git.oblomov.eu Git - git/blob - midx.c

   1 #include "cache.h"
   2 #include "config.h"
   3 #include "csum-file.h"
   4 #include "dir.h"
   5 #include "lockfile.h"
   6 #include "packfile.h"
   7 #include "object-store.h"
   8 #include "sha1-lookup.h"
   9 #include "midx.h"
  10
  11 #define MIDX_SIGNATURE 0x4d494458 /* "MIDX" */
  12 #define MIDX_VERSION 1
  13 #define MIDX_BYTE_FILE_VERSION 4
  14 #define MIDX_BYTE_HASH_VERSION 5
  15 #define MIDX_BYTE_NUM_CHUNKS 6
  16 #define MIDX_BYTE_NUM_PACKS 8
  17 #define MIDX_HASH_VERSION 1
  18 #define MIDX_HEADER_SIZE 12
  19 #define MIDX_HASH_LEN 20
  20 #define MIDX_MIN_SIZE (MIDX_HEADER_SIZE + MIDX_HASH_LEN)
  21
  22 #define MIDX_MAX_CHUNKS 5
  23 #define MIDX_CHUNK_ALIGNMENT 4
  24 #define MIDX_CHUNKID_PACKNAMES 0x504e414d /* "PNAM" */
  25 #define MIDX_CHUNKID_OIDFANOUT 0x4f494446 /* "OIDF" */
  26 #define MIDX_CHUNKID_OIDLOOKUP 0x4f49444c /* "OIDL" */
  27 #define MIDX_CHUNKID_OBJECTOFFSETS 0x4f4f4646 /* "OOFF" */
  28 #define MIDX_CHUNKID_LARGEOFFSETS 0x4c4f4646 /* "LOFF" */
  29 #define MIDX_CHUNKLOOKUP_WIDTH (sizeof(uint32_t) + sizeof(uint64_t))
  30 #define MIDX_CHUNK_FANOUT_SIZE (sizeof(uint32_t) * 256)
  31 #define MIDX_CHUNK_OFFSET_WIDTH (2 * sizeof(uint32_t))
  32 #define MIDX_CHUNK_LARGE_OFFSET_WIDTH (sizeof(uint64_t))
  33 #define MIDX_LARGE_OFFSET_NEEDED 0x80000000
  34
  35 static char *get_midx_filename(const char *object_dir)
  36 {
  37         return xstrfmt("%s/pack/multi-pack-index", object_dir);
  38 }
  39
  40 struct multi_pack_index *load_multi_pack_index(const char *object_dir, int local)
  41 {
  42         struct multi_pack_index *m = NULL;
  43         int fd;
  44         struct stat st;
  45         size_t midx_size;
  46         void *midx_map = NULL;
  47         uint32_t hash_version;
  48         char *midx_name = get_midx_filename(object_dir);
  49         uint32_t i;
  50         const char *cur_pack_name;
  51
  52         fd = git_open(midx_name);
  53
  54         if (fd < 0)
  55                 goto cleanup_fail;
  56         if (fstat(fd, &st)) {
  57                 error_errno(_("failed to read %s"), midx_name);
  58                 goto cleanup_fail;
  59         }
  60
  61         midx_size = xsize_t(st.st_size);
  62
  63         if (midx_size < MIDX_MIN_SIZE) {
  64                 error(_("multi-pack-index file %s is too small"), midx_name);
  65                 goto cleanup_fail;
  66         }
  67
  68         FREE_AND_NULL(midx_name);
  69
  70         midx_map = xmmap(NULL, midx_size, PROT_READ, MAP_PRIVATE, fd, 0);
  71
  72         FLEX_ALLOC_MEM(m, object_dir, object_dir, strlen(object_dir));
  73         m->fd = fd;
  74         m->data = midx_map;
  75         m->data_len = midx_size;
  76         m->local = local;
  77
  78         m->signature = get_be32(m->data);
  79         if (m->signature != MIDX_SIGNATURE) {
  80                 error(_("multi-pack-index signature 0x%08x does not match signature 0x%08x"),
  81                       m->signature, MIDX_SIGNATURE);
  82                 goto cleanup_fail;
  83         }
  84
  85         m->version = m->data[MIDX_BYTE_FILE_VERSION];
  86         if (m->version != MIDX_VERSION) {
  87                 error(_("multi-pack-index version %d not recognized"),
  88                       m->version);
  89                 goto cleanup_fail;
  90         }
  91
  92         hash_version = m->data[MIDX_BYTE_HASH_VERSION];
  93         if (hash_version != MIDX_HASH_VERSION) {
  94                 error(_("hash version %u does not match"), hash_version);
  95                 goto cleanup_fail;
  96         }
  97         m->hash_len = MIDX_HASH_LEN;
  98
  99         m->num_chunks = m->data[MIDX_BYTE_NUM_CHUNKS];
 100
 101         m->num_packs = get_be32(m->data + MIDX_BYTE_NUM_PACKS);
 102
 103         for (i = 0; i < m->num_chunks; i++) {
 104                 uint32_t chunk_id = get_be32(m->data + MIDX_HEADER_SIZE +
 105                                              MIDX_CHUNKLOOKUP_WIDTH * i);
 106                 uint64_t chunk_offset = get_be64(m->data + MIDX_HEADER_SIZE + 4 +
 107                                                  MIDX_CHUNKLOOKUP_WIDTH * i);
 108
 109                 switch (chunk_id) {
 110                         case MIDX_CHUNKID_PACKNAMES:
 111                                 m->chunk_pack_names = m->data + chunk_offset;
 112                                 break;
 113
 114                         case MIDX_CHUNKID_OIDFANOUT:
 115                                 m->chunk_oid_fanout = (uint32_t *)(m->data + chunk_offset);
 116                                 break;
 117
 118                         case MIDX_CHUNKID_OIDLOOKUP:
 119                                 m->chunk_oid_lookup = m->data + chunk_offset;
 120                                 break;
 121
 122                         case MIDX_CHUNKID_OBJECTOFFSETS:
 123                                 m->chunk_object_offsets = m->data + chunk_offset;
 124                                 break;
 125
 126                         case MIDX_CHUNKID_LARGEOFFSETS:
 127                                 m->chunk_large_offsets = m->data + chunk_offset;
 128                                 break;
 129
 130                         case 0:
 131                                 die(_("terminating multi-pack-index chunk id appears earlier than expected"));
 132                                 break;
 133
 134                         default:
 135                                 /*
 136                                  * Do nothing on unrecognized chunks, allowing future
 137                                  * extensions to add optional chunks.
 138                                  */
 139                                 break;
 140                 }
 141         }
 142
 143         if (!m->chunk_pack_names)
 144                 die(_("multi-pack-index missing required pack-name chunk"));
 145         if (!m->chunk_oid_fanout)
 146                 die(_("multi-pack-index missing required OID fanout chunk"));
 147         if (!m->chunk_oid_lookup)
 148                 die(_("multi-pack-index missing required OID lookup chunk"));
 149         if (!m->chunk_object_offsets)
 150                 die(_("multi-pack-index missing required object offsets chunk"));
 151
 152         m->num_objects = ntohl(m->chunk_oid_fanout[255]);
 153
 154         m->pack_names = xcalloc(m->num_packs, sizeof(*m->pack_names));
 155         m->packs = xcalloc(m->num_packs, sizeof(*m->packs));
 156
 157         cur_pack_name = (const char *)m->chunk_pack_names;
 158         for (i = 0; i < m->num_packs; i++) {
 159                 m->pack_names[i] = cur_pack_name;
 160
 161                 cur_pack_name += strlen(cur_pack_name) + 1;
 162
 163                 if (i && strcmp(m->pack_names[i], m->pack_names[i - 1]) <= 0) {
 164                         error(_("multi-pack-index pack names out of order: '%s' before '%s'"),
 165                               m->pack_names[i - 1],
 166                               m->pack_names[i]);
 167                         goto cleanup_fail;
 168                 }
 169         }
 170
 171         return m;
 172
 173 cleanup_fail:
 174         free(m);
 175         free(midx_name);
 176         if (midx_map)
 177                 munmap(midx_map, midx_size);
 178         if (0 <= fd)
 179                 close(fd);
 180         return NULL;
 181 }
 182
 183 static void close_midx(struct multi_pack_index *m)
 184 {
 185         uint32_t i;
 186         munmap((unsigned char *)m->data, m->data_len);
 187         close(m->fd);
 188         m->fd = -1;
 189
 190         for (i = 0; i < m->num_packs; i++) {
 191                 if (m->packs[i]) {
 192                         close_pack(m->packs[i]);
 193                         free(m->packs);
 194                 }
 195         }
 196         FREE_AND_NULL(m->packs);
 197         FREE_AND_NULL(m->pack_names);
 198 }
 199
 200 static int prepare_midx_pack(struct multi_pack_index *m, uint32_t pack_int_id)
 201 {
 202         struct strbuf pack_name = STRBUF_INIT;
 203
 204         if (pack_int_id >= m->num_packs)
 205                 BUG("bad pack-int-id");
 206
 207         if (m->packs[pack_int_id])
 208                 return 0;
 209
 210         strbuf_addf(&pack_name, "%s/pack/%s", m->object_dir,
 211                     m->pack_names[pack_int_id]);
 212
 213         m->packs[pack_int_id] = add_packed_git(pack_name.buf, pack_name.len, m->local);
 214         strbuf_release(&pack_name);
 215         return !m->packs[pack_int_id];
 216 }
 217
 218 int bsearch_midx(const struct object_id *oid, struct multi_pack_index *m, uint32_t *result)
 219 {
 220         return bsearch_hash(oid->hash, m->chunk_oid_fanout, m->chunk_oid_lookup,
 221                             MIDX_HASH_LEN, result);
 222 }
 223
 224 struct object_id *nth_midxed_object_oid(struct object_id *oid,
 225                                         struct multi_pack_index *m,
 226                                         uint32_t n)
 227 {
 228         if (n >= m->num_objects)
 229                 return NULL;
 230
 231         hashcpy(oid->hash, m->chunk_oid_lookup + m->hash_len * n);
 232         return oid;
 233 }
 234
 235 static off_t nth_midxed_offset(struct multi_pack_index *m, uint32_t pos)
 236 {
 237         const unsigned char *offset_data;
 238         uint32_t offset32;
 239
 240         offset_data = m->chunk_object_offsets + pos * MIDX_CHUNK_OFFSET_WIDTH;
 241         offset32 = get_be32(offset_data + sizeof(uint32_t));
 242
 243         if (m->chunk_large_offsets && offset32 & MIDX_LARGE_OFFSET_NEEDED) {
 244                 if (sizeof(offset32) < sizeof(uint64_t))
 245                         die(_("multi-pack-index stores a 64-bit offset, but off_t is too small"));
 246
 247                 offset32 ^= MIDX_LARGE_OFFSET_NEEDED;
 248                 return get_be64(m->chunk_large_offsets + sizeof(uint64_t) * offset32);
 249         }
 250
 251         return offset32;
 252 }
 253
 254 static uint32_t nth_midxed_pack_int_id(struct multi_pack_index *m, uint32_t pos)
 255 {
 256         return get_be32(m->chunk_object_offsets + pos * MIDX_CHUNK_OFFSET_WIDTH);
 257 }
 258
 259 static int nth_midxed_pack_entry(struct multi_pack_index *m, struct pack_entry *e, uint32_t pos)
 260 {
 261         uint32_t pack_int_id;
 262         struct packed_git *p;
 263
 264         if (pos >= m->num_objects)
 265                 return 0;
 266
 267         pack_int_id = nth_midxed_pack_int_id(m, pos);
 268
 269         if (prepare_midx_pack(m, pack_int_id))
 270                 die(_("error preparing packfile from multi-pack-index"));
 271         p = m->packs[pack_int_id];
 272
 273         /*
 274         * We are about to tell the caller where they can locate the
 275         * requested object.  We better make sure the packfile is
 276         * still here and can be accessed before supplying that
 277         * answer, as it may have been deleted since the MIDX was
 278         * loaded!
 279         */
 280         if (!is_pack_valid(p))
 281                 return 0;
 282
 283         e->offset = nth_midxed_offset(m, pos);
 284         e->p = p;
 285
 286         return 1;
 287 }
 288
 289 int fill_midx_entry(const struct object_id *oid, struct pack_entry *e, struct multi_pack_index *m)
 290 {
 291         uint32_t pos;
 292
 293         if (!bsearch_midx(oid, m, &pos))
 294                 return 0;
 295
 296         return nth_midxed_pack_entry(m, e, pos);
 297 }
 298
 299 int midx_contains_pack(struct multi_pack_index *m, const char *idx_name)
 300 {
 301         uint32_t first = 0, last = m->num_packs;
 302
 303         while (first < last) {
 304                 uint32_t mid = first + (last - first) / 2;
 305                 const char *current;
 306                 int cmp;
 307
 308                 current = m->pack_names[mid];
 309                 cmp = strcmp(idx_name, current);
 310                 if (!cmp)
 311                         return 1;
 312                 if (cmp > 0) {
 313                         first = mid + 1;
 314                         continue;
 315                 }
 316                 last = mid;
 317         }
 318
 319         return 0;
 320 }
 321
 322 int prepare_multi_pack_index_one(struct repository *r, const char *object_dir, int local)
 323 {
 324         struct multi_pack_index *m = r->objects->multi_pack_index;
 325         struct multi_pack_index *m_search;
 326         int config_value;
 327
 328         if (repo_config_get_bool(r, "core.multipackindex", &config_value) ||
 329             !config_value)
 330                 return 0;
 331
 332         for (m_search = m; m_search; m_search = m_search->next)
 333                 if (!strcmp(object_dir, m_search->object_dir))
 334                         return 1;
 335
 336         r->objects->multi_pack_index = load_multi_pack_index(object_dir, local);
 337
 338         if (r->objects->multi_pack_index) {
 339                 r->objects->multi_pack_index->next = m;
 340                 return 1;
 341         }
 342
 343         return 0;
 344 }
 345
 346 static size_t write_midx_header(struct hashfile *f,
 347                                 unsigned char num_chunks,
 348                                 uint32_t num_packs)
 349 {
 350         unsigned char byte_values[4];
 351
 352         hashwrite_be32(f, MIDX_SIGNATURE);
 353         byte_values[0] = MIDX_VERSION;
 354         byte_values[1] = MIDX_HASH_VERSION;
 355         byte_values[2] = num_chunks;
 356         byte_values[3] = 0; /* unused */
 357         hashwrite(f, byte_values, sizeof(byte_values));
 358         hashwrite_be32(f, num_packs);
 359
 360         return MIDX_HEADER_SIZE;
 361 }
 362
 363 struct pack_list {
 364         struct packed_git **list;
 365         char **names;
 366         uint32_t nr;
 367         uint32_t alloc_list;
 368         uint32_t alloc_names;
 369         size_t pack_name_concat_len;
 370         struct multi_pack_index *m;
 371 };
 372
 373 static void add_pack_to_midx(const char *full_path, size_t full_path_len,
 374                              const char *file_name, void *data)
 375 {
 376         struct pack_list *packs = (struct pack_list *)data;
 377
 378         if (ends_with(file_name, ".idx")) {
 379                 if (packs->m && midx_contains_pack(packs->m, file_name))
 380                         return;
 381
 382                 ALLOC_GROW(packs->list, packs->nr + 1, packs->alloc_list);
 383                 ALLOC_GROW(packs->names, packs->nr + 1, packs->alloc_names);
 384
 385                 packs->list[packs->nr] = add_packed_git(full_path,
 386                                                         full_path_len,
 387                                                         0);
 388
 389                 if (!packs->list[packs->nr]) {
 390                         warning(_("failed to add packfile '%s'"),
 391                                 full_path);
 392                         return;
 393                 }
 394
 395                 if (open_pack_index(packs->list[packs->nr])) {
 396                         warning(_("failed to open pack-index '%s'"),
 397                                 full_path);
 398                         close_pack(packs->list[packs->nr]);
 399                         FREE_AND_NULL(packs->list[packs->nr]);
 400                         return;
 401                 }
 402
 403                 packs->names[packs->nr] = xstrdup(file_name);
 404                 packs->pack_name_concat_len += strlen(file_name) + 1;
 405                 packs->nr++;
 406         }
 407 }
 408
 409 struct pack_pair {
 410         uint32_t pack_int_id;
 411         char *pack_name;
 412 };
 413
 414 static int pack_pair_compare(const void *_a, const void *_b)
 415 {
 416         struct pack_pair *a = (struct pack_pair *)_a;
 417         struct pack_pair *b = (struct pack_pair *)_b;
 418         return strcmp(a->pack_name, b->pack_name);
 419 }
 420
 421 static void sort_packs_by_name(char **pack_names, uint32_t nr_packs, uint32_t *perm)
 422 {
 423         uint32_t i;
 424         struct pack_pair *pairs;
 425
 426         ALLOC_ARRAY(pairs, nr_packs);
 427
 428         for (i = 0; i < nr_packs; i++) {
 429                 pairs[i].pack_int_id = i;
 430                 pairs[i].pack_name = pack_names[i];
 431         }
 432
 433         QSORT(pairs, nr_packs, pack_pair_compare);
 434
 435         for (i = 0; i < nr_packs; i++) {
 436                 pack_names[i] = pairs[i].pack_name;
 437                 perm[pairs[i].pack_int_id] = i;
 438         }
 439
 440         free(pairs);
 441 }
 442
 443 struct pack_midx_entry {
 444         struct object_id oid;
 445         uint32_t pack_int_id;
 446         time_t pack_mtime;
 447         uint64_t offset;
 448 };
 449
 450 static int midx_oid_compare(const void *_a, const void *_b)
 451 {
 452         const struct pack_midx_entry *a = (const struct pack_midx_entry *)_a;
 453         const struct pack_midx_entry *b = (const struct pack_midx_entry *)_b;
 454         int cmp = oidcmp(&a->oid, &b->oid);
 455
 456         if (cmp)
 457                 return cmp;
 458
 459         if (a->pack_mtime > b->pack_mtime)
 460                 return -1;
 461         else if (a->pack_mtime < b->pack_mtime)
 462                 return 1;
 463
 464         return a->pack_int_id - b->pack_int_id;
 465 }
 466
 467 static int nth_midxed_pack_midx_entry(struct multi_pack_index *m,
 468                                       uint32_t *pack_perm,
 469                                       struct pack_midx_entry *e,
 470                                       uint32_t pos)
 471 {
 472         if (pos >= m->num_objects)
 473                 return 1;
 474
 475         nth_midxed_object_oid(&e->oid, m, pos);
 476         e->pack_int_id = pack_perm[nth_midxed_pack_int_id(m, pos)];
 477         e->offset = nth_midxed_offset(m, pos);
 478
 479         /* consider objects in midx to be from "old" packs */
 480         e->pack_mtime = 0;
 481         return 0;
 482 }
 483
 484 static void fill_pack_entry(uint32_t pack_int_id,
 485                             struct packed_git *p,
 486                             uint32_t cur_object,
 487                             struct pack_midx_entry *entry)
 488 {
 489         if (!nth_packed_object_oid(&entry->oid, p, cur_object))
 490                 die(_("failed to locate object %d in packfile"), cur_object);
 491
 492         entry->pack_int_id = pack_int_id;
 493         entry->pack_mtime = p->mtime;
 494
 495         entry->offset = nth_packed_object_offset(p, cur_object);
 496 }
 497
 498 /*
 499  * It is possible to artificially get into a state where there are many
 500  * duplicate copies of objects. That can create high memory pressure if
 501  * we are to create a list of all objects before de-duplication. To reduce
 502  * this memory pressure without a significant performance drop, automatically
 503  * group objects by the first byte of their object id. Use the IDX fanout
 504  * tables to group the data, copy to a local array, then sort.
 505  *
 506  * Copy only the de-duplicated entries (selected by most-recent modified time
 507  * of a packfile containing the object).
 508  */
 509 static struct pack_midx_entry *get_sorted_entries(struct multi_pack_index *m,
 510                                                   struct packed_git **p,
 511                                                   uint32_t *perm,
 512                                                   uint32_t nr_packs,
 513                                                   uint32_t *nr_objects)
 514 {
 515         uint32_t cur_fanout, cur_pack, cur_object;
 516         uint32_t alloc_fanout, alloc_objects, total_objects = 0;
 517         struct pack_midx_entry *entries_by_fanout = NULL;
 518         struct pack_midx_entry *deduplicated_entries = NULL;
 519         uint32_t start_pack = m ? m->num_packs : 0;
 520
 521         for (cur_pack = start_pack; cur_pack < nr_packs; cur_pack++)
 522                 total_objects += p[cur_pack]->num_objects;
 523
 524         /*
 525          * As we de-duplicate by fanout value, we expect the fanout
 526          * slices to be evenly distributed, with some noise. Hence,
 527          * allocate slightly more than one 256th.
 528          */
 529         alloc_objects = alloc_fanout = total_objects > 3200 ? total_objects / 200 : 16;
 530
 531         ALLOC_ARRAY(entries_by_fanout, alloc_fanout);
 532         ALLOC_ARRAY(deduplicated_entries, alloc_objects);
 533         *nr_objects = 0;
 534
 535         for (cur_fanout = 0; cur_fanout < 256; cur_fanout++) {
 536                 uint32_t nr_fanout = 0;
 537
 538                 if (m) {
 539                         uint32_t start = 0, end;
 540
 541                         if (cur_fanout)
 542                                 start = ntohl(m->chunk_oid_fanout[cur_fanout - 1]);
 543                         end = ntohl(m->chunk_oid_fanout[cur_fanout]);
 544
 545                         for (cur_object = start; cur_object < end; cur_object++) {
 546                                 ALLOC_GROW(entries_by_fanout, nr_fanout + 1, alloc_fanout);
 547                                 nth_midxed_pack_midx_entry(m, perm,
 548                                                            &entries_by_fanout[nr_fanout],
 549                                                            cur_object);
 550                                 nr_fanout++;
 551                         }
 552                 }
 553
 554                 for (cur_pack = start_pack; cur_pack < nr_packs; cur_pack++) {
 555                         uint32_t start = 0, end;
 556
 557                         if (cur_fanout)
 558                                 start = get_pack_fanout(p[cur_pack], cur_fanout - 1);
 559                         end = get_pack_fanout(p[cur_pack], cur_fanout);
 560
 561                         for (cur_object = start; cur_object < end; cur_object++) {
 562                                 ALLOC_GROW(entries_by_fanout, nr_fanout + 1, alloc_fanout);
 563                                 fill_pack_entry(perm[cur_pack], p[cur_pack], cur_object, &entries_by_fanout[nr_fanout]);
 564                                 nr_fanout++;
 565                         }
 566                 }
 567
 568                 QSORT(entries_by_fanout, nr_fanout, midx_oid_compare);
 569
 570                 /*
 571                  * The batch is now sorted by OID and then mtime (descending).
 572                  * Take only the first duplicate.
 573                  */
 574                 for (cur_object = 0; cur_object < nr_fanout; cur_object++) {
 575                         if (cur_object && !oidcmp(&entries_by_fanout[cur_object - 1].oid,
 576                                                   &entries_by_fanout[cur_object].oid))
 577                                 continue;
 578
 579                         ALLOC_GROW(deduplicated_entries, *nr_objects + 1, alloc_objects);
 580                         memcpy(&deduplicated_entries[*nr_objects],
 581                                &entries_by_fanout[cur_object],
 582                                sizeof(struct pack_midx_entry));
 583                         (*nr_objects)++;
 584                 }
 585         }
 586
 587         free(entries_by_fanout);
 588         return deduplicated_entries;
 589 }
 590
 591 static size_t write_midx_pack_names(struct hashfile *f,
 592                                     char **pack_names,
 593                                     uint32_t num_packs)
 594 {
 595         uint32_t i;
 596         unsigned char padding[MIDX_CHUNK_ALIGNMENT];
 597         size_t written = 0;
 598
 599         for (i = 0; i < num_packs; i++) {
 600                 size_t writelen = strlen(pack_names[i]) + 1;
 601
 602                 if (i && strcmp(pack_names[i], pack_names[i - 1]) <= 0)
 603                         BUG("incorrect pack-file order: %s before %s",
 604                             pack_names[i - 1],
 605                             pack_names[i]);
 606
 607                 hashwrite(f, pack_names[i], writelen);
 608                 written += writelen;
 609         }
 610
 611         /* add padding to be aligned */
 612         i = MIDX_CHUNK_ALIGNMENT - (written % MIDX_CHUNK_ALIGNMENT);
 613         if (i < MIDX_CHUNK_ALIGNMENT) {
 614                 memset(padding, 0, sizeof(padding));
 615                 hashwrite(f, padding, i);
 616                 written += i;
 617         }
 618
 619         return written;
 620 }
 621
 622 static size_t write_midx_oid_fanout(struct hashfile *f,
 623                                     struct pack_midx_entry *objects,
 624                                     uint32_t nr_objects)
 625 {
 626         struct pack_midx_entry *list = objects;
 627         struct pack_midx_entry *last = objects + nr_objects;
 628         uint32_t count = 0;
 629         uint32_t i;
 630
 631         /*
 632         * Write the first-level table (the list is sorted,
 633         * but we use a 256-entry lookup to be able to avoid
 634         * having to do eight extra binary search iterations).
 635         */
 636         for (i = 0; i < 256; i++) {
 637                 struct pack_midx_entry *next = list;
 638
 639                 while (next < last && next->oid.hash[0] == i) {
 640                         count++;
 641                         next++;
 642                 }
 643
 644                 hashwrite_be32(f, count);
 645                 list = next;
 646         }
 647
 648         return MIDX_CHUNK_FANOUT_SIZE;
 649 }
 650
 651 static size_t write_midx_oid_lookup(struct hashfile *f, unsigned char hash_len,
 652                                     struct pack_midx_entry *objects,
 653                                     uint32_t nr_objects)
 654 {
 655         struct pack_midx_entry *list = objects;
 656         uint32_t i;
 657         size_t written = 0;
 658
 659         for (i = 0; i < nr_objects; i++) {
 660                 struct pack_midx_entry *obj = list++;
 661
 662                 if (i < nr_objects - 1) {
 663                         struct pack_midx_entry *next = list;
 664                         if (oidcmp(&obj->oid, &next->oid) >= 0)
 665                                 BUG("OIDs not in order: %s >= %s",
 666                                     oid_to_hex(&obj->oid),
 667                                     oid_to_hex(&next->oid));
 668                 }
 669
 670                 hashwrite(f, obj->oid.hash, (int)hash_len);
 671                 written += hash_len;
 672         }
 673
 674         return written;
 675 }
 676
 677 static size_t write_midx_object_offsets(struct hashfile *f, int large_offset_needed,
 678                                         struct pack_midx_entry *objects, uint32_t nr_objects)
 679 {
 680         struct pack_midx_entry *list = objects;
 681         uint32_t i, nr_large_offset = 0;
 682         size_t written = 0;
 683
 684         for (i = 0; i < nr_objects; i++) {
 685                 struct pack_midx_entry *obj = list++;
 686
 687                 hashwrite_be32(f, obj->pack_int_id);
 688
 689                 if (large_offset_needed && obj->offset >> 31)
 690                         hashwrite_be32(f, MIDX_LARGE_OFFSET_NEEDED | nr_large_offset++);
 691                 else if (!large_offset_needed && obj->offset >> 32)
 692                         BUG("object %s requires a large offset (%"PRIx64") but the MIDX is not writing large offsets!",
 693                             oid_to_hex(&obj->oid),
 694                             obj->offset);
 695                 else
 696                         hashwrite_be32(f, (uint32_t)obj->offset);
 697
 698                 written += MIDX_CHUNK_OFFSET_WIDTH;
 699         }
 700
 701         return written;
 702 }
 703
 704 static size_t write_midx_large_offsets(struct hashfile *f, uint32_t nr_large_offset,
 705                                        struct pack_midx_entry *objects, uint32_t nr_objects)
 706 {
 707         struct pack_midx_entry *list = objects;
 708         size_t written = 0;
 709
 710         while (nr_large_offset) {
 711                 struct pack_midx_entry *obj = list++;
 712                 uint64_t offset = obj->offset;
 713
 714                 if (!(offset >> 31))
 715                         continue;
 716
 717                 hashwrite_be32(f, offset >> 32);
 718                 hashwrite_be32(f, offset & 0xffffffffUL);
 719                 written += 2 * sizeof(uint32_t);
 720
 721                 nr_large_offset--;
 722         }
 723
 724         return written;
 725 }
 726
 727 int write_midx_file(const char *object_dir)
 728 {
 729         unsigned char cur_chunk, num_chunks = 0;
 730         char *midx_name;
 731         uint32_t i;
 732         struct hashfile *f = NULL;
 733         struct lock_file lk;
 734         struct pack_list packs;
 735         uint32_t *pack_perm = NULL;
 736         uint64_t written = 0;
 737         uint32_t chunk_ids[MIDX_MAX_CHUNKS + 1];
 738         uint64_t chunk_offsets[MIDX_MAX_CHUNKS + 1];
 739         uint32_t nr_entries, num_large_offsets = 0;
 740         struct pack_midx_entry *entries = NULL;
 741         int large_offsets_needed = 0;
 742
 743         midx_name = get_midx_filename(object_dir);
 744         if (safe_create_leading_directories(midx_name)) {
 745                 UNLEAK(midx_name);
 746                 die_errno(_("unable to create leading directories of %s"),
 747                           midx_name);
 748         }
 749
 750         packs.m = load_multi_pack_index(object_dir, 1);
 751
 752         packs.nr = 0;
 753         packs.alloc_list = packs.m ? packs.m->num_packs : 16;
 754         packs.alloc_names = packs.alloc_list;
 755         packs.list = NULL;
 756         packs.names = NULL;
 757         packs.pack_name_concat_len = 0;
 758         ALLOC_ARRAY(packs.list, packs.alloc_list);
 759         ALLOC_ARRAY(packs.names, packs.alloc_names);
 760
 761         if (packs.m) {
 762                 for (i = 0; i < packs.m->num_packs; i++) {
 763                         ALLOC_GROW(packs.list, packs.nr + 1, packs.alloc_list);
 764                         ALLOC_GROW(packs.names, packs.nr + 1, packs.alloc_names);
 765
 766                         packs.list[packs.nr] = NULL;
 767                         packs.names[packs.nr] = xstrdup(packs.m->pack_names[i]);
 768                         packs.pack_name_concat_len += strlen(packs.names[packs.nr]) + 1;
 769                         packs.nr++;
 770                 }
 771         }
 772
 773         for_each_file_in_pack_dir(object_dir, add_pack_to_midx, &packs);
 774
 775         if (packs.m && packs.nr == packs.m->num_packs)
 776                 goto cleanup;
 777
 778         if (packs.pack_name_concat_len % MIDX_CHUNK_ALIGNMENT)
 779                 packs.pack_name_concat_len += MIDX_CHUNK_ALIGNMENT -
 780                                               (packs.pack_name_concat_len % MIDX_CHUNK_ALIGNMENT);
 781
 782         ALLOC_ARRAY(pack_perm, packs.nr);
 783         sort_packs_by_name(packs.names, packs.nr, pack_perm);
 784
 785         entries = get_sorted_entries(packs.m, packs.list, pack_perm, packs.nr, &nr_entries);
 786
 787         for (i = 0; i < nr_entries; i++) {
 788                 if (entries[i].offset > 0x7fffffff)
 789                         num_large_offsets++;
 790                 if (entries[i].offset > 0xffffffff)
 791                         large_offsets_needed = 1;
 792         }
 793
 794         hold_lock_file_for_update(&lk, midx_name, LOCK_DIE_ON_ERROR);
 795         f = hashfd(lk.tempfile->fd, lk.tempfile->filename.buf);
 796         FREE_AND_NULL(midx_name);
 797
 798         if (packs.m)
 799                 close_midx(packs.m);
 800
 801         cur_chunk = 0;
 802         num_chunks = large_offsets_needed ? 5 : 4;
 803
 804         written = write_midx_header(f, num_chunks, packs.nr);
 805
 806         chunk_ids[cur_chunk] = MIDX_CHUNKID_PACKNAMES;
 807         chunk_offsets[cur_chunk] = written + (num_chunks + 1) * MIDX_CHUNKLOOKUP_WIDTH;
 808
 809         cur_chunk++;
 810         chunk_ids[cur_chunk] = MIDX_CHUNKID_OIDFANOUT;
 811         chunk_offsets[cur_chunk] = chunk_offsets[cur_chunk - 1] + packs.pack_name_concat_len;
 812
 813         cur_chunk++;
 814         chunk_ids[cur_chunk] = MIDX_CHUNKID_OIDLOOKUP;
 815         chunk_offsets[cur_chunk] = chunk_offsets[cur_chunk - 1] + MIDX_CHUNK_FANOUT_SIZE;
 816
 817         cur_chunk++;
 818         chunk_ids[cur_chunk] = MIDX_CHUNKID_OBJECTOFFSETS;
 819         chunk_offsets[cur_chunk] = chunk_offsets[cur_chunk - 1] + nr_entries * MIDX_HASH_LEN;
 820
 821         cur_chunk++;
 822         chunk_offsets[cur_chunk] = chunk_offsets[cur_chunk - 1] + nr_entries * MIDX_CHUNK_OFFSET_WIDTH;
 823         if (large_offsets_needed) {
 824                 chunk_ids[cur_chunk] = MIDX_CHUNKID_LARGEOFFSETS;
 825
 826                 cur_chunk++;
 827                 chunk_offsets[cur_chunk] = chunk_offsets[cur_chunk - 1] +
 828                                            num_large_offsets * MIDX_CHUNK_LARGE_OFFSET_WIDTH;
 829         }
 830
 831         chunk_ids[cur_chunk] = 0;
 832
 833         for (i = 0; i <= num_chunks; i++) {
 834                 if (i && chunk_offsets[i] < chunk_offsets[i - 1])
 835                         BUG("incorrect chunk offsets: %"PRIu64" before %"PRIu64,
 836                             chunk_offsets[i - 1],
 837                             chunk_offsets[i]);
 838
 839                 if (chunk_offsets[i] % MIDX_CHUNK_ALIGNMENT)
 840                         BUG("chunk offset %"PRIu64" is not properly aligned",
 841                             chunk_offsets[i]);
 842
 843                 hashwrite_be32(f, chunk_ids[i]);
 844                 hashwrite_be32(f, chunk_offsets[i] >> 32);
 845                 hashwrite_be32(f, chunk_offsets[i]);
 846
 847                 written += MIDX_CHUNKLOOKUP_WIDTH;
 848         }
 849
 850         for (i = 0; i < num_chunks; i++) {
 851                 if (written != chunk_offsets[i])
 852                         BUG("incorrect chunk offset (%"PRIu64" != %"PRIu64") for chunk id %"PRIx32,
 853                             chunk_offsets[i],
 854                             written,
 855                             chunk_ids[i]);
 856
 857                 switch (chunk_ids[i]) {
 858                         case MIDX_CHUNKID_PACKNAMES:
 859                                 written += write_midx_pack_names(f, packs.names, packs.nr);
 860                                 break;
 861
 862                         case MIDX_CHUNKID_OIDFANOUT:
 863                                 written += write_midx_oid_fanout(f, entries, nr_entries);
 864                                 break;
 865
 866                         case MIDX_CHUNKID_OIDLOOKUP:
 867                                 written += write_midx_oid_lookup(f, MIDX_HASH_LEN, entries, nr_entries);
 868                                 break;
 869
 870                         case MIDX_CHUNKID_OBJECTOFFSETS:
 871                                 written += write_midx_object_offsets(f, large_offsets_needed, entries, nr_entries);
 872                                 break;
 873
 874                         case MIDX_CHUNKID_LARGEOFFSETS:
 875                                 written += write_midx_large_offsets(f, num_large_offsets, entries, nr_entries);
 876                                 break;
 877
 878                         default:
 879                                 BUG("trying to write unknown chunk id %"PRIx32,
 880                                     chunk_ids[i]);
 881                 }
 882         }
 883
 884         if (written != chunk_offsets[num_chunks])
 885                 BUG("incorrect final offset %"PRIu64" != %"PRIu64,
 886                     written,
 887                     chunk_offsets[num_chunks]);
 888
 889         finalize_hashfile(f, NULL, CSUM_FSYNC | CSUM_HASH_IN_STREAM);
 890         commit_lock_file(&lk);
 891
 892 cleanup:
 893         for (i = 0; i < packs.nr; i++) {
 894                 if (packs.list[i]) {
 895                         close_pack(packs.list[i]);
 896                         free(packs.list[i]);
 897                 }
 898                 free(packs.names[i]);
 899         }
 900
 901         free(packs.list);
 902         free(packs.names);
 903         free(entries);
 904         free(pack_perm);
 905         free(midx_name);
 906         return 0;
 907 }
 908
 909 void clear_midx_file(const char *object_dir)
 910 {
 911         char *midx = get_midx_filename(object_dir);
 912
 913         if (remove_path(midx)) {
 914                 UNLEAK(midx);
 915                 die(_("failed to clear multi-pack-index at %s"), midx);
 916         }
 917
 918         free(midx);
 919 }