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<?php
/**
* A class for arbitrary precision math functions implemented in PHP
*
* PHP version 5.3
*
* @category PHPPasswordLib
* @package Core
* @subpackage BigMath
* @author Anthony Ferrara <ircmaxell@ircmaxell.com>
* @copyright 2011 The Authors
* @license http://www.opensource.org/licenses/mit-license.html MIT License
* @version Build @@version@@
*/
namespace SecurityLib\BigMath;
use SecurityLib\BaseConverter;
/**
* A class for arbitrary precision math functions implemented in PHP
*
* @category PHPPasswordLib
* @package Core
* @subpackage BigMath
*/
class PHPMath extends \SecurityLib\BigMath {
/**
* Add two numbers together
*
* @param string $left The left argument
* @param string $right The right argument
*
* @return A base-10 string of the sum of the two arguments
*/
public function add($left, $right) {
if (empty($left)) {
return $right;
} elseif (empty($right)) {
return $left;
}
$negative = '';
if ($left[0] == '-' && $right[0] == '-') {
$negative = '-';
$left = substr($left, 1);
$right = substr($right, 1);
} elseif ($left[0] == '-') {
return $this->subtract($right, substr($left, 1));
} elseif ($right[0] == '-') {
return $this->subtract($left, substr($right, 1));
}
$left = $this->normalize($left);
$right = $this->normalize($right);
$result = BaseConverter::convertFromBinary(
$this->addBinary($left, $right),
'0123456789'
);
return $negative . $result;
}
/**
* Subtract two numbers
*
* @param string $left The left argument
* @param string $right The right argument
*
* @return A base-10 string of the difference of the two arguments
*/
public function subtract($left, $right) {
if (empty($left)) {
return $right;
} elseif (empty($right)) {
return $left;
} elseif ($right[0] == '-') {
return $this->add($left, substr($right, 1));
} elseif ($left[0] == '-') {
return '-' . $this->add(ltrim($left, '-'), $right);
}
$left = $this->normalize($left);
$right = $this->normalize($right);
$results = $this->subtractBinary($left, $right);
$result = BaseConverter::convertFromBinary($results[1], '0123456789');
return $results[0] . $result;
}
/**
* Add two binary strings together
*
* @param string $left The left argument
* @param string $right The right argument
*
* @return string The binary result
*/
protected function addBinary($left, $right) {
$len = max(strlen($left), strlen($right));
$left = str_pad($left, $len, chr(0), STR_PAD_LEFT);
$right = str_pad($right, $len, chr(0), STR_PAD_LEFT);
$result = '';
$carry = 0;
for ($i = 0; $i < $len; $i++) {
$sum = ord($left[$len - $i - 1])
+ ord($right[$len - $i - 1])
+ $carry;
$result .= chr($sum % 256);
$carry = $sum >> 8;
}
while ($carry) {
$result .= chr($carry % 256);
$carry >>= 8;
}
return strrev($result);
}
/**
* Subtract two binary strings using 256's compliment
*
* @param string $left The left argument
* @param string $right The right argument
*
* @return string The binary result
*/
protected function subtractBinary($left, $right) {
$len = max(strlen($left), strlen($right));
$left = str_pad($left, $len, chr(0), STR_PAD_LEFT);
$right = str_pad($right, $len, chr(0), STR_PAD_LEFT);
$right = $this->compliment($right);
$result = $this->addBinary($left, $right);
if (strlen($result) > $len) {
// Positive Result
$carry = substr($result, 0, -1 * $len);
$result = substr($result, strlen($carry));
return array(
'',
$this->addBinary($result, $carry)
);
}
return array('-', $this->compliment($result));
}
/**
* Take the 256 base compliment
*
* @param string $string The binary string to compliment
*
* @return string The complimented string
*/
protected function compliment($string) {
$result = '';
$len = strlen($string);
for ($i = 0; $i < $len; $i++) {
$result .= chr(255 - ord($string[$i]));
}
return $result;
}
/**
* Transform a string number into a binary string using base autodetection
*
* @param string $string The string to transform
*
* @return string The binary transformed number
*/
protected function normalize($string) {
return BaseConverter::convertToBinary(
$string,
'0123456789'
);
}
}
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