Re: [PATCH 1/2] [GSOC] ref-filter: add %(raw) atom

[Phillip Wood <phillip.wood123@gmail.com>]

Hi ZheNing

On 30/05/2021 07:26, ZheNing Hu wrote:
> Phillip Wood <phillip.wood123@gmail.com> 于2021年5月29日周六 下午9:23写道：
>>
>> On 27/05/2021 17:36, Felipe Contreras wrote:
>>> ZheNing Hu via GitGitGadget wrote:
>>> [...]
>>> All we have to do is define the end point, and then we don't need i:
>>>
>>>        static int memcasecmp(const char *s1, const char *s2, size_t n)
>>>        {
>>>                const char *end = s1 + n;
>>>                for (; s1 < end; s1++, s2++) {
>>>                        int diff = tolower(*s1) - tolower(*s2);
>>>                        if (diff)
>>>                                return diff;
>>>                }
>>>                return 0;
>>>        }
>>>
>>> (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))
>>
> 
> I don’t know if we overlooked a fact: This static `memcasecmp()`
> is not a POSIX version. `tolower()` or `toupper()` are in git-compat-util.h,
> sane_istest('\0', GIT_ALPHA) == false . So in `sane_case()`, whatever
> `tolower()`, `toupper()`, they just return '\0' itself.

Well spotted, thanks for pointing that out. So memcasecmp() and 
strcasecmp() may give different results. I'm not sure if that matters - 
as I understand it the main use for the 'raw' atom is with `git cat-file 
--batch` which does not support sorting. Also although strcasecmp() uses 
the current locale it does a byte-by-byte comparison so it is 
effectively ASCII only for UTF-8 anyway.

Best Wishes

Phillip

>> Best Wishes
>>
>> Phillip
>>
>> [1] https://pubs.opengroup.org/onlinepubs/9699919799/
>> [2] https://en.wikipedia.org/wiki/Dotted_and_dotless_I#In_computing
>>
> 
> Thanks.
> --
> ZhenNing Hu
>