protected function readBinaryString($length)
    {
        if ($length == 0) {
            $buff = "";
        } else {
            if (strlen($buff = substr($this->content, $this->pos, $length)) != $length) {
                throw IOException::readError("");
            }
            $this->pos += $length;
        }

        if (!isset($this->uniqueTable[$buff])) {
            $this->uniqueTable[$buff] = true;
        }
        return new CFString($buff);
    }