Re: Domain name label length

On Mon, Dec 25, 2017 at 10:38 PM, Michael Powell <[email protected]> wrote:
> Hello,
>
> So, a domain name label looks something like this, in general, right?
>
> _label = _let >> *(_let | _dig | _hyp) >> (_let | _dig);
>
> However, another stipulation is that its length must be <=63 according
> to the RFC:
>
> https://tools.ietf.org/html/rfc1034#section-3.5
>
> So... Is there a way to constrain that using Qi?

Untested, but at least according to this post:

http://boost.2283326.n4.nabble.com/How-to-restrict-an-integer-to-digits-and-specific-range-td2681120.html

The key seems to be in Semantic Actions.

struct validate_label_length {
    template<typename Context>
    void operator()(std::string& label, Context&, bool& pass) {
        pass = label.length() <= 63;
    }
};

And which rule would be:

_label = raw[_let >> -(*(_let | _dig | _hyp) >> (_let |
_dig))][validate_label_length()];


> Cheers,
>
> Michael Powell

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