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b1e3333068
When performing a binary search over the objects in a MIDX's bitmap
(i.e. in pseudo-pack order), the reader reconstructs the pseudo-pack
ordering using a combination of (a) the preferred pack, (b) the pack's
lexical position in the MIDX based on pack names, and (c) the object
offset within the pack.
In order to perform this binary search, the reader must know the
identity of the preferred pack. This could be stored in the MIDX, but
isn't for historical reasons, mostly because it can easily be inferred
at read-time by looking at the object in the first bit position and
finding out which pack it was selected from in the MIDX, like so:
nth_midxed_pack_int_id(m, pack_pos_to_midx(m, 0));
In midx_to_pack_pos() which performs this binary search, we look up the
identity of the preferred pack before each search. This is relatively
quick, since it involves two table-driven lookups (one in the MIDX's
revindex for `pack_pos_to_midx()`, and another in the MIDX's object
table for `nth_midxed_pack_int_id()`).
But since the preferred pack does not change after the MIDX is written,
it is safe to cache this value on the MIDX itself.
Write a helper to do just that, and rewrite all of the existing
call-sites that care about the identity of the preferred pack in terms
of this new helper.
This will prepare us for a subsequent patch where we will need to binary
search through the MIDX's pseudo-pack order multiple times.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
101 lines
3.5 KiB
C
101 lines
3.5 KiB
C
#ifndef MIDX_H
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#define MIDX_H
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#include "repository.h"
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#include "string-list.h"
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struct object_id;
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struct pack_entry;
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struct repository;
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struct bitmapped_pack;
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#define GIT_TEST_MULTI_PACK_INDEX "GIT_TEST_MULTI_PACK_INDEX"
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#define GIT_TEST_MULTI_PACK_INDEX_WRITE_BITMAP \
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"GIT_TEST_MULTI_PACK_INDEX_WRITE_BITMAP"
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struct multi_pack_index {
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struct multi_pack_index *next;
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const unsigned char *data;
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size_t data_len;
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const uint32_t *revindex_data;
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const uint32_t *revindex_map;
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size_t revindex_len;
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uint32_t signature;
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unsigned char version;
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unsigned char hash_len;
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unsigned char num_chunks;
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uint32_t num_packs;
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uint32_t num_objects;
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int preferred_pack_idx;
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int local;
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const unsigned char *chunk_pack_names;
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size_t chunk_pack_names_len;
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const uint32_t *chunk_bitmapped_packs;
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size_t chunk_bitmapped_packs_len;
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const uint32_t *chunk_oid_fanout;
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const unsigned char *chunk_oid_lookup;
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const unsigned char *chunk_object_offsets;
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const unsigned char *chunk_large_offsets;
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size_t chunk_large_offsets_len;
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const unsigned char *chunk_revindex;
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size_t chunk_revindex_len;
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const char **pack_names;
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struct packed_git **packs;
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char object_dir[FLEX_ARRAY];
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};
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#define MIDX_PROGRESS (1 << 0)
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#define MIDX_WRITE_REV_INDEX (1 << 1)
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#define MIDX_WRITE_BITMAP (1 << 2)
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#define MIDX_WRITE_BITMAP_HASH_CACHE (1 << 3)
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#define MIDX_WRITE_BITMAP_LOOKUP_TABLE (1 << 4)
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const unsigned char *get_midx_checksum(struct multi_pack_index *m);
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void get_midx_filename(struct strbuf *out, const char *object_dir);
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void get_midx_rev_filename(struct strbuf *out, struct multi_pack_index *m);
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struct multi_pack_index *load_multi_pack_index(const char *object_dir, int local);
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int prepare_midx_pack(struct repository *r, struct multi_pack_index *m, uint32_t pack_int_id);
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int nth_bitmapped_pack(struct repository *r, struct multi_pack_index *m,
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struct bitmapped_pack *bp, uint32_t pack_int_id);
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int bsearch_midx(const struct object_id *oid, struct multi_pack_index *m, uint32_t *result);
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off_t nth_midxed_offset(struct multi_pack_index *m, uint32_t pos);
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uint32_t nth_midxed_pack_int_id(struct multi_pack_index *m, uint32_t pos);
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struct object_id *nth_midxed_object_oid(struct object_id *oid,
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struct multi_pack_index *m,
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uint32_t n);
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int fill_midx_entry(struct repository *r, const struct object_id *oid, struct pack_entry *e, struct multi_pack_index *m);
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int midx_contains_pack(struct multi_pack_index *m,
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const char *idx_or_pack_name);
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int midx_locate_pack(struct multi_pack_index *m, const char *idx_or_pack_name,
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uint32_t *pos);
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int midx_preferred_pack(struct multi_pack_index *m, uint32_t *pack_int_id);
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int prepare_multi_pack_index_one(struct repository *r, const char *object_dir, int local);
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/*
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* Variant of write_midx_file which writes a MIDX containing only the packs
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* specified in packs_to_include.
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*/
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int write_midx_file(const char *object_dir,
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const char *preferred_pack_name,
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const char *refs_snapshot,
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unsigned flags);
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int write_midx_file_only(const char *object_dir,
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struct string_list *packs_to_include,
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const char *preferred_pack_name,
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const char *refs_snapshot,
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unsigned flags);
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void clear_midx_file(struct repository *r);
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int verify_midx_file(struct repository *r, const char *object_dir, unsigned flags);
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int expire_midx_packs(struct repository *r, const char *object_dir, unsigned flags);
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int midx_repack(struct repository *r, const char *object_dir, size_t batch_size, unsigned flags);
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void close_midx(struct multi_pack_index *m);
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#endif
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