pack-revindex: implement `midx_pair_to_pack_pos()`

Now that we have extracted the `midx_key_to_pack_pos()` function, we can
implement the `midx_pair_to_pack_pos()` function which accepts (pack_id,
offset) tuples and returns an index into the psuedo-pack order.

This will be used in a following commit in order to figure out whether
or not the MIDX chose a given delta's base object from the same pack as
the delta resides in. It will do so by locating the base object's offset
in the pack, and then performing a binary search using the same pack ID
with the base object's offset.

If (and only if) it finds a match (at any position) we can guarantee
that the MIDX selected both halves of the delta/base pair from the same
pack.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Taylor Blau 2023-12-14 17:24:30 -05:00 committed by Junio C Hamano
parent e1bfe30c4d
commit dbd5c520d2
2 changed files with 14 additions and 0 deletions

View File

@ -564,3 +564,14 @@ int midx_to_pack_pos(struct multi_pack_index *m, uint32_t at, uint32_t *pos)
return midx_key_to_pack_pos(m, &key, pos);
}
int midx_pair_to_pack_pos(struct multi_pack_index *m, uint32_t pack_int_id,
off_t ofs, uint32_t *pos)
{
struct midx_pack_key key = {
.pack = pack_int_id,
.offset = ofs,
.midx = m,
};
return midx_key_to_pack_pos(m, &key, pos);
}

View File

@ -142,4 +142,7 @@ uint32_t pack_pos_to_midx(struct multi_pack_index *m, uint32_t pos);
*/
int midx_to_pack_pos(struct multi_pack_index *midx, uint32_t at, uint32_t *pos);
int midx_pair_to_pack_pos(struct multi_pack_index *midx, uint32_t pack_id,
off_t ofs, uint32_t *pos);
#endif