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