pack-bitmap-write.c

   1 #include "git-compat-util.h"
   2 #include "environment.h"
   3 #include "gettext.h"
   4 #include "hex.h"
   5 #include "object-store-ll.h"
   6 #include "commit.h"
   7 #include "tag.h"
   8 #include "diff.h"
   9 #include "revision.h"
  10 #include "list-objects.h"
  11 #include "progress.h"
  12 #include "pack-revindex.h"
  13 #include "pack.h"
  14 #include "pack-bitmap.h"
  15 #include "hash-lookup.h"
  16 #include "pack-objects.h"
  17 #include "path.h"
  18 #include "commit-reach.h"
  19 #include "prio-queue.h"
  20 #include "trace2.h"
  21 #include "tree.h"
  22 #include "tree-walk.h"
  23
  24 struct bitmapped_commit {
  25         struct commit *commit;
  26         struct ewah_bitmap *bitmap;
  27         struct ewah_bitmap *write_as;
  28         int flags;
  29         int xor_offset;
  30         uint32_t commit_pos;
  31 };
  32
  33 struct bitmap_writer {
  34         struct ewah_bitmap *commits;
  35         struct ewah_bitmap *trees;
  36         struct ewah_bitmap *blobs;
  37         struct ewah_bitmap *tags;
  38
  39         kh_oid_map_t *bitmaps;
  40         struct packing_data *to_pack;
  41
  42         struct bitmapped_commit *selected;
  43         unsigned int selected_nr, selected_alloc;
  44
  45         struct progress *progress;
  46         int show_progress;
  47         unsigned char pack_checksum[GIT_MAX_RAWSZ];
  48 };
  49
  50 static struct bitmap_writer writer;
  51
  52 void bitmap_writer_show_progress(int show)
  53 {
  54         writer.show_progress = show;
  55 }
  56
  57 /**
  58  * Build the initial type index for the packfile or multi-pack-index
  59  */
  60 void bitmap_writer_build_type_index(struct packing_data *to_pack,
  61                                     struct pack_idx_entry **index,
  62                                     uint32_t index_nr)
  63 {
  64         uint32_t i;
  65
  66         writer.commits = ewah_new();
  67         writer.trees = ewah_new();
  68         writer.blobs = ewah_new();
  69         writer.tags = ewah_new();
  70         ALLOC_ARRAY(to_pack->in_pack_pos, to_pack->nr_objects);
  71
  72         for (i = 0; i < index_nr; ++i) {
  73                 struct object_entry *entry = (struct object_entry *)index[i];
  74                 enum object_type real_type;
  75
  76                 oe_set_in_pack_pos(to_pack, entry, i);
  77
  78                 switch (oe_type(entry)) {
  79                 case OBJ_COMMIT:
  80                 case OBJ_TREE:
  81                 case OBJ_BLOB:
  82                 case OBJ_TAG:
  83                         real_type = oe_type(entry);
  84                         break;
  85
  86                 default:
  87                         real_type = oid_object_info(to_pack->repo,
  88                                                     &entry->idx.oid, NULL);
  89                         break;
  90                 }
  91
  92                 switch (real_type) {
  93                 case OBJ_COMMIT:
  94                         ewah_set(writer.commits, i);
  95                         break;
  96
  97                 case OBJ_TREE:
  98                         ewah_set(writer.trees, i);
  99                         break;
 100
 101                 case OBJ_BLOB:
 102                         ewah_set(writer.blobs, i);
 103                         break;
 104
 105                 case OBJ_TAG:
 106                         ewah_set(writer.tags, i);
 107                         break;
 108
 109                 default:
 110                         die("Missing type information for %s (%d/%d)",
 111                             oid_to_hex(&entry->idx.oid), real_type,
 112                             oe_type(entry));
 113                 }
 114         }
 115 }
 116
 117 /**
 118  * Compute the actual bitmaps
 119  */
 120
 121 static inline void push_bitmapped_commit(struct commit *commit)
 122 {
 123         if (writer.selected_nr >= writer.selected_alloc) {
 124                 writer.selected_alloc = (writer.selected_alloc + 32) * 2;
 125                 REALLOC_ARRAY(writer.selected, writer.selected_alloc);
 126         }
 127
 128         writer.selected[writer.selected_nr].commit = commit;
 129         writer.selected[writer.selected_nr].bitmap = NULL;
 130         writer.selected[writer.selected_nr].flags = 0;
 131
 132         writer.selected_nr++;
 133 }
 134
 135 static uint32_t find_object_pos(const struct object_id *oid, int *found)
 136 {
 137         struct object_entry *entry = packlist_find(writer.to_pack, oid);
 138
 139         if (!entry) {
 140                 if (found)
 141                         *found = 0;
 142                 warning("Failed to write bitmap index. Packfile doesn't have full closure "
 143                         "(object %s is missing)", oid_to_hex(oid));
 144                 return 0;
 145         }
 146
 147         if (found)
 148                 *found = 1;
 149         return oe_in_pack_pos(writer.to_pack, entry);
 150 }
 151
 152 static void compute_xor_offsets(void)
 153 {
 154         static const int MAX_XOR_OFFSET_SEARCH = 10;
 155
 156         int i, next = 0;
 157
 158         while (next < writer.selected_nr) {
 159                 struct bitmapped_commit *stored = &writer.selected[next];
 160
 161                 int best_offset = 0;
 162                 struct ewah_bitmap *best_bitmap = stored->bitmap;
 163                 struct ewah_bitmap *test_xor;
 164
 165                 for (i = 1; i <= MAX_XOR_OFFSET_SEARCH; ++i) {
 166                         int curr = next - i;
 167
 168                         if (curr < 0)
 169                                 break;
 170
 171                         test_xor = ewah_pool_new();
 172                         ewah_xor(writer.selected[curr].bitmap, stored->bitmap, test_xor);
 173
 174                         if (test_xor->buffer_size < best_bitmap->buffer_size) {
 175                                 if (best_bitmap != stored->bitmap)
 176                                         ewah_pool_free(best_bitmap);
 177
 178                                 best_bitmap = test_xor;
 179                                 best_offset = i;
 180                         } else {
 181                                 ewah_pool_free(test_xor);
 182                         }
 183                 }
 184
 185                 stored->xor_offset = best_offset;
 186                 stored->write_as = best_bitmap;
 187
 188                 next++;
 189         }
 190 }
 191
 192 struct bb_commit {
 193         struct commit_list *reverse_edges;
 194         struct bitmap *commit_mask;
 195         struct bitmap *bitmap;
 196         unsigned selected:1,
 197                  maximal:1;
 198         unsigned idx; /* within selected array */
 199 };
 200
 201 define_commit_slab(bb_data, struct bb_commit);
 202
 203 struct bitmap_builder {
 204         struct bb_data data;
 205         struct commit **commits;
 206         size_t commits_nr, commits_alloc;
 207 };
 208
 209 static void bitmap_builder_init(struct bitmap_builder *bb,
 210                                 struct bitmap_writer *writer,
 211                                 struct bitmap_index *old_bitmap)
 212 {
 213         struct rev_info revs;
 214         struct commit *commit;
 215         struct commit_list *reusable = NULL;
 216         struct commit_list *r;
 217         unsigned int i, num_maximal = 0;
 218
 219         memset(bb, 0, sizeof(*bb));
 220         init_bb_data(&bb->data);
 221
 222         reset_revision_walk();
 223         repo_init_revisions(writer->to_pack->repo, &revs, NULL);
 224         revs.topo_order = 1;
 225         revs.first_parent_only = 1;
 226
 227         for (i = 0; i < writer->selected_nr; i++) {
 228                 struct commit *c = writer->selected[i].commit;
 229                 struct bb_commit *ent = bb_data_at(&bb->data, c);
 230
 231                 ent->selected = 1;
 232                 ent->maximal = 1;
 233                 ent->idx = i;
 234
 235                 ent->commit_mask = bitmap_new();
 236                 bitmap_set(ent->commit_mask, i);
 237
 238                 add_pending_object(&revs, &c->object, "");
 239         }
 240
 241         if (prepare_revision_walk(&revs))
 242                 die("revision walk setup failed");
 243
 244         while ((commit = get_revision(&revs))) {
 245                 struct commit_list *p = commit->parents;
 246                 struct bb_commit *c_ent;
 247
 248                 parse_commit_or_die(commit);
 249
 250                 c_ent = bb_data_at(&bb->data, commit);
 251
 252                 /*
 253                  * If there is no commit_mask, there is no reason to iterate
 254                  * over this commit; it is not selected (if it were, it would
 255                  * not have a blank commit mask) and all its children have
 256                  * existing bitmaps (see the comment starting with "This commit
 257                  * has an existing bitmap" below), so it does not contribute
 258                  * anything to the final bitmap file or its descendants.
 259                  */
 260                 if (!c_ent->commit_mask)
 261                         continue;
 262
 263                 if (old_bitmap && bitmap_for_commit(old_bitmap, commit)) {
 264                         /*
 265                          * This commit has an existing bitmap, so we can
 266                          * get its bits immediately without an object
 267                          * walk. That is, it is reusable as-is and there is no
 268                          * need to continue walking beyond it.
 269                          *
 270                          * Mark it as such and add it to bb->commits separately
 271                          * to avoid allocating a position in the commit mask.
 272                          */
 273                         commit_list_insert(commit, &reusable);
 274                         goto next;
 275                 }
 276
 277                 if (c_ent->maximal) {
 278                         num_maximal++;
 279                         ALLOC_GROW(bb->commits, bb->commits_nr + 1, bb->commits_alloc);
 280                         bb->commits[bb->commits_nr++] = commit;
 281                 }
 282
 283                 if (p) {
 284                         struct bb_commit *p_ent = bb_data_at(&bb->data, p->item);
 285                         int c_not_p, p_not_c;
 286
 287                         if (!p_ent->commit_mask) {
 288                                 p_ent->commit_mask = bitmap_new();
 289                                 c_not_p = 1;
 290                                 p_not_c = 0;
 291                         } else {
 292                                 c_not_p = bitmap_is_subset(c_ent->commit_mask, p_ent->commit_mask);
 293                                 p_not_c = bitmap_is_subset(p_ent->commit_mask, c_ent->commit_mask);
 294                         }
 295
 296                         if (!c_not_p)
 297                                 continue;
 298
 299                         bitmap_or(p_ent->commit_mask, c_ent->commit_mask);
 300
 301                         if (p_not_c)
 302                                 p_ent->maximal = 1;
 303                         else {
 304                                 p_ent->maximal = 0;
 305                                 free_commit_list(p_ent->reverse_edges);
 306                                 p_ent->reverse_edges = NULL;
 307                         }
 308
 309                         if (c_ent->maximal) {
 310                                 commit_list_insert(commit, &p_ent->reverse_edges);
 311                         } else {
 312                                 struct commit_list *cc = c_ent->reverse_edges;
 313
 314                                 for (; cc; cc = cc->next) {
 315                                         if (!commit_list_contains(cc->item, p_ent->reverse_edges))
 316                                                 commit_list_insert(cc->item, &p_ent->reverse_edges);
 317                                 }
 318                         }
 319                 }
 320
 321 next:
 322                 bitmap_free(c_ent->commit_mask);
 323                 c_ent->commit_mask = NULL;
 324         }
 325
 326         for (r = reusable; r; r = r->next) {
 327                 ALLOC_GROW(bb->commits, bb->commits_nr + 1, bb->commits_alloc);
 328                 bb->commits[bb->commits_nr++] = r->item;
 329         }
 330
 331         trace2_data_intmax("pack-bitmap-write", the_repository,
 332                            "num_selected_commits", writer->selected_nr);
 333         trace2_data_intmax("pack-bitmap-write", the_repository,
 334                            "num_maximal_commits", num_maximal);
 335
 336         release_revisions(&revs);
 337         free_commit_list(reusable);
 338 }
 339
 340 static void bitmap_builder_clear(struct bitmap_builder *bb)
 341 {
 342         clear_bb_data(&bb->data);
 343         free(bb->commits);
 344         bb->commits_nr = bb->commits_alloc = 0;
 345 }
 346
 347 static int fill_bitmap_tree(struct bitmap *bitmap,
 348                             struct tree *tree)
 349 {
 350         int found;
 351         uint32_t pos;
 352         struct tree_desc desc;
 353         struct name_entry entry;
 354
 355         /*
 356          * If our bit is already set, then there is nothing to do. Both this
 357          * tree and all of its children will be set.
 358          */
 359         pos = find_object_pos(&tree->object.oid, &found);
 360         if (!found)
 361                 return -1;
 362         if (bitmap_get(bitmap, pos))
 363                 return 0;
 364         bitmap_set(bitmap, pos);
 365
 366         if (parse_tree(tree) < 0)
 367                 die("unable to load tree object %s",
 368                     oid_to_hex(&tree->object.oid));
 369         init_tree_desc(&desc, tree->buffer, tree->size);
 370
 371         while (tree_entry(&desc, &entry)) {
 372                 switch (object_type(entry.mode)) {
 373                 case OBJ_TREE:
 374                         if (fill_bitmap_tree(bitmap,
 375                                              lookup_tree(the_repository, &entry.oid)) < 0)
 376                                 return -1;
 377                         break;
 378                 case OBJ_BLOB:
 379                         pos = find_object_pos(&entry.oid, &found);
 380                         if (!found)
 381                                 return -1;
 382                         bitmap_set(bitmap, pos);
 383                         break;
 384                 default:
 385                         /* Gitlink, etc; not reachable */
 386                         break;
 387                 }
 388         }
 389
 390         free_tree_buffer(tree);
 391         return 0;
 392 }
 393
 394 static int reused_bitmaps_nr;
 395
 396 static int fill_bitmap_commit(struct bb_commit *ent,
 397                               struct commit *commit,
 398                               struct prio_queue *queue,
 399                               struct prio_queue *tree_queue,
 400                               struct bitmap_index *old_bitmap,
 401                               const uint32_t *mapping)
 402 {
 403         int found;
 404         uint32_t pos;
 405         if (!ent->bitmap)
 406                 ent->bitmap = bitmap_new();
 407
 408         prio_queue_put(queue, commit);
 409
 410         while (queue->nr) {
 411                 struct commit_list *p;
 412                 struct commit *c = prio_queue_get(queue);
 413
 414                 if (old_bitmap && mapping) {
 415                         struct ewah_bitmap *old = bitmap_for_commit(old_bitmap, c);
 416                         struct bitmap *remapped = bitmap_new();
 417                         /*
 418                          * If this commit has an old bitmap, then translate that
 419                          * bitmap and add its bits to this one. No need to walk
 420                          * parents or the tree for this commit.
 421                          */
 422                         if (old && !rebuild_bitmap(mapping, old, remapped)) {
 423                                 bitmap_or(ent->bitmap, remapped);
 424                                 bitmap_free(remapped);
 425                                 reused_bitmaps_nr++;
 426                                 continue;
 427                         }
 428                         bitmap_free(remapped);
 429                 }
 430
 431                 /*
 432                  * Mark ourselves and queue our tree. The commit
 433                  * walk ensures we cover all parents.
 434                  */
 435                 pos = find_object_pos(&c->object.oid, &found);
 436                 if (!found)
 437                         return -1;
 438                 bitmap_set(ent->bitmap, pos);
 439                 prio_queue_put(tree_queue,
 440                                repo_get_commit_tree(the_repository, c));
 441
 442                 for (p = c->parents; p; p = p->next) {
 443                         pos = find_object_pos(&p->item->object.oid, &found);
 444                         if (!found)
 445                                 return -1;
 446                         if (!bitmap_get(ent->bitmap, pos)) {
 447                                 bitmap_set(ent->bitmap, pos);
 448                                 prio_queue_put(queue, p->item);
 449                         }
 450                 }
 451         }
 452
 453         while (tree_queue->nr) {
 454                 if (fill_bitmap_tree(ent->bitmap,
 455                                      prio_queue_get(tree_queue)) < 0)
 456                         return -1;
 457         }
 458         return 0;
 459 }
 460
 461 static void store_selected(struct bb_commit *ent, struct commit *commit)
 462 {
 463         struct bitmapped_commit *stored = &writer.selected[ent->idx];
 464         khiter_t hash_pos;
 465         int hash_ret;
 466
 467         stored->bitmap = bitmap_to_ewah(ent->bitmap);
 468
 469         hash_pos = kh_put_oid_map(writer.bitmaps, commit->object.oid, &hash_ret);
 470         if (hash_ret == 0)
 471                 die("Duplicate entry when writing index: %s",
 472                     oid_to_hex(&commit->object.oid));
 473         kh_value(writer.bitmaps, hash_pos) = stored;
 474 }
 475
 476 int bitmap_writer_build(struct packing_data *to_pack)
 477 {
 478         struct bitmap_builder bb;
 479         size_t i;
 480         int nr_stored = 0; /* for progress */
 481         struct prio_queue queue = { compare_commits_by_gen_then_commit_date };
 482         struct prio_queue tree_queue = { NULL };
 483         struct bitmap_index *old_bitmap;
 484         uint32_t *mapping;
 485         int closed = 1; /* until proven otherwise */
 486
 487         writer.bitmaps = kh_init_oid_map();
 488         writer.to_pack = to_pack;
 489
 490         if (writer.show_progress)
 491                 writer.progress = start_progress("Building bitmaps", writer.selected_nr);
 492         trace2_region_enter("pack-bitmap-write", "building_bitmaps_total",
 493                             the_repository);
 494
 495         old_bitmap = prepare_bitmap_git(to_pack->repo);
 496         if (old_bitmap)
 497                 mapping = create_bitmap_mapping(old_bitmap, to_pack);
 498         else
 499                 mapping = NULL;
 500
 501         bitmap_builder_init(&bb, &writer, old_bitmap);
 502         for (i = bb.commits_nr; i > 0; i--) {
 503                 struct commit *commit = bb.commits[i-1];
 504                 struct bb_commit *ent = bb_data_at(&bb.data, commit);
 505                 struct commit *child;
 506                 int reused = 0;
 507
 508                 if (fill_bitmap_commit(ent, commit, &queue, &tree_queue,
 509                                        old_bitmap, mapping) < 0) {
 510                         closed = 0;
 511                         break;
 512                 }
 513
 514                 if (ent->selected) {
 515                         store_selected(ent, commit);
 516                         nr_stored++;
 517                         display_progress(writer.progress, nr_stored);
 518                 }
 519
 520                 while ((child = pop_commit(&ent->reverse_edges))) {
 521                         struct bb_commit *child_ent =
 522                                 bb_data_at(&bb.data, child);
 523
 524                         if (child_ent->bitmap)
 525                                 bitmap_or(child_ent->bitmap, ent->bitmap);
 526                         else if (reused)
 527                                 child_ent->bitmap = bitmap_dup(ent->bitmap);
 528                         else {
 529                                 child_ent->bitmap = ent->bitmap;
 530                                 reused = 1;
 531                         }
 532                 }
 533                 if (!reused)
 534                         bitmap_free(ent->bitmap);
 535                 ent->bitmap = NULL;
 536         }
 537         clear_prio_queue(&queue);
 538         clear_prio_queue(&tree_queue);
 539         bitmap_builder_clear(&bb);
 540         free_bitmap_index(old_bitmap);
 541         free(mapping);
 542
 543         trace2_region_leave("pack-bitmap-write", "building_bitmaps_total",
 544                             the_repository);
 545         trace2_data_intmax("pack-bitmap-write", the_repository,
 546                            "building_bitmaps_reused", reused_bitmaps_nr);
 547
 548         stop_progress(&writer.progress);
 549
 550         if (closed)
 551                 compute_xor_offsets();
 552         return closed ? 0 : -1;
 553 }
 554
 555 /**
 556  * Select the commits that will be bitmapped
 557  */
 558 static inline unsigned int next_commit_index(unsigned int idx)
 559 {
 560         static const unsigned int MIN_COMMITS = 100;
 561         static const unsigned int MAX_COMMITS = 5000;
 562
 563         static const unsigned int MUST_REGION = 100;
 564         static const unsigned int MIN_REGION = 20000;
 565
 566         unsigned int offset, next;
 567
 568         if (idx <= MUST_REGION)
 569                 return 0;
 570
 571         if (idx <= MIN_REGION) {
 572                 offset = idx - MUST_REGION;
 573                 return (offset < MIN_COMMITS) ? offset : MIN_COMMITS;
 574         }
 575
 576         offset = idx - MIN_REGION;
 577         next = (offset < MAX_COMMITS) ? offset : MAX_COMMITS;
 578
 579         return (next > MIN_COMMITS) ? next : MIN_COMMITS;
 580 }
 581
 582 static int date_compare(const void *_a, const void *_b)
 583 {
 584         struct commit *a = *(struct commit **)_a;
 585         struct commit *b = *(struct commit **)_b;
 586         return (long)b->date - (long)a->date;
 587 }
 588
 589 void bitmap_writer_select_commits(struct commit **indexed_commits,
 590                                   unsigned int indexed_commits_nr,
 591                                   int max_bitmaps)
 592 {
 593         unsigned int i = 0, j, next;
 594
 595         QSORT(indexed_commits, indexed_commits_nr, date_compare);
 596
 597         if (indexed_commits_nr < 100) {
 598                 for (i = 0; i < indexed_commits_nr; ++i)
 599                         push_bitmapped_commit(indexed_commits[i]);
 600                 return;
 601         }
 602
 603         if (writer.show_progress)
 604                 writer.progress = start_progress("Selecting bitmap commits", 0);
 605
 606         for (;;) {
 607                 struct commit *chosen = NULL;
 608
 609                 next = next_commit_index(i);
 610
 611                 if (i + next >= indexed_commits_nr)
 612                         break;
 613
 614                 if (max_bitmaps > 0 && writer.selected_nr >= max_bitmaps) {
 615                         writer.selected_nr = max_bitmaps;
 616                         break;
 617                 }
 618
 619                 if (next == 0) {
 620                         chosen = indexed_commits[i];
 621                 } else {
 622                         chosen = indexed_commits[i + next];
 623
 624                         for (j = 0; j <= next; ++j) {
 625                                 struct commit *cm = indexed_commits[i + j];
 626
 627                                 if ((cm->object.flags & NEEDS_BITMAP) != 0) {
 628                                         chosen = cm;
 629                                         break;
 630                                 }
 631
 632                                 if (cm->parents && cm->parents->next)
 633                                         chosen = cm;
 634                         }
 635                 }
 636
 637                 push_bitmapped_commit(chosen);
 638
 639                 i += next + 1;
 640                 display_progress(writer.progress, i);
 641         }
 642
 643         stop_progress(&writer.progress);
 644 }
 645
 646
 647 static int hashwrite_ewah_helper(void *f, const void *buf, size_t len)
 648 {
 649         /* hashwrite will die on error */
 650         hashwrite(f, buf, len);
 651         return len;
 652 }
 653
 654 /**
 655  * Write the bitmap index to disk
 656  */
 657 static inline void dump_bitmap(struct hashfile *f, struct ewah_bitmap *bitmap)
 658 {
 659         if (ewah_serialize_to(bitmap, hashwrite_ewah_helper, f) < 0)
 660                 die("Failed to write bitmap index");
 661 }
 662
 663 static const struct object_id *oid_access(size_t pos, const void *table)
 664 {
 665         const struct pack_idx_entry * const *index = table;
 666         return &index[pos]->oid;
 667 }
 668
 669 static void write_selected_commits_v1(struct hashfile *f,
 670                                       uint32_t *commit_positions,
 671                                       off_t *offsets)
 672 {
 673         int i;
 674
 675         for (i = 0; i < writer.selected_nr; ++i) {
 676                 struct bitmapped_commit *stored = &writer.selected[i];
 677
 678                 if (offsets)
 679                         offsets[i] = hashfile_total(f);
 680
 681                 hashwrite_be32(f, commit_positions[i]);
 682                 hashwrite_u8(f, stored->xor_offset);
 683                 hashwrite_u8(f, stored->flags);
 684
 685                 dump_bitmap(f, stored->write_as);
 686         }
 687 }
 688
 689 static int table_cmp(const void *_va, const void *_vb, void *_data)
 690 {
 691         uint32_t *commit_positions = _data;
 692         uint32_t a = commit_positions[*(uint32_t *)_va];
 693         uint32_t b = commit_positions[*(uint32_t *)_vb];
 694
 695         if (a > b)
 696                 return 1;
 697         else if (a < b)
 698                 return -1;
 699
 700         return 0;
 701 }
 702
 703 static void write_lookup_table(struct hashfile *f,
 704                                uint32_t *commit_positions,
 705                                off_t *offsets)
 706 {
 707         uint32_t i;
 708         uint32_t *table, *table_inv;
 709
 710         ALLOC_ARRAY(table, writer.selected_nr);
 711         ALLOC_ARRAY(table_inv, writer.selected_nr);
 712
 713         for (i = 0; i < writer.selected_nr; i++)
 714                 table[i] = i;
 715
 716         /*
 717          * At the end of this sort table[j] = i means that the i'th
 718          * bitmap corresponds to j'th bitmapped commit (among the selected
 719          * commits) in lex order of OIDs.
 720          */
 721         QSORT_S(table, writer.selected_nr, table_cmp, commit_positions);
 722
 723         /* table_inv helps us discover that relationship (i'th bitmap
 724          * to j'th commit by j = table_inv[i])
 725          */
 726         for (i = 0; i < writer.selected_nr; i++)
 727                 table_inv[table[i]] = i;
 728
 729         trace2_region_enter("pack-bitmap-write", "writing_lookup_table", the_repository);
 730         for (i = 0; i < writer.selected_nr; i++) {
 731                 struct bitmapped_commit *selected = &writer.selected[table[i]];
 732                 uint32_t xor_offset = selected->xor_offset;
 733                 uint32_t xor_row;
 734
 735                 if (xor_offset) {
 736                         /*
 737                          * xor_index stores the index (in the bitmap entries)
 738                          * of the corresponding xor bitmap. But we need to convert
 739                          * this index into lookup table's index. So, table_inv[xor_index]
 740                          * gives us the index position w.r.t. the lookup table.
 741                          *
 742                          * If "k = table[i] - xor_offset" then the xor base is the k'th
 743                          * bitmap. `table_inv[k]` gives us the position of that bitmap
 744                          * in the lookup table.
 745                          */
 746                         uint32_t xor_index = table[i] - xor_offset;
 747                         xor_row = table_inv[xor_index];
 748                 } else {
 749                         xor_row = 0xffffffff;
 750                 }
 751
 752                 hashwrite_be32(f, commit_positions[table[i]]);
 753                 hashwrite_be64(f, (uint64_t)offsets[table[i]]);
 754                 hashwrite_be32(f, xor_row);
 755         }
 756         trace2_region_leave("pack-bitmap-write", "writing_lookup_table", the_repository);
 757
 758         free(table);
 759         free(table_inv);
 760 }
 761
 762 static void write_hash_cache(struct hashfile *f,
 763                              struct pack_idx_entry **index,
 764                              uint32_t index_nr)
 765 {
 766         uint32_t i;
 767
 768         for (i = 0; i < index_nr; ++i) {
 769                 struct object_entry *entry = (struct object_entry *)index[i];
 770                 hashwrite_be32(f, entry->hash);
 771         }
 772 }
 773
 774 void bitmap_writer_set_checksum(const unsigned char *sha1)
 775 {
 776         hashcpy(writer.pack_checksum, sha1);
 777 }
 778
 779 void bitmap_writer_finish(struct pack_idx_entry **index,
 780                           uint32_t index_nr,
 781                           const char *filename,
 782                           uint16_t options)
 783 {
 784         static uint16_t default_version = 1;
 785         static uint16_t flags = BITMAP_OPT_FULL_DAG;
 786         struct strbuf tmp_file = STRBUF_INIT;
 787         struct hashfile *f;
 788         uint32_t *commit_positions = NULL;
 789         off_t *offsets = NULL;
 790         uint32_t i;
 791
 792         struct bitmap_disk_header header;
 793
 794         int fd = odb_mkstemp(&tmp_file, "pack/tmp_bitmap_XXXXXX");
 795
 796         f = hashfd(fd, tmp_file.buf);
 797
 798         memcpy(header.magic, BITMAP_IDX_SIGNATURE, sizeof(BITMAP_IDX_SIGNATURE));
 799         header.version = htons(default_version);
 800         header.options = htons(flags | options);
 801         header.entry_count = htonl(writer.selected_nr);
 802         hashcpy(header.checksum, writer.pack_checksum);
 803
 804         hashwrite(f, &header, sizeof(header) - GIT_MAX_RAWSZ + the_hash_algo->rawsz);
 805         dump_bitmap(f, writer.commits);
 806         dump_bitmap(f, writer.trees);
 807         dump_bitmap(f, writer.blobs);
 808         dump_bitmap(f, writer.tags);
 809
 810         if (options & BITMAP_OPT_LOOKUP_TABLE)
 811                 CALLOC_ARRAY(offsets, index_nr);
 812
 813         ALLOC_ARRAY(commit_positions, writer.selected_nr);
 814
 815         for (i = 0; i < writer.selected_nr; i++) {
 816                 struct bitmapped_commit *stored = &writer.selected[i];
 817                 int commit_pos = oid_pos(&stored->commit->object.oid, index, index_nr, oid_access);
 818
 819                 if (commit_pos < 0)
 820                         BUG(_("trying to write commit not in index"));
 821
 822                 commit_positions[i] = commit_pos;
 823         }
 824
 825         write_selected_commits_v1(f, commit_positions, offsets);
 826
 827         if (options & BITMAP_OPT_LOOKUP_TABLE)
 828                 write_lookup_table(f, commit_positions, offsets);
 829
 830         if (options & BITMAP_OPT_HASH_CACHE)
 831                 write_hash_cache(f, index, index_nr);
 832
 833         finalize_hashfile(f, NULL, FSYNC_COMPONENT_PACK_METADATA,
 834                           CSUM_HASH_IN_STREAM | CSUM_FSYNC | CSUM_CLOSE);
 835
 836         if (adjust_shared_perm(tmp_file.buf))
 837                 die_errno("unable to make temporary bitmap file readable");
 838
 839         if (rename(tmp_file.buf, filename))
 840                 die_errno("unable to rename temporary bitmap file to '%s'", filename);
 841
 842         strbuf_release(&tmp_file);
 843         free(commit_positions);
 844         free(offsets);
 845 }