mirrors/git
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

hash: add a function to finalize object IDs

Browse Source 
To avoid the penalty of having to branch in hash comparison functions,
we'll want to always compare the full hash member in a struct object_id,
which will require that SHA-1 object IDs be zero-padded.  To do so, add
a function which finalizes a hash context and writes it into an object
ID that performs this padding.

Move the definition of struct object_id and the constant definitions
higher up so we they are available for us to use.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
brian m. carlson
2021-04-26 01:02:52 +00:00
committed by Junio C Hamano
parent c3b4e4ee36
commit ab795f0d77
2 changed files with 52 additions and 23 deletions
Download Patch File Download Diff File Expand all files Collapse all files

25
object-file.c
View File

@ -89,6 +89,12 @@ static void git_hash_sha1_final(unsigned char *hash, git_hash_ctx *ctx)
git_SHA1_Final(hash, &ctx->sha1);
}
static void git_hash_sha1_final_oid(struct object_id *oid, git_hash_ctx *ctx)
{
git_SHA1_Final(oid->hash, &ctx->sha1);
memset(oid->hash + GIT_SHA1_RAWSZ, 0, GIT_MAX_RAWSZ - GIT_SHA1_RAWSZ);
}
static void git_hash_sha256_init(git_hash_ctx *ctx)
{
@ -110,6 +116,16 @@ static void git_hash_sha256_final(unsigned char *hash, git_hash_ctx *ctx)
git_SHA256_Final(hash, &ctx->sha256);
}
static void git_hash_sha256_final_oid(struct object_id *oid, git_hash_ctx *ctx)
{
git_SHA256_Final(oid->hash, &ctx->sha256);
/*
* This currently does nothing, so the compiler should optimize it out,
* but keep it in case we extend the hash size again.
*/
memset(oid->hash + GIT_SHA256_RAWSZ, 0, GIT_MAX_RAWSZ - GIT_SHA256_RAWSZ);
}
static void git_hash_unknown_init(git_hash_ctx *ctx)
{
BUG("trying to init unknown hash");
@ -130,6 +146,12 @@ static void git_hash_unknown_final(unsigned char *hash, git_hash_ctx *ctx)
BUG("trying to finalize unknown hash");
}
static void git_hash_unknown_final_oid(struct object_id *oid, git_hash_ctx *ctx)
{
BUG("trying to finalize unknown hash");
}
const struct git_hash_algo hash_algos[GIT_HASH_NALGOS] = {
{
NULL,
@ -141,6 +163,7 @@ const struct git_hash_algo hash_algos[GIT_HASH_NALGOS] = {
git_hash_unknown_clone,
git_hash_unknown_update,
git_hash_unknown_final,
git_hash_unknown_final_oid,
NULL,
NULL,
},
@ -155,6 +178,7 @@ const struct git_hash_algo hash_algos[GIT_HASH_NALGOS] = {
git_hash_sha1_clone,
git_hash_sha1_update,
git_hash_sha1_final,
git_hash_sha1_final_oid,
&empty_tree_oid,
&empty_blob_oid,
},
@ -169,6 +193,7 @@ const struct git_hash_algo hash_algos[GIT_HASH_NALGOS] = {
git_hash_sha256_clone,
git_hash_sha256_update,
git_hash_sha256_final,
git_hash_sha256_final_oid,
&empty_tree_oid_sha256,
&empty_blob_oid_sha256,
}