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1#ifndef PACK_REVINDEX_H
2#define PACK_REVINDEX_H
3
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 * The revindex can also be used with a multi-pack index (MIDX). In this
19 * setting:
20 *
21 * - index position refers to an object's numeric position within the MIDX
22 *
23 * - pack position refers to an object's position within a non-existent pack
24 * described by the MIDX. The pack structure is described in
25 * gitformat-pack(5).
26 *
27 * It is effectively a concatanation of all packs in the MIDX (ordered by
28 * their numeric ID within the MIDX) in their original order within each
29 * pack), removing duplicates, and placing the preferred pack (if any)
30 * first.
31 */
32
33
34#define RIDX_SIGNATURE 0x52494458 /* "RIDX" */
35#define RIDX_VERSION 1
36
37#define GIT_TEST_NO_WRITE_REV_INDEX "GIT_TEST_NO_WRITE_REV_INDEX"
38#define GIT_TEST_REV_INDEX_DIE_IN_MEMORY "GIT_TEST_REV_INDEX_DIE_IN_MEMORY"
39#define GIT_TEST_REV_INDEX_DIE_ON_DISK "GIT_TEST_REV_INDEX_DIE_ON_DISK"
40
41struct packed_git;
42struct multi_pack_index;
43struct repository;
44
45/*
46 * load_pack_revindex populates the revindex's internal data-structures for the
47 * given pack, returning zero on success and a negative value otherwise.
48 *
49 * If a '.rev' file is present it is mmap'd, and pointers are assigned into it
50 * (instead of using the in-memory variant).
51 */
52int load_pack_revindex(struct repository *r, struct packed_git *p);
53
54/*
55 * Specifically load a pack revindex from disk.
56 *
57 * Returns 0 on success, 1 on "no .rev file", and -1 when there is an
58 * error parsing the .rev file.
59 */
60int load_pack_revindex_from_disk(struct packed_git *p);
61
62/*
63 * verify_pack_revindex verifies that the on-disk rev-index for the given
64 * pack-file is the same that would be created if written from scratch.
65 *
66 * A negative number is returned on error.
67 */
68int verify_pack_revindex(struct packed_git *p);
69
70/*
71 * load_midx_revindex loads the '.rev' file corresponding to the given
72 * multi-pack index by mmap-ing it and assigning pointers in the
73 * multi_pack_index to point at it.
74 *
75 * A negative number is returned on error.
76 */
77int load_midx_revindex(struct multi_pack_index *m);
78
79/*
80 * Frees resources associated with a multi-pack reverse index.
81 *
82 * A negative number is returned on error.
83 */
84int close_midx_revindex(struct multi_pack_index *m);
85
86/*
87 * offset_to_pack_pos converts an object offset to a pack position. This
88 * function returns zero on success, and a negative number otherwise. The
89 * parameter 'pos' is usable only on success.
90 *
91 * If the reverse index has not yet been loaded, this function loads it lazily,
92 * and returns an negative number if an error was encountered.
93 *
94 * This function runs in time O(log N) with the number of objects in the pack.
95 */
96int offset_to_pack_pos(struct packed_git *p, off_t ofs, uint32_t *pos);
97
98/*
99 * pack_pos_to_index converts the given pack-relative position 'pos' by
100 * returning an index-relative position.
101 *
102 * If the reverse index has not yet been loaded, or the position is out of
103 * bounds, this function aborts.
104 *
105 * This function runs in constant time.
106 */
107uint32_t pack_pos_to_index(struct packed_git *p, uint32_t pos);
108
109/*
110 * pack_pos_to_offset converts the given pack-relative position 'pos' into a
111 * pack offset. For a pack with 'N' objects, asking for position 'N' will return
112 * the total size (in bytes) of the pack.
113 *
114 * If the reverse index has not yet been loaded, or the position is out of
115 * bounds, this function aborts.
116 *
117 * This function runs in constant time under both in-memory and on-disk reverse
118 * indexes, but an additional step is taken to consult the corresponding .idx
119 * file when using the on-disk format.
120 */
121off_t pack_pos_to_offset(struct packed_git *p, uint32_t pos);
122
123/*
124 * pack_pos_to_midx converts the object at position "pos" within the MIDX
125 * pseudo-pack into a MIDX position.
126 *
127 * If the reverse index has not yet been loaded, or the position is out of
128 * bounds, this function aborts.
129 *
130 * This function runs in constant time.
131 */
132uint32_t pack_pos_to_midx(struct multi_pack_index *m, uint32_t pos);
133
134/*
135 * midx_to_pack_pos converts from the MIDX-relative position at "at" to the
136 * corresponding pack position.
137 *
138 * If the reverse index has not yet been loaded, or the position is out of
139 * bounds, this function aborts.
140 *
141 * This function runs in time O(log N) with the number of objects in the MIDX.
142 */
143int midx_to_pack_pos(struct multi_pack_index *midx, uint32_t at, uint32_t *pos);
144
145int midx_pair_to_pack_pos(struct multi_pack_index *midx, uint32_t pack_id,
146 off_t ofs, uint32_t *pos);
147
148#endif