public function read_longlong()
    {
        $this->bitcount = $this->bits = 0;

        list(, $hi, $lo) = unpack('N2', $this->rawread(8));
        $msb = self::getLongMSB($hi);

        if (empty($this->is64bits)) {
            if ($msb) {
                $hi = sprintf('%u', $hi);
            }
            if (self::getLongMSB($lo)) {
                $lo = sprintf('%u', $lo);
            }
        }

        return bcadd($this->is64bits && !$msb ? $hi << 32 : bcmul($hi, '4294967296', 0), $lo, 0);
    }