Re: mbcel module for Gnulib?, incomplete multibyte sequences

[Paul Eggert]

On 2023-07-21 17:33, Bruno Haible wrote:
> It gets this info from mbrtoc32, which on most platforms gets this info
> from mbrtowc. This multibyte scanner knows when the bytes it has seen
> so far constitute
>    - a complete character, or
>    - an invalid character, or
>    - an incomplete character (i.e. if additional bytes may lead to a
>      complete character).

Ah, I had thought that the idea was to treat all the bytes of a byte 
sequence from 10646-1[1] R.2 Table 1 as a single invalid "character" 
(i.e., not a real character) if the byte sequence is not valid UTF-8. 
That's what Kuhn seems to be suggesting in [2].

But what you're saying is something different, that could be implemented 
by calling mbrtoc32.

For example, as I understand it, the byte sequence F4 90 80 80, which I 
had thought you were saying would be treated as a single byte sequence 
[F4 90 80 80] because that's in R.2 Table 1, would instead be treated as 
[F4 90] [80] [80], because [F4 90] is not an incomplete character 
(additional bytes cannot lead to a complete character).

Is this right?

[1]: https://www.cl.cam.ac.uk/~mgk25/ucs/ISO-10646-UTF-8.html
[2]: https://www.cl.cam.ac.uk/~mgk25/ucs/examples/UTF-8-test.txt