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 int parse_commit_in_graph(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         prepare_commit_graph();
 326         if (commit_graph && find_commit_in_graph(item, commit_graph, &pos))
 327                 return fill_commit_in_graph(item, commit_graph, pos);
 328         return 0;
 329 }
 330
 331 void load_commit_graph_info(struct commit *item)
 332 {
 333         uint32_t pos;
 334         if (!core_commit_graph)
 335                 return;
 336         prepare_commit_graph();
 337         if (commit_graph && find_commit_in_graph(item, commit_graph, &pos))
 338                 fill_commit_graph_info(item, commit_graph, pos);
 339 }
 340
 341 static struct tree *load_tree_for_commit(struct commit_graph *g, struct commit *c)
 342 {
 343         struct object_id oid;
 344         const unsigned char *commit_data = g->chunk_commit_data +
 345                                            GRAPH_DATA_WIDTH * (c->graph_pos);
 346
 347         hashcpy(oid.hash, commit_data);
 348         c->maybe_tree = lookup_tree(&oid);
 349
 350         return c->maybe_tree;
 351 }
 352
 353 struct tree *get_commit_tree_in_graph(const struct commit *c)
 354 {
 355         if (c->maybe_tree)
 356                 return c->maybe_tree;
 357         if (c->graph_pos == COMMIT_NOT_FROM_GRAPH)
 358                 BUG("get_commit_tree_in_graph called from non-commit-graph commit");
 359
 360         return load_tree_for_commit(commit_graph, (struct commit *)c);
 361 }
 362
 363 static void write_graph_chunk_fanout(struct hashfile *f,
 364                                      struct commit **commits,
 365                                      int nr_commits)
 366 {
 367         int i, count = 0;
 368         struct commit **list = commits;
 369
 370         /*
 371          * Write the first-level table (the list is sorted,
 372          * but we use a 256-entry lookup to be able to avoid
 373          * having to do eight extra binary search iterations).
 374          */
 375         for (i = 0; i < 256; i++) {
 376                 while (count < nr_commits) {
 377                         if ((*list)->object.oid.hash[0] != i)
 378                                 break;
 379                         count++;
 380                         list++;
 381                 }
 382
 383                 hashwrite_be32(f, count);
 384         }
 385 }
 386
 387 static void write_graph_chunk_oids(struct hashfile *f, int hash_len,
 388                                    struct commit **commits, int nr_commits)
 389 {
 390         struct commit **list = commits;
 391         int count;
 392         for (count = 0; count < nr_commits; count++, list++)
 393                 hashwrite(f, (*list)->object.oid.hash, (int)hash_len);
 394 }
 395
 396 static const unsigned char *commit_to_sha1(size_t index, void *table)
 397 {
 398         struct commit **commits = table;
 399         return commits[index]->object.oid.hash;
 400 }
 401
 402 static void write_graph_chunk_data(struct hashfile *f, int hash_len,
 403                                    struct commit **commits, int nr_commits)
 404 {
 405         struct commit **list = commits;
 406         struct commit **last = commits + nr_commits;
 407         uint32_t num_extra_edges = 0;
 408
 409         while (list < last) {
 410                 struct commit_list *parent;
 411                 int edge_value;
 412                 uint32_t packedDate[2];
 413
 414                 parse_commit(*list);
 415                 hashwrite(f, get_commit_tree_oid(*list)->hash, hash_len);
 416
 417                 parent = (*list)->parents;
 418
 419                 if (!parent)
 420                         edge_value = GRAPH_PARENT_NONE;
 421                 else {
 422                         edge_value = sha1_pos(parent->item->object.oid.hash,
 423                                               commits,
 424                                               nr_commits,
 425                                               commit_to_sha1);
 426
 427                         if (edge_value < 0)
 428                                 edge_value = GRAPH_PARENT_MISSING;
 429                 }
 430
 431                 hashwrite_be32(f, edge_value);
 432
 433                 if (parent)
 434                         parent = parent->next;
 435
 436                 if (!parent)
 437                         edge_value = GRAPH_PARENT_NONE;
 438                 else if (parent->next)
 439                         edge_value = GRAPH_OCTOPUS_EDGES_NEEDED | num_extra_edges;
 440                 else {
 441                         edge_value = sha1_pos(parent->item->object.oid.hash,
 442                                               commits,
 443                                               nr_commits,
 444                                               commit_to_sha1);
 445                         if (edge_value < 0)
 446                                 edge_value = GRAPH_PARENT_MISSING;
 447                 }
 448
 449                 hashwrite_be32(f, edge_value);
 450
 451                 if (edge_value & GRAPH_OCTOPUS_EDGES_NEEDED) {
 452                         do {
 453                                 num_extra_edges++;
 454                                 parent = parent->next;
 455                         } while (parent);
 456                 }
 457
 458                 if (sizeof((*list)->date) > 4)
 459                         packedDate[0] = htonl(((*list)->date >> 32) & 0x3);
 460                 else
 461                         packedDate[0] = 0;
 462
 463                 packedDate[0] |= htonl((*list)->generation << 2);
 464
 465                 packedDate[1] = htonl((*list)->date);
 466                 hashwrite(f, packedDate, 8);
 467
 468                 list++;
 469         }
 470 }
 471
 472 static void write_graph_chunk_large_edges(struct hashfile *f,
 473                                           struct commit **commits,
 474                                           int nr_commits)
 475 {
 476         struct commit **list = commits;
 477         struct commit **last = commits + nr_commits;
 478         struct commit_list *parent;
 479
 480         while (list < last) {
 481                 int num_parents = 0;
 482                 for (parent = (*list)->parents; num_parents < 3 && parent;
 483                      parent = parent->next)
 484                         num_parents++;
 485
 486                 if (num_parents <= 2) {
 487                         list++;
 488                         continue;
 489                 }
 490
 491                 /* Since num_parents > 2, this initializer is safe. */
 492                 for (parent = (*list)->parents->next; parent; parent = parent->next) {
 493                         int edge_value = sha1_pos(parent->item->object.oid.hash,
 494                                                   commits,
 495                                                   nr_commits,
 496                                                   commit_to_sha1);
 497
 498                         if (edge_value < 0)
 499                                 edge_value = GRAPH_PARENT_MISSING;
 500                         else if (!parent->next)
 501                                 edge_value |= GRAPH_LAST_EDGE;
 502
 503                         hashwrite_be32(f, edge_value);
 504                 }
 505
 506                 list++;
 507         }
 508 }
 509
 510 static int commit_compare(const void *_a, const void *_b)
 511 {
 512         const struct object_id *a = (const struct object_id *)_a;
 513         const struct object_id *b = (const struct object_id *)_b;
 514         return oidcmp(a, b);
 515 }
 516
 517 struct packed_commit_list {
 518         struct commit **list;
 519         int nr;
 520         int alloc;
 521 };
 522
 523 struct packed_oid_list {
 524         struct object_id *list;
 525         int nr;
 526         int alloc;
 527 };
 528
 529 static int add_packed_commits(const struct object_id *oid,
 530                               struct packed_git *pack,
 531                               uint32_t pos,
 532                               void *data)
 533 {
 534         struct packed_oid_list *list = (struct packed_oid_list*)data;
 535         enum object_type type;
 536         off_t offset = nth_packed_object_offset(pack, pos);
 537         struct object_info oi = OBJECT_INFO_INIT;
 538
 539         oi.typep = &type;
 540         if (packed_object_info(the_repository, pack, offset, &oi) < 0)
 541                 die("unable to get type of object %s", oid_to_hex(oid));
 542
 543         if (type != OBJ_COMMIT)
 544                 return 0;
 545
 546         ALLOC_GROW(list->list, list->nr + 1, list->alloc);
 547         oidcpy(&(list->list[list->nr]), oid);
 548         list->nr++;
 549
 550         return 0;
 551 }
 552
 553 static void add_missing_parents(struct packed_oid_list *oids, struct commit *commit)
 554 {
 555         struct commit_list *parent;
 556         for (parent = commit->parents; parent; parent = parent->next) {
 557                 if (!(parent->item->object.flags & UNINTERESTING)) {
 558                         ALLOC_GROW(oids->list, oids->nr + 1, oids->alloc);
 559                         oidcpy(&oids->list[oids->nr], &(parent->item->object.oid));
 560                         oids->nr++;
 561                         parent->item->object.flags |= UNINTERESTING;
 562                 }
 563         }
 564 }
 565
 566 static void close_reachable(struct packed_oid_list *oids)
 567 {
 568         int i;
 569         struct commit *commit;
 570
 571         for (i = 0; i < oids->nr; i++) {
 572                 commit = lookup_commit(&oids->list[i]);
 573                 if (commit)
 574                         commit->object.flags |= UNINTERESTING;
 575         }
 576
 577         /*
 578          * As this loop runs, oids->nr may grow, but not more
 579          * than the number of missing commits in the reachable
 580          * closure.
 581          */
 582         for (i = 0; i < oids->nr; i++) {
 583                 commit = lookup_commit(&oids->list[i]);
 584
 585                 if (commit && !parse_commit(commit))
 586                         add_missing_parents(oids, commit);
 587         }
 588
 589         for (i = 0; i < oids->nr; i++) {
 590                 commit = lookup_commit(&oids->list[i]);
 591
 592                 if (commit)
 593                         commit->object.flags &= ~UNINTERESTING;
 594         }
 595 }
 596
 597 static void compute_generation_numbers(struct packed_commit_list* commits)
 598 {
 599         int i;
 600         struct commit_list *list = NULL;
 601
 602         for (i = 0; i < commits->nr; i++) {
 603                 if (commits->list[i]->generation != GENERATION_NUMBER_INFINITY &&
 604                     commits->list[i]->generation != GENERATION_NUMBER_ZERO)
 605                         continue;
 606
 607                 commit_list_insert(commits->list[i], &list);
 608                 while (list) {
 609                         struct commit *current = list->item;
 610                         struct commit_list *parent;
 611                         int all_parents_computed = 1;
 612                         uint32_t max_generation = 0;
 613
 614                         for (parent = current->parents; parent; parent = parent->next) {
 615                                 if (parent->item->generation == GENERATION_NUMBER_INFINITY ||
 616                                     parent->item->generation == GENERATION_NUMBER_ZERO) {
 617                                         all_parents_computed = 0;
 618                                         commit_list_insert(parent->item, &list);
 619                                         break;
 620                                 } else if (parent->item->generation > max_generation) {
 621                                         max_generation = parent->item->generation;
 622                                 }
 623                         }
 624
 625                         if (all_parents_computed) {
 626                                 current->generation = max_generation + 1;
 627                                 pop_commit(&list);
 628
 629                                 if (current->generation > GENERATION_NUMBER_MAX)
 630                                         current->generation = GENERATION_NUMBER_MAX;
 631                         }
 632                 }
 633         }
 634 }
 635
 636 void write_commit_graph(const char *obj_dir,
 637                         const char **pack_indexes,
 638                         int nr_packs,
 639                         const char **commit_hex,
 640                         int nr_commits,
 641                         int append)
 642 {
 643         struct packed_oid_list oids;
 644         struct packed_commit_list commits;
 645         struct hashfile *f;
 646         uint32_t i, count_distinct = 0;
 647         char *graph_name;
 648         struct lock_file lk = LOCK_INIT;
 649         uint32_t chunk_ids[5];
 650         uint64_t chunk_offsets[5];
 651         int num_chunks;
 652         int num_extra_edges;
 653         struct commit_list *parent;
 654
 655         oids.nr = 0;
 656         oids.alloc = approximate_object_count() / 4;
 657
 658         if (append) {
 659                 prepare_commit_graph_one(obj_dir);
 660                 if (commit_graph)
 661                         oids.alloc += commit_graph->num_commits;
 662         }
 663
 664         if (oids.alloc < 1024)
 665                 oids.alloc = 1024;
 666         ALLOC_ARRAY(oids.list, oids.alloc);
 667
 668         if (append && commit_graph) {
 669                 for (i = 0; i < commit_graph->num_commits; i++) {
 670                         const unsigned char *hash = commit_graph->chunk_oid_lookup +
 671                                 commit_graph->hash_len * i;
 672                         hashcpy(oids.list[oids.nr++].hash, hash);
 673                 }
 674         }
 675
 676         if (pack_indexes) {
 677                 struct strbuf packname = STRBUF_INIT;
 678                 int dirlen;
 679                 strbuf_addf(&packname, "%s/pack/", obj_dir);
 680                 dirlen = packname.len;
 681                 for (i = 0; i < nr_packs; i++) {
 682                         struct packed_git *p;
 683                         strbuf_setlen(&packname, dirlen);
 684                         strbuf_addstr(&packname, pack_indexes[i]);
 685                         p = add_packed_git(packname.buf, packname.len, 1);
 686                         if (!p)
 687                                 die("error adding pack %s", packname.buf);
 688                         if (open_pack_index(p))
 689                                 die("error opening index for %s", packname.buf);
 690                         for_each_object_in_pack(p, add_packed_commits, &oids);
 691                         close_pack(p);
 692                 }
 693                 strbuf_release(&packname);
 694         }
 695
 696         if (commit_hex) {
 697                 for (i = 0; i < nr_commits; i++) {
 698                         const char *end;
 699                         struct object_id oid;
 700                         struct commit *result;
 701
 702                         if (commit_hex[i] && parse_oid_hex(commit_hex[i], &oid, &end))
 703                                 continue;
 704
 705                         result = lookup_commit_reference_gently(&oid, 1);
 706
 707                         if (result) {
 708                                 ALLOC_GROW(oids.list, oids.nr + 1, oids.alloc);
 709                                 oidcpy(&oids.list[oids.nr], &(result->object.oid));
 710                                 oids.nr++;
 711                         }
 712                 }
 713         }
 714
 715         if (!pack_indexes && !commit_hex)
 716                 for_each_packed_object(add_packed_commits, &oids, 0);
 717
 718         close_reachable(&oids);
 719
 720         QSORT(oids.list, oids.nr, commit_compare);
 721
 722         count_distinct = 1;
 723         for (i = 1; i < oids.nr; i++) {
 724                 if (oidcmp(&oids.list[i-1], &oids.list[i]))
 725                         count_distinct++;
 726         }
 727
 728         if (count_distinct >= GRAPH_PARENT_MISSING)
 729                 die(_("the commit graph format cannot write %d commits"), count_distinct);
 730
 731         commits.nr = 0;
 732         commits.alloc = count_distinct;
 733         ALLOC_ARRAY(commits.list, commits.alloc);
 734
 735         num_extra_edges = 0;
 736         for (i = 0; i < oids.nr; i++) {
 737                 int num_parents = 0;
 738                 if (i > 0 && !oidcmp(&oids.list[i-1], &oids.list[i]))
 739                         continue;
 740
 741                 commits.list[commits.nr] = lookup_commit(&oids.list[i]);
 742                 parse_commit(commits.list[commits.nr]);
 743
 744                 for (parent = commits.list[commits.nr]->parents;
 745                      parent; parent = parent->next)
 746                         num_parents++;
 747
 748                 if (num_parents > 2)
 749                         num_extra_edges += num_parents - 1;
 750
 751                 commits.nr++;
 752         }
 753         num_chunks = num_extra_edges ? 4 : 3;
 754
 755         if (commits.nr >= GRAPH_PARENT_MISSING)
 756                 die(_("too many commits to write graph"));
 757
 758         compute_generation_numbers(&commits);
 759
 760         graph_name = get_commit_graph_filename(obj_dir);
 761         if (safe_create_leading_directories(graph_name))
 762                 die_errno(_("unable to create leading directories of %s"),
 763                           graph_name);
 764
 765         hold_lock_file_for_update(&lk, graph_name, LOCK_DIE_ON_ERROR);
 766         f = hashfd(lk.tempfile->fd, lk.tempfile->filename.buf);
 767
 768         hashwrite_be32(f, GRAPH_SIGNATURE);
 769
 770         hashwrite_u8(f, GRAPH_VERSION);
 771         hashwrite_u8(f, GRAPH_OID_VERSION);
 772         hashwrite_u8(f, num_chunks);
 773         hashwrite_u8(f, 0); /* unused padding byte */
 774
 775         chunk_ids[0] = GRAPH_CHUNKID_OIDFANOUT;
 776         chunk_ids[1] = GRAPH_CHUNKID_OIDLOOKUP;
 777         chunk_ids[2] = GRAPH_CHUNKID_DATA;
 778         if (num_extra_edges)
 779                 chunk_ids[3] = GRAPH_CHUNKID_LARGEEDGES;
 780         else
 781                 chunk_ids[3] = 0;
 782         chunk_ids[4] = 0;
 783
 784         chunk_offsets[0] = 8 + (num_chunks + 1) * GRAPH_CHUNKLOOKUP_WIDTH;
 785         chunk_offsets[1] = chunk_offsets[0] + GRAPH_FANOUT_SIZE;
 786         chunk_offsets[2] = chunk_offsets[1] + GRAPH_OID_LEN * commits.nr;
 787         chunk_offsets[3] = chunk_offsets[2] + (GRAPH_OID_LEN + 16) * commits.nr;
 788         chunk_offsets[4] = chunk_offsets[3] + 4 * num_extra_edges;
 789
 790         for (i = 0; i <= num_chunks; i++) {
 791                 uint32_t chunk_write[3];
 792
 793                 chunk_write[0] = htonl(chunk_ids[i]);
 794                 chunk_write[1] = htonl(chunk_offsets[i] >> 32);
 795                 chunk_write[2] = htonl(chunk_offsets[i] & 0xffffffff);
 796                 hashwrite(f, chunk_write, 12);
 797         }
 798
 799         write_graph_chunk_fanout(f, commits.list, commits.nr);
 800         write_graph_chunk_oids(f, GRAPH_OID_LEN, commits.list, commits.nr);
 801         write_graph_chunk_data(f, GRAPH_OID_LEN, commits.list, commits.nr);
 802         write_graph_chunk_large_edges(f, commits.list, commits.nr);
 803
 804         close_commit_graph();
 805         finalize_hashfile(f, NULL, CSUM_HASH_IN_STREAM | CSUM_FSYNC);
 806         commit_lock_file(&lk);
 807
 808         free(oids.list);
 809         oids.alloc = 0;
 810         oids.nr = 0;
 811 }