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pixelfed/app/Util/Blurhash/Base83.php

39 lines
1.3 KiB
PHP

<?php
namespace App\Util\Blurhash;
use InvalidArgumentException;
class Base83 {
private const ALPHABET = [
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D',
'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R',
'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't',
'u', 'v', 'w', 'x', 'y', 'z', '#', '$', '%', '*', '+', ',', '-', '.',
':', ';', '=', '?', '@', '[', ']', '^', '_', '{', '|', '}', '~'
];
private const BASE = 83;
public static function encode(int $value, int $length): string {
if (floor($value / (self::BASE ** $length)) != 0) {
throw new InvalidArgumentException('Specified length is too short to encode given value.');
}
$result = '';
for ($i = 1; $i <= $length; $i++) {
$digit = floor($value / (self::BASE ** ($length - $i))) % self::BASE;
$result .= self::ALPHABET[$digit];
}
return $result;
}
public static function decode(string $hash): int {
$result = 0;
foreach (str_split($hash) as $char) {
$result = $result * self::BASE + (int) array_search($char, self::ALPHABET, true);
}
return (int) $result;
}
}