[PATCH 02/10] pack-objects: read delta base oid into object_id struct
- From
Jeff King <peff@peff.net>
- Date
- Feb 24, 2020, 04:29 UTC
- Message-ID
- <20200224042944.GB1018190@coredump.intra.peff.net>
- In-Reply-To
- <20200224042625.GA1015553@coredump.intra.peff.net>
When we're considering reusing an on-disk delta, we get the oid of the base as a pointer to unsigned char bytes of the hash, either into the packfile itself (for REF_DELTA) or into the pack idx (using the revindex to convert the offset into an index entry).
Instead, we'd prefer to use a more type-safe object_id as much as possible. We can get the pack idx using nth_packed_object_id() instead. For the packfile bytes, we can copy them out using oidread().
This doesn't even incur an extra copy overall, since the next thing we'd always do with that pointer is pass it to can_reuse_delta(), which needs an object_id anyway (and called oidread() itself). So this patch also converts that function to take the object_id directly.
Note that we did previously use NULL as a sentinel value when the object isn't a delta. We could probably get away with using the null oid for this, but instead we'll use an explicit boolean flag, which should make things more obvious for people reading the code later.
Signed-off-by: Jeff King <peff@peff.net> --- Astute readers may notice that if we didn't do the error-conversion in the previous patch, we could keep the sentinel value semantics with something like:
struct object_id *base_ref = NULL; struct object_id base_ref_storage; ... base_ref = nth_packed_object_oid(&base_ref_storage, p, nr);
but that's not any fewer lines, and IMHO it's much less obvious what's going on compared to the boolean flag I used here.
builtin/pack-objects.c | 35 ++++++++++++++++++----------------- 1 file changed, 18 insertions(+), 17 deletions(-)
diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c index de8335e2bd..8692ab3fe6 100644 --- a/builtin/pack-objects.c +++ b/builtin/pack-objects.c @@ -1618,23 +1618,17 @@ static void cleanup_preferred_base(void) * deltify other objects against, in order to avoid * circular deltas. */ -static int can_reuse_delta(const unsigned char *base_sha1, +static int can_reuse_delta(const struct object_id *base_oid, struct object_entry *delta, struct object_entry **base_out) { struct object_entry *base; - struct object_id base_oid; - - if (!base_sha1) - return 0; - - oidread(&base_oid, base_sha1); /* * First see if we're already sending the base (or it's explicitly in * our "excluded" list). */ - base = packlist_find(&to_pack, &base_oid); + base = packlist_find(&to_pack, base_oid); if (base) { if (!in_same_island(&delta->idx.oid, &base->idx.oid)) return 0; @@ -1647,9 +1641,9 @@ static int can_reuse_delta(const unsigned char *base_sha1, * even if it was buried too deep in history to make it into the * packing list. */ - if (thin && bitmap_has_oid_in_uninteresting(bitmap_git, &base_oid)) { + if (thin && bitmap_has_oid_in_uninteresting(bitmap_git, base_oid)) { if (use_delta_islands) { - if (!in_same_island(&delta->idx.oid, &base_oid)) + if (!in_same_island(&delta->idx.oid, base_oid)) return 0; } *base_out = NULL; @@ -1666,7 +1660,8 @@ static void check_object(struct object_entry *entry) if (IN_PACK(entry)) { struct packed_git *p = IN_PACK(entry); struct pack_window *w_curs = NULL; - const unsigned char *base_ref = NULL; + int have_base = 0; + struct object_id base_ref; struct object_entry *base_entry; unsigned long used, used_0; unsigned long avail; @@ -1707,9 +1702,13 @@ static void check_object(struct object_entry *entry) unuse_pack(&w_curs); return; case OBJ_REF_DELTA: - if (reuse_delta && !entry->preferred_base) - base_ref = use_pack(p, &w_curs, - entry->in_pack_offset + used, NULL); + if (reuse_delta && !entry->preferred_base) { + oidread(&base_ref, + use_pack(p, &w_curs, + entry->in_pack_offset + used, + NULL)); + have_base = 1; + } entry->in_pack_header_size = used + the_hash_algo->rawsz; break; case OBJ_OFS_DELTA: @@ -1739,13 +1738,15 @@ static void check_object(struct object_entry *entry) revidx = find_pack_revindex(p, ofs); if (!revidx) goto give_up; - base_ref = nth_packed_object_sha1(p, revidx->nr); + if (!nth_packed_object_id(&base_ref, p, revidx->nr)) + have_base = 1; } entry->in_pack_header_size = used + used_0; break; } - if (can_reuse_delta(base_ref, entry, &base_entry)) { + if (have_base && + can_reuse_delta(&base_ref, entry, &base_entry)) { oe_set_type(entry, entry->in_pack_type); SET_SIZE(entry, in_pack_size); /* delta size */ SET_DELTA_SIZE(entry, in_pack_size); @@ -1755,7 +1756,7 @@ static void check_object(struct object_entry *entry) entry->delta_sibling_idx = base_entry->delta_child_idx; SET_DELTA_CHILD(base_entry, entry); } else { - SET_DELTA_EXT(entry, base_ref); + SET_DELTA_EXT(entry, base_ref.hash); } unuse_pack(&w_curs);
-- 2.25.1.823.g95c5488cf7