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