diff options
Diffstat (limited to 'pack-revindex.h')
-rw-r--r-- | pack-revindex.h | 54 |
1 files changed, 54 insertions, 0 deletions
diff --git a/pack-revindex.h b/pack-revindex.h index 848331d5d6..5a218aaa66 100644 --- a/pack-revindex.h +++ b/pack-revindex.h @@ -1,6 +1,21 @@ #ifndef PACK_REVINDEX_H #define PACK_REVINDEX_H +/** + * A revindex allows converting efficiently between three properties + * of an object within a pack: + * + * - index position: the numeric position within the list of sorted object ids + * found in the .idx file + * + * - pack position: the numeric position within the list of objects in their + * order within the actual .pack file (i.e., 0 is the first object in the + * .pack, 1 is the second, and so on) + * + * - offset: the byte offset within the .pack file at which the object contents + * can be found + */ + struct packed_git; struct revindex_entry { @@ -8,9 +23,48 @@ struct revindex_entry { unsigned int nr; }; +/* + * load_pack_revindex populates the revindex's internal data-structures for the + * given pack, returning zero on success and a negative value otherwise. + */ int load_pack_revindex(struct packed_git *p); int find_revindex_position(struct packed_git *p, off_t ofs); struct revindex_entry *find_pack_revindex(struct packed_git *p, off_t ofs); +/* + * offset_to_pack_pos converts an object offset to a pack position. This + * function returns zero on success, and a negative number otherwise. The + * parameter 'pos' is usable only on success. + * + * If the reverse index has not yet been loaded, this function loads it lazily, + * and returns an negative number if an error was encountered. + * + * This function runs in time O(log N) with the number of objects in the pack. + */ +int offset_to_pack_pos(struct packed_git *p, off_t ofs, uint32_t *pos); + +/* + * pack_pos_to_index converts the given pack-relative position 'pos' by + * returning an index-relative position. + * + * If the reverse index has not yet been loaded, or the position is out of + * bounds, this function aborts. + * + * This function runs in constant time. + */ +uint32_t pack_pos_to_index(struct packed_git *p, uint32_t pos); + +/* + * pack_pos_to_offset converts the given pack-relative position 'pos' into a + * pack offset. For a pack with 'N' objects, asking for position 'N' will return + * the total size (in bytes) of the pack. + * + * If the reverse index has not yet been loaded, or the position is out of + * bounds, this function aborts. + * + * This function runs in constant time. + */ +off_t pack_pos_to_offset(struct packed_git *p, uint32_t pos); + #endif |