function ByteString::fromRandom

File

vendor/symfony/string/ByteString.php, line 46

Class

ByteString

Represents a binary-safe string of bytes.

Namespace

Symfony\Component\String

Code

public static function fromRandom(int $length = 16, ?string $alphabet = null) : self {
    if ($length <= 0) {
        throw new InvalidArgumentException(\sprintf('A strictly positive length is expected, "%d" given.', $length));
    }
    $alphabet ??= self::ALPHABET_ALPHANUMERIC;
    $alphabetSize = \strlen($alphabet);
    $bits = (int) ceil(log($alphabetSize, 2.0));
    if ($bits <= 0 || $bits > 56) {
        throw new InvalidArgumentException('The length of the alphabet must in the [2^1, 2^56] range.');
    }
    if (\PHP_VERSION_ID >= 80300) {
        return new static((new Randomizer())->getBytesFromString($alphabet, $length));
    }
    $ret = '';
    while ($length > 0) {
        $urandomLength = (int) ceil(2 * $length * $bits / 8.0);
        $data = random_bytes($urandomLength);
        $unpackedData = 0;
        $unpackedBits = 0;
        for ($i = 0; $i < $urandomLength && $length > 0; ++$i) {
            // Unpack 8 bits
            $unpackedData = $unpackedData << 8 | \ord($data[$i]);
            $unpackedBits += 8;
            // While we have enough bits to select a character from the alphabet, keep
            // consuming the random data
            for (; $unpackedBits >= $bits && $length > 0; $unpackedBits -= $bits) {
                $index = $unpackedData & (1 << $bits) - 1;
                $unpackedData >>= $bits;
                // Unfortunately, the alphabet size is not necessarily a power of two.
                // Worst case, it is 2^k + 1, which means we need (k+1) bits and we
                // have around a 50% chance of missing as k gets larger
                if ($index < $alphabetSize) {
                    $ret .= $alphabet[$index];
                    --$length;
                }
            }
        }
    }
    return new static($ret);
}