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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 | ||
e8c58f89 | 19 | |
2f4ba2a8 TB |
20 | #define RIDX_SIGNATURE 0x52494458 /* "RIDX" */ |
21 | #define RIDX_VERSION 1 | |
22 | ||
e8c58f89 | 23 | #define GIT_TEST_WRITE_REV_INDEX "GIT_TEST_WRITE_REV_INDEX" |
ec8e7760 | 24 | #define GIT_TEST_REV_INDEX_DIE_IN_MEMORY "GIT_TEST_REV_INDEX_DIE_IN_MEMORY" |
e8c58f89 | 25 | |
9d98bbf5 JK |
26 | struct packed_git; |
27 | ||
f33fb6e4 TB |
28 | /* |
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. | |
2f4ba2a8 TB |
31 | * |
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). | |
f33fb6e4 | 34 | */ |
4828ce98 | 35 | int load_pack_revindex(struct packed_git *p); |
92e5c77c | 36 | |
f33fb6e4 TB |
37 | /* |
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. | |
41 | * | |
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. | |
44 | * | |
45 | * This function runs in time O(log N) with the number of objects in the pack. | |
46 | */ | |
47 | int offset_to_pack_pos(struct packed_git *p, off_t ofs, uint32_t *pos); | |
48 | ||
49 | /* | |
50 | * pack_pos_to_index converts the given pack-relative position 'pos' by | |
51 | * returning an index-relative position. | |
52 | * | |
53 | * If the reverse index has not yet been loaded, or the position is out of | |
54 | * bounds, this function aborts. | |
55 | * | |
56 | * This function runs in constant time. | |
57 | */ | |
58 | uint32_t pack_pos_to_index(struct packed_git *p, uint32_t pos); | |
59 | ||
60 | /* | |
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. | |
64 | * | |
65 | * If the reverse index has not yet been loaded, or the position is out of | |
66 | * bounds, this function aborts. | |
67 | * | |
2f4ba2a8 TB |
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. | |
f33fb6e4 TB |
71 | */ |
72 | off_t pack_pos_to_offset(struct packed_git *p, uint32_t pos); | |
73 | ||
3449f8c4 | 74 | #endif |