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<?php
declare(strict_types=1);
namespace Base32;
/**
* Base32 encoder and decoder.
*
* RFC 4648 compliant
*
* @see 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>
* @author Sam Williams <sam@badcow.co>
*
* @see http://christianriesen.com
*
* @license MIT License see LICENSE file
*/
class Base32
{
/**
* Alphabet for encoding and decoding base32.
*
* @var string
*/
protected const ALPHABET = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ234567=';
protected const BASE32HEX_PATTERN = '/[^A-Z2-7]/';
/**
* Maps the Base32 character to its corresponding bit value.
*/
protected const MAPPING = [
'=' => 0b00000,
'A' => 0b00000,
'B' => 0b00001,
'C' => 0b00010,
'D' => 0b00011,
'E' => 0b00100,
'F' => 0b00101,
'G' => 0b00110,
'H' => 0b00111,
'I' => 0b01000,
'J' => 0b01001,
'K' => 0b01010,
'L' => 0b01011,
'M' => 0b01100,
'N' => 0b01101,
'O' => 0b01110,
'P' => 0b01111,
'Q' => 0b10000,
'R' => 0b10001,
'S' => 0b10010,
'T' => 0b10011,
'U' => 0b10100,
'V' => 0b10101,
'W' => 0b10110,
'X' => 0b10111,
'Y' => 0b11000,
'Z' => 0b11001,
'2' => 0b11010,
'3' => 0b11011,
'4' => 0b11100,
'5' => 0b11101,
'6' => 0b11110,
'7' => 0b11111,
];
/**
* Encodes into base32.
*
* @param string $string Clear text string
*
* @return string Base32 encoded string
*/
public static function encode(string $string): string
{
// Empty string results in empty string
if ('' === $string) {
return '';
}
$encoded = '';
//Set the initial values
$n = $bitLen = $val = 0;
$len = \strlen($string);
//Pad the end of the string - this ensures that there are enough zeros
$string .= \str_repeat(\chr(0), 4);
//Explode string into integers
$chars = (array) \unpack('C*', $string, 0);
while ($n < $len || 0 !== $bitLen) {
//If the bit length has fallen below 5, shift left 8 and add the next character.
if ($bitLen < 5) {
$val = $val << 8;
$bitLen += 8;
$n++;
$val += $chars[$n];
}
$shift = $bitLen - 5;
$encoded .= ($n - (int)($bitLen > 8) > $len && 0 == $val) ? '=' : static::ALPHABET[$val >> $shift];
$val = $val & ((1 << $shift) - 1);
$bitLen -= 5;
}
return $encoded;
}
/**
* Decodes base32.
*
* @param string $base32String Base32 encoded string
*
* @return string Clear text string
*/
public static function decode(string $base32String): string
{
// Only work in upper cases
$base32String = \strtoupper($base32String);
// Remove anything that is not base32 alphabet
$base32String = \preg_replace(static::BASE32HEX_PATTERN, '', $base32String);
// Empty string results in empty string
if ('' === $base32String || null === $base32String) {
return '';
}
$decoded = '';
//Set the initial values
$len = \strlen($base32String);
$n = 0;
$bitLen = 5;
$val = static::MAPPING[$base32String[0]];
while ($n < $len) {
//If the bit length has fallen below 8, shift left 5 and add the next pentet.
if ($bitLen < 8) {
$val = $val << 5;
$bitLen += 5;
$n++;
$pentet = $base32String[$n] ?? '=';
//If the new pentet is padding, make this the last iteration.
if ('=' === $pentet) {
$n = $len;
}
$val += static::MAPPING[$pentet];
continue;
}
$shift = $bitLen - 8;
$decoded .= \chr($val >> $shift);
$val = $val & ((1 << $shift) - 1);
$bitLen -= 8;
}
return $decoded;
}
}