git.oblomov.eu Git - git/blob - commit-graph.c

   1 #include "cache.h"
   2 #include "config.h"
   3 #include "dir.h"
   4 #include "git-compat-util.h"
   5 #include "lockfile.h"
   6 #include "pack.h"
   7 #include "packfile.h"
   8 #include "commit.h"
   9 #include "object.h"
  10 #include "revision.h"
  11 #include "sha1-lookup.h"
  12 #include "commit-graph.h"
  13 #include "object-store.h"
  14
  15 #define GRAPH_SIGNATURE 0x43475048 /* "CGPH" */
  16 #define GRAPH_CHUNKID_OIDFANOUT 0x4f494446 /* "OIDF" */
  17 #define GRAPH_CHUNKID_OIDLOOKUP 0x4f49444c /* "OIDL" */
  18 #define GRAPH_CHUNKID_DATA 0x43444154 /* "CDAT" */
  19 #define GRAPH_CHUNKID_LARGEEDGES 0x45444745 /* "EDGE" */
  20
  21 #define GRAPH_DATA_WIDTH 36
  22
  23 #define GRAPH_VERSION_1 0x1
  24 #define GRAPH_VERSION GRAPH_VERSION_1
  25
  26 #define GRAPH_OID_VERSION_SHA1 1
  27 #define GRAPH_OID_LEN_SHA1 GIT_SHA1_RAWSZ
  28 #define GRAPH_OID_VERSION GRAPH_OID_VERSION_SHA1
  29 #define GRAPH_OID_LEN GRAPH_OID_LEN_SHA1
  30
  31 #define GRAPH_OCTOPUS_EDGES_NEEDED 0x80000000
  32 #define GRAPH_PARENT_MISSING 0x7fffffff
  33 #define GRAPH_EDGE_LAST_MASK 0x7fffffff
  34 #define GRAPH_PARENT_NONE 0x70000000
  35
  36 #define GRAPH_LAST_EDGE 0x80000000
  37
  38 #define GRAPH_HEADER_SIZE 8
  39 #define GRAPH_FANOUT_SIZE (4 * 256)
  40 #define GRAPH_CHUNKLOOKUP_WIDTH 12
  41 #define GRAPH_MIN_SIZE (GRAPH_HEADER_SIZE + 4 * GRAPH_CHUNKLOOKUP_WIDTH \
  42                         + GRAPH_FANOUT_SIZE + GRAPH_OID_LEN)
  43
  44 char *get_commit_graph_filename(const char *obj_dir)
  45 {
  46         return xstrfmt("%s/info/commit-graph", obj_dir);
  47 }
  48
  49 static struct commit_graph *alloc_commit_graph(void)
  50 {
  51         struct commit_graph *g = xcalloc(1, sizeof(*g));
  52         g->graph_fd = -1;
  53
  54         return g;
  55 }
  56
  57 struct commit_graph *load_commit_graph_one(const char *graph_file)
  58 {
  59         void *graph_map;
  60         const unsigned char *data, *chunk_lookup;
  61         size_t graph_size;
  62         struct stat st;
  63         uint32_t i;
  64         struct commit_graph *graph;
  65         int fd = git_open(graph_file);
  66         uint64_t last_chunk_offset;
  67         uint32_t last_chunk_id;
  68         uint32_t graph_signature;
  69         unsigned char graph_version, hash_version;
  70
  71         if (fd < 0)
  72                 return NULL;
  73         if (fstat(fd, &st)) {
  74                 close(fd);
  75                 return NULL;
  76         }
  77         graph_size = xsize_t(st.st_size);
  78
  79         if (graph_size < GRAPH_MIN_SIZE) {
  80                 close(fd);
  81                 die("graph file %s is too small", graph_file);
  82         }
  83         graph_map = xmmap(NULL, graph_size, PROT_READ, MAP_PRIVATE, fd, 0);
  84         data = (const unsigned char *)graph_map;
  85
  86         graph_signature = get_be32(data);
  87         if (graph_signature != GRAPH_SIGNATURE) {
  88                 error("graph signature %X does not match signature %X",
  89                       graph_signature, GRAPH_SIGNATURE);
  90                 goto cleanup_fail;
  91         }
  92
  93         graph_version = *(unsigned char*)(data + 4);
  94         if (graph_version != GRAPH_VERSION) {
  95                 error("graph version %X does not match version %X",
  96                       graph_version, GRAPH_VERSION);
  97                 goto cleanup_fail;
  98         }
  99
 100         hash_version = *(unsigned char*)(data + 5);
 101         if (hash_version != GRAPH_OID_VERSION) {
 102                 error("hash version %X does not match version %X",
 103                       hash_version, GRAPH_OID_VERSION);
 104                 goto cleanup_fail;
 105         }
 106
 107         graph = alloc_commit_graph();
 108
 109         graph->hash_len = GRAPH_OID_LEN;
 110         graph->num_chunks = *(unsigned char*)(data + 6);
 111         graph->graph_fd = fd;
 112         graph->data = graph_map;
 113         graph->data_len = graph_size;
 114
 115         last_chunk_id = 0;
 116         last_chunk_offset = 8;
 117         chunk_lookup = data + 8;
 118         for (i = 0; i < graph->num_chunks; i++) {
 119                 uint32_t chunk_id = get_be32(chunk_lookup + 0);
 120                 uint64_t chunk_offset = get_be64(chunk_lookup + 4);
 121                 int chunk_repeated = 0;
 122
 123                 chunk_lookup += GRAPH_CHUNKLOOKUP_WIDTH;
 124
 125                 if (chunk_offset > graph_size - GIT_MAX_RAWSZ) {
 126                         error("improper chunk offset %08x%08x", (uint32_t)(chunk_offset >> 32),
 127                               (uint32_t)chunk_offset);
 128                         goto cleanup_fail;
 129                 }
 130
 131                 switch (chunk_id) {
 132                 case GRAPH_CHUNKID_OIDFANOUT:
 133                         if (graph->chunk_oid_fanout)
 134                                 chunk_repeated = 1;
 135                         else
 136                                 graph->chunk_oid_fanout = (uint32_t*)(data + chunk_offset);
 137                         break;
 138
 139                 case GRAPH_CHUNKID_OIDLOOKUP:
 140                         if (graph->chunk_oid_lookup)
 141                                 chunk_repeated = 1;
 142                         else
 143                                 graph->chunk_oid_lookup = data + chunk_offset;
 144                         break;
 145
 146                 case GRAPH_CHUNKID_DATA:
 147                         if (graph->chunk_commit_data)
 148                                 chunk_repeated = 1;
 149                         else
 150                                 graph->chunk_commit_data = data + chunk_offset;
 151                         break;
 152
 153                 case GRAPH_CHUNKID_LARGEEDGES:
 154                         if (graph->chunk_large_edges)
 155                                 chunk_repeated = 1;
 156                         else
 157                                 graph->chunk_large_edges = data + chunk_offset;
 158                         break;
 159                 }
 160
 161                 if (chunk_repeated) {
 162                         error("chunk id %08x appears multiple times", chunk_id);
 163                         goto cleanup_fail;
 164                 }
 165
 166                 if (last_chunk_id == GRAPH_CHUNKID_OIDLOOKUP)
 167                 {
 168                         graph->num_commits = (chunk_offset - last_chunk_offset)
 169                                              / graph->hash_len;
 170                 }
 171
 172                 last_chunk_id = chunk_id;
 173                 last_chunk_offset = chunk_offset;
 174         }
 175
 176         return graph;
 177
 178 cleanup_fail:
 179         munmap(graph_map, graph_size);
 180         close(fd);
 181         exit(1);
 182 }
 183
 184 /* global storage */
 185 static struct commit_graph *commit_graph = NULL;
 186
 187 static void prepare_commit_graph_one(const char *obj_dir)
 188 {
 189         char *graph_name;
 190
 191         if (commit_graph)
 192                 return;
 193
 194         graph_name = get_commit_graph_filename(obj_dir);
 195         commit_graph = load_commit_graph_one(graph_name);
 196
 197         FREE_AND_NULL(graph_name);
 198 }
 199
 200 static int prepare_commit_graph_run_once = 0;
 201 static void prepare_commit_graph(void)
 202 {
 203         struct alternate_object_database *alt;
 204         char *obj_dir;
 205
 206         if (prepare_commit_graph_run_once)
 207                 return;
 208         prepare_commit_graph_run_once = 1;
 209
 210         obj_dir = get_object_directory();
 211         prepare_commit_graph_one(obj_dir);
 212         prepare_alt_odb(the_repository);
 213         for (alt = the_repository->objects->alt_odb_list;
 214              !commit_graph && alt;
 215              alt = alt->next)
 216                 prepare_commit_graph_one(alt->path);
 217 }
 218
 219 static void close_commit_graph(void)
 220 {
 221         if (!commit_graph)
 222                 return;
 223
 224         if (commit_graph->graph_fd >= 0) {
 225                 munmap((void *)commit_graph->data, commit_graph->data_len);
 226                 commit_graph->data = NULL;
 227                 close(commit_graph->graph_fd);
 228         }
 229
 230         FREE_AND_NULL(commit_graph);
 231 }
 232
 233 static int bsearch_graph(struct commit_graph *g, struct object_id *oid, uint32_t *pos)
 234 {
 235         return bsearch_hash(oid->hash, g->chunk_oid_fanout,
 236                             g->chunk_oid_lookup, g->hash_len, pos);
 237 }
 238
 239 static struct commit_list **insert_parent_or_die(struct commit_graph *g,
 240                                                  uint64_t pos,
 241                                                  struct commit_list **pptr)
 242 {
 243         struct commit *c;
 244         struct object_id oid;
 245         hashcpy(oid.hash, g->chunk_oid_lookup + g->hash_len * pos);
 246         c = lookup_commit(&oid);
 247         if (!c)
 248                 die("could not find commit %s", oid_to_hex(&oid));
 249         c->graph_pos = pos;
 250         return &commit_list_insert(c, pptr)->next;
 251 }
 252
 253 static void fill_commit_graph_info(struct commit *item, struct commit_graph *g, uint32_t pos)
 254 {
 255         const unsigned char *commit_data = g->chunk_commit_data + GRAPH_DATA_WIDTH * pos;
 256         item->graph_pos = pos;
 257         item->generation = get_be32(commit_data + g->hash_len + 8) >> 2;
 258 }
 259
 260 static int fill_commit_in_graph(struct commit *item, struct commit_graph *g, uint32_t pos)
 261 {
 262         uint32_t edge_value;
 263         uint32_t *parent_data_ptr;
 264         uint64_t date_low, date_high;
 265         struct commit_list **pptr;
 266         const unsigned char *commit_data = g->chunk_commit_data + (g->hash_len + 16) * pos;
 267
 268         item->object.parsed = 1;
 269         item->graph_pos = pos;
 270
 271         item->maybe_tree = NULL;
 272
 273         date_high = get_be32(commit_data + g->hash_len + 8) & 0x3;
 274         date_low = get_be32(commit_data + g->hash_len + 12);
 275         item->date = (timestamp_t)((date_high << 32) | date_low);
 276
 277         item->generation = get_be32(commit_data + g->hash_len + 8) >> 2;
 278
 279         pptr = &item->parents;
 280
 281         edge_value = get_be32(commit_data + g->hash_len);
 282         if (edge_value == GRAPH_PARENT_NONE)
 283                 return 1;
 284         pptr = insert_parent_or_die(g, edge_value, pptr);
 285
 286         edge_value = get_be32(commit_data + g->hash_len + 4);
 287         if (edge_value == GRAPH_PARENT_NONE)
 288                 return 1;
 289         if (!(edge_value & GRAPH_OCTOPUS_EDGES_NEEDED)) {
 290                 pptr = insert_parent_or_die(g, edge_value, pptr);
 291                 return 1;
 292         }
 293
 294         parent_data_ptr = (uint32_t*)(g->chunk_large_edges +
 295                           4 * (uint64_t)(edge_value & GRAPH_EDGE_LAST_MASK));
 296         do {
 297                 edge_value = get_be32(parent_data_ptr);
 298                 pptr = insert_parent_or_die(g,
 299                                             edge_value & GRAPH_EDGE_LAST_MASK,
 300                                             pptr);
 301                 parent_data_ptr++;
 302         } while (!(edge_value & GRAPH_LAST_EDGE));
 303
 304         return 1;
 305 }
 306
 307 static int find_commit_in_graph(struct commit *item, struct commit_graph *g, uint32_t *pos)
 308 {
 309         if (item->graph_pos != COMMIT_NOT_FROM_GRAPH) {
 310                 *pos = item->graph_pos;
 311                 return 1;
 312         } else {
 313                 return bsearch_graph(g, &(item->object.oid), pos);
 314         }
 315 }
 316
 317 static int parse_commit_in_graph_one(struct commit_graph *g, struct commit *item)
 318 {
 319         uint32_t pos;
 320
 321         if (!core_commit_graph)
 322                 return 0;
 323         if (item->object.parsed)
 324                 return 1;
 325
 326         if (find_commit_in_graph(item, g, &pos))
 327                 return fill_commit_in_graph(item, g, pos);
 328
 329         return 0;
 330 }
 331
 332 int parse_commit_in_graph(struct commit *item)
 333 {
 334         if (!core_commit_graph)
 335                 return 0;
 336
 337         prepare_commit_graph();
 338         if (commit_graph)
 339                 return parse_commit_in_graph_one(commit_graph, item);
 340         return 0;
 341 }
 342
 343 void load_commit_graph_info(struct commit *item)
 344 {
 345         uint32_t pos;
 346         if (!core_commit_graph)
 347                 return;
 348         prepare_commit_graph();
 349         if (commit_graph && find_commit_in_graph(item, commit_graph, &pos))
 350                 fill_commit_graph_info(item, commit_graph, pos);
 351 }
 352
 353 static struct tree *load_tree_for_commit(struct commit_graph *g, struct commit *c)
 354 {
 355         struct object_id oid;
 356         const unsigned char *commit_data = g->chunk_commit_data +
 357                                            GRAPH_DATA_WIDTH * (c->graph_pos);
 358
 359         hashcpy(oid.hash, commit_data);
 360         c->maybe_tree = lookup_tree(&oid);
 361
 362         return c->maybe_tree;
 363 }
 364
 365 struct tree *get_commit_tree_in_graph(const struct commit *c)
 366 {
 367         if (c->maybe_tree)
 368                 return c->maybe_tree;
 369         if (c->graph_pos == COMMIT_NOT_FROM_GRAPH)
 370                 BUG("get_commit_tree_in_graph called from non-commit-graph commit");
 371
 372         return load_tree_for_commit(commit_graph, (struct commit *)c);
 373 }
 374
 375 static void write_graph_chunk_fanout(struct hashfile *f,
 376                                      struct commit **commits,
 377                                      int nr_commits)
 378 {
 379         int i, count = 0;
 380         struct commit **list = commits;
 381
 382         /*
 383          * Write the first-level table (the list is sorted,
 384          * but we use a 256-entry lookup to be able to avoid
 385          * having to do eight extra binary search iterations).
 386          */
 387         for (i = 0; i < 256; i++) {
 388                 while (count < nr_commits) {
 389                         if ((*list)->object.oid.hash[0] != i)
 390                                 break;
 391                         count++;
 392                         list++;
 393                 }
 394
 395                 hashwrite_be32(f, count);
 396         }
 397 }
 398
 399 static void write_graph_chunk_oids(struct hashfile *f, int hash_len,
 400                                    struct commit **commits, int nr_commits)
 401 {
 402         struct commit **list = commits;
 403         int count;
 404         for (count = 0; count < nr_commits; count++, list++)
 405                 hashwrite(f, (*list)->object.oid.hash, (int)hash_len);
 406 }
 407
 408 static const unsigned char *commit_to_sha1(size_t index, void *table)
 409 {
 410         struct commit **commits = table;
 411         return commits[index]->object.oid.hash;
 412 }
 413
 414 static void write_graph_chunk_data(struct hashfile *f, int hash_len,
 415                                    struct commit **commits, int nr_commits)
 416 {
 417         struct commit **list = commits;
 418         struct commit **last = commits + nr_commits;
 419         uint32_t num_extra_edges = 0;
 420
 421         while (list < last) {
 422                 struct commit_list *parent;
 423                 int edge_value;
 424                 uint32_t packedDate[2];
 425
 426                 parse_commit(*list);
 427                 hashwrite(f, get_commit_tree_oid(*list)->hash, hash_len);
 428
 429                 parent = (*list)->parents;
 430
 431                 if (!parent)
 432                         edge_value = GRAPH_PARENT_NONE;
 433                 else {
 434                         edge_value = sha1_pos(parent->item->object.oid.hash,
 435                                               commits,
 436                                               nr_commits,
 437                                               commit_to_sha1);
 438
 439                         if (edge_value < 0)
 440                                 edge_value = GRAPH_PARENT_MISSING;
 441                 }
 442
 443                 hashwrite_be32(f, edge_value);
 444
 445                 if (parent)
 446                         parent = parent->next;
 447
 448                 if (!parent)
 449                         edge_value = GRAPH_PARENT_NONE;
 450                 else if (parent->next)
 451                         edge_value = GRAPH_OCTOPUS_EDGES_NEEDED | num_extra_edges;
 452                 else {
 453                         edge_value = sha1_pos(parent->item->object.oid.hash,
 454                                               commits,
 455                                               nr_commits,
 456                                               commit_to_sha1);
 457                         if (edge_value < 0)
 458                                 edge_value = GRAPH_PARENT_MISSING;
 459                 }
 460
 461                 hashwrite_be32(f, edge_value);
 462
 463                 if (edge_value & GRAPH_OCTOPUS_EDGES_NEEDED) {
 464                         do {
 465                                 num_extra_edges++;
 466                                 parent = parent->next;
 467                         } while (parent);
 468                 }
 469
 470                 if (sizeof((*list)->date) > 4)
 471                         packedDate[0] = htonl(((*list)->date >> 32) & 0x3);
 472                 else
 473                         packedDate[0] = 0;
 474
 475                 packedDate[0] |= htonl((*list)->generation << 2);
 476
 477                 packedDate[1] = htonl((*list)->date);
 478                 hashwrite(f, packedDate, 8);
 479
 480                 list++;
 481         }
 482 }
 483
 484 static void write_graph_chunk_large_edges(struct hashfile *f,
 485                                           struct commit **commits,
 486                                           int nr_commits)
 487 {
 488         struct commit **list = commits;
 489         struct commit **last = commits + nr_commits;
 490         struct commit_list *parent;
 491
 492         while (list < last) {
 493                 int num_parents = 0;
 494                 for (parent = (*list)->parents; num_parents < 3 && parent;
 495                      parent = parent->next)
 496                         num_parents++;
 497
 498                 if (num_parents <= 2) {
 499                         list++;
 500                         continue;
 501                 }
 502
 503                 /* Since num_parents > 2, this initializer is safe. */
 504                 for (parent = (*list)->parents->next; parent; parent = parent->next) {
 505                         int edge_value = sha1_pos(parent->item->object.oid.hash,
 506                                                   commits,
 507                                                   nr_commits,
 508                                                   commit_to_sha1);
 509
 510                         if (edge_value < 0)
 511                                 edge_value = GRAPH_PARENT_MISSING;
 512                         else if (!parent->next)
 513                                 edge_value |= GRAPH_LAST_EDGE;
 514
 515                         hashwrite_be32(f, edge_value);
 516                 }
 517
 518                 list++;
 519         }
 520 }
 521
 522 static int commit_compare(const void *_a, const void *_b)
 523 {
 524         const struct object_id *a = (const struct object_id *)_a;
 525         const struct object_id *b = (const struct object_id *)_b;
 526         return oidcmp(a, b);
 527 }
 528
 529 struct packed_commit_list {
 530         struct commit **list;
 531         int nr;
 532         int alloc;
 533 };
 534
 535 struct packed_oid_list {
 536         struct object_id *list;
 537         int nr;
 538         int alloc;
 539 };
 540
 541 static int add_packed_commits(const struct object_id *oid,
 542                               struct packed_git *pack,
 543                               uint32_t pos,
 544                               void *data)
 545 {
 546         struct packed_oid_list *list = (struct packed_oid_list*)data;
 547         enum object_type type;
 548         off_t offset = nth_packed_object_offset(pack, pos);
 549         struct object_info oi = OBJECT_INFO_INIT;
 550
 551         oi.typep = &type;
 552         if (packed_object_info(the_repository, pack, offset, &oi) < 0)
 553                 die("unable to get type of object %s", oid_to_hex(oid));
 554
 555         if (type != OBJ_COMMIT)
 556                 return 0;
 557
 558         ALLOC_GROW(list->list, list->nr + 1, list->alloc);
 559         oidcpy(&(list->list[list->nr]), oid);
 560         list->nr++;
 561
 562         return 0;
 563 }
 564
 565 static void add_missing_parents(struct packed_oid_list *oids, struct commit *commit)
 566 {
 567         struct commit_list *parent;
 568         for (parent = commit->parents; parent; parent = parent->next) {
 569                 if (!(parent->item->object.flags & UNINTERESTING)) {
 570                         ALLOC_GROW(oids->list, oids->nr + 1, oids->alloc);
 571                         oidcpy(&oids->list[oids->nr], &(parent->item->object.oid));
 572                         oids->nr++;
 573                         parent->item->object.flags |= UNINTERESTING;
 574                 }
 575         }
 576 }
 577
 578 static void close_reachable(struct packed_oid_list *oids)
 579 {
 580         int i;
 581         struct commit *commit;
 582
 583         for (i = 0; i < oids->nr; i++) {
 584                 commit = lookup_commit(&oids->list[i]);
 585                 if (commit)
 586                         commit->object.flags |= UNINTERESTING;
 587         }
 588
 589         /*
 590          * As this loop runs, oids->nr may grow, but not more
 591          * than the number of missing commits in the reachable
 592          * closure.
 593          */
 594         for (i = 0; i < oids->nr; i++) {
 595                 commit = lookup_commit(&oids->list[i]);
 596
 597                 if (commit && !parse_commit(commit))
 598                         add_missing_parents(oids, commit);
 599         }
 600
 601         for (i = 0; i < oids->nr; i++) {
 602                 commit = lookup_commit(&oids->list[i]);
 603
 604                 if (commit)
 605                         commit->object.flags &= ~UNINTERESTING;
 606         }
 607 }
 608
 609 static void compute_generation_numbers(struct packed_commit_list* commits)
 610 {
 611         int i;
 612         struct commit_list *list = NULL;
 613
 614         for (i = 0; i < commits->nr; i++) {
 615                 if (commits->list[i]->generation != GENERATION_NUMBER_INFINITY &&
 616                     commits->list[i]->generation != GENERATION_NUMBER_ZERO)
 617                         continue;
 618
 619                 commit_list_insert(commits->list[i], &list);
 620                 while (list) {
 621                         struct commit *current = list->item;
 622                         struct commit_list *parent;
 623                         int all_parents_computed = 1;
 624                         uint32_t max_generation = 0;
 625
 626                         for (parent = current->parents; parent; parent = parent->next) {
 627                                 if (parent->item->generation == GENERATION_NUMBER_INFINITY ||
 628                                     parent->item->generation == GENERATION_NUMBER_ZERO) {
 629                                         all_parents_computed = 0;
 630                                         commit_list_insert(parent->item, &list);
 631                                         break;
 632                                 } else if (parent->item->generation > max_generation) {
 633                                         max_generation = parent->item->generation;
 634                                 }
 635                         }
 636
 637                         if (all_parents_computed) {
 638                                 current->generation = max_generation + 1;
 639                                 pop_commit(&list);
 640
 641                                 if (current->generation > GENERATION_NUMBER_MAX)
 642                                         current->generation = GENERATION_NUMBER_MAX;
 643                         }
 644                 }
 645         }
 646 }
 647
 648 void write_commit_graph(const char *obj_dir,
 649                         const char **pack_indexes,
 650                         int nr_packs,
 651                         const char **commit_hex,
 652                         int nr_commits,
 653                         int append)
 654 {
 655         struct packed_oid_list oids;
 656         struct packed_commit_list commits;
 657         struct hashfile *f;
 658         uint32_t i, count_distinct = 0;
 659         char *graph_name;
 660         struct lock_file lk = LOCK_INIT;
 661         uint32_t chunk_ids[5];
 662         uint64_t chunk_offsets[5];
 663         int num_chunks;
 664         int num_extra_edges;
 665         struct commit_list *parent;
 666
 667         oids.nr = 0;
 668         oids.alloc = approximate_object_count() / 4;
 669
 670         if (append) {
 671                 prepare_commit_graph_one(obj_dir);
 672                 if (commit_graph)
 673                         oids.alloc += commit_graph->num_commits;
 674         }
 675
 676         if (oids.alloc < 1024)
 677                 oids.alloc = 1024;
 678         ALLOC_ARRAY(oids.list, oids.alloc);
 679
 680         if (append && commit_graph) {
 681                 for (i = 0; i < commit_graph->num_commits; i++) {
 682                         const unsigned char *hash = commit_graph->chunk_oid_lookup +
 683                                 commit_graph->hash_len * i;
 684                         hashcpy(oids.list[oids.nr++].hash, hash);
 685                 }
 686         }
 687
 688         if (pack_indexes) {
 689                 struct strbuf packname = STRBUF_INIT;
 690                 int dirlen;
 691                 strbuf_addf(&packname, "%s/pack/", obj_dir);
 692                 dirlen = packname.len;
 693                 for (i = 0; i < nr_packs; i++) {
 694                         struct packed_git *p;
 695                         strbuf_setlen(&packname, dirlen);
 696                         strbuf_addstr(&packname, pack_indexes[i]);
 697                         p = add_packed_git(packname.buf, packname.len, 1);
 698                         if (!p)
 699                                 die("error adding pack %s", packname.buf);
 700                         if (open_pack_index(p))
 701                                 die("error opening index for %s", packname.buf);
 702                         for_each_object_in_pack(p, add_packed_commits, &oids);
 703                         close_pack(p);
 704                 }
 705                 strbuf_release(&packname);
 706         }
 707
 708         if (commit_hex) {
 709                 for (i = 0; i < nr_commits; i++) {
 710                         const char *end;
 711                         struct object_id oid;
 712                         struct commit *result;
 713
 714                         if (commit_hex[i] && parse_oid_hex(commit_hex[i], &oid, &end))
 715                                 continue;
 716
 717                         result = lookup_commit_reference_gently(&oid, 1);
 718
 719                         if (result) {
 720                                 ALLOC_GROW(oids.list, oids.nr + 1, oids.alloc);
 721                                 oidcpy(&oids.list[oids.nr], &(result->object.oid));
 722                                 oids.nr++;
 723                         }
 724                 }
 725         }
 726
 727         if (!pack_indexes && !commit_hex)
 728                 for_each_packed_object(add_packed_commits, &oids, 0);
 729
 730         close_reachable(&oids);
 731
 732         QSORT(oids.list, oids.nr, commit_compare);
 733
 734         count_distinct = 1;
 735         for (i = 1; i < oids.nr; i++) {
 736                 if (oidcmp(&oids.list[i-1], &oids.list[i]))
 737                         count_distinct++;
 738         }
 739
 740         if (count_distinct >= GRAPH_PARENT_MISSING)
 741                 die(_("the commit graph format cannot write %d commits"), count_distinct);
 742
 743         commits.nr = 0;
 744         commits.alloc = count_distinct;
 745         ALLOC_ARRAY(commits.list, commits.alloc);
 746
 747         num_extra_edges = 0;
 748         for (i = 0; i < oids.nr; i++) {
 749                 int num_parents = 0;
 750                 if (i > 0 && !oidcmp(&oids.list[i-1], &oids.list[i]))
 751                         continue;
 752
 753                 commits.list[commits.nr] = lookup_commit(&oids.list[i]);
 754                 parse_commit(commits.list[commits.nr]);
 755
 756                 for (parent = commits.list[commits.nr]->parents;
 757                      parent; parent = parent->next)
 758                         num_parents++;
 759
 760                 if (num_parents > 2)
 761                         num_extra_edges += num_parents - 1;
 762
 763                 commits.nr++;
 764         }
 765         num_chunks = num_extra_edges ? 4 : 3;
 766
 767         if (commits.nr >= GRAPH_PARENT_MISSING)
 768                 die(_("too many commits to write graph"));
 769
 770         compute_generation_numbers(&commits);
 771
 772         graph_name = get_commit_graph_filename(obj_dir);
 773         if (safe_create_leading_directories(graph_name))
 774                 die_errno(_("unable to create leading directories of %s"),
 775                           graph_name);
 776
 777         hold_lock_file_for_update(&lk, graph_name, LOCK_DIE_ON_ERROR);
 778         f = hashfd(lk.tempfile->fd, lk.tempfile->filename.buf);
 779
 780         hashwrite_be32(f, GRAPH_SIGNATURE);
 781
 782         hashwrite_u8(f, GRAPH_VERSION);
 783         hashwrite_u8(f, GRAPH_OID_VERSION);
 784         hashwrite_u8(f, num_chunks);
 785         hashwrite_u8(f, 0); /* unused padding byte */
 786
 787         chunk_ids[0] = GRAPH_CHUNKID_OIDFANOUT;
 788         chunk_ids[1] = GRAPH_CHUNKID_OIDLOOKUP;
 789         chunk_ids[2] = GRAPH_CHUNKID_DATA;
 790         if (num_extra_edges)
 791                 chunk_ids[3] = GRAPH_CHUNKID_LARGEEDGES;
 792         else
 793                 chunk_ids[3] = 0;
 794         chunk_ids[4] = 0;
 795
 796         chunk_offsets[0] = 8 + (num_chunks + 1) * GRAPH_CHUNKLOOKUP_WIDTH;
 797         chunk_offsets[1] = chunk_offsets[0] + GRAPH_FANOUT_SIZE;
 798         chunk_offsets[2] = chunk_offsets[1] + GRAPH_OID_LEN * commits.nr;
 799         chunk_offsets[3] = chunk_offsets[2] + (GRAPH_OID_LEN + 16) * commits.nr;
 800         chunk_offsets[4] = chunk_offsets[3] + 4 * num_extra_edges;
 801
 802         for (i = 0; i <= num_chunks; i++) {
 803                 uint32_t chunk_write[3];
 804
 805                 chunk_write[0] = htonl(chunk_ids[i]);
 806                 chunk_write[1] = htonl(chunk_offsets[i] >> 32);
 807                 chunk_write[2] = htonl(chunk_offsets[i] & 0xffffffff);
 808                 hashwrite(f, chunk_write, 12);
 809         }
 810
 811         write_graph_chunk_fanout(f, commits.list, commits.nr);
 812         write_graph_chunk_oids(f, GRAPH_OID_LEN, commits.list, commits.nr);
 813         write_graph_chunk_data(f, GRAPH_OID_LEN, commits.list, commits.nr);
 814         write_graph_chunk_large_edges(f, commits.list, commits.nr);
 815
 816         close_commit_graph();
 817         finalize_hashfile(f, NULL, CSUM_HASH_IN_STREAM | CSUM_FSYNC);
 818         commit_lock_file(&lk);
 819
 820         free(oids.list);
 821         oids.alloc = 0;
 822         oids.nr = 0;
 823 }