1 #ifndef PACK_REVINDEX_H
2 #define PACK_REVINDEX_H
5 * A revindex allows converting efficiently between three properties
6 * of an object within a pack:
8 * - index position: the numeric position within the list of sorted object ids
9 * found in the .idx file
11 * - pack position: the numeric position within the list of objects in their
12 * order within the actual .pack file (i.e., 0 is the first object in the
13 * .pack, 1 is the second, and so on)
15 * - offset: the byte offset within the .pack file at which the object contents
20 #define RIDX_SIGNATURE 0x52494458 /* "RIDX" */
21 #define RIDX_VERSION 1
23 #define GIT_TEST_WRITE_REV_INDEX "GIT_TEST_WRITE_REV_INDEX"
24 #define GIT_TEST_REV_INDEX_DIE_IN_MEMORY "GIT_TEST_REV_INDEX_DIE_IN_MEMORY"
29 * load_pack_revindex populates the revindex's internal data-structures for the
30 * given pack, returning zero on success and a negative value otherwise.
32 * If a '.rev' file is present it is mmap'd, and pointers are assigned into it
33 * (instead of using the in-memory variant).
35 int load_pack_revindex(struct packed_git *p);
38 * offset_to_pack_pos converts an object offset to a pack position. This
39 * function returns zero on success, and a negative number otherwise. The
40 * parameter 'pos' is usable only on success.
42 * If the reverse index has not yet been loaded, this function loads it lazily,
43 * and returns an negative number if an error was encountered.
45 * This function runs in time O(log N) with the number of objects in the pack.
47 int offset_to_pack_pos(struct packed_git *p, off_t ofs, uint32_t *pos);
50 * pack_pos_to_index converts the given pack-relative position 'pos' by
51 * returning an index-relative position.
53 * If the reverse index has not yet been loaded, or the position is out of
54 * bounds, this function aborts.
56 * This function runs in constant time.
58 uint32_t pack_pos_to_index(struct packed_git *p, uint32_t pos);
61 * pack_pos_to_offset converts the given pack-relative position 'pos' into a
62 * pack offset. For a pack with 'N' objects, asking for position 'N' will return
63 * the total size (in bytes) of the pack.
65 * If the reverse index has not yet been loaded, or the position is out of
66 * bounds, this function aborts.
68 * This function runs in constant time under both in-memory and on-disk reverse
69 * indexes, but an additional step is taken to consult the corresponding .idx
70 * file when using the on-disk format.
72 off_t pack_pos_to_offset(struct packed_git *p, uint32_t pos);