Commit 3d475f46 authored by Derrick Stolee's avatar Derrick Stolee Committed by Junio C Hamano

packfile: define and use bsearch_pack()

The method bsearch_hash() generalizes binary searches using a
fanout table. The only consumer is currently find_pack_entry_one().
It requires a bit of pointer arithmetic to align the fanout table
and the lookup table depending on the pack-index version.

Extract the pack-index pointer arithmetic to a new method,
bsearch_pack(), so this can be re-used in other code paths.
Signed-off-by: default avatarDerrick Stolee <dstolee@microsoft.com>
Signed-off-by: default avatarJunio C Hamano <gitster@pobox.com>
parent 626fd982
......@@ -1654,6 +1654,29 @@ void *unpack_entry(struct packed_git *p, off_t obj_offset,
return data;
}
int bsearch_pack(const struct object_id *oid, const struct packed_git *p, uint32_t *result)
{
const unsigned char *index_fanout = p->index_data;
const unsigned char *index_lookup;
int index_lookup_width;
if (!index_fanout)
BUG("bsearch_pack called without a valid pack-index");
index_lookup = index_fanout + 4 * 256;
if (p->index_version == 1) {
index_lookup_width = 24;
index_lookup += 4;
} else {
index_lookup_width = 20;
index_fanout += 8;
index_lookup += 8;
}
return bsearch_hash(oid->hash, (const uint32_t*)index_fanout,
index_lookup, index_lookup_width, result);
}
const unsigned char *nth_packed_object_sha1(struct packed_git *p,
uint32_t n)
{
......@@ -1720,30 +1743,17 @@ off_t nth_packed_object_offset(const struct packed_git *p, uint32_t n)
off_t find_pack_entry_one(const unsigned char *sha1,
struct packed_git *p)
{
const uint32_t *level1_ofs = p->index_data;
const unsigned char *index = p->index_data;
unsigned stride;
struct object_id oid;
uint32_t result;
if (!index) {
if (open_pack_index(p))
return 0;
level1_ofs = p->index_data;
index = p->index_data;
}
if (p->index_version > 1) {
level1_ofs += 2;
index += 8;
}
index += 4 * 256;
if (p->index_version > 1) {
stride = 20;
} else {
stride = 24;
index += 4;
}
if (bsearch_hash(sha1, level1_ofs, index, stride, &result))
hashcpy(oid.hash, sha1);
if (bsearch_pack(&oid, p, &result))
return nth_packed_object_offset(p, result);
return 0;
}
......
......@@ -78,6 +78,14 @@ extern struct packed_git *add_packed_git(const char *path, size_t path_len, int
*/
extern void check_pack_index_ptr(const struct packed_git *p, const void *ptr);
/*
* Perform binary search on a pack-index for a given oid. Packfile is expected to
* have a valid pack-index.
*
* See 'bsearch_hash' for more information.
*/
int bsearch_pack(const struct object_id *oid, const struct packed_git *p, uint32_t *result);
/*
* Return the SHA-1 of the nth object within the specified packfile.
* Open the index if it is not already open. The return value points
......
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