src/midx.h

   1 /*
   2  * Copyright (C) the libgit2 contributors. All rights reserved.
   3  *
   4  * This file is part of libgit2, distributed under the GNU GPL v2 with
   5  * a Linking Exception. For full terms see the included COPYING file.
   6  */
   7
   8 #ifndef INCLUDE_midx_h__
   9 #define INCLUDE_midx_h__
  10
  11 #include "common.h"
  12
  13 #include <ctype.h>
  14
  15 #include "map.h"
  16 #include "mwindow.h"
  17
  18 /*
  19  * A multi-pack-index file.
  20  *
  21  * This file contains a merged index for multiple independent .pack files. This
  22  * can help speed up locating objects without requiring a garbage collection
  23  * cycle to create a single .pack file.
  24  *
  25  * Support for this feature was added in git 2.21, and requires the
  26  * `core.multiPackIndex` config option to be set.
  27  */
  28 typedef struct git_midx_file {
  29         git_map index_map;
  30
  31         /* The table of Packfile Names. */
  32         git_vector packfile_names;
  33
  34         /* The OID Fanout table. */
  35         const uint32_t *oid_fanout;
  36         /* The total number of objects in the index. */
  37         uint32_t num_objects;
  38
  39         /* The OID Lookup table. */
  40         git_oid *oid_lookup;
  41
  42         /* The Object Offsets table. Each entry has two 4-byte fields with the pack index and the offset. */
  43         const unsigned char *object_offsets;
  44
  45         /* The Object Large Offsets table. */
  46         const unsigned char *object_large_offsets;
  47         /* The number of entries in the Object Large Offsets table. Each entry has an 8-byte with an offset */
  48         size_t num_object_large_offsets;
  49
  50         /* The trailer of the file. Contains the SHA1-checksum of the whole file. */
  51         git_oid checksum;
  52 } git_midx_file;
  53
  54 /*
  55  * An entry in the multi-pack-index file. Similar in purpose to git_pack_entry.
  56  */
  57 typedef struct git_midx_entry {
  58         /* The index within idx->packfile_names where the packfile name can be found. */
  59         size_t pack_index;
  60         /* The offset within the .pack file where the requested object is found. */
  61         off64_t offset;
  62         /* The SHA-1 hash of the requested object. */
  63         git_oid sha1;
  64 } git_midx_entry;
  65
  66 int git_midx_open(
  67                 git_midx_file **idx_out,
  68                 const char *path);
  69 int git_midx_entry_find(
  70                 git_midx_entry *e,
  71                 git_midx_file *idx,
  72                 const git_oid *short_oid,
  73                 size_t len);
  74 void git_midx_close(git_midx_file *idx);
  75 void git_midx_free(git_midx_file *idx);
  76
  77 /* This is exposed for use in the fuzzers. */
  78 int git_midx_parse(
  79                 git_midx_file *idx,
  80                 const unsigned char *data,
  81                 size_t size);
  82
  83 #endif