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#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
*/
#define RIDX_SIGNATURE 0x52494458 /* "RIDX" */
#define RIDX_VERSION 1
struct packed_git;
/*
* load_pack_revindex populates the revindex's internal data-structures for the
* given pack, returning zero on success and a negative value otherwise.
*
* If a '.rev' file is present it is mmap'd, and pointers are assigned into it
* (instead of using the in-memory variant).
*/
int load_pack_revindex(struct packed_git *p);
/*
* 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 under both in-memory and on-disk reverse
* indexes, but an additional step is taken to consult the corresponding .idx
* file when using the on-disk format.
*/
off_t pack_pos_to_offset(struct packed_git *p, uint32_t pos);
#endif
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