From: Phillip Wood <phillip.wood123@gmail.com>
Date: Sun, 30 May 2021 13:05:55 GMT
Subject: Re: [PATCH 1/2] [GSOC] ref-filter: add %(raw) atom
Message-ID: <2c28515c-89b1-79dd-35a2-492eac6b7347@gmail.com>
In-Reply-To: <CAOLTT8TEkrxAgHvkCVXZDQpn0xSQAe_y7uMF89Q4QWwVd7MDcA@mail.gmail.com>

Hi ZheNing

On 30/05/2021 07:29, ZheNing Hu wrote:
> Felipe Contreras <felipe.contreras@gmail.com> 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
>