From: "brian m. carlson" <sandals@crustytoothpaste.net>
To: Jeff King <peff@peff.net>
Cc: Christian Couder <chriscool@tuxfamily.org>, git@vger.kernel.org
Subject: Re: [PATCH v2 01/24] builtin/pack-objects: make hash agnostic
Date: Mon, 24 Feb 2020 03:42:59 +0000 [thread overview]
Message-ID: <20200224034259.GG6462@camp.crustytoothpaste.net> (raw)
In-Reply-To: <20200223215759.GC564691@coredump.intra.peff.net>
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On 2020-02-23 at 21:57:59, Jeff King wrote:
> On Sat, Feb 22, 2020 at 08:17:26PM +0000, brian m. carlson wrote:
>
> > Avoid hard-coding a hash size, instead preferring to use the_hash_algo.
> > [...]
> > - hashwrite(out, base_sha1, 20);
> > + hashwrite(out, base_sha1, the_hash_algo->rawsz);
>
> Yeah, looks obviously correct (and I think this is new from the
> pack-reuse patches of mine that Christian sent recently).
I believe it is, which is why I CC'd you on it.
> The name "base_sha1" is clearly not great either. It could be changed
> trivially, but the real sin is that it comes from
> nth_packed_object_sha1(). It could be replaced with
> nth_packed_object_oid() at the cost of an extra hash copy, which isn't
> too bad.
I probably should send a series getting rid of the rest of the "sha1"
places in our code, because there are a lot of them, but I just haven't
gotten around to it yet. And yeah, as you mentioned, there are still a
lot of places using nth_packed_object_sha1.
> It would be nice to get rid of that function entirely. In most cases,
> it's either free to do so (we end up copying the result into an oid
> anyway) or we pay for one extra hashcpy (out of the mmap into a local
> struct). But the one in pack-check.c:verify_packfile() is tricky; we
> store a pointer per object into the index mmap, and we'd have to switch
> to storing an oid per object. Given that the code isn't commonly run
> (and other operations like _generating_ the index in the first place are
> clearly OK with the extra memory hit), I think I'd be OK with that in
> the name of cleanliness.
Yeah, that's why I hadn't switched it out earlier.
> I think it would also be correct to cast the mmap'd bytes to a "struct
> object_id" given that the struct contains the hash bytes as the first
> member. I worry a little that we'd get no compiler warning of the
> breakage if that assumption changes, but it also seems unlikely to do
> so.
In the future, struct object_id will get a new member (an algorithm
value), but I think it's fine to make the assumption that the hash bytes
are first.
--
brian m. carlson: Houston, Texas, US
OpenPGP: https://keybase.io/bk2204
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next prev parent reply other threads:[~2020-02-24 3:43 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-22 20:17 [PATCH v2 00/24] SHA-256 stage 4 implementation, part 1/3 brian m. carlson
2020-02-22 20:17 ` [PATCH v2 01/24] builtin/pack-objects: make hash agnostic brian m. carlson
2020-02-23 21:57 ` Jeff King
2020-02-24 3:01 ` Jeff King
2020-02-24 3:42 ` brian m. carlson [this message]
2020-02-24 4:20 ` Jeff King
2020-02-22 20:17 ` [PATCH v2 02/24] hash: implement and use a context cloning function brian m. carlson
2020-02-22 20:17 ` [PATCH v2 03/24] hex: introduce parsing variants taking hash algorithms brian m. carlson
2020-02-22 20:17 ` [PATCH v2 04/24] hex: add functions to parse hex object IDs in any algorithm brian m. carlson
2020-02-22 20:17 ` [PATCH v2 05/24] repository: require a build flag to use SHA-256 brian m. carlson
2020-02-22 20:17 ` [PATCH v2 06/24] t: use hash-specific lookup tables to define test constants brian m. carlson
2020-02-22 20:17 ` [PATCH v2 07/24] t6300: abstract away SHA-1-specific constants brian m. carlson
2020-02-24 18:01 ` Junio C Hamano
2020-02-24 18:12 ` Jeff King
2020-02-24 20:41 ` Junio C Hamano
2020-02-22 20:17 ` [PATCH v2 08/24] t6300: make hash algorithm independent brian m. carlson
2020-02-22 20:17 ` [PATCH v2 09/24] t/helper/test-dump-split-index: initialize git repository brian m. carlson
2020-02-22 20:17 ` [PATCH v2 10/24] t/helper: initialize repository if necessary brian m. carlson
2020-02-24 18:05 ` Junio C Hamano
2020-02-25 0:05 ` brian m. carlson
2020-02-22 20:17 ` [PATCH v2 11/24] t/helper: make repository tests hash independent brian m. carlson
2020-02-22 20:17 ` [PATCH v2 12/24] setup: allow check_repository_format to read repository format brian m. carlson
2020-02-22 20:17 ` [PATCH v2 13/24] builtin/init-db: allow specifying hash algorithm on command line brian m. carlson
2020-02-24 18:14 ` Junio C Hamano
2020-02-25 0:11 ` brian m. carlson
2020-02-22 20:17 ` [PATCH v2 14/24] builtin/init-db: add environment variable for new repo hash brian m. carlson
2020-02-22 20:17 ` [PATCH v2 15/24] init-db: move writing repo version into a function brian m. carlson
2020-02-22 20:17 ` [PATCH v2 16/24] worktree: allow repository version 1 brian m. carlson
2020-02-22 20:17 ` [PATCH v2 17/24] commit: use expected signature header for SHA-256 brian m. carlson
2020-02-24 18:24 ` Junio C Hamano
2020-02-22 20:17 ` [PATCH v2 18/24] gpg-interface: improve interface for parsing tags brian m. carlson
2020-02-24 18:26 ` Junio C Hamano
2020-02-25 10:29 ` Johannes Schindelin
2020-02-25 19:25 ` Junio C Hamano
2020-02-26 3:05 ` brian m. carlson
2020-02-26 3:11 ` Junio C Hamano
2020-02-26 2:23 ` brian m. carlson
2020-02-27 13:24 ` Johannes Schindelin
2020-02-27 15:06 ` Junio C Hamano
2020-02-22 20:17 ` [PATCH v2 19/24] tag: store SHA-256 signatures in a header brian m. carlson
2020-02-24 18:30 ` Junio C Hamano
2020-02-22 20:17 ` [PATCH v2 20/24] fast-import: permit reading multiple marks files brian m. carlson
2020-06-05 16:14 ` Junio C Hamano
2020-06-05 16:26 ` Junio C Hamano
2020-06-05 22:39 ` brian m. carlson
2020-06-05 22:53 ` Junio C Hamano
2020-02-22 20:17 ` [PATCH v2 21/24] fast-import: add helper function for inserting mark object entries brian m. carlson
2020-02-22 20:17 ` [PATCH v2 22/24] fast-import: make find_marks work on any mark set brian m. carlson
2020-02-22 20:17 ` [PATCH v2 23/24] fast-import: add a generic function to iterate over marks brian m. carlson
2020-02-22 20:17 ` [PATCH v2 24/24] fast-import: add options for rewriting submodules brian m. carlson
2020-02-24 18:34 ` [PATCH v2 00/24] SHA-256 stage 4 implementation, part 1/3 Junio C Hamano
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