Re: [PATCH 2/2] commit: don't check for space twice when looking for header

["René Scharfe" <l.s.r@web.de>]

Am 27.02.2017 um 23:27 schrieb Jakub Narębski:
> W dniu 25.02.2017 o 20:27, René Scharfe pisze:
>> Both standard_header_field() and excluded_header_field() check if
>> there's a space after the buffer that's handed to them.  We already
>> check in the caller if that space is present.  Don't bother calling
>> the functions if it's missing, as they are guaranteed to return 0 in
>> that case, and remove the now redundant checks from them.
>>
>> Signed-off-by: Rene Scharfe <l.s.r@web.de>
>> ---
>>  commit.c | 18 ++++++++----------
>>  1 file changed, 8 insertions(+), 10 deletions(-)
>>
>> diff --git a/commit.c b/commit.c
>> index 173c6d3818..fab8269731 100644
>> --- a/commit.c
>> +++ b/commit.c
>> @@ -1308,11 +1308,11 @@ void for_each_mergetag(each_mergetag_fn fn, struct commit *commit, void *data)
>>
>>  static inline int standard_header_field(const char *field, size_t len)
>>  {
>> -	return ((len == 4 && !memcmp(field, "tree ", 5)) ||
>> -		(len == 6 && !memcmp(field, "parent ", 7)) ||
>> -		(len == 6 && !memcmp(field, "author ", 7)) ||
>> -		(len == 9 && !memcmp(field, "committer ", 10)) ||
>> -		(len == 8 && !memcmp(field, "encoding ", 9)));
>> +	return ((len == 4 && !memcmp(field, "tree", 4)) ||
>> +		(len == 6 && !memcmp(field, "parent", 6)) ||
>> +		(len == 6 && !memcmp(field, "author", 6)) ||
>> +		(len == 9 && !memcmp(field, "committer", 9)) ||
>> +		(len == 8 && !memcmp(field, "encoding", 8)));
>
> I agree (for what it is worth from me) with the rest of changes,
> but I think current code is better self-documenting for this
> function.

Having a function that is given a buffer/length pair and accessing the 
byte after it raises questions, though. :)

Nicer than keeping the space would be to use excluded_header_field() for 
standard headers as well as a next step, I think -- but that would be a 
bit slower.

>
>>  }
>>
>>  static int excluded_header_field(const char *field, size_t len, const char **exclude)
>> @@ -1322,8 +1322,7 @@ static int excluded_header_field(const char *field, size_t len, const char **exc
>>
>>  	while (*exclude) {
>>  		size_t xlen = strlen(*exclude);
>> -		if (len == xlen &&
>> -		    !memcmp(field, *exclude, xlen) && field[xlen] == ' ')
>> +		if (len == xlen && !memcmp(field, *exclude, xlen))
>>  			return 1;
>>  		exclude++;
>>  	}
>> @@ -1357,9 +1356,8 @@ static struct commit_extra_header *read_commit_extra_header_lines(
>>  		eof = memchr(line, ' ', next - line);
>>  		if (!eof)
>>  			eof = next;
>> -
>> -		if (standard_header_field(line, eof - line) ||
>> -		    excluded_header_field(line, eof - line, exclude))
>> +		else if (standard_header_field(line, eof - line) ||
>> +			 excluded_header_field(line, eof - line, exclude))
>>  			continue;
>>
>>  		it = xcalloc(1, sizeof(*it));
>>
>