Felipe Contreras <felipe.contreras@xxxxxxxxx> 于2021年5月29日周六 下午11:24写道：
>
> Phillip Wood wrote:
> > On 27/05/2021 17:36, Felipe Contreras wrote:
> > > ZheNing Hu via GitGitGadget wrote:
> > > [...]
> > >> +static int memcasecmp(const void *vs1, const void *vs2, size_t n)
> > >
> > > Why void *? We can delcare as char *.
> >
> > If you look at how this function is used you'll see
> > int (*cmp_fn)(const void *, const void *, size_t);
> > cmp_fn = s->sort_flags & REF_SORTING_ICASE
> > ? memcasecmp : memcmp;
>
> Yeah, but why?
>
> We know we are comparing two char *. Presumably the reason is that
> memcmp and memcasecmp use void *, but that could be remedied with:
>
> cmp_fn = (int (*)(const char *, const char *, size_t))memcmp;
>
> That way the same cmp_fn could be used for the two cases.
>
> Either way I don't care particularly much. It also could be possible to
> use void * and do the casting in tolower().
>
I agree with Phillip's point of view here:
It would be better for memcasecmp and memcmp to be consistent.
> > > (and I personally prefer lower to upper)
> >
> > We should be using tolower() as that is what POSIX specifies for
> > strcasecmp() [1] which we are trying to emulate and there are cases[2] where
> > (tolower(c1) == tolower(c2)) != (toupper(c1) == toupper(c2))
>
> That's true.
>
How about something like this:
static int memcasecmp(const void *vs1, const void *vs2, size_t n)
{
- size_t i;
- const char *s1 = (const char *)vs1;
- const char *s2 = (const char *)vs2;
-
- for (i = 0; i < n; i++) {
- unsigned char u1 = s1[i];
- unsigned char u2 = s2[i];
- int U1 = toupper (u1);
- int U2 = toupper (u2);
- int diff = (UCHAR_MAX <= INT_MAX ? U1 - U2
- : U1 < U2 ? -1 : U2 < U1);
+ const char *s1 = (const void *)vs1;
+ const char *s2 = (const void *)vs2;
+ const char *end = s1 + n;
+
+ for (; s1 < end; s1++, s2++) {
+ int diff = tolower(*s1) - tolower(*s2);
if (diff)
return diff;
}
}
> --
> Felipe Contreras
Thanks.
--
ZheNing Hu
