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: Derrick Stolee <dsto...@microsoft.com>
---
packfile.c | 42 ++++++++++++++++++++++++++----------------
packfile.h | 8 ++++++++
2 files changed, 34 insertions(+), 16 deletions(-)
diff --git a/packfile.c b/packfile.c
index f26395ecab..69d3afda6c 100644
--- a/packfile.c
+++ b/packfile.c
@@ -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;
}
diff --git a/packfile.h b/packfile.h
index a7fca598d6..ec08cb2bb0 100644
--- a/packfile.h
+++ b/packfile.h
@@ -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
--
2.17.0.rc0
