pack-revindex.h

   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
  19 struct packed_git;
  20
  21 /*
  22  * load_pack_revindex populates the revindex's internal data-structures for the
  23  * given pack, returning zero on success and a negative value otherwise.
  24  */
  25 int load_pack_revindex(struct packed_git *p);
  26
  27 /*
  28  * offset_to_pack_pos converts an object offset to a pack position. This
  29  * function returns zero on success, and a negative number otherwise. The
  30  * parameter 'pos' is usable only on success.
  31  *
  32  * If the reverse index has not yet been loaded, this function loads it lazily,
  33  * and returns an negative number if an error was encountered.
  34  *
  35  * This function runs in time O(log N) with the number of objects in the pack.
  36  */
  37 int offset_to_pack_pos(struct packed_git *p, off_t ofs, uint32_t *pos);
  38
  39 /*
  40  * pack_pos_to_index converts the given pack-relative position 'pos' by
  41  * returning an index-relative position.
  42  *
  43  * If the reverse index has not yet been loaded, or the position is out of
  44  * bounds, this function aborts.
  45  *
  46  * This function runs in constant time.
  47  */
  48 uint32_t pack_pos_to_index(struct packed_git *p, uint32_t pos);
  49
  50 /*
  51  * pack_pos_to_offset converts the given pack-relative position 'pos' into a
  52  * pack offset. For a pack with 'N' objects, asking for position 'N' will return
  53  * the total size (in bytes) of the pack.
  54  *
  55  * If the reverse index has not yet been loaded, or the position is out of
  56  * bounds, this function aborts.
  57  *
  58  * This function runs in constant time.
  59  */
  60 off_t pack_pos_to_offset(struct packed_git *p, uint32_t pos);
  61
  62 #endif