src/pack.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_pack_h__
   9 #define INCLUDE_pack_h__
  10
  11 #include <zlib.h>
  12
  13 #include "git2/oid.h"
  14
  15 #include "common.h"
  16 #include "map.h"
  17 #include "mwindow.h"
  18 #include "odb.h"
  19 #include "oidmap.h"
  20 #include "array.h"
  21
  22 #define GIT_PACK_FILE_MODE 0444
  23
  24 #define PACK_SIGNATURE 0x5041434b       /* "PACK" */
  25 #define PACK_VERSION 2
  26 #define pack_version_ok(v) ((v) == htonl(2) || (v) == htonl(3))
  27 struct git_pack_header {
  28         uint32_t hdr_signature;
  29         uint32_t hdr_version;
  30         uint32_t hdr_entries;
  31 };
  32
  33 /*
  34  * The first four bytes of index formats later than version 1 should
  35  * start with this signature, as all older git binaries would find this
  36  * value illegal and abort reading the file.
  37  *
  38  * This is the case because the number of objects in a packfile
  39  * cannot exceed 1,431,660,000 as every object would need at least
  40  * 3 bytes of data and the overall packfile cannot exceed 4 GiB with
  41  * version 1 of the index file due to the offsets limited to 32 bits.
  42  * Clearly the signature exceeds this maximum.
  43  *
  44  * Very old git binaries will also compare the first 4 bytes to the
  45  * next 4 bytes in the index and abort with a "non-monotonic index"
  46  * error if the second 4 byte word is smaller than the first 4
  47  * byte word. This would be true in the proposed future index
  48  * format as idx_signature would be greater than idx_version.
  49  */
  50
  51 #define PACK_IDX_SIGNATURE 0xff744f63   /* "\377tOc" */
  52
  53 struct git_pack_idx_header {
  54         uint32_t idx_signature;
  55         uint32_t idx_version;
  56 };
  57
  58 typedef struct git_pack_cache_entry {
  59         size_t last_usage; /* enough? */
  60         git_atomic refcount;
  61         git_rawobj raw;
  62 } git_pack_cache_entry;
  63
  64 struct pack_chain_elem {
  65         git_off_t base_key;
  66         git_off_t offset;
  67         size_t size;
  68         git_otype type;
  69 };
  70
  71 typedef git_array_t(struct pack_chain_elem) git_dependency_chain;
  72
  73 #include "offmap.h"
  74 #include "oidmap.h"
  75
  76 #define GIT_PACK_CACHE_MEMORY_LIMIT 16 * 1024 * 1024
  77 #define GIT_PACK_CACHE_SIZE_LIMIT 1024 * 1024 /* don't bother caching anything over 1MB */
  78
  79 typedef struct {
  80         size_t memory_used;
  81         size_t memory_limit;
  82         size_t use_ctr;
  83         git_mutex lock;
  84         git_offmap *entries;
  85 } git_pack_cache;
  86
  87 struct git_pack_file {
  88         git_mwindow_file mwf;
  89         git_map index_map;
  90         git_mutex lock; /* protect updates to mwf and index_map */
  91         git_atomic refcount;
  92
  93         uint32_t num_objects;
  94         uint32_t num_bad_objects;
  95         git_oid *bad_object_sha1; /* array of git_oid */
  96
  97         int index_version;
  98         git_time_t mtime;
  99         unsigned pack_local:1, pack_keep:1, has_cache:1;
 100         git_oidmap *idx_cache;
 101         git_oid **oids;
 102
 103         git_pack_cache bases; /* delta base cache */
 104
 105         /* something like ".git/objects/pack/xxxxx.pack" */
 106         char pack_name[GIT_FLEX_ARRAY]; /* more */
 107 };
 108
 109 struct git_pack_entry {
 110         git_off_t offset;
 111         git_oid sha1;
 112         struct git_pack_file *p;
 113 };
 114
 115 typedef struct git_packfile_stream {
 116         git_off_t curpos;
 117         int done;
 118         z_stream zstream;
 119         struct git_pack_file *p;
 120         git_mwindow *mw;
 121 } git_packfile_stream;
 122
 123 size_t git_packfile__object_header(unsigned char *hdr, size_t size, git_otype type);
 124
 125 int git_packfile__name(char **out, const char *path);
 126
 127 int git_packfile_unpack_header(
 128                 size_t *size_p,
 129                 git_otype *type_p,
 130                 git_mwindow_file *mwf,
 131                 git_mwindow **w_curs,
 132                 git_off_t *curpos);
 133
 134 int git_packfile_resolve_header(
 135                 size_t *size_p,
 136                 git_otype *type_p,
 137                 struct git_pack_file *p,
 138                 git_off_t offset);
 139
 140 int git_packfile_unpack(git_rawobj *obj, struct git_pack_file *p, git_off_t *obj_offset);
 141
 142 int git_packfile_stream_open(git_packfile_stream *obj, struct git_pack_file *p, git_off_t curpos);
 143 ssize_t git_packfile_stream_read(git_packfile_stream *obj, void *buffer, size_t len);
 144 void git_packfile_stream_free(git_packfile_stream *obj);
 145
 146 git_off_t get_delta_base(struct git_pack_file *p, git_mwindow **w_curs,
 147                 git_off_t *curpos, git_otype type,
 148                 git_off_t delta_obj_offset);
 149
 150 void git_packfile_free(struct git_pack_file *p);
 151 int git_packfile_alloc(struct git_pack_file **pack_out, const char *path);
 152
 153 int git_pack_entry_find(
 154                 struct git_pack_entry *e,
 155                 struct git_pack_file *p,
 156                 const git_oid *short_oid,
 157                 size_t len);
 158 int git_pack_foreach_entry(
 159                 struct git_pack_file *p,
 160                 git_odb_foreach_cb cb,
 161                 void *data);
 162
 163 #endif