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<?php
namespace Base32;
/**
* Base32 encoder and decoder
*
* Last update: 2012-06-20
*
* RFC 4648 compliant
* @link http://www.ietf.org/rfc/rfc4648.txt
*
* Some groundwork based on this class
* https://github.com/NTICompass/PHP-Base32
*
* @author Christian Riesen <chris.riesen@gmail.com>
* @link http://christianriesen.com
* @license MIT License see LICENSE file
*/
class Base32
{
/**
* Alphabet for encoding and decoding base32
*
* @var array
*/
private static $alphabet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ234567=';
/**
* Creates an array from a binary string into a given chunk size
*
* @param string $binaryString String to chunk
* @param integer $bits Number of bits per chunk
* @return array
*/
private static function chunk($binaryString, $bits)
{
$binaryString = chunk_split($binaryString, $bits, ' ');
if (substr($binaryString, (strlen($binaryString)) - 1) == ' ') {
$binaryString = substr($binaryString, 0, strlen($binaryString)-1);
}
return explode(' ', $binaryString);
}
/**
* Encodes into base32
*
* @param string $string Clear text string
* @return string Base32 encoded string
*/
public static function encode($string)
{
if (strlen($string) == 0) {
// Gives an empty string
return '';
}
// Convert string to binary
$binaryString = '';
foreach (str_split($string) as $s) {
// Return each character as an 8-bit binary string
$binaryString .= sprintf('%08b', ord($s));
}
// Break into 5-bit chunks, then break that into an array
$binaryArray = self::chunk($binaryString, 5);
// Pad array to be divisible by 8
while (count($binaryArray) % 8 !== 0) {
$binaryArray[] = null;
}
$base32String = '';
// Encode in base32
foreach ($binaryArray as $bin) {
$char = 32;
if (!is_null($bin)) {
// Pad the binary strings
$bin = str_pad($bin, 5, 0, STR_PAD_RIGHT);
$char = bindec($bin);
}
// Base32 character
$base32String .= self::$alphabet[$char];
}
return $base32String;
}
/**
* Decodes base32
*
* @param string $base32String Base32 encoded string
* @return string Clear text string
*/
public static function decode($base32String)
{
// Only work in upper cases
$base32String = strtoupper($base32String);
// Remove anything that is not base32 alphabet
$pattern = '/[^A-Z2-7]/';
$base32String = preg_replace($pattern, '', $base32String);
if (strlen($base32String) == 0) {
// Gives an empty string
return '';
}
$base32Array = str_split($base32String);
$string = '';
foreach ($base32Array as $str) {
$char = strpos(self::$alphabet, $str);
// Ignore the padding character
if ($char !== 32) {
$string .= sprintf('%05b', $char);
}
}
while (strlen($string) %8 !== 0) {
$string = substr($string, 0, strlen($string)-1);
}
$binaryArray = self::chunk($string, 8);
$realString = '';
foreach ($binaryArray as $bin) {
// Pad each value to 8 bits
$bin = str_pad($bin, 8, 0, STR_PAD_RIGHT);
// Convert binary strings to ASCII
$realString .= chr(bindec($bin));
}
return $realString;
}
}
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