git.oblomov.eu Git - git/blob - pack-bitmap.c

   1 #include "cache.h"
   2 #include "commit.h"
   3 #include "tag.h"
   4 #include "diff.h"
   5 #include "revision.h"
   6 #include "progress.h"
   7 #include "list-objects.h"
   8 #include "pack.h"
   9 #include "pack-bitmap.h"
  10 #include "pack-revindex.h"
  11 #include "pack-objects.h"
  12 #include "packfile.h"
  13 #include "repository.h"
  14 #include "object-store.h"
  15
  16 /*
  17  * An entry on the bitmap index, representing the bitmap for a given
  18  * commit.
  19  */
  20 struct stored_bitmap {
  21         struct object_id oid;
  22         struct ewah_bitmap *root;
  23         struct stored_bitmap *xor;
  24         int flags;
  25 };
  26
  27 /*
  28  * The active bitmap index for a repository. By design, repositories only have
  29  * a single bitmap index available (the index for the biggest packfile in
  30  * the repository), since bitmap indexes need full closure.
  31  *
  32  * If there is more than one bitmap index available (e.g. because of alternates),
  33  * the active bitmap index is the largest one.
  34  */
  35 struct bitmap_index {
  36         /* Packfile to which this bitmap index belongs to */
  37         struct packed_git *pack;
  38
  39         /*
  40          * Mark the first `reuse_objects` in the packfile as reused:
  41          * they will be sent as-is without using them for repacking
  42          * calculations
  43          */
  44         uint32_t reuse_objects;
  45
  46         /* mmapped buffer of the whole bitmap index */
  47         unsigned char *map;
  48         size_t map_size; /* size of the mmaped buffer */
  49         size_t map_pos; /* current position when loading the index */
  50
  51         /*
  52          * Type indexes.
  53          *
  54          * Each bitmap marks which objects in the packfile  are of the given
  55          * type. This provides type information when yielding the objects from
  56          * the packfile during a walk, which allows for better delta bases.
  57          */
  58         struct ewah_bitmap *commits;
  59         struct ewah_bitmap *trees;
  60         struct ewah_bitmap *blobs;
  61         struct ewah_bitmap *tags;
  62
  63         /* Map from object ID -> `stored_bitmap` for all the bitmapped commits */
  64         kh_oid_map_t *bitmaps;
  65
  66         /* Number of bitmapped commits */
  67         uint32_t entry_count;
  68
  69         /* If not NULL, this is a name-hash cache pointing into map. */
  70         uint32_t *hashes;
  71
  72         /*
  73          * Extended index.
  74          *
  75          * When trying to perform bitmap operations with objects that are not
  76          * packed in `pack`, these objects are added to this "fake index" and
  77          * are assumed to appear at the end of the packfile for all operations
  78          */
  79         struct eindex {
  80                 struct object **objects;
  81                 uint32_t *hashes;
  82                 uint32_t count, alloc;
  83                 kh_oid_pos_t *positions;
  84         } ext_index;
  85
  86         /* Bitmap result of the last performed walk */
  87         struct bitmap *result;
  88
  89         /* "have" bitmap from the last performed walk */
  90         struct bitmap *haves;
  91
  92         /* Version of the bitmap index */
  93         unsigned int version;
  94 };
  95
  96 static struct ewah_bitmap *lookup_stored_bitmap(struct stored_bitmap *st)
  97 {
  98         struct ewah_bitmap *parent;
  99         struct ewah_bitmap *composed;
 100
 101         if (st->xor == NULL)
 102                 return st->root;
 103
 104         composed = ewah_pool_new();
 105         parent = lookup_stored_bitmap(st->xor);
 106         ewah_xor(st->root, parent, composed);
 107
 108         ewah_pool_free(st->root);
 109         st->root = composed;
 110         st->xor = NULL;
 111
 112         return composed;
 113 }
 114
 115 /*
 116  * Read a bitmap from the current read position on the mmaped
 117  * index, and increase the read position accordingly
 118  */
 119 static struct ewah_bitmap *read_bitmap_1(struct bitmap_index *index)
 120 {
 121         struct ewah_bitmap *b = ewah_pool_new();
 122
 123         ssize_t bitmap_size = ewah_read_mmap(b,
 124                 index->map + index->map_pos,
 125                 index->map_size - index->map_pos);
 126
 127         if (bitmap_size < 0) {
 128                 error("Failed to load bitmap index (corrupted?)");
 129                 ewah_pool_free(b);
 130                 return NULL;
 131         }
 132
 133         index->map_pos += bitmap_size;
 134         return b;
 135 }
 136
 137 static int load_bitmap_header(struct bitmap_index *index)
 138 {
 139         struct bitmap_disk_header *header = (void *)index->map;
 140
 141         if (index->map_size < sizeof(*header) + the_hash_algo->rawsz)
 142                 return error("Corrupted bitmap index (missing header data)");
 143
 144         if (memcmp(header->magic, BITMAP_IDX_SIGNATURE, sizeof(BITMAP_IDX_SIGNATURE)) != 0)
 145                 return error("Corrupted bitmap index file (wrong header)");
 146
 147         index->version = ntohs(header->version);
 148         if (index->version != 1)
 149                 return error("Unsupported version for bitmap index file (%d)", index->version);
 150
 151         /* Parse known bitmap format options */
 152         {
 153                 uint32_t flags = ntohs(header->options);
 154
 155                 if ((flags & BITMAP_OPT_FULL_DAG) == 0)
 156                         return error("Unsupported options for bitmap index file "
 157                                 "(Git requires BITMAP_OPT_FULL_DAG)");
 158
 159                 if (flags & BITMAP_OPT_HASH_CACHE) {
 160                         unsigned char *end = index->map + index->map_size - the_hash_algo->rawsz;
 161                         index->hashes = ((uint32_t *)end) - index->pack->num_objects;
 162                 }
 163         }
 164
 165         index->entry_count = ntohl(header->entry_count);
 166         index->map_pos += sizeof(*header) - GIT_MAX_RAWSZ + the_hash_algo->rawsz;
 167         return 0;
 168 }
 169
 170 static struct stored_bitmap *store_bitmap(struct bitmap_index *index,
 171                                           struct ewah_bitmap *root,
 172                                           const unsigned char *hash,
 173                                           struct stored_bitmap *xor_with,
 174                                           int flags)
 175 {
 176         struct stored_bitmap *stored;
 177         khiter_t hash_pos;
 178         int ret;
 179
 180         stored = xmalloc(sizeof(struct stored_bitmap));
 181         stored->root = root;
 182         stored->xor = xor_with;
 183         stored->flags = flags;
 184         oidread(&stored->oid, hash);
 185
 186         hash_pos = kh_put_oid_map(index->bitmaps, stored->oid, &ret);
 187
 188         /* a 0 return code means the insertion succeeded with no changes,
 189          * because the SHA1 already existed on the map. this is bad, there
 190          * shouldn't be duplicated commits in the index */
 191         if (ret == 0) {
 192                 error("Duplicate entry in bitmap index: %s", hash_to_hex(hash));
 193                 return NULL;
 194         }
 195
 196         kh_value(index->bitmaps, hash_pos) = stored;
 197         return stored;
 198 }
 199
 200 static inline uint32_t read_be32(const unsigned char *buffer, size_t *pos)
 201 {
 202         uint32_t result = get_be32(buffer + *pos);
 203         (*pos) += sizeof(result);
 204         return result;
 205 }
 206
 207 static inline uint8_t read_u8(const unsigned char *buffer, size_t *pos)
 208 {
 209         return buffer[(*pos)++];
 210 }
 211
 212 #define MAX_XOR_OFFSET 160
 213
 214 static int load_bitmap_entries_v1(struct bitmap_index *index)
 215 {
 216         uint32_t i;
 217         struct stored_bitmap *recent_bitmaps[MAX_XOR_OFFSET] = { NULL };
 218
 219         for (i = 0; i < index->entry_count; ++i) {
 220                 int xor_offset, flags;
 221                 struct ewah_bitmap *bitmap = NULL;
 222                 struct stored_bitmap *xor_bitmap = NULL;
 223                 uint32_t commit_idx_pos;
 224                 const unsigned char *sha1;
 225
 226                 commit_idx_pos = read_be32(index->map, &index->map_pos);
 227                 xor_offset = read_u8(index->map, &index->map_pos);
 228                 flags = read_u8(index->map, &index->map_pos);
 229
 230                 sha1 = nth_packed_object_sha1(index->pack, commit_idx_pos);
 231
 232                 bitmap = read_bitmap_1(index);
 233                 if (!bitmap)
 234                         return -1;
 235
 236                 if (xor_offset > MAX_XOR_OFFSET || xor_offset > i)
 237                         return error("Corrupted bitmap pack index");
 238
 239                 if (xor_offset > 0) {
 240                         xor_bitmap = recent_bitmaps[(i - xor_offset) % MAX_XOR_OFFSET];
 241
 242                         if (xor_bitmap == NULL)
 243                                 return error("Invalid XOR offset in bitmap pack index");
 244                 }
 245
 246                 recent_bitmaps[i % MAX_XOR_OFFSET] = store_bitmap(
 247                         index, bitmap, sha1, xor_bitmap, flags);
 248         }
 249
 250         return 0;
 251 }
 252
 253 static char *pack_bitmap_filename(struct packed_git *p)
 254 {
 255         size_t len;
 256
 257         if (!strip_suffix(p->pack_name, ".pack", &len))
 258                 BUG("pack_name does not end in .pack");
 259         return xstrfmt("%.*s.bitmap", (int)len, p->pack_name);
 260 }
 261
 262 static int open_pack_bitmap_1(struct bitmap_index *bitmap_git, struct packed_git *packfile)
 263 {
 264         int fd;
 265         struct stat st;
 266         char *idx_name;
 267
 268         if (open_pack_index(packfile))
 269                 return -1;
 270
 271         idx_name = pack_bitmap_filename(packfile);
 272         fd = git_open(idx_name);
 273         free(idx_name);
 274
 275         if (fd < 0)
 276                 return -1;
 277
 278         if (fstat(fd, &st)) {
 279                 close(fd);
 280                 return -1;
 281         }
 282
 283         if (bitmap_git->pack) {
 284                 warning("ignoring extra bitmap file: %s", packfile->pack_name);
 285                 close(fd);
 286                 return -1;
 287         }
 288
 289         bitmap_git->pack = packfile;
 290         bitmap_git->map_size = xsize_t(st.st_size);
 291         bitmap_git->map = xmmap(NULL, bitmap_git->map_size, PROT_READ, MAP_PRIVATE, fd, 0);
 292         bitmap_git->map_pos = 0;
 293         close(fd);
 294
 295         if (load_bitmap_header(bitmap_git) < 0) {
 296                 munmap(bitmap_git->map, bitmap_git->map_size);
 297                 bitmap_git->map = NULL;
 298                 bitmap_git->map_size = 0;
 299                 return -1;
 300         }
 301
 302         return 0;
 303 }
 304
 305 static int load_pack_bitmap(struct bitmap_index *bitmap_git)
 306 {
 307         assert(bitmap_git->map);
 308
 309         bitmap_git->bitmaps = kh_init_oid_map();
 310         bitmap_git->ext_index.positions = kh_init_oid_pos();
 311         if (load_pack_revindex(bitmap_git->pack))
 312                 goto failed;
 313
 314         if (!(bitmap_git->commits = read_bitmap_1(bitmap_git)) ||
 315                 !(bitmap_git->trees = read_bitmap_1(bitmap_git)) ||
 316                 !(bitmap_git->blobs = read_bitmap_1(bitmap_git)) ||
 317                 !(bitmap_git->tags = read_bitmap_1(bitmap_git)))
 318                 goto failed;
 319
 320         if (load_bitmap_entries_v1(bitmap_git) < 0)
 321                 goto failed;
 322
 323         return 0;
 324
 325 failed:
 326         munmap(bitmap_git->map, bitmap_git->map_size);
 327         bitmap_git->map = NULL;
 328         bitmap_git->map_size = 0;
 329
 330         kh_destroy_oid_map(bitmap_git->bitmaps);
 331         bitmap_git->bitmaps = NULL;
 332
 333         kh_destroy_oid_pos(bitmap_git->ext_index.positions);
 334         bitmap_git->ext_index.positions = NULL;
 335
 336         return -1;
 337 }
 338
 339 static int open_pack_bitmap(struct repository *r,
 340                             struct bitmap_index *bitmap_git)
 341 {
 342         struct packed_git *p;
 343         int ret = -1;
 344
 345         assert(!bitmap_git->map);
 346
 347         for (p = get_all_packs(r); p; p = p->next) {
 348                 if (open_pack_bitmap_1(bitmap_git, p) == 0)
 349                         ret = 0;
 350         }
 351
 352         return ret;
 353 }
 354
 355 struct bitmap_index *prepare_bitmap_git(struct repository *r)
 356 {
 357         struct bitmap_index *bitmap_git = xcalloc(1, sizeof(*bitmap_git));
 358
 359         if (!open_pack_bitmap(r, bitmap_git) && !load_pack_bitmap(bitmap_git))
 360                 return bitmap_git;
 361
 362         free_bitmap_index(bitmap_git);
 363         return NULL;
 364 }
 365
 366 struct include_data {
 367         struct bitmap_index *bitmap_git;
 368         struct bitmap *base;
 369         struct bitmap *seen;
 370 };
 371
 372 static inline int bitmap_position_extended(struct bitmap_index *bitmap_git,
 373                                            const struct object_id *oid)
 374 {
 375         kh_oid_pos_t *positions = bitmap_git->ext_index.positions;
 376         khiter_t pos = kh_get_oid_pos(positions, *oid);
 377
 378         if (pos < kh_end(positions)) {
 379                 int bitmap_pos = kh_value(positions, pos);
 380                 return bitmap_pos + bitmap_git->pack->num_objects;
 381         }
 382
 383         return -1;
 384 }
 385
 386 static inline int bitmap_position_packfile(struct bitmap_index *bitmap_git,
 387                                            const struct object_id *oid)
 388 {
 389         off_t offset = find_pack_entry_one(oid->hash, bitmap_git->pack);
 390         if (!offset)
 391                 return -1;
 392
 393         return find_revindex_position(bitmap_git->pack, offset);
 394 }
 395
 396 static int bitmap_position(struct bitmap_index *bitmap_git,
 397                            const struct object_id *oid)
 398 {
 399         int pos = bitmap_position_packfile(bitmap_git, oid);
 400         return (pos >= 0) ? pos : bitmap_position_extended(bitmap_git, oid);
 401 }
 402
 403 static int ext_index_add_object(struct bitmap_index *bitmap_git,
 404                                 struct object *object, const char *name)
 405 {
 406         struct eindex *eindex = &bitmap_git->ext_index;
 407
 408         khiter_t hash_pos;
 409         int hash_ret;
 410         int bitmap_pos;
 411
 412         hash_pos = kh_put_oid_pos(eindex->positions, object->oid, &hash_ret);
 413         if (hash_ret > 0) {
 414                 if (eindex->count >= eindex->alloc) {
 415                         eindex->alloc = (eindex->alloc + 16) * 3 / 2;
 416                         REALLOC_ARRAY(eindex->objects, eindex->alloc);
 417                         REALLOC_ARRAY(eindex->hashes, eindex->alloc);
 418                 }
 419
 420                 bitmap_pos = eindex->count;
 421                 eindex->objects[eindex->count] = object;
 422                 eindex->hashes[eindex->count] = pack_name_hash(name);
 423                 kh_value(eindex->positions, hash_pos) = bitmap_pos;
 424                 eindex->count++;
 425         } else {
 426                 bitmap_pos = kh_value(eindex->positions, hash_pos);
 427         }
 428
 429         return bitmap_pos + bitmap_git->pack->num_objects;
 430 }
 431
 432 struct bitmap_show_data {
 433         struct bitmap_index *bitmap_git;
 434         struct bitmap *base;
 435 };
 436
 437 static void show_object(struct object *object, const char *name, void *data_)
 438 {
 439         struct bitmap_show_data *data = data_;
 440         int bitmap_pos;
 441
 442         bitmap_pos = bitmap_position(data->bitmap_git, &object->oid);
 443
 444         if (bitmap_pos < 0)
 445                 bitmap_pos = ext_index_add_object(data->bitmap_git, object,
 446                                                   name);
 447
 448         bitmap_set(data->base, bitmap_pos);
 449 }
 450
 451 static void show_commit(struct commit *commit, void *data)
 452 {
 453 }
 454
 455 static int add_to_include_set(struct bitmap_index *bitmap_git,
 456                               struct include_data *data,
 457                               const struct object_id *oid,
 458                               int bitmap_pos)
 459 {
 460         khiter_t hash_pos;
 461
 462         if (data->seen && bitmap_get(data->seen, bitmap_pos))
 463                 return 0;
 464
 465         if (bitmap_get(data->base, bitmap_pos))
 466                 return 0;
 467
 468         hash_pos = kh_get_oid_map(bitmap_git->bitmaps, *oid);
 469         if (hash_pos < kh_end(bitmap_git->bitmaps)) {
 470                 struct stored_bitmap *st = kh_value(bitmap_git->bitmaps, hash_pos);
 471                 bitmap_or_ewah(data->base, lookup_stored_bitmap(st));
 472                 return 0;
 473         }
 474
 475         bitmap_set(data->base, bitmap_pos);
 476         return 1;
 477 }
 478
 479 static int should_include(struct commit *commit, void *_data)
 480 {
 481         struct include_data *data = _data;
 482         int bitmap_pos;
 483
 484         bitmap_pos = bitmap_position(data->bitmap_git, &commit->object.oid);
 485         if (bitmap_pos < 0)
 486                 bitmap_pos = ext_index_add_object(data->bitmap_git,
 487                                                   (struct object *)commit,
 488                                                   NULL);
 489
 490         if (!add_to_include_set(data->bitmap_git, data, &commit->object.oid,
 491                                 bitmap_pos)) {
 492                 struct commit_list *parent = commit->parents;
 493
 494                 while (parent) {
 495                         parent->item->object.flags |= SEEN;
 496                         parent = parent->next;
 497                 }
 498
 499                 return 0;
 500         }
 501
 502         return 1;
 503 }
 504
 505 static struct bitmap *find_objects(struct bitmap_index *bitmap_git,
 506                                    struct rev_info *revs,
 507                                    struct object_list *roots,
 508                                    struct bitmap *seen)
 509 {
 510         struct bitmap *base = NULL;
 511         int needs_walk = 0;
 512
 513         struct object_list *not_mapped = NULL;
 514
 515         /*
 516          * Go through all the roots for the walk. The ones that have bitmaps
 517          * on the bitmap index will be `or`ed together to form an initial
 518          * global reachability analysis.
 519          *
 520          * The ones without bitmaps in the index will be stored in the
 521          * `not_mapped_list` for further processing.
 522          */
 523         while (roots) {
 524                 struct object *object = roots->item;
 525                 roots = roots->next;
 526
 527                 if (object->type == OBJ_COMMIT) {
 528                         khiter_t pos = kh_get_oid_map(bitmap_git->bitmaps, object->oid);
 529
 530                         if (pos < kh_end(bitmap_git->bitmaps)) {
 531                                 struct stored_bitmap *st = kh_value(bitmap_git->bitmaps, pos);
 532                                 struct ewah_bitmap *or_with = lookup_stored_bitmap(st);
 533
 534                                 if (base == NULL)
 535                                         base = ewah_to_bitmap(or_with);
 536                                 else
 537                                         bitmap_or_ewah(base, or_with);
 538
 539                                 object->flags |= SEEN;
 540                                 continue;
 541                         }
 542                 }
 543
 544                 object_list_insert(object, &not_mapped);
 545         }
 546
 547         /*
 548          * Best case scenario: We found bitmaps for all the roots,
 549          * so the resulting `or` bitmap has the full reachability analysis
 550          */
 551         if (not_mapped == NULL)
 552                 return base;
 553
 554         roots = not_mapped;
 555
 556         /*
 557          * Let's iterate through all the roots that don't have bitmaps to
 558          * check if we can determine them to be reachable from the existing
 559          * global bitmap.
 560          *
 561          * If we cannot find them in the existing global bitmap, we'll need
 562          * to push them to an actual walk and run it until we can confirm
 563          * they are reachable
 564          */
 565         while (roots) {
 566                 struct object *object = roots->item;
 567                 int pos;
 568
 569                 roots = roots->next;
 570                 pos = bitmap_position(bitmap_git, &object->oid);
 571
 572                 if (pos < 0 || base == NULL || !bitmap_get(base, pos)) {
 573                         object->flags &= ~UNINTERESTING;
 574                         add_pending_object(revs, object, "");
 575                         needs_walk = 1;
 576                 } else {
 577                         object->flags |= SEEN;
 578                 }
 579         }
 580
 581         if (needs_walk) {
 582                 struct include_data incdata;
 583                 struct bitmap_show_data show_data;
 584
 585                 if (base == NULL)
 586                         base = bitmap_new();
 587
 588                 incdata.bitmap_git = bitmap_git;
 589                 incdata.base = base;
 590                 incdata.seen = seen;
 591
 592                 revs->include_check = should_include;
 593                 revs->include_check_data = &incdata;
 594
 595                 if (prepare_revision_walk(revs))
 596                         die("revision walk setup failed");
 597
 598                 show_data.bitmap_git = bitmap_git;
 599                 show_data.base = base;
 600
 601                 traverse_commit_list(revs, show_commit, show_object,
 602                                      &show_data);
 603         }
 604
 605         return base;
 606 }
 607
 608 static void show_extended_objects(struct bitmap_index *bitmap_git,
 609                                   show_reachable_fn show_reach)
 610 {
 611         struct bitmap *objects = bitmap_git->result;
 612         struct eindex *eindex = &bitmap_git->ext_index;
 613         uint32_t i;
 614
 615         for (i = 0; i < eindex->count; ++i) {
 616                 struct object *obj;
 617
 618                 if (!bitmap_get(objects, bitmap_git->pack->num_objects + i))
 619                         continue;
 620
 621                 obj = eindex->objects[i];
 622                 show_reach(&obj->oid, obj->type, 0, eindex->hashes[i], NULL, 0);
 623         }
 624 }
 625
 626 static void show_objects_for_type(
 627         struct bitmap_index *bitmap_git,
 628         struct ewah_bitmap *type_filter,
 629         enum object_type object_type,
 630         show_reachable_fn show_reach)
 631 {
 632         size_t pos = 0, i = 0;
 633         uint32_t offset;
 634
 635         struct ewah_iterator it;
 636         eword_t filter;
 637
 638         struct bitmap *objects = bitmap_git->result;
 639
 640         if (bitmap_git->reuse_objects == bitmap_git->pack->num_objects)
 641                 return;
 642
 643         ewah_iterator_init(&it, type_filter);
 644
 645         while (i < objects->word_alloc && ewah_iterator_next(&filter, &it)) {
 646                 eword_t word = objects->words[i] & filter;
 647
 648                 for (offset = 0; offset < BITS_IN_EWORD; ++offset) {
 649                         struct object_id oid;
 650                         struct revindex_entry *entry;
 651                         uint32_t hash = 0;
 652
 653                         if ((word >> offset) == 0)
 654                                 break;
 655
 656                         offset += ewah_bit_ctz64(word >> offset);
 657
 658                         if (pos + offset < bitmap_git->reuse_objects)
 659                                 continue;
 660
 661                         entry = &bitmap_git->pack->revindex[pos + offset];
 662                         nth_packed_object_oid(&oid, bitmap_git->pack, entry->nr);
 663
 664                         if (bitmap_git->hashes)
 665                                 hash = get_be32(bitmap_git->hashes + entry->nr);
 666
 667                         show_reach(&oid, object_type, 0, hash, bitmap_git->pack, entry->offset);
 668                 }
 669
 670                 pos += BITS_IN_EWORD;
 671                 i++;
 672         }
 673 }
 674
 675 static int in_bitmapped_pack(struct bitmap_index *bitmap_git,
 676                              struct object_list *roots)
 677 {
 678         while (roots) {
 679                 struct object *object = roots->item;
 680                 roots = roots->next;
 681
 682                 if (find_pack_entry_one(object->oid.hash, bitmap_git->pack) > 0)
 683                         return 1;
 684         }
 685
 686         return 0;
 687 }
 688
 689 struct bitmap_index *prepare_bitmap_walk(struct rev_info *revs)
 690 {
 691         unsigned int i;
 692
 693         struct object_list *wants = NULL;
 694         struct object_list *haves = NULL;
 695
 696         struct bitmap *wants_bitmap = NULL;
 697         struct bitmap *haves_bitmap = NULL;
 698
 699         struct bitmap_index *bitmap_git = xcalloc(1, sizeof(*bitmap_git));
 700         /* try to open a bitmapped pack, but don't parse it yet
 701          * because we may not need to use it */
 702         if (open_pack_bitmap(revs->repo, bitmap_git) < 0)
 703                 goto cleanup;
 704
 705         for (i = 0; i < revs->pending.nr; ++i) {
 706                 struct object *object = revs->pending.objects[i].item;
 707
 708                 if (object->type == OBJ_NONE)
 709                         parse_object_or_die(&object->oid, NULL);
 710
 711                 while (object->type == OBJ_TAG) {
 712                         struct tag *tag = (struct tag *) object;
 713
 714                         if (object->flags & UNINTERESTING)
 715                                 object_list_insert(object, &haves);
 716                         else
 717                                 object_list_insert(object, &wants);
 718
 719                         if (!tag->tagged)
 720                                 die("bad tag");
 721                         object = parse_object_or_die(&tag->tagged->oid, NULL);
 722                 }
 723
 724                 if (object->flags & UNINTERESTING)
 725                         object_list_insert(object, &haves);
 726                 else
 727                         object_list_insert(object, &wants);
 728         }
 729
 730         /*
 731          * if we have a HAVES list, but none of those haves is contained
 732          * in the packfile that has a bitmap, we don't have anything to
 733          * optimize here
 734          */
 735         if (haves && !in_bitmapped_pack(bitmap_git, haves))
 736                 goto cleanup;
 737
 738         /* if we don't want anything, we're done here */
 739         if (!wants)
 740                 goto cleanup;
 741
 742         /*
 743          * now we're going to use bitmaps, so load the actual bitmap entries
 744          * from disk. this is the point of no return; after this the rev_list
 745          * becomes invalidated and we must perform the revwalk through bitmaps
 746          */
 747         if (load_pack_bitmap(bitmap_git) < 0)
 748                 goto cleanup;
 749
 750         object_array_clear(&revs->pending);
 751
 752         if (haves) {
 753                 revs->ignore_missing_links = 1;
 754                 haves_bitmap = find_objects(bitmap_git, revs, haves, NULL);
 755                 reset_revision_walk();
 756                 revs->ignore_missing_links = 0;
 757
 758                 if (haves_bitmap == NULL)
 759                         BUG("failed to perform bitmap walk");
 760         }
 761
 762         wants_bitmap = find_objects(bitmap_git, revs, wants, haves_bitmap);
 763
 764         if (!wants_bitmap)
 765                 BUG("failed to perform bitmap walk");
 766
 767         if (haves_bitmap)
 768                 bitmap_and_not(wants_bitmap, haves_bitmap);
 769
 770         bitmap_git->result = wants_bitmap;
 771         bitmap_git->haves = haves_bitmap;
 772
 773         return bitmap_git;
 774
 775 cleanup:
 776         free_bitmap_index(bitmap_git);
 777         return NULL;
 778 }
 779
 780 static void try_partial_reuse(struct bitmap_index *bitmap_git,
 781                               size_t pos,
 782                               struct bitmap *reuse,
 783                               struct pack_window **w_curs)
 784 {
 785         struct revindex_entry *revidx;
 786         off_t offset;
 787         enum object_type type;
 788         unsigned long size;
 789
 790         if (pos >= bitmap_git->pack->num_objects)
 791                 return; /* not actually in the pack */
 792
 793         revidx = &bitmap_git->pack->revindex[pos];
 794         offset = revidx->offset;
 795         type = unpack_object_header(bitmap_git->pack, w_curs, &offset, &size);
 796         if (type < 0)
 797                 return; /* broken packfile, punt */
 798
 799         if (type == OBJ_REF_DELTA || type == OBJ_OFS_DELTA) {
 800                 off_t base_offset;
 801                 int base_pos;
 802
 803                 /*
 804                  * Find the position of the base object so we can look it up
 805                  * in our bitmaps. If we can't come up with an offset, or if
 806                  * that offset is not in the revidx, the pack is corrupt.
 807                  * There's nothing we can do, so just punt on this object,
 808                  * and the normal slow path will complain about it in
 809                  * more detail.
 810                  */
 811                 base_offset = get_delta_base(bitmap_git->pack, w_curs,
 812                                              &offset, type, revidx->offset);
 813                 if (!base_offset)
 814                         return;
 815                 base_pos = find_revindex_position(bitmap_git->pack, base_offset);
 816                 if (base_pos < 0)
 817                         return;
 818
 819                 /*
 820                  * We assume delta dependencies always point backwards. This
 821                  * lets us do a single pass, and is basically always true
 822                  * due to the way OFS_DELTAs work. You would not typically
 823                  * find REF_DELTA in a bitmapped pack, since we only bitmap
 824                  * packs we write fresh, and OFS_DELTA is the default). But
 825                  * let's double check to make sure the pack wasn't written with
 826                  * odd parameters.
 827                  */
 828                 if (base_pos >= pos)
 829                         return;
 830
 831                 /*
 832                  * And finally, if we're not sending the base as part of our
 833                  * reuse chunk, then don't send this object either. The base
 834                  * would come after us, along with other objects not
 835                  * necessarily in the pack, which means we'd need to convert
 836                  * to REF_DELTA on the fly. Better to just let the normal
 837                  * object_entry code path handle it.
 838                  */
 839                 if (!bitmap_get(reuse, base_pos))
 840                         return;
 841         }
 842
 843         /*
 844          * If we got here, then the object is OK to reuse. Mark it.
 845          */
 846         bitmap_set(reuse, pos);
 847 }
 848
 849 int reuse_partial_packfile_from_bitmap(struct bitmap_index *bitmap_git,
 850                                        struct packed_git **packfile_out,
 851                                        uint32_t *entries,
 852                                        struct bitmap **reuse_out)
 853 {
 854         struct bitmap *result = bitmap_git->result;
 855         struct bitmap *reuse;
 856         struct pack_window *w_curs = NULL;
 857         size_t i = 0;
 858         uint32_t offset;
 859
 860         assert(result);
 861
 862         while (i < result->word_alloc && result->words[i] == (eword_t)~0)
 863                 i++;
 864
 865         /* Don't mark objects not in the packfile */
 866         if (i > bitmap_git->pack->num_objects / BITS_IN_EWORD)
 867                 i = bitmap_git->pack->num_objects / BITS_IN_EWORD;
 868
 869         reuse = bitmap_word_alloc(i);
 870         memset(reuse->words, 0xFF, i * sizeof(eword_t));
 871
 872         for (; i < result->word_alloc; ++i) {
 873                 eword_t word = result->words[i];
 874                 size_t pos = (i * BITS_IN_EWORD);
 875
 876                 for (offset = 0; offset < BITS_IN_EWORD; ++offset) {
 877                         if ((word >> offset) == 0)
 878                                 break;
 879
 880                         offset += ewah_bit_ctz64(word >> offset);
 881                         try_partial_reuse(bitmap_git, pos + offset, reuse, &w_curs);
 882                 }
 883         }
 884
 885         unuse_pack(&w_curs);
 886
 887         *entries = bitmap_popcount(reuse);
 888         if (!*entries) {
 889                 bitmap_free(reuse);
 890                 return -1;
 891         }
 892
 893         /*
 894          * Drop any reused objects from the result, since they will not
 895          * need to be handled separately.
 896          */
 897         bitmap_and_not(result, reuse);
 898         *packfile_out = bitmap_git->pack;
 899         *reuse_out = reuse;
 900         return 0;
 901 }
 902
 903 int bitmap_walk_contains(struct bitmap_index *bitmap_git,
 904                          struct bitmap *bitmap, const struct object_id *oid)
 905 {
 906         int idx;
 907
 908         if (!bitmap)
 909                 return 0;
 910
 911         idx = bitmap_position(bitmap_git, oid);
 912         return idx >= 0 && bitmap_get(bitmap, idx);
 913 }
 914
 915 void traverse_bitmap_commit_list(struct bitmap_index *bitmap_git,
 916                                  show_reachable_fn show_reachable)
 917 {
 918         assert(bitmap_git->result);
 919
 920         show_objects_for_type(bitmap_git, bitmap_git->commits,
 921                 OBJ_COMMIT, show_reachable);
 922         show_objects_for_type(bitmap_git, bitmap_git->trees,
 923                 OBJ_TREE, show_reachable);
 924         show_objects_for_type(bitmap_git, bitmap_git->blobs,
 925                 OBJ_BLOB, show_reachable);
 926         show_objects_for_type(bitmap_git, bitmap_git->tags,
 927                 OBJ_TAG, show_reachable);
 928
 929         show_extended_objects(bitmap_git, show_reachable);
 930 }
 931
 932 static uint32_t count_object_type(struct bitmap_index *bitmap_git,
 933                                   enum object_type type)
 934 {
 935         struct bitmap *objects = bitmap_git->result;
 936         struct eindex *eindex = &bitmap_git->ext_index;
 937
 938         uint32_t i = 0, count = 0;
 939         struct ewah_iterator it;
 940         eword_t filter;
 941
 942         switch (type) {
 943         case OBJ_COMMIT:
 944                 ewah_iterator_init(&it, bitmap_git->commits);
 945                 break;
 946
 947         case OBJ_TREE:
 948                 ewah_iterator_init(&it, bitmap_git->trees);
 949                 break;
 950
 951         case OBJ_BLOB:
 952                 ewah_iterator_init(&it, bitmap_git->blobs);
 953                 break;
 954
 955         case OBJ_TAG:
 956                 ewah_iterator_init(&it, bitmap_git->tags);
 957                 break;
 958
 959         default:
 960                 return 0;
 961         }
 962
 963         while (i < objects->word_alloc && ewah_iterator_next(&filter, &it)) {
 964                 eword_t word = objects->words[i++] & filter;
 965                 count += ewah_bit_popcount64(word);
 966         }
 967
 968         for (i = 0; i < eindex->count; ++i) {
 969                 if (eindex->objects[i]->type == type &&
 970                         bitmap_get(objects, bitmap_git->pack->num_objects + i))
 971                         count++;
 972         }
 973
 974         return count;
 975 }
 976
 977 void count_bitmap_commit_list(struct bitmap_index *bitmap_git,
 978                               uint32_t *commits, uint32_t *trees,
 979                               uint32_t *blobs, uint32_t *tags)
 980 {
 981         assert(bitmap_git->result);
 982
 983         if (commits)
 984                 *commits = count_object_type(bitmap_git, OBJ_COMMIT);
 985
 986         if (trees)
 987                 *trees = count_object_type(bitmap_git, OBJ_TREE);
 988
 989         if (blobs)
 990                 *blobs = count_object_type(bitmap_git, OBJ_BLOB);
 991
 992         if (tags)
 993                 *tags = count_object_type(bitmap_git, OBJ_TAG);
 994 }
 995
 996 struct bitmap_test_data {
 997         struct bitmap_index *bitmap_git;
 998         struct bitmap *base;
 999         struct progress *prg;
1000         size_t seen;
1001 };
1002
1003 static void test_show_object(struct object *object, const char *name,
1004                              void *data)
1005 {
1006         struct bitmap_test_data *tdata = data;
1007         int bitmap_pos;
1008
1009         bitmap_pos = bitmap_position(tdata->bitmap_git, &object->oid);
1010         if (bitmap_pos < 0)
1011                 die("Object not in bitmap: %s\n", oid_to_hex(&object->oid));
1012
1013         bitmap_set(tdata->base, bitmap_pos);
1014         display_progress(tdata->prg, ++tdata->seen);
1015 }
1016
1017 static void test_show_commit(struct commit *commit, void *data)
1018 {
1019         struct bitmap_test_data *tdata = data;
1020         int bitmap_pos;
1021
1022         bitmap_pos = bitmap_position(tdata->bitmap_git,
1023                                      &commit->object.oid);
1024         if (bitmap_pos < 0)
1025                 die("Object not in bitmap: %s\n", oid_to_hex(&commit->object.oid));
1026
1027         bitmap_set(tdata->base, bitmap_pos);
1028         display_progress(tdata->prg, ++tdata->seen);
1029 }
1030
1031 void test_bitmap_walk(struct rev_info *revs)
1032 {
1033         struct object *root;
1034         struct bitmap *result = NULL;
1035         khiter_t pos;
1036         size_t result_popcnt;
1037         struct bitmap_test_data tdata;
1038         struct bitmap_index *bitmap_git;
1039
1040         if (!(bitmap_git = prepare_bitmap_git(revs->repo)))
1041                 die("failed to load bitmap indexes");
1042
1043         if (revs->pending.nr != 1)
1044                 die("you must specify exactly one commit to test");
1045
1046         fprintf(stderr, "Bitmap v%d test (%d entries loaded)\n",
1047                 bitmap_git->version, bitmap_git->entry_count);
1048
1049         root = revs->pending.objects[0].item;
1050         pos = kh_get_oid_map(bitmap_git->bitmaps, root->oid);
1051
1052         if (pos < kh_end(bitmap_git->bitmaps)) {
1053                 struct stored_bitmap *st = kh_value(bitmap_git->bitmaps, pos);
1054                 struct ewah_bitmap *bm = lookup_stored_bitmap(st);
1055
1056                 fprintf(stderr, "Found bitmap for %s. %d bits / %08x checksum\n",
1057                         oid_to_hex(&root->oid), (int)bm->bit_size, ewah_checksum(bm));
1058
1059                 result = ewah_to_bitmap(bm);
1060         }
1061
1062         if (result == NULL)
1063                 die("Commit %s doesn't have an indexed bitmap", oid_to_hex(&root->oid));
1064
1065         revs->tag_objects = 1;
1066         revs->tree_objects = 1;
1067         revs->blob_objects = 1;
1068
1069         result_popcnt = bitmap_popcount(result);
1070
1071         if (prepare_revision_walk(revs))
1072                 die("revision walk setup failed");
1073
1074         tdata.bitmap_git = bitmap_git;
1075         tdata.base = bitmap_new();
1076         tdata.prg = start_progress("Verifying bitmap entries", result_popcnt);
1077         tdata.seen = 0;
1078
1079         traverse_commit_list(revs, &test_show_commit, &test_show_object, &tdata);
1080
1081         stop_progress(&tdata.prg);
1082
1083         if (bitmap_equals(result, tdata.base))
1084                 fprintf(stderr, "OK!\n");
1085         else
1086                 fprintf(stderr, "Mismatch!\n");
1087
1088         free_bitmap_index(bitmap_git);
1089 }
1090
1091 static int rebuild_bitmap(uint32_t *reposition,
1092                           struct ewah_bitmap *source,
1093                           struct bitmap *dest)
1094 {
1095         uint32_t pos = 0;
1096         struct ewah_iterator it;
1097         eword_t word;
1098
1099         ewah_iterator_init(&it, source);
1100
1101         while (ewah_iterator_next(&word, &it)) {
1102                 uint32_t offset, bit_pos;
1103
1104                 for (offset = 0; offset < BITS_IN_EWORD; ++offset) {
1105                         if ((word >> offset) == 0)
1106                                 break;
1107
1108                         offset += ewah_bit_ctz64(word >> offset);
1109
1110                         bit_pos = reposition[pos + offset];
1111                         if (bit_pos > 0)
1112                                 bitmap_set(dest, bit_pos - 1);
1113                         else /* can't reuse, we don't have the object */
1114                                 return -1;
1115                 }
1116
1117                 pos += BITS_IN_EWORD;
1118         }
1119         return 0;
1120 }
1121
1122 int rebuild_existing_bitmaps(struct bitmap_index *bitmap_git,
1123                              struct packing_data *mapping,
1124                              kh_oid_map_t *reused_bitmaps,
1125                              int show_progress)
1126 {
1127         uint32_t i, num_objects;
1128         uint32_t *reposition;
1129         struct bitmap *rebuild;
1130         struct stored_bitmap *stored;
1131         struct progress *progress = NULL;
1132
1133         khiter_t hash_pos;
1134         int hash_ret;
1135
1136         num_objects = bitmap_git->pack->num_objects;
1137         reposition = xcalloc(num_objects, sizeof(uint32_t));
1138
1139         for (i = 0; i < num_objects; ++i) {
1140                 struct object_id oid;
1141                 struct revindex_entry *entry;
1142                 struct object_entry *oe;
1143
1144                 entry = &bitmap_git->pack->revindex[i];
1145                 nth_packed_object_oid(&oid, bitmap_git->pack, entry->nr);
1146                 oe = packlist_find(mapping, &oid, NULL);
1147
1148                 if (oe)
1149                         reposition[i] = oe_in_pack_pos(mapping, oe) + 1;
1150         }
1151
1152         rebuild = bitmap_new();
1153         i = 0;
1154
1155         if (show_progress)
1156                 progress = start_progress("Reusing bitmaps", 0);
1157
1158         kh_foreach_value(bitmap_git->bitmaps, stored, {
1159                 if (stored->flags & BITMAP_FLAG_REUSE) {
1160                         if (!rebuild_bitmap(reposition,
1161                                             lookup_stored_bitmap(stored),
1162                                             rebuild)) {
1163                                 hash_pos = kh_put_oid_map(reused_bitmaps,
1164                                                           stored->oid,
1165                                                           &hash_ret);
1166                                 kh_value(reused_bitmaps, hash_pos) =
1167                                         bitmap_to_ewah(rebuild);
1168                         }
1169                         bitmap_reset(rebuild);
1170                         display_progress(progress, ++i);
1171                 }
1172         });
1173
1174         stop_progress(&progress);
1175
1176         free(reposition);
1177         bitmap_free(rebuild);
1178         return 0;
1179 }
1180
1181 void free_bitmap_index(struct bitmap_index *b)
1182 {
1183         if (!b)
1184                 return;
1185
1186         if (b->map)
1187                 munmap(b->map, b->map_size);
1188         ewah_pool_free(b->commits);
1189         ewah_pool_free(b->trees);
1190         ewah_pool_free(b->blobs);
1191         ewah_pool_free(b->tags);
1192         kh_destroy_oid_map(b->bitmaps);
1193         free(b->ext_index.objects);
1194         free(b->ext_index.hashes);
1195         bitmap_free(b->result);
1196         bitmap_free(b->haves);
1197         free(b);
1198 }
1199
1200 int bitmap_has_oid_in_uninteresting(struct bitmap_index *bitmap_git,
1201                                     const struct object_id *oid)
1202 {
1203         return bitmap_git &&
1204                 bitmap_walk_contains(bitmap_git, bitmap_git->haves, oid);
1205 }