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3449f8c4 NP |
1 | #ifndef PACK_REVINDEX_H |
2 | #define PACK_REVINDEX_H | |
3 | ||
f33fb6e4 TB |
4 | /** |
5 | * A revindex allows converting efficiently between three properties | |
6 | * of an object within a pack: | |
7 | * | |
8 | * - index position: the numeric position within the list of sorted object ids | |
9 | * found in the .idx file | |
10 | * | |
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) | |
14 | * | |
15 | * - offset: the byte offset within the .pack file at which the object contents | |
16 | * can be found | |
17 | */ | |
18 | ||
9d98bbf5 JK |
19 | struct packed_git; |
20 | ||
3449f8c4 NP |
21 | struct revindex_entry { |
22 | off_t offset; | |
23 | unsigned int nr; | |
24 | }; | |
25 | ||
f33fb6e4 TB |
26 | /* |
27 | * load_pack_revindex populates the revindex's internal data-structures for the | |
28 | * given pack, returning zero on success and a negative value otherwise. | |
29 | */ | |
4828ce98 | 30 | int load_pack_revindex(struct packed_git *p); |
9d98bbf5 | 31 | int find_revindex_position(struct packed_git *p, off_t ofs); |
92e5c77c | 32 | |
3449f8c4 NP |
33 | struct revindex_entry *find_pack_revindex(struct packed_git *p, off_t ofs); |
34 | ||
f33fb6e4 TB |
35 | /* |
36 | * offset_to_pack_pos converts an object offset to a pack position. This | |
37 | * function returns zero on success, and a negative number otherwise. The | |
38 | * parameter 'pos' is usable only on success. | |
39 | * | |
40 | * If the reverse index has not yet been loaded, this function loads it lazily, | |
41 | * and returns an negative number if an error was encountered. | |
42 | * | |
43 | * This function runs in time O(log N) with the number of objects in the pack. | |
44 | */ | |
45 | int offset_to_pack_pos(struct packed_git *p, off_t ofs, uint32_t *pos); | |
46 | ||
47 | /* | |
48 | * pack_pos_to_index converts the given pack-relative position 'pos' by | |
49 | * returning an index-relative position. | |
50 | * | |
51 | * If the reverse index has not yet been loaded, or the position is out of | |
52 | * bounds, this function aborts. | |
53 | * | |
54 | * This function runs in constant time. | |
55 | */ | |
56 | uint32_t pack_pos_to_index(struct packed_git *p, uint32_t pos); | |
57 | ||
58 | /* | |
59 | * pack_pos_to_offset converts the given pack-relative position 'pos' into a | |
60 | * pack offset. For a pack with 'N' objects, asking for position 'N' will return | |
61 | * the total size (in bytes) of the pack. | |
62 | * | |
63 | * If the reverse index has not yet been loaded, or the position is out of | |
64 | * bounds, this function aborts. | |
65 | * | |
66 | * This function runs in constant time. | |
67 | */ | |
68 | off_t pack_pos_to_offset(struct packed_git *p, uint32_t pos); | |
69 | ||
3449f8c4 | 70 | #endif |