protected function _unicode()
    {
        $str_unicode = '';

        $this->__get('bytes');
        $this->col_bytes->rewind();
        $int_nb_bytes = count($this->col_bytes);

        foreach ($this->col_bytes as $k => $src) {

            if (is_string($src)) {
                $str_bin = (string) decbin(hexdec($src));
            } else {
                $str_bin = (string) decbin($src->value);
            }

            if ($int_nb_bytes > 1) {
                if ($k == 0) {
                    $str_unicode .= substr($str_bin, $int_nb_bytes + 1);
                } else {
                    $str_unicode .= substr($str_bin, 2);
                }
            } else {
                $str_unicode .= substr($str_bin, 0);
            }
        }

        return new N(bindec($str_unicode));
    }