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From: Bert Wesarg <bert.wesarg@googlemail.com>
To: Jeff King <peff@peff.net>
Cc: git@vger.kernel.org, "Junio C Hamano" <gitster@pobox.com>,
	"Jakub Narebski" <jnareb@gmail.com>, "Ted Ts\'o" <tytso@mit.edu>,
	"Jonathan Nieder" <jrnieder@gmail.com>,
	"Ævar Arnfjörð" <avarab@gmail.com>,
	"Clemens Buchacher" <drizzd@aon.at>,
	"Shawn O. Pearce" <spearce@spearce.org>
Subject: Re: [RFC/PATCHv2 2/6] add metadata-cache infrastructure
Date: Wed, 13 Jul 2011 10:45:52 +0200
Message-ID: <CAKPyHN1tixwJPJHG+wY34HVLYGT4fD9Sc-qJ8=on8EWfW-H6aw@mail.gmail.com> (raw)
In-Reply-To: <20110713083139.GA26838@sigill.intra.peff.net>

On Wed, Jul 13, 2011 at 10:31, Jeff King <peff@peff.net> wrote:
> On Wed, Jul 13, 2011 at 10:18:28AM +0200, Bert Wesarg wrote:
>
>> > +static int record_size(const struct metadata_cache *c)
>> > +{
>> > +       /* a record is a 20-byte sha1 plus the width of the value */
>> > +       return c->mem.width + 20;
>>
>> You are circumventing your own API. Why do you don't use the
>> decoration_width() accessor here? I don't see any check that
>> METADATA_CACHE_INIT("frotz", 0, NULL) is invalid neither in the
>> documentation nor in the code.
>
> "struct decoration" has the "0 width means store a void pointer" rule
> for compatibility with existing callers. But I never intended for
> metadata-cache to have such an exception. Nor would it make sense to
> store a void pointer. The pointer would be written to disk, and would
> then be meaningless during the next run of the program.
>
> I didn't figure anyone would assume the same special rule held for
> metadata-cache; the fact that it is implemented using "struct
> decoration" is not part of its public API. But I guess I was wrong.

You're right here, that it is not part of the public API, but you're
not wrong about your guess. But when reading this patch series, the
reader obviously knows that the metadata-cache uses a struct
decoration for the in-memory values. Thus the reader knows that 0 is
special for struct decoration, and that there is an API to get the
width from the struct decoration.

>
> It might make sense to put:
>
>  if (!c->mem.width)
>          die("BUG: zero-width metadata-cache");
>
> into the initialization function to make it more clear, and make a note
> in the API documentation.

That should be good. Thanks.

Bert

> -Peff
>

  reply index

Thread overview: 56+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-07-13  6:47 [RFC/PATCHv2 0/6] generation numbers for faster traversals Jeff King
2011-07-13  6:57 ` [RFC/PATCHv2 1/6] decorate: allow storing values instead of pointers Jeff King
2011-07-13 17:52   ` Jonathan Nieder
2011-07-13 20:08     ` Jeff King
2011-07-14 17:34       ` Jeff King
2011-07-14 17:51         ` [PATCH 1/3] implement generic key/value map Jeff King
2011-07-14 18:52           ` Bert Wesarg
2011-07-14 18:54             ` Bert Wesarg
2011-07-14 18:55               ` Jeff King
2011-07-14 19:07                 ` Bert Wesarg
2011-07-14 19:14                   ` Jeff King
2011-07-14 19:18                     ` Bert Wesarg
2011-07-14 17:52         ` [PATCH 2/3] fast-export: use object to uint32 map instead of "decorate" Jeff King
2011-07-15  9:40           ` Sverre Rabbelier
2011-07-15 20:00             ` Jeff King
2011-07-14 17:53         ` [PATCH 3/3] decorate: use "map" for the underlying implementation Jeff King
2011-07-14 21:06         ` [RFC/PATCHv2 1/6] decorate: allow storing values instead of pointers Junio C Hamano
2011-08-04 22:43           ` [RFC/PATCH 0/5] macro-based key/value maps Jeff King
2011-08-04 22:45             ` [PATCH 1/5] implement generic key/value map Jeff King
2011-08-04 22:46             ` [PATCH 2/5] fast-export: use object to uint32 map instead of "decorate" Jeff King
2011-08-04 22:46             ` [PATCH 3/5] decorate: use "map" for the underlying implementation Jeff King
2011-08-04 22:46             ` [PATCH 4/5] map: implement persistent maps Jeff King
2011-08-04 22:46             ` [PATCH 5/5] implement metadata cache subsystem Jeff King
2011-08-05 11:03             ` [RFC/PATCH 0/5] macro-based key/value maps Jeff King
2011-08-05 15:31               ` René Scharfe
2011-08-06  6:30                 ` Jeff King
2011-07-13  7:04 ` [RFC/PATCHv2 2/6] add metadata-cache infrastructure Jeff King
2011-07-13  8:18   ` Bert Wesarg
2011-07-13  8:31     ` Jeff King
2011-07-13  8:45       ` Bert Wesarg [this message]
2011-07-13 19:18         ` Jeff King
2011-07-13 19:40       ` Junio C Hamano
2011-07-13 19:33   ` Junio C Hamano
2011-07-13 20:25     ` Jeff King
2011-07-13  7:05 ` [RFC/PATCHv2 3/6] commit: add commit_generation function Jeff King
2011-07-13 14:26   ` Eric Sunshine
2011-07-13  7:05 ` [RFC/PATCHv2 4/6] pretty: support %G to show the generation number of a commit Jeff King
2011-07-13  7:06 ` [RFC/PATCHv2 5/6] check commit generation cache validity against grafts Jeff King
2011-07-13 14:26   ` Eric Sunshine
2011-07-13 19:35     ` Jeff King
2011-07-13  7:06 ` [RFC/PATCHv2 6/6] limit "contains" traversals based on commit generation Jeff King
2011-07-13  7:23   ` Jeff King
2011-07-13 20:33     ` Junio C Hamano
2011-07-13 20:58       ` Jeff King
2011-07-13 21:12         ` Junio C Hamano
2011-07-13 21:18           ` Jeff King
2011-07-15 18:22   ` Junio C Hamano
2011-07-15 20:40     ` Jeff King
2011-07-15 21:04       ` Junio C Hamano
2011-07-15 21:14         ` Jeff King
2011-07-15 21:01 ` Generation numbers and replacement objects Jakub Narebski
2011-07-15 21:10   ` Jeff King
2011-07-16 21:10     ` Jakub Narebski
2011-08-04 22:48 [RFC/PATCH 0/2] patch-id caching Jeff King
2011-08-04 22:49 ` [PATCH 1/2] cherry: read default config Jeff King
2011-08-04 22:49 ` [PATCH 2/2] cache patch ids on disk Jeff King
2011-08-04 22:52   ` Jeff King

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