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pack-bitmap: use object_id when loading on-disk bitmaps 

A pack bitmap file contains the index position of the commit for each
bitmap, which we then translate into an object id via
nth_packed_object_sha1(). In preparation for that function going away,
we can switch to the more type-safe nth_packed_object_id().

Note that even though the result ends up in an object_id this does incur
an extra copy of the hash (into our temporary object_id, and then into
the final malloc'd stored_bitmap struct). This shouldn't make any
measurable difference. If it did, we could avoid this copy _and_ the
copy of the rest of the items by allocating the stored_bitmap struct
beforehand and reading directly into it from the bitmap file. Or better
still, if this is a bottleneck, we could introduce an on-disk index to
the bitmap file so we don't have to read every single entry to use just
one of them. So it's not worth worrying about micro-optimizing out this
one hash copy.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Jeff King 2020-02-23 23:32:27 -05:00 committed by Junio C Hamano
parent f66d4e0250
commit 500e4f2366
1 changed files with 6 additions and 6 deletions
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12
pack-bitmap.c
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@ -169,7 +169,7 @@ static int load_bitmap_header(struct bitmap_index *index)
static struct stored_bitmap *store_bitmap(struct bitmap_index *index,
struct ewah_bitmap *root,
const unsigned char *hash,
const struct object_id *oid,
struct stored_bitmap *xor_with,
int flags)
{
@ -181,7 +181,7 @@ static struct stored_bitmap *store_bitmap(struct bitmap_index *index,
stored->root = root;
stored->xor = xor_with;
stored->flags = flags;
oidread(&stored->oid, hash);
oidcpy(&stored->oid, oid);
hash_pos = kh_put_oid_map(index->bitmaps, stored->oid, &ret);
@ -189,7 +189,7 @@ static struct stored_bitmap *store_bitmap(struct bitmap_index *index,
* because the SHA1 already existed on the map. this is bad, there
* shouldn't be duplicated commits in the index */
if (ret == 0) {
error("Duplicate entry in bitmap index: %s", hash_to_hex(hash));
error("Duplicate entry in bitmap index: %s", oid_to_hex(oid));
return NULL;
}
@ -221,13 +221,13 @@ static int load_bitmap_entries_v1(struct bitmap_index *index)
struct ewah_bitmap *bitmap = NULL;
struct stored_bitmap *xor_bitmap = NULL;
uint32_t commit_idx_pos;
const unsigned char *sha1;
struct object_id oid;
commit_idx_pos = read_be32(index->map, &index->map_pos);
xor_offset = read_u8(index->map, &index->map_pos);
flags = read_u8(index->map, &index->map_pos);
sha1 = nth_packed_object_sha1(index->pack, commit_idx_pos);
nth_packed_object_id(&oid, index->pack, commit_idx_pos);
bitmap = read_bitmap_1(index);
if (!bitmap)
@ -244,7 +244,7 @@ static int load_bitmap_entries_v1(struct bitmap_index *index)
}
recent_bitmaps[i % MAX_XOR_OFFSET] = store_bitmap(
index, bitmap, sha1, xor_bitmap, flags);
index, bitmap, &oid, xor_bitmap, flags);
}
return 0;