |
| 33 | * |
| 34 | * @return A base-10 string of the sum of the two arguments |
| 35 | */ |
| 36 | public function add($left, $right) { |
| 37 | if (empty($left)) { |
| 38 | return $right; |
| 39 | } elseif (empty($right)) { |
| 40 | return $left; |
| 41 | } |
| 42 | $negative = ''; |
| 43 | if ($left[0] == '-' && $right[0] == '-') { |
| 44 | $negative = '-'; |
| 45 | $left = substr($left, 1); |
| 46 | $right = substr($right, 1); |
| 47 | } elseif ($left[0] == '-') { |
| 48 | return $this->subtract($right, substr($left, 1)); |
| 49 | } elseif ($right[0] == '-') { |
| 50 | return $this->subtract($left, substr($right, 1)); |
| 51 | } |
| 52 | $left = $this->normalize($left); |
| 53 | $right = $this->normalize($right); |
| 54 | $result = BaseConverter::convertFromBinary( |
| 55 | $this->addBinary($left, $right), |
| 56 | '0123456789' |
| 57 | ); |
| 58 | return $negative . $result; |
| 59 | } |
| 60 | |
| 61 | /** |
| 62 | * Subtract two numbers |
| 63 | * |
| 64 | * @param string $left The left argument |
| 65 | * @param string $right The right argument |
| 66 | * |
| 67 | * @return A base-10 string of the difference of the two arguments |
| 68 | */ |
| 69 | public function subtract($left, $right) { |
| 70 | if (empty($left)) { |
| 71 | return $right; |
| 72 | } elseif (empty($right)) { |
| 73 | return $left; |
| 74 | } elseif ($right[0] == '-') { |
| 75 | return $this->add($left, substr($right, 1)); |
| 76 | } elseif ($left[0] == '-') { |
| 77 | return '-' . $this->add(ltrim($left, '-'), $right); |
| 78 | } |
| 79 | $left = $this->normalize($left); |
| 80 | $right = $this->normalize($right); |
| 81 | $results = $this->subtractBinary($left, $right); |
| 82 | $result = BaseConverter::convertFromBinary($results[1], '0123456789'); |
| 83 | return $results[0] . $result; |
| 84 | } |
| 85 | |
| 86 | /** |
| 87 | * Add two binary strings together |
| 88 | * |
| 89 | * @param string $left The left argument |
| 90 | * @param string $right The right argument |
| 91 | * |
| 92 | * @return string The binary result |
| 93 | */ |
| 94 | protected function addBinary($left, $right) { |
| 95 | $len = max(strlen($left), strlen($right)); |
| 96 | $left = str_pad($left, $len, chr(0), STR_PAD_LEFT); |
| 97 | $right = str_pad($right, $len, chr(0), STR_PAD_LEFT); |
| 98 | $result = ''; |
| 99 | $carry = 0; |
| 100 | for ($i = 0; $i < $len; $i++) { |
| 101 | $sum = ord($left[$len - $i - 1]) |
| 102 | + ord($right[$len - $i - 1]) |
| 103 | + $carry; |
| 104 | $result .= chr($sum % 256); |
| 105 | $carry = $sum >> 8; |
| 106 | } |
| 107 | while ($carry) { |
| 108 | $result .= chr($carry % 256); |
| 109 | $carry >>= 8; |
| 110 | } |
| 111 | return strrev($result); |
| 112 | } |
| 113 | |
| 114 | /** |
| 115 | * Subtract two binary strings using 256's compliment |
| 116 | * |
| 117 | * @param string $left The left argument |
| 118 | * @param string $right The right argument |
| 119 | * |
| 120 | * @return string The binary result |
| 121 | */ |
| 122 | protected function subtractBinary($left, $right) { |
| 123 | $len = max(strlen($left), strlen($right)); |
| 124 | $left = str_pad($left, $len, chr(0), STR_PAD_LEFT); |
| 125 | $right = str_pad($right, $len, chr(0), STR_PAD_LEFT); |
| 126 | $right = $this->compliment($right); |
| 127 | $result = $this->addBinary($left, $right); |
| 128 | if (strlen($result) > $len) { |
| 129 | // Positive Result |
| 130 | $carry = substr($result, 0, -1 * $len); |
| 131 | $result = substr($result, strlen($carry)); |
| 132 | return array( |
| 133 | '', |
| 134 | $this->addBinary($result, $carry) |
| 135 | ); |
| 136 | } |
| 137 | return array('-', $this->compliment($result)); |
| 138 | } |
| 139 | |
| 140 | /** |
| 141 | * Take the 256 base compliment |
| 142 | * |
| 143 | * @param string $string The binary string to compliment |
| 144 | * |
| 145 | * @return string The complimented string |
| 146 | */ |
| 147 | protected function compliment($string) { |
| 148 | $result = ''; |
| 149 | $len = strlen($string); |
| 150 | for ($i = 0; $i < $len; $i++) { |
| 151 | $result .= chr(255 - ord($string[$i])); |
| 152 | } |
| 153 | return $result; |
| 154 | } |
| 155 | |
| 156 | /** |
| 157 | * Transform a string number into a binary string using base autodetection |
| 158 | * |
| 159 | * @param string $string The string to transform |
| 160 | * |
| 161 | * @return string The binary transformed number |
| 162 | */ |
| 163 | protected function normalize($string) { |
| 164 | return BaseConverter::convertToBinary( |
| 165 | $string, |
| 166 | '0123456789' |
| 167 | ); |
| 168 | } |
| 169 | |
| 170 | } |