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midx: teach midx_fanout_add_midx_fanout() about incremental MIDXs

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The function `midx_fanout_add_midx_fanout()` is used to help construct
the fanout table when generating a MIDX by reusing data from an existing
MIDX.

Prepare this function to work with incremental MIDXs by making a few
changes:

  - The bounds checks need to be adjusted to start object lookups taking
    into account the number of objects in the previous MIDX layer (i.e.,
    by starting the lookups at position `m->num_objects_in_base` instead
    of position 0).

  - Likewise, the bounds checks need to end at `m->num_objects_in_base`
    objects after `m->num_objects`.

  - Finally, `midx_fanout_add_midx_fanout()` needs to recur on earlier
    MIDX layers when dealing with an incremental MIDX chain by calling
    itself when given a MIDX with a non-NULL `base_midx`.

Note that after 0c5a62f14b (midx-write.c: do not read existing MIDX with
`packs_to_include`, 2024-06-11), we do not use this function with an
existing MIDX (incremental or not) when generating a MIDX with
--stdin-packs, and likewise for incremental MIDXs.

But it is still used when adding the fanout table from an incremental
MIDX when generating a non-incremental MIDX (without --stdin-packs, of
course).

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Taylor Blau
2024-08-06 11:37:52 -04:00
committed by Junio C Hamano
parent b31f2aac56
commit 97fd770ea1
1 changed files with 8 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

12
midx-write.c
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@ -196,7 +196,7 @@ static int nth_midxed_pack_midx_entry(struct multi_pack_index *m,
struct pack_midx_entry *e, struct pack_midx_entry *e,
uint32_t pos) uint32_t pos)
{ {
if (pos >= m->num_objects) if (pos >= m->num_objects + m->num_objects_in_base)
return 1; return 1;
nth_midxed_object_oid(&e->oid, m, pos); nth_midxed_object_oid(&e->oid, m, pos);
@ -247,12 +247,16 @@ static void midx_fanout_add_midx_fanout(struct midx_fanout *fanout,
uint32_t cur_fanout, uint32_t cur_fanout,
int preferred_pack) int preferred_pack)
{ {
uint32_t start = 0, end; uint32_t start = m->num_objects_in_base, end;
uint32_t cur_object; uint32_t cur_object;
if (m->base_midx)
midx_fanout_add_midx_fanout(fanout, m->base_midx, cur_fanout,
preferred_pack);
if (cur_fanout) if (cur_fanout)
start = ntohl(m->chunk_oid_fanout[cur_fanout - 1]); start += ntohl(m->chunk_oid_fanout[cur_fanout - 1]);
end = ntohl(m->chunk_oid_fanout[cur_fanout]); end = m->num_objects_in_base + ntohl(m->chunk_oid_fanout[cur_fanout]);
for (cur_object = start; cur_object < end; cur_object++) { for (cur_object = start; cur_object < end; cur_object++) {
if ((preferred_pack > -1) && if ((preferred_pack > -1) &&