Re: [PATCH v2 2/2] sha1_file: improve sha1_file_name() perfs

[Jeff Hostetler <git@jeffhostetler.com>]

On 1/17/2018 12:54 PM, Christian Couder wrote:
> As sha1_file_name() could be performance sensitive, let's
> try to make it faster by seeding the initial buffer size
> to avoid any need to realloc and by using strbuf_addstr()
> and strbuf_addc() instead of strbuf_addf().
> 
> Helped-by: Derrick Stolee <stolee@gmail.com>
> Helped-by: Jeff Hostetler <git@jeffhostetler.com>
> Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
> ---
>   sha1_file.c | 8 +++++++-
>   1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/sha1_file.c b/sha1_file.c
> index f66c21b2da..1a94716962 100644
> --- a/sha1_file.c
> +++ b/sha1_file.c
> @@ -323,8 +323,14 @@ static void fill_sha1_path(struct strbuf *buf, const unsigned char *sha1)
>   
>   void sha1_file_name(struct strbuf *buf, const unsigned char *sha1)
>   {
> -	strbuf_addf(buf, "%s/", get_object_directory());
> +	const char *obj_dir = get_object_directory();
> +	size_t extra = strlen(obj_dir) + 1 + GIT_MAX_HEXSZ;

Very minor nit.  Should this be "+3" rather than "+1"?
One for the slash after obj_dir, one for the slash between
"xx/y[38]", and one for the trailing NUL.

>   
> +	if (extra > strbuf_avail(buf))
> +		strbuf_grow(buf, extra);
> +
> +	strbuf_addstr(buf, obj_dir);
> +	strbuf_addch(buf, '/');
>   	fill_sha1_path(buf, sha1);
>   }
>   
>