packfile: expose function to read object stream for an offset

The function `packfile_store_read_object_stream()` takes as input an object ID and then constructs a `struct odb_read_stream` from it. In a subsequent commit we'll want to create an object stream for a given combination of packfile and offset though, which is not something that can currently be done. Extract a new function `packfile_read_object_stream()` that makes this functionality available. Signed-off-by: Patrick Steinhardt <ps@pks.im> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Patrick Steinhardt committed Feb 23, 2026 at 17:00 UTC 41b42e3527eb6b0ab4b557d16adedcd255c9045f
2 files changed +29 -16
packfile.c
+24 -16
@@ -2553,32 +2553,28 @@ static int close_istream_pack_non_delta(struct odb_read_stream *_st)
2553 return 0;
2554 }
2555
2556 -int packfile_store_read_object_stream(struct odb_read_stream **out,
2557 - struct packfile_store *store,
2558 - const struct object_id *oid)
2556 +int packfile_read_object_stream(struct odb_read_stream **out,
2557 + const struct object_id *oid,
2558 + struct packed_git *pack,
2559 + off_t offset)
2560 {
2561 struct odb_packed_read_stream *stream;
2562 struct pack_window *window = NULL;
2562 - struct object_info oi = OBJECT_INFO_INIT;
2563 enum object_type in_pack_type;
2564 unsigned long size;
2565
2566 - oi.sizep = &size;
2566 + in_pack_type = unpack_object_header(pack, &window, &offset, &size);
2567 + unuse_pack(&window);
2568
2568 - if (packfile_store_read_object_info(store, oid, &oi, 0) ||
2569 - oi.u.packed.type == PACKED_OBJECT_TYPE_REF_DELTA ||
2570 - oi.u.packed.type == PACKED_OBJECT_TYPE_OFS_DELTA ||
2571 - repo_settings_get_big_file_threshold(store->source->odb->repo) >= size)
2569 + if (repo_settings_get_big_file_threshold(pack->repo) >= size)
2570 return -1;
2571
2574 - in_pack_type = unpack_object_header(oi.u.packed.pack,
2575 - &window,
2576 - &oi.u.packed.offset,
2577 - &size);
2578 - unuse_pack(&window);
2572 switch (in_pack_type) {
2573 default:
2574 return -1; /* we do not do deltas for now */
2575 + case OBJ_BAD:
2576 + mark_bad_packed_object(pack, oid);
2577 + return -1;
2578 case OBJ_COMMIT:
2579 case OBJ_TREE:
2580 case OBJ_BLOB:
@@ -2592,10 +2588,22 @@ int packfile_store_read_object_stream(struct odb_read_stream **out,
2588 stream->base.type = in_pack_type;
2589 stream->base.size = size;
2590 stream->z_state = ODB_PACKED_READ_STREAM_UNINITIALIZED;
2595 - stream->pack = oi.u.packed.pack;
2596 - stream->pos = oi.u.packed.offset;
2591 + stream->pack = pack;
2592 + stream->pos = offset;
2593
2594 *out = &stream->base;
2595
2596 return 0;
2597 }
2598 +
2599 +int packfile_store_read_object_stream(struct odb_read_stream **out,
2600 + struct packfile_store *store,
2601 + const struct object_id *oid)
2602 +{
2603 + struct pack_entry e;
2604 +
2605 + if (!find_pack_entry(store, oid, &e))
2606 + return -1;
2607 +
2608 + return packfile_read_object_stream(out, oid, e.p, e.offset);
2609 +}
packfile.h
+5
@@ -436,6 +436,11 @@ off_t get_delta_base(struct packed_git *p, struct pack_window **w_curs,
436 off_t *curpos, enum object_type type,
437 off_t delta_obj_offset);
438
439 +int packfile_read_object_stream(struct odb_read_stream **out,
440 + const struct object_id *oid,
441 + struct packed_git *pack,
442 + off_t offset);
443 +
444 void release_pack_memory(size_t);
445
446 /* global flag to enable extra checks when accessing packed objects */