CryptLib/Core/BaseConverter.php

   1 <?php
   2
   3 /**
   4  * A Utility class for converting between raw binary strings and a given
   5  * list of characters
   6  *
   7  * PHP version 5.3
   8  *
   9  * @category   PHPCryptLib
  10  * @package    Core
  11  * @author     Anthony Ferrara <ircmaxell@ircmaxell.com>
  12  * @copyright  2011 The Authors
  13  * @license    http://www.opensource.org/licenses/mit-license.html  MIT License
  14  * @version    Build @@version@@
  15  */
  16
  17 namespace CryptLib\Core;
  18
  19 /**
  20  * A Utility class for converting between raw binary strings and a given
  21  * list of characters
  22  *
  23  * @category   PHPCryptLib
  24  * @package    Core
  25  * @author     Anthony Ferrara <ircmaxell@ircmaxell.com>
  26  */
  27 class BaseConverter {
  28
  29     /**
  30      * Convert from a raw binary string to a string of characters
  31      *
  32      * @param string $string     The string to convert from
  33      * @param string $characters The list of characters to convert to
  34      *
  35      * @return string The converted string
  36      */
  37     public static function convertFromBinary($string, $characters) {
  38         if ($string === '' || empty($characters)) {
  39             return '';
  40         }
  41         $string   = str_split($string);
  42         $callback = function($str) {
  43                 return ord($str);
  44             };
  45         $string    = array_map($callback, $string);
  46         $converted = static::baseConvert($string, 256, strlen($characters));
  47         $callback  = function ($num) use ($characters) {
  48                 return $characters[$num];
  49             };
  50         $ret = implode('', array_map($callback, $converted));
  51         return $ret;
  52     }
  53
  54     /**
  55      * Convert to a raw binary string from a string of characters
  56      *
  57      * @param string $string     The string to convert from
  58      * @param string $characters The list of characters to convert to
  59      *
  60      * @return string The converted string
  61      */
  62     public static function convertToBinary($string, $characters) {
  63         if (empty($string) || empty($characters)) {
  64             return '';
  65         }
  66         $string   = str_split($string);
  67         $callback = function($str) use ($characters) {
  68                 return strpos($characters, $str);
  69             };
  70         $string    = array_map($callback, $string);
  71         $converted = static::baseConvert($string, strlen($characters), 256);
  72         $callback  = function ($num) {
  73                 return chr($num);
  74             };
  75         return implode('', array_map($callback, $converted));
  76     }
  77
  78     /**
  79      * Convert an array of input blocks to another numeric base
  80      *
  81      * This function was modified from an implementation found on StackOverflow.
  82      * Special Thanks to @KeithRandall for supplying the implementation.
  83      *
  84      * @param int[] $source  The source number, as an array
  85      * @param int   $srcBase The source base as an integer
  86      * @param int   $dstBase The destination base as an integer
  87      *
  88      * @see http://codegolf.stackexchange.com/questions/1620/arb/1626#1626
  89      * @return int[] An array of integers in the encoded base
  90      */
  91     public static function baseConvert(array $source, $srcBase, $dstBase) {
  92         if ($dstBase < 2) {
  93             $message = sprintf('Invalid Destination Base: %d', $dstBase);
  94             throw new \InvalidArgumentException($message);
  95         }
  96         $result = array();
  97         $count  = count($source);
  98         while ($count) {
  99             $itMax     = $count;
 100             $remainder = $count = $i = 0;
 101             while($i < $itMax) {
 102                 $dividend  = $source[$i++] + $remainder * $srcBase;
 103                 $remainder = $dividend % $dstBase;
 104                 $res       = ($dividend - $remainder) / $dstBase;
 105                 if ($count || $res) {
 106                     $source[$count++] = $res;
 107                 }
 108             }
 109             $result[] = $remainder;
 110         }
 111         return array_reverse($result);
 112     }
 113
 114 }