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midx: introduce `bsearch_one_midx()` 

The `bsearch_midx()` function will be extended in a following commit to
search for the location of a given object ID across all MIDXs in a chain
(or the single non-chain MIDX if no chain is available).

While most callers will naturally want to use the updated
`bsearch_midx()` function, there are a handful of special cases that
will want finer control and will only want to search through a single
MIDX.

For instance, the object abbreviation code, which cares about object IDs
near to where we'd expect to find a match in a MIDX. In that case, we
want to look at the nearby matches in each layer of the MIDX chain, not
just a single one).

Split the more fine-grained control out into a separate function called
`bsearch_one_midx()` which searches only a single MIDX.

At present both `bsearch_midx()` and `bsearch_one_midx()` have identical
behavior, but the following commit will rewrite the former to be aware
of incremental MIDXs for the remaining non-special case callers.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
maint
Taylor Blau 2024-08-06 11:37:30 -04:00 committed by Junio C Hamano
parent 60750e1eb9
commit 3f5f1cff92
3 changed files with 71 additions and 50 deletions
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17
midx.c
View File

@ -330,10 +330,21 @@ int nth_bitmapped_pack(struct repository *r, struct multi_pack_index *m,
return 0;
}

int bsearch_midx(const struct object_id *oid, struct multi_pack_index *m, uint32_t *result)
int bsearch_one_midx(const struct object_id *oid, struct multi_pack_index *m,
uint32_t *result)
{
return bsearch_hash(oid->hash, m->chunk_oid_fanout, m->chunk_oid_lookup,
the_hash_algo->rawsz, result);
int ret = bsearch_hash(oid->hash, m->chunk_oid_fanout,
m->chunk_oid_lookup, the_hash_algo->rawsz,
result);
if (result)
*result += m->num_objects_in_base;
return ret;
}

int bsearch_midx(const struct object_id *oid, struct multi_pack_index *m,
uint32_t *result)
{
return bsearch_one_midx(oid, m, result);
}

struct object_id *nth_midxed_object_oid(struct object_id *oid,

5
midx.h
View File

@ -90,7 +90,10 @@ struct multi_pack_index *load_multi_pack_index(const char *object_dir, int local
int prepare_midx_pack(struct repository *r, struct multi_pack_index *m, uint32_t pack_int_id);
int nth_bitmapped_pack(struct repository *r, struct multi_pack_index *m,
struct bitmapped_pack *bp, uint32_t pack_int_id);
int bsearch_midx(const struct object_id *oid, struct multi_pack_index *m, uint32_t *result);
int bsearch_one_midx(const struct object_id *oid, struct multi_pack_index *m,
uint32_t *result);
int bsearch_midx(const struct object_id *oid, struct multi_pack_index *m,
uint32_t *result);
off_t nth_midxed_offset(struct multi_pack_index *m, uint32_t pos);
uint32_t nth_midxed_pack_int_id(struct multi_pack_index *m, uint32_t pos);
struct object_id *nth_midxed_object_oid(struct object_id *oid,

99
object-name.c
View File

@ -134,28 +134,32 @@ static int match_hash(unsigned len, const unsigned char *a, const unsigned char
static void unique_in_midx(struct multi_pack_index *m,
struct disambiguate_state *ds)
{
uint32_t num, i, first = 0;
const struct object_id *current = NULL;
int len = ds->len > ds->repo->hash_algo->hexsz ?
ds->repo->hash_algo->hexsz : ds->len;
num = m->num_objects;
for (; m; m = m->base_midx) {
uint32_t num, i, first = 0;
const struct object_id *current = NULL;
int len = ds->len > ds->repo->hash_algo->hexsz ?
ds->repo->hash_algo->hexsz : ds->len;

if (!num)
return;
if (!m->num_objects)
continue;

bsearch_midx(&ds->bin_pfx, m, &first);
num = m->num_objects + m->num_objects_in_base;

/*
* At this point, "first" is the location of the lowest object
* with an object name that could match "bin_pfx". See if we have
* 0, 1 or more objects that actually match(es).
*/
for (i = first; i < num && !ds->ambiguous; i++) {
struct object_id oid;
current = nth_midxed_object_oid(&oid, m, i);
if (!match_hash(len, ds->bin_pfx.hash, current->hash))
break;
update_candidates(ds, current);
bsearch_one_midx(&ds->bin_pfx, m, &first);

/*
* At this point, "first" is the location of the lowest
* object with an object name that could match
* "bin_pfx". See if we have 0, 1 or more objects that
* actually match(es).
*/
for (i = first; i < num && !ds->ambiguous; i++) {
struct object_id oid;
current = nth_midxed_object_oid(&oid, m, i);
if (!match_hash(len, ds->bin_pfx.hash, current->hash))
break;
update_candidates(ds, current);
}
}
}

@ -708,37 +712,40 @@ static int repo_extend_abbrev_len(struct repository *r UNUSED,
static void find_abbrev_len_for_midx(struct multi_pack_index *m,
struct min_abbrev_data *mad)
{
int match = 0;
uint32_t num, first = 0;
struct object_id oid;
const struct object_id *mad_oid;
for (; m; m = m->base_midx) {
int match = 0;
uint32_t num, first = 0;
struct object_id oid;
const struct object_id *mad_oid;

if (!m->num_objects)
return;
if (!m->num_objects)
continue;

num = m->num_objects;
mad_oid = mad->oid;
match = bsearch_midx(mad_oid, m, &first);
num = m->num_objects + m->num_objects_in_base;
mad_oid = mad->oid;
match = bsearch_one_midx(mad_oid, m, &first);

/*
* first is now the position in the packfile where we would insert
* mad->hash if it does not exist (or the position of mad->hash if
* it does exist). Hence, we consider a maximum of two objects
* nearby for the abbreviation length.
*/
mad->init_len = 0;
if (!match) {
if (nth_midxed_object_oid(&oid, m, first))
extend_abbrev_len(&oid, mad);
} else if (first < num - 1) {
if (nth_midxed_object_oid(&oid, m, first + 1))
extend_abbrev_len(&oid, mad);
/*
* first is now the position in the packfile where we
* would insert mad->hash if it does not exist (or the
* position of mad->hash if it does exist). Hence, we
* consider a maximum of two objects nearby for the
* abbreviation length.
*/
mad->init_len = 0;
if (!match) {
if (nth_midxed_object_oid(&oid, m, first))
extend_abbrev_len(&oid, mad);
} else if (first < num - 1) {
if (nth_midxed_object_oid(&oid, m, first + 1))
extend_abbrev_len(&oid, mad);
}
if (first > 0) {
if (nth_midxed_object_oid(&oid, m, first - 1))
extend_abbrev_len(&oid, mad);
}
mad->init_len = mad->cur_len;
}
if (first > 0) {
if (nth_midxed_object_oid(&oid, m, first - 1))
extend_abbrev_len(&oid, mad);
}
mad->init_len = mad->cur_len;
}

static void find_abbrev_len_for_pack(struct packed_git *p,