Hi ZheNing
On 30/05/2021 07:29, ZheNing Hu wrote:
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;
I think the new version looks fine apart from these casts. vs1 declared
as 'const void *' in the function signature so this cast does not do
anything. You could cast using (const char *) instead if you wanted but
that is not required as you can assign a 'const void *' to 'const
whatever *' without a cast.
Best Wishes
Phillip
+ 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
