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9f7f10a282
Back in e8c58f894b (t: support GIT_TEST_WRITE_REV_INDEX, 2021-01-25), we
added a test knob to conditionally enable writing a ".rev" file when
indexing a pack. At the time, this was used to ensure that the test
suite worked even when ".rev" files were written, which served as a
stress-test for the on-disk reverse index implementation.
Now that reading from on-disk ".rev" files is enabled by default, the
test knob `GIT_TEST_WRITE_REV_INDEX` no longer has any meaning.
We could get rid of the option entirely, but there would be no
convenient way to test Git when ".rev" files *aren't* in place.
Instead of getting rid of the option, invert its meaning to instead
disable writing ".rev" files, thereby running the test suite in a mode
where the reverse index is generated from scratch.
This ensures that, when GIT_TEST_NO_WRITE_REV_INDEX is set to some
spelling of "true", we are still running and exercising Git's behavior
when forced to generate reverse indexes from scratch. Do so by setting
it in the linux-TEST-vars CI run to ensure that we are maintaining good
coverage of this now-legacy code.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Acked-by: Derrick Stolee <derrickstolee@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
130 lines
4.4 KiB
C
130 lines
4.4 KiB
C
#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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* The revindex can also be used with a multi-pack index (MIDX). In this
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* setting:
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*
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* - index position refers to an object's numeric position within the MIDX
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*
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* - pack position refers to an object's position within a non-existent pack
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* described by the MIDX. The pack structure is described in
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* gitformat-pack(5).
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*
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* It is effectively a concatanation of all packs in the MIDX (ordered by
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* their numeric ID within the MIDX) in their original order within each
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* pack), removing duplicates, and placing the preferred pack (if any)
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* first.
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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_NO_WRITE_REV_INDEX "GIT_TEST_NO_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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#define GIT_TEST_REV_INDEX_DIE_ON_DISK "GIT_TEST_REV_INDEX_DIE_ON_DISK"
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struct packed_git;
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struct multi_pack_index;
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struct repository;
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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 repository *r, struct packed_git *p);
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/*
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* load_midx_revindex loads the '.rev' file corresponding to the given
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* multi-pack index by mmap-ing it and assigning pointers in the
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* multi_pack_index to point at it.
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*
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* A negative number is returned on error.
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*/
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int load_midx_revindex(struct multi_pack_index *m);
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/*
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* Frees resources associated with a multi-pack reverse index.
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*
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* A negative number is returned on error.
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*/
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int close_midx_revindex(struct multi_pack_index *m);
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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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/*
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* pack_pos_to_midx converts the object at position "pos" within the MIDX
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* pseudo-pack into a MIDX 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_midx(struct multi_pack_index *m, uint32_t pos);
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/*
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* midx_to_pack_pos converts from the MIDX-relative position at "at" to the
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* corresponding pack 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 time O(log N) with the number of objects in the MIDX.
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*/
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int midx_to_pack_pos(struct multi_pack_index *midx, uint32_t at, uint32_t *pos);
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#endif
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