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74 lines
2.5 KiB
74 lines
2.5 KiB
#ifndef PACK_REVINDEX_H |
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#define PACK_REVINDEX_H |
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/** |
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* A revindex allows converting efficiently between three properties |
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* of an object within a pack: |
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* |
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* - index position: the numeric position within the list of sorted object ids |
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* found in the .idx file |
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* |
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* - pack position: the numeric position within the list of objects in their |
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* order within the actual .pack file (i.e., 0 is the first object in the |
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* .pack, 1 is the second, and so on) |
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* |
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* - offset: the byte offset within the .pack file at which the object contents |
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* can be found |
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*/ |
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#define RIDX_SIGNATURE 0x52494458 /* "RIDX" */ |
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#define RIDX_VERSION 1 |
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#define GIT_TEST_WRITE_REV_INDEX "GIT_TEST_WRITE_REV_INDEX" |
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#define GIT_TEST_REV_INDEX_DIE_IN_MEMORY "GIT_TEST_REV_INDEX_DIE_IN_MEMORY" |
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struct packed_git; |
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/* |
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* load_pack_revindex populates the revindex's internal data-structures for the |
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* given pack, returning zero on success and a negative value otherwise. |
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* |
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* If a '.rev' file is present it is mmap'd, and pointers are assigned into it |
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* (instead of using the in-memory variant). |
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*/ |
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int load_pack_revindex(struct packed_git *p); |
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/* |
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* offset_to_pack_pos converts an object offset to a pack position. This |
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* function returns zero on success, and a negative number otherwise. The |
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* parameter 'pos' is usable only on success. |
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* |
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* If the reverse index has not yet been loaded, this function loads it lazily, |
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* and returns an negative number if an error was encountered. |
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* |
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* This function runs in time O(log N) with the number of objects in the pack. |
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*/ |
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int offset_to_pack_pos(struct packed_git *p, off_t ofs, uint32_t *pos); |
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/* |
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* pack_pos_to_index converts the given pack-relative position 'pos' by |
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* returning an index-relative position. |
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* |
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* If the reverse index has not yet been loaded, or the position is out of |
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* bounds, this function aborts. |
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* |
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* This function runs in constant time. |
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*/ |
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uint32_t pack_pos_to_index(struct packed_git *p, uint32_t pos); |
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/* |
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* pack_pos_to_offset converts the given pack-relative position 'pos' into a |
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* pack offset. For a pack with 'N' objects, asking for position 'N' will return |
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* the total size (in bytes) of the pack. |
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* |
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* If the reverse index has not yet been loaded, or the position is out of |
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* bounds, this function aborts. |
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* |
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* This function runs in constant time under both in-memory and on-disk reverse |
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* indexes, but an additional step is taken to consult the corresponding .idx |
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* file when using the on-disk format. |
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*/ |
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off_t pack_pos_to_offset(struct packed_git *p, uint32_t pos); |
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#endif
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