Subject: Re: [PATCH 3/3] pretty=format: Avoid some expensive calculations when not needed

From: René Scharfe <[email-masked]>
Date: Mon, 05 Nov 2007 21:21:03 +0100

Junio C Hamano schrieb:
> Johannes Schindelin <[email-masked]> writes:
> 
>> Unfortunately, we cannot reuse the result of that function, which
>> would be cleaner: there are more users than just git log.  Most
>> notably, git-archive with "$Format:...$" substitution.
> 
> That makes sense.
> 
> 
>> diff --git a/pretty.c b/pretty.c
>> index 490cede..241e91c 100644
>> --- a/pretty.c
>> +++ b/pretty.c
>> @@ -393,6 +393,7 @@ void format_commit_message(const struct commit *commit,
>>  	int i;
>>  	enum { HEADER, SUBJECT, BODY } state;
>>  	const char *msg = commit->buffer;
>> +	char *active = interp_find_active(format, table, ARRAY_SIZE(table));
>> ...
>> +	if (active[IHASH])
>> +		interp_set_entry(table, IHASH,
>> +				sha1_to_hex(commit->object.sha1));
>> +	if (active[IHASH_ABBREV])
>> +		interp_set_entry(table, IHASH_ABBREV,
>>  			find_unique_abbrev(commit->object.sha1,
>>  				DEFAULT_ABBREV));
> 
> Instead of allocating a separate array and freeing at the end,
> wouldn't it make more sense to have a bitfield that records what
> is used by the format string inside the array elements?

How about (ab)using the value field?  Let interp_find_active() mark
unneeded entries with NULL, and the rest with some cookie.  All table
entries with non-NULL values need to be initialized.  interp_set_entry()
needs to be aware of this cookie, as it mustn't free() it.  The cookie
could be the address of a static char* in interpolate.c.