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 struct revindex_entry {
  22         off_t offset;
  23         unsigned int nr;
  24 };
  25
  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  */
  30 int load_pack_revindex(struct packed_git *p);
  31
  32 /*
  33  * offset_to_pack_pos converts an object offset to a pack position. This
  34  * function returns zero on success, and a negative number otherwise. The
  35  * parameter 'pos' is usable only on success.
  36  *
  37  * If the reverse index has not yet been loaded, this function loads it lazily,
  38  * and returns an negative number if an error was encountered.
  39  *
  40  * This function runs in time O(log N) with the number of objects in the pack.
  41  */
  42 int offset_to_pack_pos(struct packed_git *p, off_t ofs, uint32_t *pos);
  43
  44 /*
  45  * pack_pos_to_index converts the given pack-relative position 'pos' by
  46  * returning an index-relative position.
  47  *
  48  * If the reverse index has not yet been loaded, or the position is out of
  49  * bounds, this function aborts.
  50  *
  51  * This function runs in constant time.
  52  */
  53 uint32_t pack_pos_to_index(struct packed_git *p, uint32_t pos);
  54
  55 /*
  56  * pack_pos_to_offset converts the given pack-relative position 'pos' into a
  57  * pack offset. For a pack with 'N' objects, asking for position 'N' will return
  58  * the total size (in bytes) of the pack.
  59  *
  60  * If the reverse index has not yet been loaded, or the position is out of
  61  * bounds, this function aborts.
  62  *
  63  * This function runs in constant time.
  64  */
  65 off_t pack_pos_to_offset(struct packed_git *p, uint32_t pos);
  66
  67 #endif