From 3d475f46a8225a9cc549ac5cb2c51d6ecd9e0f7c Mon Sep 17 00:00:00 2001 From: Derrick Stolee Date: Thu, 22 Mar 2018 13:40:09 -0400 Subject: [PATCH] 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: Derrick Stolee Signed-off-by: Junio C Hamano --- 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 @@ out: 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 @@ -79,6 +79,14 @@ 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 * at the SHA-1 within the mmapped index. Return NULL if there is an -- 2.11.4.GIT