Felipe Contreras <felipe.contre...@gmail.com> writes:

> On Wed, May 1, 2013 at 11:20 AM, Ramkumar Ramachandra
> <artag...@gmail.com> wrote:
>> The @-parsing loop unnecessarily checks for the sequence "@{" from
>> len - 2 unnecessarily.  We can safely check from len - 4: write out a
>> comment justifying this.
>>
>> Signed-off-by: Ramkumar Ramachandra <artag...@gmail.com>
>> ---
>>  sha1_name.c | 18 +++++++++++++++++-
>>  1 file changed, 17 insertions(+), 1 deletion(-)
>>
>> diff --git a/sha1_name.c b/sha1_name.c
>> index 3820f28..be1d12c 100644
>> --- a/sha1_name.c
>> +++ b/sha1_name.c
>> @@ -445,7 +445,23 @@ static int get_sha1_basic(const char *str, int len, 
>> unsigned char *sha1)
>>         /* basic@{time or number or -number} format to query ref-log */
>>         reflog_len = at = 0;
>>         if (len && str[len-1] == '}') {
>> -               for (at = len-2; at >= 0; at--) {
>> +               /* str = @}
>> +                *       ^
>> +                *       len - 2; expression is senseless
>> +                *
>> +                * str = @{}
>> +                *       ^
>> +                *       len - 3; expression is still senseless
>> +                *
>> +                * str = @{.}
>> +                *       ^
>> +                *       len - 4 where . is any character; expression
>> +                *       is worth investigating
>> +                *
>> +                * Therefore, if str ends with }, search three
>> +                * characters earlier for @{
>> +                */
>
> I think this comment is overkill.
>
>> +               for (at = len - 4; at >= 0; at--) {
>
> The change seems OK to me, but there's no need to explain where you
> are starting, and if there's a need:
>
> /* start from where reflogs can start: @{.} */
>
> Does the trick nicely.

As the fact that nobody noticed nor bothered with the two-byte
optimization opportunity shows that this is trickier than trivial, I
agree with both of you that this change deserves an in-code comment.

    Start checking at len - 4, because there has to be at least one
    byte inside "@{.}" for it to be worth checking.

would be sufficient.  The 16-line comment is way overkill.

Not that I think this change really matters, though.

>>                         if (str[at] == '@' && str[at+1] == '{') {
>>                                 if (!upstream_mark(str + at, len - at)) {
>>                                         reflog_len = (len-1) - (at+2);
>> --
--
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