From: "brian m. carlson" <sandals@crustytoothpaste.net>
To: "Martin Ågren" <martin.agren@gmail.com>
Cc: "Git Mailing List" <git@vger.kernel.org>,
"Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>,
"Junio C Hamano" <gitster@pobox.com>,
"Eric Sunshine" <sunshine@sunshineco.com>
Subject: Re: [PATCH 18/41] index-pack: abstract away hash function constant
Date: Tue, 24 Apr 2018 23:51:50 +0000 [thread overview]
Message-ID: <20180424235150.GD245996@genre.crustytoothpaste.net> (raw)
In-Reply-To: <CAN0heSouHbAj8TbiROe=XRsBJ788Vi6P4a_Wvv=7OrdsXqQXHw@mail.gmail.com>
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On Tue, Apr 24, 2018 at 11:50:16AM +0200, Martin Ågren wrote:
> On 24 April 2018 at 01:39, brian m. carlson
> <sandals@crustytoothpaste.net> wrote:
> > The code for reading certain pack v2 offsets had a hard-coded 5
> > representing the number of uint32_t words that we needed to skip over.
> > Specify this value in terms of a value from the_hash_algo.
> >
> > Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
> > ---
> > builtin/index-pack.c | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/builtin/index-pack.c b/builtin/index-pack.c
> > index d81473e722..c1f94a7da6 100644
> > --- a/builtin/index-pack.c
> > +++ b/builtin/index-pack.c
> > @@ -1543,12 +1543,13 @@ static void read_v2_anomalous_offsets(struct packed_git *p,
> > {
> > const uint32_t *idx1, *idx2;
> > uint32_t i;
> > + const uint32_t hashwords = the_hash_algo->rawsz / sizeof(uint32_t);
>
> Should we round up? Or just what should we do if a length is not
> divisible by 4? (I am not aware of any such hash functions, but one
> could exist for all I know.) Another question is whether such an
> index-pack v2 will ever contain non-SHA-1 oids to begin with. I can't
> find anything suggesting that it could, but this is unfamiliar code to
> me.
I opted not to simply because I know that our current hash is 20 bytes
and the new one will be 32, and I know those are both divisible by 4. I
feel confident that any future hash we choose will also be divisible by
4, and the code is going to be complicated if it isn't.
I agree that pack v2 is not going to have anything but SHA-1. However,
writing all the code such that it's algorithm agnostic means that we can
do testing of new algorithms by wholesale replacing the algorithm with a
new one, which simplifies things considerably.
--
brian m. carlson: Houston, Texas, US
OpenPGP: https://keybase.io/bk2204
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next prev parent reply other threads:[~2018-04-24 23:52 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-23 23:39 [PATCH 00/41] object_id part 13 brian m. carlson
2018-04-23 23:39 ` [PATCH 01/41] cache: add a function to read an object ID from a buffer brian m. carlson
2018-04-24 9:39 ` Martin Ågren
2018-05-01 9:36 ` Duy Nguyen
2018-05-01 23:58 ` brian m. carlson
2018-04-23 23:39 ` [PATCH 02/41] server-info: remove unused members from struct pack_info brian m. carlson
2018-04-24 9:41 ` Martin Ågren
2018-05-01 9:39 ` Duy Nguyen
2018-04-23 23:39 ` [PATCH 03/41] Remove unused member in struct object_context brian m. carlson
2018-05-01 9:50 ` Duy Nguyen
2018-04-23 23:39 ` [PATCH 04/41] packfile: remove unused member from struct pack_entry brian m. carlson
2018-05-01 10:01 ` Duy Nguyen
2018-04-23 23:39 ` [PATCH 05/41] packfile: convert has_sha1_pack to object_id brian m. carlson
2018-04-23 23:39 ` [PATCH 06/41] sha1_file: convert freshen functions " brian m. carlson
2018-04-23 23:39 ` [PATCH 07/41] packfile: convert find_pack_entry " brian m. carlson
2018-04-23 23:39 ` [PATCH 08/41] packfile: abstract away hash constant values brian m. carlson
2018-05-01 10:22 ` Duy Nguyen
2018-05-02 0:11 ` brian m. carlson
2018-05-02 15:26 ` Duy Nguyen
2018-05-02 23:05 ` brian m. carlson
2018-04-23 23:39 ` [PATCH 09/41] pack-objects: abstract away hash algorithm brian m. carlson
2018-05-01 10:26 ` Duy Nguyen
2018-04-23 23:39 ` [PATCH 10/41] pack-redundant: " brian m. carlson
2018-04-23 23:39 ` [PATCH 11/41] tree-walk: avoid hard-coded 20 constant brian m. carlson
2018-04-23 23:39 ` [PATCH 12/41] tree-walk: convert get_tree_entry_follow_symlinks to object_id brian m. carlson
2018-04-23 23:39 ` [PATCH 13/41] fsck: convert static functions to struct object_id brian m. carlson
2018-04-23 23:39 ` [PATCH 14/41] submodule-config: convert structures to object_id brian m. carlson
2018-04-23 23:39 ` [PATCH 15/41] split-index: convert struct split_index " brian m. carlson
2018-04-23 23:39 ` [PATCH 16/41] Update struct index_state to use struct object_id brian m. carlson
2018-04-23 23:39 ` [PATCH 17/41] pack-redundant: convert linked lists " brian m. carlson
2018-04-23 23:39 ` [PATCH 18/41] index-pack: abstract away hash function constant brian m. carlson
2018-04-24 9:50 ` Martin Ågren
2018-04-24 23:51 ` brian m. carlson [this message]
2018-04-25 18:49 ` Martin Ågren
2018-04-26 15:46 ` Duy Nguyen
2018-04-27 21:08 ` brian m. carlson
2018-04-28 5:41 ` Duy Nguyen
2018-04-23 23:39 ` [PATCH 19/41] commit: convert uses of get_sha1_hex to get_oid_hex brian m. carlson
2018-04-23 23:39 ` [PATCH 20/41] dir: convert struct untracked_cache_dir to object_id brian m. carlson
2018-04-23 23:39 ` [PATCH 21/41] http: eliminate hard-coded constants brian m. carlson
2018-04-24 9:53 ` Martin Ågren
2018-04-24 23:44 ` Junio C Hamano
2018-04-25 1:29 ` brian m. carlson
2018-04-23 23:39 ` [PATCH 22/41] revision: replace use of " brian m. carlson
2018-04-23 23:39 ` [PATCH 23/41] upload-pack: replace use of several " brian m. carlson
2018-04-24 7:53 ` Simon Ruderich
2018-04-23 23:39 ` [PATCH 24/41] diff: specify abbreviation size in terms of the_hash_algo brian m. carlson
2018-04-23 23:39 ` [PATCH 25/41] builtin/receive-pack: avoid hard-coded constants for push certs brian m. carlson
2018-04-24 9:58 ` Martin Ågren
2018-04-25 2:00 ` brian m. carlson
2018-04-25 5:06 ` Martin Ågren
2018-04-23 23:39 ` [PATCH 26/41] builtin/am: convert uses of EMPTY_TREE_SHA1_BIN to the_hash_algo brian m. carlson
2018-04-23 23:39 ` [PATCH 27/41] builtin/merge: switch tree functions to use object_id brian m. carlson
2018-04-23 23:39 ` [PATCH 28/41] merge: convert empty tree constant to the_hash_algo brian m. carlson
2018-04-23 23:39 ` [PATCH 29/41] sequencer: convert one use of EMPTY_TREE_SHA1_HEX brian m. carlson
2018-04-23 23:39 ` [PATCH 30/41] submodule: convert several uses " brian m. carlson
2018-04-23 23:39 ` [PATCH 31/41] wt-status: convert two " brian m. carlson
2018-04-24 10:03 ` Martin Ågren
2018-05-01 2:29 ` brian m. carlson
2018-04-23 23:39 ` [PATCH 32/41] builtin/receive-pack: convert one use " brian m. carlson
2018-04-23 23:39 ` [PATCH 33/41] builtin/reset: convert use of EMPTY_TREE_SHA1_BIN brian m. carlson
2018-04-23 23:39 ` [PATCH 34/41] sha1_file: convert cached object code to struct object_id brian m. carlson
2018-04-23 23:39 ` [PATCH 35/41] cache-tree: use is_empty_tree_oid brian m. carlson
2018-04-23 23:39 ` [PATCH 36/41] sequencer: use the_hash_algo for empty tree object ID brian m. carlson
2018-04-23 23:39 ` [PATCH 37/41] dir: use the_hash_algo for empty blob " brian m. carlson
2018-04-23 23:39 ` [PATCH 38/41] sha1_file: only expose empty object constants through git_hash_algo brian m. carlson
2018-04-23 23:39 ` [PATCH 39/41] Update shell scripts to compute empty tree object ID brian m. carlson
2018-05-01 10:42 ` Duy Nguyen
2018-05-04 1:29 ` brian m. carlson
2018-04-23 23:39 ` [PATCH 40/41] add--interactive: compute the empty tree value brian m. carlson
2018-04-23 23:39 ` [PATCH 41/41] merge-one-file: compute empty blob object ID brian m. carlson
2018-04-24 1:00 ` SZEDER Gábor
2018-04-24 1:03 ` brian m. carlson
2018-04-30 18:03 ` [PATCH 00/41] object_id part 13 Duy Nguyen
2018-04-30 23:59 ` brian m. carlson
2018-05-01 10:51 ` Duy Nguyen
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