commit-graph.c

   1 #include "cache.h"
   2 #include "config.h"
   3 #include "git-compat-util.h"
   4 #include "lockfile.h"
   5 #include "pack.h"
   6 #include "packfile.h"
   7 #include "commit.h"
   8 #include "object.h"
   9 #include "revision.h"
  10 #include "sha1-lookup.h"
  11 #include "commit-graph.h"
  12 #include "object-store.h"
  13
  14 #define GRAPH_SIGNATURE 0x43475048 /* "CGPH" */
  15 #define GRAPH_CHUNKID_OIDFANOUT 0x4f494446 /* "OIDF" */
  16 #define GRAPH_CHUNKID_OIDLOOKUP 0x4f49444c /* "OIDL" */
  17 #define GRAPH_CHUNKID_DATA 0x43444154 /* "CDAT" */
  18 #define GRAPH_CHUNKID_LARGEEDGES 0x45444745 /* "EDGE" */
  19
  20 #define GRAPH_DATA_WIDTH 36
  21
  22 #define GRAPH_VERSION_1 0x1
  23 #define GRAPH_VERSION GRAPH_VERSION_1
  24
  25 #define GRAPH_OID_VERSION_SHA1 1
  26 #define GRAPH_OID_LEN_SHA1 GIT_SHA1_RAWSZ
  27 #define GRAPH_OID_VERSION GRAPH_OID_VERSION_SHA1
  28 #define GRAPH_OID_LEN GRAPH_OID_LEN_SHA1
  29
  30 #define GRAPH_OCTOPUS_EDGES_NEEDED 0x80000000
  31 #define GRAPH_PARENT_MISSING 0x7fffffff
  32 #define GRAPH_EDGE_LAST_MASK 0x7fffffff
  33 #define GRAPH_PARENT_NONE 0x70000000
  34
  35 #define GRAPH_LAST_EDGE 0x80000000
  36
  37 #define GRAPH_FANOUT_SIZE (4 * 256)
  38 #define GRAPH_CHUNKLOOKUP_WIDTH 12
  39 #define GRAPH_MIN_SIZE (5 * GRAPH_CHUNKLOOKUP_WIDTH + GRAPH_FANOUT_SIZE + \
  40                         GRAPH_OID_LEN + 8)
  41
  42 char *get_commit_graph_filename(const char *obj_dir)
  43 {
  44         return xstrfmt("%s/info/commit-graph", obj_dir);
  45 }
  46
  47 static struct commit_graph *alloc_commit_graph(void)
  48 {
  49         struct commit_graph *g = xcalloc(1, sizeof(*g));
  50         g->graph_fd = -1;
  51
  52         return g;
  53 }
  54
  55 struct commit_graph *load_commit_graph_one(const char *graph_file)
  56 {
  57         void *graph_map;
  58         const unsigned char *data, *chunk_lookup;
  59         size_t graph_size;
  60         struct stat st;
  61         uint32_t i;
  62         struct commit_graph *graph;
  63         int fd = git_open(graph_file);
  64         uint64_t last_chunk_offset;
  65         uint32_t last_chunk_id;
  66         uint32_t graph_signature;
  67         unsigned char graph_version, hash_version;
  68
  69         if (fd < 0)
  70                 return NULL;
  71         if (fstat(fd, &st)) {
  72                 close(fd);
  73                 return NULL;
  74         }
  75         graph_size = xsize_t(st.st_size);
  76
  77         if (graph_size < GRAPH_MIN_SIZE) {
  78                 close(fd);
  79                 die("graph file %s is too small", graph_file);
  80         }
  81         graph_map = xmmap(NULL, graph_size, PROT_READ, MAP_PRIVATE, fd, 0);
  82         data = (const unsigned char *)graph_map;
  83
  84         graph_signature = get_be32(data);
  85         if (graph_signature != GRAPH_SIGNATURE) {
  86                 error("graph signature %X does not match signature %X",
  87                       graph_signature, GRAPH_SIGNATURE);
  88                 goto cleanup_fail;
  89         }
  90
  91         graph_version = *(unsigned char*)(data + 4);
  92         if (graph_version != GRAPH_VERSION) {
  93                 error("graph version %X does not match version %X",
  94                       graph_version, GRAPH_VERSION);
  95                 goto cleanup_fail;
  96         }
  97
  98         hash_version = *(unsigned char*)(data + 5);
  99         if (hash_version != GRAPH_OID_VERSION) {
 100                 error("hash version %X does not match version %X",
 101                       hash_version, GRAPH_OID_VERSION);
 102                 goto cleanup_fail;
 103         }
 104
 105         graph = alloc_commit_graph();
 106
 107         graph->hash_len = GRAPH_OID_LEN;
 108         graph->num_chunks = *(unsigned char*)(data + 6);
 109         graph->graph_fd = fd;
 110         graph->data = graph_map;
 111         graph->data_len = graph_size;
 112
 113         last_chunk_id = 0;
 114         last_chunk_offset = 8;
 115         chunk_lookup = data + 8;
 116         for (i = 0; i < graph->num_chunks; i++) {
 117                 uint32_t chunk_id = get_be32(chunk_lookup + 0);
 118                 uint64_t chunk_offset = get_be64(chunk_lookup + 4);
 119                 int chunk_repeated = 0;
 120
 121                 chunk_lookup += GRAPH_CHUNKLOOKUP_WIDTH;
 122
 123                 if (chunk_offset > graph_size - GIT_MAX_RAWSZ) {
 124                         error("improper chunk offset %08x%08x", (uint32_t)(chunk_offset >> 32),
 125                               (uint32_t)chunk_offset);
 126                         goto cleanup_fail;
 127                 }
 128
 129                 switch (chunk_id) {
 130                 case GRAPH_CHUNKID_OIDFANOUT:
 131                         if (graph->chunk_oid_fanout)
 132                                 chunk_repeated = 1;
 133                         else
 134                                 graph->chunk_oid_fanout = (uint32_t*)(data + chunk_offset);
 135                         break;
 136
 137                 case GRAPH_CHUNKID_OIDLOOKUP:
 138                         if (graph->chunk_oid_lookup)
 139                                 chunk_repeated = 1;
 140                         else
 141                                 graph->chunk_oid_lookup = data + chunk_offset;
 142                         break;
 143
 144                 case GRAPH_CHUNKID_DATA:
 145                         if (graph->chunk_commit_data)
 146                                 chunk_repeated = 1;
 147                         else
 148                                 graph->chunk_commit_data = data + chunk_offset;
 149                         break;
 150
 151                 case GRAPH_CHUNKID_LARGEEDGES:
 152                         if (graph->chunk_large_edges)
 153                                 chunk_repeated = 1;
 154                         else
 155                                 graph->chunk_large_edges = data + chunk_offset;
 156                         break;
 157                 }
 158
 159                 if (chunk_repeated) {
 160                         error("chunk id %08x appears multiple times", chunk_id);
 161                         goto cleanup_fail;
 162                 }
 163
 164                 if (last_chunk_id == GRAPH_CHUNKID_OIDLOOKUP)
 165                 {
 166                         graph->num_commits = (chunk_offset - last_chunk_offset)
 167                                              / graph->hash_len;
 168                 }
 169
 170                 last_chunk_id = chunk_id;
 171                 last_chunk_offset = chunk_offset;
 172         }
 173
 174         return graph;
 175
 176 cleanup_fail:
 177         munmap(graph_map, graph_size);
 178         close(fd);
 179         exit(1);
 180 }
 181
 182 /* global storage */
 183 static struct commit_graph *commit_graph = NULL;
 184
 185 static void prepare_commit_graph_one(const char *obj_dir)
 186 {
 187         char *graph_name;
 188
 189         if (commit_graph)
 190                 return;
 191
 192         graph_name = get_commit_graph_filename(obj_dir);
 193         commit_graph = load_commit_graph_one(graph_name);
 194
 195         FREE_AND_NULL(graph_name);
 196 }
 197
 198 static int prepare_commit_graph_run_once = 0;
 199 static void prepare_commit_graph(void)
 200 {
 201         struct alternate_object_database *alt;
 202         char *obj_dir;
 203
 204         if (prepare_commit_graph_run_once)
 205                 return;
 206         prepare_commit_graph_run_once = 1;
 207
 208         obj_dir = get_object_directory();
 209         prepare_commit_graph_one(obj_dir);
 210         prepare_alt_odb(the_repository);
 211         for (alt = the_repository->objects->alt_odb_list;
 212              !commit_graph && alt;
 213              alt = alt->next)
 214                 prepare_commit_graph_one(alt->path);
 215 }
 216
 217 static void close_commit_graph(void)
 218 {
 219         if (!commit_graph)
 220                 return;
 221
 222         if (commit_graph->graph_fd >= 0) {
 223                 munmap((void *)commit_graph->data, commit_graph->data_len);
 224                 commit_graph->data = NULL;
 225                 close(commit_graph->graph_fd);
 226         }
 227
 228         FREE_AND_NULL(commit_graph);
 229 }
 230
 231 static int bsearch_graph(struct commit_graph *g, struct object_id *oid, uint32_t *pos)
 232 {
 233         return bsearch_hash(oid->hash, g->chunk_oid_fanout,
 234                             g->chunk_oid_lookup, g->hash_len, pos);
 235 }
 236
 237 static struct commit_list **insert_parent_or_die(struct commit_graph *g,
 238                                                  uint64_t pos,
 239                                                  struct commit_list **pptr)
 240 {
 241         struct commit *c;
 242         struct object_id oid;
 243         hashcpy(oid.hash, g->chunk_oid_lookup + g->hash_len * pos);
 244         c = lookup_commit(&oid);
 245         if (!c)
 246                 die("could not find commit %s", oid_to_hex(&oid));
 247         c->graph_pos = pos;
 248         return &commit_list_insert(c, pptr)->next;
 249 }
 250
 251 static int fill_commit_in_graph(struct commit *item, struct commit_graph *g, uint32_t pos)
 252 {
 253         struct object_id oid;
 254         uint32_t edge_value;
 255         uint32_t *parent_data_ptr;
 256         uint64_t date_low, date_high;
 257         struct commit_list **pptr;
 258         const unsigned char *commit_data = g->chunk_commit_data + (g->hash_len + 16) * pos;
 259
 260         item->object.parsed = 1;
 261         item->graph_pos = pos;
 262
 263         hashcpy(oid.hash, commit_data);
 264         item->tree = lookup_tree(&oid);
 265
 266         date_high = get_be32(commit_data + g->hash_len + 8) & 0x3;
 267         date_low = get_be32(commit_data + g->hash_len + 12);
 268         item->date = (timestamp_t)((date_high << 32) | date_low);
 269
 270         pptr = &item->parents;
 271
 272         edge_value = get_be32(commit_data + g->hash_len);
 273         if (edge_value == GRAPH_PARENT_NONE)
 274                 return 1;
 275         pptr = insert_parent_or_die(g, edge_value, pptr);
 276
 277         edge_value = get_be32(commit_data + g->hash_len + 4);
 278         if (edge_value == GRAPH_PARENT_NONE)
 279                 return 1;
 280         if (!(edge_value & GRAPH_OCTOPUS_EDGES_NEEDED)) {
 281                 pptr = insert_parent_or_die(g, edge_value, pptr);
 282                 return 1;
 283         }
 284
 285         parent_data_ptr = (uint32_t*)(g->chunk_large_edges +
 286                           4 * (uint64_t)(edge_value & GRAPH_EDGE_LAST_MASK));
 287         do {
 288                 edge_value = get_be32(parent_data_ptr);
 289                 pptr = insert_parent_or_die(g,
 290                                             edge_value & GRAPH_EDGE_LAST_MASK,
 291                                             pptr);
 292                 parent_data_ptr++;
 293         } while (!(edge_value & GRAPH_LAST_EDGE));
 294
 295         return 1;
 296 }
 297
 298 int parse_commit_in_graph(struct commit *item)
 299 {
 300         if (!core_commit_graph)
 301                 return 0;
 302         if (item->object.parsed)
 303                 return 1;
 304
 305         prepare_commit_graph();
 306         if (commit_graph) {
 307                 uint32_t pos;
 308                 int found;
 309                 if (item->graph_pos != COMMIT_NOT_FROM_GRAPH) {
 310                         pos = item->graph_pos;
 311                         found = 1;
 312                 } else {
 313                         found = bsearch_graph(commit_graph, &(item->object.oid), &pos);
 314                 }
 315
 316                 if (found)
 317                         return fill_commit_in_graph(item, commit_graph, pos);
 318         }
 319
 320         return 0;
 321 }
 322
 323 static void write_graph_chunk_fanout(struct hashfile *f,
 324                                      struct commit **commits,
 325                                      int nr_commits)
 326 {
 327         int i, count = 0;
 328         struct commit **list = commits;
 329
 330         /*
 331          * Write the first-level table (the list is sorted,
 332          * but we use a 256-entry lookup to be able to avoid
 333          * having to do eight extra binary search iterations).
 334          */
 335         for (i = 0; i < 256; i++) {
 336                 while (count < nr_commits) {
 337                         if ((*list)->object.oid.hash[0] != i)
 338                                 break;
 339                         count++;
 340                         list++;
 341                 }
 342
 343                 hashwrite_be32(f, count);
 344         }
 345 }
 346
 347 static void write_graph_chunk_oids(struct hashfile *f, int hash_len,
 348                                    struct commit **commits, int nr_commits)
 349 {
 350         struct commit **list = commits;
 351         int count;
 352         for (count = 0; count < nr_commits; count++, list++)
 353                 hashwrite(f, (*list)->object.oid.hash, (int)hash_len);
 354 }
 355
 356 static const unsigned char *commit_to_sha1(size_t index, void *table)
 357 {
 358         struct commit **commits = table;
 359         return commits[index]->object.oid.hash;
 360 }
 361
 362 static void write_graph_chunk_data(struct hashfile *f, int hash_len,
 363                                    struct commit **commits, int nr_commits)
 364 {
 365         struct commit **list = commits;
 366         struct commit **last = commits + nr_commits;
 367         uint32_t num_extra_edges = 0;
 368
 369         while (list < last) {
 370                 struct commit_list *parent;
 371                 int edge_value;
 372                 uint32_t packedDate[2];
 373
 374                 parse_commit(*list);
 375                 hashwrite(f, (*list)->tree->object.oid.hash, hash_len);
 376
 377                 parent = (*list)->parents;
 378
 379                 if (!parent)
 380                         edge_value = GRAPH_PARENT_NONE;
 381                 else {
 382                         edge_value = sha1_pos(parent->item->object.oid.hash,
 383                                               commits,
 384                                               nr_commits,
 385                                               commit_to_sha1);
 386
 387                         if (edge_value < 0)
 388                                 edge_value = GRAPH_PARENT_MISSING;
 389                 }
 390
 391                 hashwrite_be32(f, edge_value);
 392
 393                 if (parent)
 394                         parent = parent->next;
 395
 396                 if (!parent)
 397                         edge_value = GRAPH_PARENT_NONE;
 398                 else if (parent->next)
 399                         edge_value = GRAPH_OCTOPUS_EDGES_NEEDED | num_extra_edges;
 400                 else {
 401                         edge_value = sha1_pos(parent->item->object.oid.hash,
 402                                               commits,
 403                                               nr_commits,
 404                                               commit_to_sha1);
 405                         if (edge_value < 0)
 406                                 edge_value = GRAPH_PARENT_MISSING;
 407                 }
 408
 409                 hashwrite_be32(f, edge_value);
 410
 411                 if (edge_value & GRAPH_OCTOPUS_EDGES_NEEDED) {
 412                         do {
 413                                 num_extra_edges++;
 414                                 parent = parent->next;
 415                         } while (parent);
 416                 }
 417
 418                 if (sizeof((*list)->date) > 4)
 419                         packedDate[0] = htonl(((*list)->date >> 32) & 0x3);
 420                 else
 421                         packedDate[0] = 0;
 422
 423                 packedDate[1] = htonl((*list)->date);
 424                 hashwrite(f, packedDate, 8);
 425
 426                 list++;
 427         }
 428 }
 429
 430 static void write_graph_chunk_large_edges(struct hashfile *f,
 431                                           struct commit **commits,
 432                                           int nr_commits)
 433 {
 434         struct commit **list = commits;
 435         struct commit **last = commits + nr_commits;
 436         struct commit_list *parent;
 437
 438         while (list < last) {
 439                 int num_parents = 0;
 440                 for (parent = (*list)->parents; num_parents < 3 && parent;
 441                      parent = parent->next)
 442                         num_parents++;
 443
 444                 if (num_parents <= 2) {
 445                         list++;
 446                         continue;
 447                 }
 448
 449                 /* Since num_parents > 2, this initializer is safe. */
 450                 for (parent = (*list)->parents->next; parent; parent = parent->next) {
 451                         int edge_value = sha1_pos(parent->item->object.oid.hash,
 452                                                   commits,
 453                                                   nr_commits,
 454                                                   commit_to_sha1);
 455
 456                         if (edge_value < 0)
 457                                 edge_value = GRAPH_PARENT_MISSING;
 458                         else if (!parent->next)
 459                                 edge_value |= GRAPH_LAST_EDGE;
 460
 461                         hashwrite_be32(f, edge_value);
 462                 }
 463
 464                 list++;
 465         }
 466 }
 467
 468 static int commit_compare(const void *_a, const void *_b)
 469 {
 470         const struct object_id *a = (const struct object_id *)_a;
 471         const struct object_id *b = (const struct object_id *)_b;
 472         return oidcmp(a, b);
 473 }
 474
 475 struct packed_commit_list {
 476         struct commit **list;
 477         int nr;
 478         int alloc;
 479 };
 480
 481 struct packed_oid_list {
 482         struct object_id *list;
 483         int nr;
 484         int alloc;
 485 };
 486
 487 static int add_packed_commits(const struct object_id *oid,
 488                               struct packed_git *pack,
 489                               uint32_t pos,
 490                               void *data)
 491 {
 492         struct packed_oid_list *list = (struct packed_oid_list*)data;
 493         enum object_type type;
 494         off_t offset = nth_packed_object_offset(pack, pos);
 495         struct object_info oi = OBJECT_INFO_INIT;
 496
 497         oi.typep = &type;
 498         if (packed_object_info(pack, offset, &oi) < 0)
 499                 die("unable to get type of object %s", oid_to_hex(oid));
 500
 501         if (type != OBJ_COMMIT)
 502                 return 0;
 503
 504         ALLOC_GROW(list->list, list->nr + 1, list->alloc);
 505         oidcpy(&(list->list[list->nr]), oid);
 506         list->nr++;
 507
 508         return 0;
 509 }
 510
 511 static void add_missing_parents(struct packed_oid_list *oids, struct commit *commit)
 512 {
 513         struct commit_list *parent;
 514         for (parent = commit->parents; parent; parent = parent->next) {
 515                 if (!(parent->item->object.flags & UNINTERESTING)) {
 516                         ALLOC_GROW(oids->list, oids->nr + 1, oids->alloc);
 517                         oidcpy(&oids->list[oids->nr], &(parent->item->object.oid));
 518                         oids->nr++;
 519                         parent->item->object.flags |= UNINTERESTING;
 520                 }
 521         }
 522 }
 523
 524 static void close_reachable(struct packed_oid_list *oids)
 525 {
 526         int i;
 527         struct commit *commit;
 528
 529         for (i = 0; i < oids->nr; i++) {
 530                 commit = lookup_commit(&oids->list[i]);
 531                 if (commit)
 532                         commit->object.flags |= UNINTERESTING;
 533         }
 534
 535         /*
 536          * As this loop runs, oids->nr may grow, but not more
 537          * than the number of missing commits in the reachable
 538          * closure.
 539          */
 540         for (i = 0; i < oids->nr; i++) {
 541                 commit = lookup_commit(&oids->list[i]);
 542
 543                 if (commit && !parse_commit(commit))
 544                         add_missing_parents(oids, commit);
 545         }
 546
 547         for (i = 0; i < oids->nr; i++) {
 548                 commit = lookup_commit(&oids->list[i]);
 549
 550                 if (commit)
 551                         commit->object.flags &= ~UNINTERESTING;
 552         }
 553 }
 554
 555 void write_commit_graph(const char *obj_dir,
 556                         const char **pack_indexes,
 557                         int nr_packs,
 558                         const char **commit_hex,
 559                         int nr_commits,
 560                         int append)
 561 {
 562         struct packed_oid_list oids;
 563         struct packed_commit_list commits;
 564         struct hashfile *f;
 565         uint32_t i, count_distinct = 0;
 566         char *graph_name;
 567         int fd;
 568         struct lock_file lk = LOCK_INIT;
 569         uint32_t chunk_ids[5];
 570         uint64_t chunk_offsets[5];
 571         int num_chunks;
 572         int num_extra_edges;
 573         struct commit_list *parent;
 574
 575         oids.nr = 0;
 576         oids.alloc = approximate_object_count() / 4;
 577
 578         if (append) {
 579                 prepare_commit_graph_one(obj_dir);
 580                 if (commit_graph)
 581                         oids.alloc += commit_graph->num_commits;
 582         }
 583
 584         if (oids.alloc < 1024)
 585                 oids.alloc = 1024;
 586         ALLOC_ARRAY(oids.list, oids.alloc);
 587
 588         if (append && commit_graph) {
 589                 for (i = 0; i < commit_graph->num_commits; i++) {
 590                         const unsigned char *hash = commit_graph->chunk_oid_lookup +
 591                                 commit_graph->hash_len * i;
 592                         hashcpy(oids.list[oids.nr++].hash, hash);
 593                 }
 594         }
 595
 596         if (pack_indexes) {
 597                 struct strbuf packname = STRBUF_INIT;
 598                 int dirlen;
 599                 strbuf_addf(&packname, "%s/pack/", obj_dir);
 600                 dirlen = packname.len;
 601                 for (i = 0; i < nr_packs; i++) {
 602                         struct packed_git *p;
 603                         strbuf_setlen(&packname, dirlen);
 604                         strbuf_addstr(&packname, pack_indexes[i]);
 605                         p = add_packed_git(packname.buf, packname.len, 1);
 606                         if (!p)
 607                                 die("error adding pack %s", packname.buf);
 608                         if (open_pack_index(p))
 609                                 die("error opening index for %s", packname.buf);
 610                         for_each_object_in_pack(p, add_packed_commits, &oids);
 611                         close_pack(p);
 612                 }
 613                 strbuf_release(&packname);
 614         }
 615
 616         if (commit_hex) {
 617                 for (i = 0; i < nr_commits; i++) {
 618                         const char *end;
 619                         struct object_id oid;
 620                         struct commit *result;
 621
 622                         if (commit_hex[i] && parse_oid_hex(commit_hex[i], &oid, &end))
 623                                 continue;
 624
 625                         result = lookup_commit_reference_gently(&oid, 1);
 626
 627                         if (result) {
 628                                 ALLOC_GROW(oids.list, oids.nr + 1, oids.alloc);
 629                                 oidcpy(&oids.list[oids.nr], &(result->object.oid));
 630                                 oids.nr++;
 631                         }
 632                 }
 633         }
 634
 635         if (!pack_indexes && !commit_hex)
 636                 for_each_packed_object(add_packed_commits, &oids, 0);
 637
 638         close_reachable(&oids);
 639
 640         QSORT(oids.list, oids.nr, commit_compare);
 641
 642         count_distinct = 1;
 643         for (i = 1; i < oids.nr; i++) {
 644                 if (oidcmp(&oids.list[i-1], &oids.list[i]))
 645                         count_distinct++;
 646         }
 647
 648         if (count_distinct >= GRAPH_PARENT_MISSING)
 649                 die(_("the commit graph format cannot write %d commits"), count_distinct);
 650
 651         commits.nr = 0;
 652         commits.alloc = count_distinct;
 653         ALLOC_ARRAY(commits.list, commits.alloc);
 654
 655         num_extra_edges = 0;
 656         for (i = 0; i < oids.nr; i++) {
 657                 int num_parents = 0;
 658                 if (i > 0 && !oidcmp(&oids.list[i-1], &oids.list[i]))
 659                         continue;
 660
 661                 commits.list[commits.nr] = lookup_commit(&oids.list[i]);
 662                 parse_commit(commits.list[commits.nr]);
 663
 664                 for (parent = commits.list[commits.nr]->parents;
 665                      parent; parent = parent->next)
 666                         num_parents++;
 667
 668                 if (num_parents > 2)
 669                         num_extra_edges += num_parents - 1;
 670
 671                 commits.nr++;
 672         }
 673         num_chunks = num_extra_edges ? 4 : 3;
 674
 675         if (commits.nr >= GRAPH_PARENT_MISSING)
 676                 die(_("too many commits to write graph"));
 677
 678         graph_name = get_commit_graph_filename(obj_dir);
 679         fd = hold_lock_file_for_update(&lk, graph_name, 0);
 680
 681         if (fd < 0) {
 682                 struct strbuf folder = STRBUF_INIT;
 683                 strbuf_addstr(&folder, graph_name);
 684                 strbuf_setlen(&folder, strrchr(folder.buf, '/') - folder.buf);
 685
 686                 if (mkdir(folder.buf, 0777) < 0)
 687                         die_errno(_("cannot mkdir %s"), folder.buf);
 688                 strbuf_release(&folder);
 689
 690                 fd = hold_lock_file_for_update(&lk, graph_name, LOCK_DIE_ON_ERROR);
 691
 692                 if (fd < 0)
 693                         die_errno("unable to create '%s'", graph_name);
 694         }
 695
 696         f = hashfd(lk.tempfile->fd, lk.tempfile->filename.buf);
 697
 698         hashwrite_be32(f, GRAPH_SIGNATURE);
 699
 700         hashwrite_u8(f, GRAPH_VERSION);
 701         hashwrite_u8(f, GRAPH_OID_VERSION);
 702         hashwrite_u8(f, num_chunks);
 703         hashwrite_u8(f, 0); /* unused padding byte */
 704
 705         chunk_ids[0] = GRAPH_CHUNKID_OIDFANOUT;
 706         chunk_ids[1] = GRAPH_CHUNKID_OIDLOOKUP;
 707         chunk_ids[2] = GRAPH_CHUNKID_DATA;
 708         if (num_extra_edges)
 709                 chunk_ids[3] = GRAPH_CHUNKID_LARGEEDGES;
 710         else
 711                 chunk_ids[3] = 0;
 712         chunk_ids[4] = 0;
 713
 714         chunk_offsets[0] = 8 + (num_chunks + 1) * GRAPH_CHUNKLOOKUP_WIDTH;
 715         chunk_offsets[1] = chunk_offsets[0] + GRAPH_FANOUT_SIZE;
 716         chunk_offsets[2] = chunk_offsets[1] + GRAPH_OID_LEN * commits.nr;
 717         chunk_offsets[3] = chunk_offsets[2] + (GRAPH_OID_LEN + 16) * commits.nr;
 718         chunk_offsets[4] = chunk_offsets[3] + 4 * num_extra_edges;
 719
 720         for (i = 0; i <= num_chunks; i++) {
 721                 uint32_t chunk_write[3];
 722
 723                 chunk_write[0] = htonl(chunk_ids[i]);
 724                 chunk_write[1] = htonl(chunk_offsets[i] >> 32);
 725                 chunk_write[2] = htonl(chunk_offsets[i] & 0xffffffff);
 726                 hashwrite(f, chunk_write, 12);
 727         }
 728
 729         write_graph_chunk_fanout(f, commits.list, commits.nr);
 730         write_graph_chunk_oids(f, GRAPH_OID_LEN, commits.list, commits.nr);
 731         write_graph_chunk_data(f, GRAPH_OID_LEN, commits.list, commits.nr);
 732         write_graph_chunk_large_edges(f, commits.list, commits.nr);
 733
 734         close_commit_graph();
 735         finalize_hashfile(f, NULL, CSUM_HASH_IN_STREAM | CSUM_FSYNC);
 736         commit_lock_file(&lk);
 737
 738         free(oids.list);
 739         oids.alloc = 0;
 740         oids.nr = 0;
 741 }