ParagonIE_Sodium_Core32_Ed25519::check_S_lt_L

    public static function check_S_lt_L($S)
    {
        if (self::strlen($S) < 32) {
            throw new SodiumException('Signature must be 32 bytes');
        }
        static $L = array(
            0xed, 0xd3, 0xf5, 0x5c, 0x1a, 0x63, 0x12, 0x58,
            0xd6, 0x9c, 0xf7, 0xa2, 0xde, 0xf9, 0xde, 0x14,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x10
        );
        /** @var array<int, int> $L */
        $c = 0;
        $n = 1;
        $i = 32;

        do {
            --$i;
            $x = self::chrToInt($S[$i]);
            $c |= (
                (($x - $L[$i]) >> 8) & $n
            );
            $n &= (
                (($x ^ $L[$i]) - 1) >> 8
            );
        } while ($i !== 0);

        return $c === 0;
    }