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From: Taylor Blau <me@ttaylorr.com>
To: Jeff King <peff@peff.net>
Cc: Taylor Blau <me@ttaylorr.com>, git@vger.kernel.org, jrnieder@gmail.com
Subject: Re: [PATCH 01/20] pack-revindex: introduce a new API
Date: Tue, 12 Jan 2021 11:27:58 -0500
Message-ID: <X/3ODgaa9wr65M09@nand.local> (raw)
In-Reply-To: <X/1guCOGWybOzIS7@coredump.intra.peff.net>

On Tue, Jan 12, 2021 at 03:41:28AM -0500, Jeff King wrote:
> > There are four ways to interact with the reverse index. Accordingly,
> > four functions will be exported from 'pack-revindex.h' by the time that
> > the existing API is removed. A caller may:
>
> This tells us what the new API functions do. That's useful, but should
> it be in the header file itself, documenting each function?

Mm, that's a good idea. I took your suggestion for a comment at the top
of pack-revindex.h directly, and then added some of my own commentary
above each function. I avoided documenting the functions we're about to
remove for obvious reasons.

I think that the commit message is OK as-is, since it provides more of a
rationale of what operations need to exist, rather than the specifics of
each implementation.

We'll have to update these again when the on-disk format exists (i.e.,
because all of the runtimes become constant with the exception of going
to the index), but that's a topic for another series.

> > +int offset_to_pack_pos(struct packed_git *p, off_t ofs, uint32_t *pos)
>
> The types here make sense. off_t is clearly needed for a pack offset,
> and uint32_t is correct for the position fields, because packs have a
> 4-byte object count.
>
> Separating the error return from the out-parameter makes the interface
> slightly more awkward, but is needed to use the properly-sized types.
> Makes sense.

Yep, exactly.

> > +int offset_to_pack_pos(struct packed_git *p, off_t ofs, uint32_t *pos)
> > +{
> > +	int ret;
> > +
> > +	if (load_pack_revindex(p) < 0)
> > +		return -1;
>
> This one lazy-loads the revindex for us, which seems handy...
>
> > +uint32_t pack_pos_to_index(struct packed_git *p, uint32_t pos)
> > +{
> > +	if (!p->revindex)
> > +		BUG("pack_pos_to_index: reverse index not yet loaded");
> > +	if (pos >= p->num_objects)
> > +		BUG("pack_pos_to_index: out-of-bounds object at %"PRIu32, pos);
> > +	return p->revindex[pos].nr;
> > +}
>
> But these ones don't. I'm glad we at least catch it with a BUG(), but it
> makes the API a little funny. Returning an error here would require a
> similarly awkward out-parameter, I guess.

It is awkward, but (as you note downthread) the callers of
pack_pos_to_index() make it difficult to do so, so I didn't pursue it
here.

> -Peff

Thanks,
Taylor

  parent reply index

Thread overview: 121+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-08 18:16 [PATCH 00/20] pack-revindex: prepare for on-disk reverse index Taylor Blau
2021-01-08 18:16 ` [PATCH 01/20] pack-revindex: introduce a new API Taylor Blau
2021-01-12  8:41   ` Jeff King
2021-01-12  9:41     ` Jeff King
2021-01-12 16:27     ` Taylor Blau [this message]
2021-01-13  8:06   ` Junio C Hamano
2021-01-13  8:54     ` Junio C Hamano
2021-01-13 13:17     ` Jeff King
2021-01-13 16:23     ` Taylor Blau
2021-01-08 18:16 ` [PATCH 02/20] write_reuse_object(): convert to new revindex API Taylor Blau
2021-01-12  8:47   ` Jeff King
2021-01-12 16:31     ` Taylor Blau
2021-01-13 13:02       ` Jeff King
2021-01-08 18:16 ` [PATCH 03/20] write_reused_pack_one(): " Taylor Blau
2021-01-12  8:50   ` Jeff King
2021-01-12 16:34     ` Taylor Blau
2021-01-08 18:16 ` [PATCH 04/20] write_reused_pack_verbatim(): " Taylor Blau
2021-01-12  8:50   ` Jeff King
2021-01-08 18:17 ` [PATCH 05/20] check_object(): " Taylor Blau
2021-01-11 11:43   ` Derrick Stolee
2021-01-11 16:15     ` Taylor Blau
2021-01-12  8:54       ` Jeff King
2021-01-12  8:51   ` Jeff King
2021-01-08 18:17 ` [PATCH 06/20] bitmap_position_packfile(): " Taylor Blau
2021-01-08 18:17 ` [PATCH 07/20] show_objects_for_type(): " Taylor Blau
2021-01-12  8:57   ` Jeff King
2021-01-12 16:35     ` Taylor Blau
2021-01-08 18:17 ` [PATCH 08/20] get_size_by_pos(): " Taylor Blau
2021-01-08 18:17 ` [PATCH 09/20] try_partial_reuse(): " Taylor Blau
2021-01-12  9:06   ` Jeff King
2021-01-12 16:47     ` Taylor Blau
2021-01-08 18:17 ` [PATCH 10/20] rebuild_existing_bitmaps(): " Taylor Blau
2021-01-08 18:17 ` [PATCH 11/20] get_delta_base_oid(): " Taylor Blau
2021-01-08 18:17 ` [PATCH 12/20] retry_bad_packed_offset(): " Taylor Blau
2021-01-08 18:17 ` [PATCH 13/20] packed_object_info(): " Taylor Blau
2021-01-12  9:11   ` Jeff King
2021-01-12 16:51     ` Taylor Blau
2021-01-08 18:17 ` [PATCH 14/20] unpack_entry(): " Taylor Blau
2021-01-12  9:22   ` Jeff King
2021-01-12 16:56     ` Taylor Blau
2021-01-08 18:17 ` [PATCH 15/20] for_each_object_in_pack(): " Taylor Blau
2021-01-08 18:17 ` [PATCH 16/20] builtin/gc.c: guess the size of the revindex Taylor Blau
2021-01-11 11:52   ` Derrick Stolee
2021-01-11 16:23     ` Taylor Blau
2021-01-11 17:09       ` Derrick Stolee
2021-01-12  9:28         ` Jeff King
2021-01-08 18:17 ` [PATCH 17/20] pack-revindex: remove unused 'find_pack_revindex()' Taylor Blau
2021-01-08 18:17 ` [PATCH 18/20] pack-revindex: remove unused 'find_revindex_position()' Taylor Blau
2021-01-11 11:57   ` Derrick Stolee
2021-01-11 16:27     ` Taylor Blau
2021-01-11 17:11       ` Derrick Stolee
2021-01-12  9:32   ` Jeff King
2021-01-12 16:59     ` Taylor Blau
2021-01-13 13:05       ` Jeff King
2021-01-08 18:18 ` [PATCH 19/20] pack-revindex: hide the definition of 'revindex_entry' Taylor Blau
2021-01-11 11:57   ` Derrick Stolee
2021-01-12  9:34   ` Jeff King
2021-01-08 18:18 ` [PATCH 20/20] pack-revindex.c: avoid direct revindex access in 'offset_to_pack_pos()' Taylor Blau
2021-01-12  9:37   ` Jeff King
2021-01-12 17:02     ` Taylor Blau
2021-01-11 12:07 ` [PATCH 00/20] pack-revindex: prepare for on-disk reverse index Derrick Stolee
2021-01-11 16:30   ` Taylor Blau
2021-01-11 17:15     ` Derrick Stolee
2021-01-11 17:29       ` Taylor Blau
2021-01-11 18:40       ` Junio C Hamano
2021-01-12  9:45 ` Jeff King
2021-01-12 17:07   ` Taylor Blau
2021-01-13  0:23 ` Junio C Hamano
2021-01-13  0:52   ` Taylor Blau
2021-01-13  2:15     ` Junio C Hamano
2021-01-13  3:23       ` Taylor Blau
2021-01-13  8:21         ` Junio C Hamano
2021-01-13 13:13           ` Jeff King
2021-01-13 15:34             ` Taylor Blau
2021-01-13 20:06               ` Junio C Hamano
2021-01-13 20:13                 ` Taylor Blau
2021-01-13 20:22                 ` Jeff King
2021-01-13 22:23 ` [PATCH v2 " Taylor Blau
2021-01-13 22:23   ` [PATCH v2 01/20] pack-revindex: introduce a new API Taylor Blau
2021-01-14  6:46     ` Junio C Hamano
2021-01-14 12:00       ` Derrick Stolee
2021-01-14 17:06       ` Taylor Blau
2021-01-14 19:19         ` Jeff King
2021-01-14 20:47           ` Junio C Hamano
2021-01-13 22:23   ` [PATCH v2 02/20] write_reuse_object(): convert to new revindex API Taylor Blau
2021-01-13 22:23   ` [PATCH v2 03/20] write_reused_pack_one(): " Taylor Blau
2021-01-13 22:23   ` [PATCH v2 04/20] write_reused_pack_verbatim(): " Taylor Blau
2021-01-13 22:23   ` [PATCH v2 05/20] check_object(): " Taylor Blau
2021-01-13 22:23   ` [PATCH v2 06/20] bitmap_position_packfile(): " Taylor Blau
2021-01-13 22:23   ` [PATCH v2 07/20] show_objects_for_type(): " Taylor Blau
2021-01-13 22:24   ` [PATCH v2 08/20] get_size_by_pos(): " Taylor Blau
2021-01-13 22:24   ` [PATCH v2 09/20] try_partial_reuse(): " Taylor Blau
2021-01-13 22:24   ` [PATCH v2 10/20] rebuild_existing_bitmaps(): " Taylor Blau
2021-01-13 22:24   ` [PATCH v2 11/20] get_delta_base_oid(): " Taylor Blau
2021-01-13 22:24   ` [PATCH v2 12/20] retry_bad_packed_offset(): " Taylor Blau
2021-01-13 22:24   ` [PATCH v2 13/20] packed_object_info(): " Taylor Blau
2021-01-13 22:24   ` [PATCH v2 14/20] unpack_entry(): " Taylor Blau
2021-01-13 22:24   ` [PATCH v2 15/20] for_each_object_in_pack(): " Taylor Blau
2021-01-14  6:43     ` Junio C Hamano
2021-01-14 17:00       ` Taylor Blau
2021-01-14 19:33       ` Jeff King
2021-01-14 20:11         ` Jeff King
2021-01-14 20:15           ` Taylor Blau
2021-01-15  2:22             ` Junio C Hamano
2021-01-15  2:29               ` Taylor Blau
2021-01-14 20:51         ` Junio C Hamano
2021-01-13 22:24   ` [PATCH v2 16/20] builtin/gc.c: guess the size of the revindex Taylor Blau
2021-01-14  6:33     ` Junio C Hamano
2021-01-14 16:53       ` Taylor Blau
2021-01-14 19:43         ` Jeff King
2021-01-13 22:24   ` [PATCH v2 17/20] pack-revindex: remove unused 'find_pack_revindex()' Taylor Blau
2021-01-13 22:25   ` [PATCH v2 18/20] pack-revindex: remove unused 'find_revindex_position()' Taylor Blau
2021-01-14  6:42     ` Junio C Hamano
2021-01-13 22:25   ` [PATCH v2 19/20] pack-revindex: hide the definition of 'revindex_entry' Taylor Blau
2021-01-13 22:25   ` [PATCH v2 20/20] pack-revindex.c: avoid direct revindex access in 'offset_to_pack_pos()' Taylor Blau
2021-01-14  6:42     ` Junio C Hamano
2021-01-14 16:56       ` Taylor Blau
2021-01-14 19:51   ` [PATCH v2 00/20] pack-revindex: prepare for on-disk reverse index Jeff King
2021-01-14 20:53     ` Junio C Hamano
2021-01-15  9:32       ` Jeff King
2021-01-15  9:33         ` Jeff King

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