Re: [PATCH 8/9] sha1-file: use loose object cache for quick existence check

["René Scharfe" <l.s.r@web.de>]

Am 05.12.2018 um 09:15 schrieb Jeff King:
> On Wed, Dec 05, 2018 at 01:51:36AM -0500, Jeff King wrote:
> 
>>> This
>>> function is easily converted to struct object_id, though, as its single
>>> caller can pass one on -- this makes the copy unnecessary.
>>
>> If you mean modifying sha1_loose_object_info() to take an oid, then
>> sure, I agree that is a good step forward (and that is exactly the "punt
>> until" moment I meant).
> 
> So the simple thing is to do that, and then have it pass oid->hash to
> the other functions it uses.

Yes.

> If we start to convert those, there's a
> little bit of a rabbit hole, but it's actually not too bad.

You don't need to crawl in just for quick_has_loose(), but eventually
everything has to be converted.  It seems a bit much for one patch, but
perhaps that's just my ever-decreasing attention span speaking.

Converting one function prototype or struct member at a time seems
about the right amount of change per patch to me.  That's not always
possible due to entanglement, of course.

> Most of the spill-over is into the dumb-http code. Note that it actually
> uses sha1 itself! That probably needs to be the_hash_algo (though I'm
> not even sure how we'd negotiate the algorithm across a dumb fetch). At
> any rate, I don't think this patch makes anything _worse_ in that
> respect.

Right.

> diff --git a/sha1-file.c b/sha1-file.c
> index 3ddf4c9426..0705709036 100644
> --- a/sha1-file.c
> +++ b/sha1-file.c
> @@ -333,12 +333,12 @@ int raceproof_create_file(const char *path, create_file_fn fn, void *cb)
>  	return ret;
>  }
>  
> -static void fill_sha1_path(struct strbuf *buf, const unsigned char *sha1)
> +static void fill_loose_path(struct strbuf *buf, const struct object_id *oid)

The new name fits.

> @@ -879,15 +879,15 @@ int git_open_cloexec(const char *name, int flags)
>   * Note that it may point to static storage and is only valid until another
>   * call to stat_sha1_file().
>   */
> -static int stat_sha1_file(struct repository *r, const unsigned char *sha1,
> -			  struct stat *st, const char **path)
> +static int stat_loose_object(struct repository *r, const struct object_id *oid,
> +			     struct stat *st, const char **path)

Hmm, read_sha1_file() was renamed to read_object_file() earlier this
year, and I'd have expected this to become stat_object_file().  Names..

Anyway, the comment above and one a few lines below should be updated
as well.

>  {
>  	struct object_directory *odb;
>  	static struct strbuf buf = STRBUF_INIT;
>  
>  	prepare_alt_odb(r);
>  	for (odb = r->objects->odb; odb; odb = odb->next) {
> -		*path = odb_loose_path(odb, &buf, sha1);
> +		*path = odb_loose_path(odb, &buf, oid);
>  		if (!lstat(*path, st))
>  			return 0;
>  	}
> @@ -900,7 +900,7 @@ static int stat_sha1_file(struct repository *r, const unsigned char *sha1,
>   * descriptor. See the caveats on the "path" parameter above.
>   */
>  static int open_sha1_file(struct repository *r,
> -			  const unsigned char *sha1, const char **path)
> +			  const struct object_id *oid, const char **path)

That function should lose the "sha1" in its name as well.

> -static void *map_sha1_file_1(struct repository *r, const char *path,
> -			     const unsigned char *sha1, unsigned long *size)
> +static void *map_loose_object_1(struct repository *r, const char *path,
> +			     const struct object_id *oid, unsigned long *size)

Similarly, map_object_file_1()?

> -void *map_sha1_file(struct repository *r,
> -		    const unsigned char *sha1, unsigned long *size)
> +void *map_loose_object(struct repository *r,
> +		       const struct object_id *oid,
> +		       unsigned long *size)

Similar.

> @@ -1045,7 +1043,9 @@ static int unpack_sha1_header_to_strbuf(git_zstream *stream, unsigned char *map,
>  	return -1;
>  }
>  
> -static void *unpack_sha1_rest(git_zstream *stream, void *buffer, unsigned long size, const unsigned char *sha1)
> +static void *unpack_loose_rest(git_zstream *stream,
> +			       void *buffer, unsigned long size,
> +			       const struct object_id *oid)

Hmm, both old and new name here look weird to me at this point.

> -static int sha1_loose_object_info(struct repository *r,
> -				  const unsigned char *sha1,
> -				  struct object_info *oi, int flags)
> +static int loose_object_info(struct repository *r,
> +			     const struct object_id *oid,
> +			     struct object_info *oi, int flags)

And nothing of value was lost. :)

René