Dominique wrote:
> > Patch 8.2.2654
> > Problem: Vim9: getting a character from a string can be slow.
> > Solution: Avoid a function call to get the character byte size. (#8000)
> > Files: src/vim9execute.vim
> ...snip...
> > for (nbyte = 0; nbyte < slen; ++clen)
> > ! {
> > ! if (str[nbyte] < 0x80 && str[nbyte + 1] < 0x80)
> > ! ++nbyte;
> > ! else if (enc_utf8)
> > ! nbyte += utfc_ptr2len(str + nbyte);
> > ! else
> > ! nbyte += mb_ptr2len(str + nbyte);
> > ! }
>
> Is this correct? I would have thought that the following line is
> correct for utf8 encoding but not for all other encodings:
>
> if (str[nbyte] < 0x80 && str[nbyte + 1] < 0x80)
>
> So I think that loop should rather be something like this:
>
> if (enc_utf8)
> for (nbyte = 0; nbyte < slen; ++clen)
> {
> if (str[nbyte] < 0x80 && str[nbyte + 1] < 0x80)
> ++nbyte;
> else
> nbyte += utfc_ptr2len(str + nbyte);
> }
> else
> for (nbyte = 0; nbyte < slen; ++clen)
> nbyte += mb_ptr2len(str + nbyte);
You can compare with some benchmark what the difference is. I would
think that enc_utf8 is cached and the choice between utfc_ptr2len() and
mb_ptr2len() doesn't make a measurable difference. Not worth for
duplicating the loop.
AFAIK there is no encoding where a character with a first byte below
0x80 takes more than one byte.
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