Re: netsec 682578f 4/6: Add option to bypass NSM TLS checks on local networks

[Eli Zaretskii <eliz@gnu.org>]

> From: Robert Pluim <rpluim@gmail.com>
> Cc: emacs-devel@gnu.org
> Date: Tue, 17 Jul 2018 12:09:10 +0200
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> >
> > Then I think we should test that it's either a unibyte string or a
> > string whose size in bytes is equal to its size in characters, and
> > signal an error if that doesn't hold.
> 
> So I tried using STRING_MULTIBYTE, but of course eww uses
> puny-encode-domain on unicode hostnames, and that returns a multibyte
> string that only contains ASCII characters. Rather than opening that
> can of worms, I settled on checking
> 
> SBYTES (host) != SCHARS (host)

This will signal an error for unibyte strings, because there SBYTES is
always -1.  So I think you should do this instead:

  STRING_MULTIBYTE (host) && SBYTES (host) != SCHARS (host)

> I couldn't find an "is this a pure-ASCII string" function.

It is rarely needed, IME.