pack-objects.c

   1 #include "cache.h"
   2 #include "object.h"
   3 #include "delta.h"
   4 #include "pack.h"
   5 #include "csum-file.h"
   6
   7 static const char pack_usage[] = "git-pack-objects [--non-empty] [--local] [--incremental] [--window=N] [--depth=N] {--stdout | base-name} < object-list";
   8
   9 struct object_entry {
  10         unsigned char sha1[20];
  11         unsigned long size;
  12         unsigned long offset;
  13         unsigned int depth;
  14         unsigned int hash;
  15         enum object_type type;
  16         unsigned long delta_size;
  17         struct object_entry *delta;
  18 };
  19
  20 static unsigned char object_list_sha1[20];
  21 static int non_empty = 0;
  22 static int local = 0;
  23 static int incremental = 0;
  24 static struct object_entry **sorted_by_sha, **sorted_by_type;
  25 static struct object_entry *objects = NULL;
  26 static int nr_objects = 0, nr_alloc = 0;
  27 static const char *base_name;
  28 static unsigned char pack_file_sha1[20];
  29
  30 static void *delta_against(void *buf, unsigned long size, struct object_entry *entry)
  31 {
  32         unsigned long othersize, delta_size;
  33         char type[10];
  34         void *otherbuf = read_sha1_file(entry->delta->sha1, type, &othersize);
  35         void *delta_buf;
  36
  37         if (!otherbuf)
  38                 die("unable to read %s", sha1_to_hex(entry->delta->sha1));
  39         delta_buf = diff_delta(otherbuf, othersize,
  40                                buf, size, &delta_size, 0);
  41         if (!delta_buf || delta_size != entry->delta_size)
  42                 die("delta size changed");
  43         free(buf);
  44         free(otherbuf);
  45         return delta_buf;
  46 }
  47
  48 /*
  49  * The per-object header is a pretty dense thing, which is
  50  *  - first byte: low four bits are "size", then three bits of "type",
  51  *    and the high bit is "size continues".
  52  *  - each byte afterwards: low seven bits are size continuation,
  53  *    with the high bit being "size continues"
  54  */
  55 static int encode_header(enum object_type type, unsigned long size, unsigned char *hdr)
  56 {
  57         int n = 1;
  58         unsigned char c;
  59
  60         if (type < OBJ_COMMIT || type > OBJ_DELTA)
  61                 die("bad type %d", type);
  62
  63         c = (type << 4) | (size & 15);
  64         size >>= 4;
  65         while (size) {
  66                 *hdr++ = c | 0x80;
  67                 c = size & 0x7f;
  68                 size >>= 7;
  69                 n++;
  70         }
  71         *hdr = c;
  72         return n;
  73 }
  74
  75 static unsigned long write_object(struct sha1file *f, struct object_entry *entry)
  76 {
  77         unsigned long size;
  78         char type[10];
  79         void *buf = read_sha1_file(entry->sha1, type, &size);
  80         unsigned char header[10];
  81         unsigned hdrlen, datalen;
  82         enum object_type obj_type;
  83
  84         if (!buf)
  85                 die("unable to read %s", sha1_to_hex(entry->sha1));
  86         if (size != entry->size)
  87                 die("object %s size inconsistency (%lu vs %lu)", sha1_to_hex(entry->sha1), size, entry->size);
  88
  89         /*
  90          * The object header is a byte of 'type' followed by zero or
  91          * more bytes of length.  For deltas, the 20 bytes of delta sha1
  92          * follows that.
  93          */
  94         obj_type = entry->type;
  95         if (entry->delta) {
  96                 buf = delta_against(buf, size, entry);
  97                 size = entry->delta_size;
  98                 obj_type = OBJ_DELTA;
  99         }
 100         hdrlen = encode_header(obj_type, size, header);
 101         sha1write(f, header, hdrlen);
 102         if (entry->delta) {
 103                 sha1write(f, entry->delta, 20);
 104                 hdrlen += 20;
 105         }
 106         datalen = sha1write_compressed(f, buf, size);
 107         free(buf);
 108         return hdrlen + datalen;
 109 }
 110
 111 static unsigned long write_one(struct sha1file *f,
 112                                struct object_entry *e,
 113                                unsigned long offset)
 114 {
 115         if (e->offset)
 116                 /* offset starts from header size and cannot be zero
 117                  * if it is written already.
 118                  */
 119                 return offset;
 120         e->offset = offset;
 121         offset += write_object(f, e);
 122         /* if we are deltified, write out its base object. */
 123         if (e->delta)
 124                 offset = write_one(f, e->delta, offset);
 125         return offset;
 126 }
 127
 128 static void write_pack_file(void)
 129 {
 130         int i;
 131         struct sha1file *f;
 132         unsigned long offset;
 133         unsigned long mb;
 134         struct pack_header hdr;
 135
 136         if (!base_name)
 137                 f = sha1fd(1, "<stdout>");
 138         else
 139                 f = sha1create("%s-%s.%s", base_name, sha1_to_hex(object_list_sha1), "pack");
 140         hdr.hdr_signature = htonl(PACK_SIGNATURE);
 141         hdr.hdr_version = htonl(PACK_VERSION);
 142         hdr.hdr_entries = htonl(nr_objects);
 143         sha1write(f, &hdr, sizeof(hdr));
 144         offset = sizeof(hdr);
 145         for (i = 0; i < nr_objects; i++)
 146                 offset = write_one(f, objects + i, offset);
 147
 148         sha1close(f, pack_file_sha1, 1);
 149         mb = offset >> 20;
 150         offset &= 0xfffff;
 151 }
 152
 153 static void write_index_file(void)
 154 {
 155         int i;
 156         struct sha1file *f = sha1create("%s-%s.%s", base_name, sha1_to_hex(object_list_sha1), "idx");
 157         struct object_entry **list = sorted_by_sha;
 158         struct object_entry **last = list + nr_objects;
 159         unsigned int array[256];
 160
 161         /*
 162          * Write the first-level table (the list is sorted,
 163          * but we use a 256-entry lookup to be able to avoid
 164          * having to do eight extra binary search iterations).
 165          */
 166         for (i = 0; i < 256; i++) {
 167                 struct object_entry **next = list;
 168                 while (next < last) {
 169                         struct object_entry *entry = *next;
 170                         if (entry->sha1[0] != i)
 171                                 break;
 172                         next++;
 173                 }
 174                 array[i] = htonl(next - sorted_by_sha);
 175                 list = next;
 176         }
 177         sha1write(f, array, 256 * sizeof(int));
 178
 179         /*
 180          * Write the actual SHA1 entries..
 181          */
 182         list = sorted_by_sha;
 183         for (i = 0; i < nr_objects; i++) {
 184                 struct object_entry *entry = *list++;
 185                 unsigned int offset = htonl(entry->offset);
 186                 sha1write(f, &offset, 4);
 187                 sha1write(f, entry->sha1, 20);
 188         }
 189         sha1write(f, pack_file_sha1, 20);
 190         sha1close(f, NULL, 1);
 191 }
 192
 193 static int add_object_entry(unsigned char *sha1, unsigned int hash)
 194 {
 195         unsigned int idx = nr_objects;
 196         struct object_entry *entry;
 197
 198         if (incremental || local) {
 199                 struct packed_git *p;
 200
 201                 for (p = packed_git; p; p = p->next) {
 202                         struct pack_entry e;
 203
 204                         if (find_pack_entry_one(sha1, &e, p)) {
 205                                 if (incremental)
 206                                         return 0;
 207                                 if (local && !p->pack_local)
 208                                         return 0;
 209                         }
 210                 }
 211         }
 212
 213         if (idx >= nr_alloc) {
 214                 unsigned int needed = (idx + 1024) * 3 / 2;
 215                 objects = xrealloc(objects, needed * sizeof(*entry));
 216                 nr_alloc = needed;
 217         }
 218         entry = objects + idx;
 219         memset(entry, 0, sizeof(*entry));
 220         memcpy(entry->sha1, sha1, 20);
 221         entry->hash = hash;
 222         nr_objects = idx+1;
 223         return 1;
 224 }
 225
 226 static void check_object(struct object_entry *entry)
 227 {
 228         char type[20];
 229
 230         if (!sha1_object_info(entry->sha1, type, &entry->size)) {
 231                 if (!strcmp(type, "commit")) {
 232                         entry->type = OBJ_COMMIT;
 233                 } else if (!strcmp(type, "tree")) {
 234                         entry->type = OBJ_TREE;
 235                 } else if (!strcmp(type, "blob")) {
 236                         entry->type = OBJ_BLOB;
 237                 } else if (!strcmp(type, "tag")) {
 238                         entry->type = OBJ_TAG;
 239                 } else
 240                         die("unable to pack object %s of type %s",
 241                             sha1_to_hex(entry->sha1), type);
 242         }
 243         else
 244                 die("unable to get type of object %s",
 245                     sha1_to_hex(entry->sha1));
 246 }
 247
 248 static void get_object_details(void)
 249 {
 250         int i;
 251         struct object_entry *entry = objects;
 252
 253         for (i = 0; i < nr_objects; i++)
 254                 check_object(entry++);
 255 }
 256
 257 typedef int (*entry_sort_t)(const struct object_entry *, const struct object_entry *);
 258
 259 static entry_sort_t current_sort;
 260
 261 static int sort_comparator(const void *_a, const void *_b)
 262 {
 263         struct object_entry *a = *(struct object_entry **)_a;
 264         struct object_entry *b = *(struct object_entry **)_b;
 265         return current_sort(a,b);
 266 }
 267
 268 static struct object_entry **create_sorted_list(entry_sort_t sort)
 269 {
 270         struct object_entry **list = xmalloc(nr_objects * sizeof(struct object_entry *));
 271         int i;
 272
 273         for (i = 0; i < nr_objects; i++)
 274                 list[i] = objects + i;
 275         current_sort = sort;
 276         qsort(list, nr_objects, sizeof(struct object_entry *), sort_comparator);
 277         return list;
 278 }
 279
 280 static int sha1_sort(const struct object_entry *a, const struct object_entry *b)
 281 {
 282         return memcmp(a->sha1, b->sha1, 20);
 283 }
 284
 285 static int type_size_sort(const struct object_entry *a, const struct object_entry *b)
 286 {
 287         if (a->type < b->type)
 288                 return -1;
 289         if (a->type > b->type)
 290                 return 1;
 291         if (a->hash < b->hash)
 292                 return -1;
 293         if (a->hash > b->hash)
 294                 return 1;
 295         if (a->size < b->size)
 296                 return -1;
 297         if (a->size > b->size)
 298                 return 1;
 299         return a < b ? -1 : (a > b);
 300 }
 301
 302 struct unpacked {
 303         struct object_entry *entry;
 304         void *data;
 305 };
 306
 307 /*
 308  * We search for deltas _backwards_ in a list sorted by type and
 309  * by size, so that we see progressively smaller and smaller files.
 310  * That's because we prefer deltas to be from the bigger file
 311  * to the smaller - deletes are potentially cheaper, but perhaps
 312  * more importantly, the bigger file is likely the more recent
 313  * one.
 314  */
 315 static int try_delta(struct unpacked *cur, struct unpacked *old, unsigned max_depth)
 316 {
 317         struct object_entry *cur_entry = cur->entry;
 318         struct object_entry *old_entry = old->entry;
 319         unsigned long size, oldsize, delta_size, sizediff;
 320         long max_size;
 321         void *delta_buf;
 322
 323         /* Don't bother doing diffs between different types */
 324         if (cur_entry->type != old_entry->type)
 325                 return -1;
 326
 327         size = cur_entry->size;
 328         if (size < 50)
 329                 return -1;
 330         oldsize = old_entry->size;
 331         sizediff = oldsize > size ? oldsize - size : size - oldsize;
 332         if (sizediff > size / 8)
 333                 return -1;
 334         if (old_entry->depth >= max_depth)
 335                 return 0;
 336
 337         /*
 338          * NOTE!
 339          *
 340          * We always delta from the bigger to the smaller, since that's
 341          * more space-efficient (deletes don't have to say _what_ they
 342          * delete).
 343          */
 344         max_size = size / 2 - 20;
 345         if (cur_entry->delta)
 346                 max_size = cur_entry->delta_size-1;
 347         if (sizediff >= max_size)
 348                 return -1;
 349         delta_buf = diff_delta(old->data, oldsize,
 350                                cur->data, size, &delta_size, max_size);
 351         if (!delta_buf)
 352                 return 0;
 353         cur_entry->delta = old_entry;
 354         cur_entry->delta_size = delta_size;
 355         cur_entry->depth = old_entry->depth + 1;
 356         free(delta_buf);
 357         return 0;
 358 }
 359
 360 static void find_deltas(struct object_entry **list, int window, int depth)
 361 {
 362         int i, idx;
 363         unsigned int array_size = window * sizeof(struct unpacked);
 364         struct unpacked *array = xmalloc(array_size);
 365
 366         memset(array, 0, array_size);
 367         i = nr_objects;
 368         idx = 0;
 369         while (--i >= 0) {
 370                 struct object_entry *entry = list[i];
 371                 struct unpacked *n = array + idx;
 372                 unsigned long size;
 373                 char type[10];
 374                 int j;
 375
 376                 free(n->data);
 377                 n->entry = entry;
 378                 n->data = read_sha1_file(entry->sha1, type, &size);
 379                 if (size != entry->size)
 380                         die("object %s inconsistent object length (%lu vs %lu)", sha1_to_hex(entry->sha1), size, entry->size);
 381                 j = window;
 382                 while (--j > 0) {
 383                         unsigned int other_idx = idx + j;
 384                         struct unpacked *m;
 385                         if (other_idx >= window)
 386                                 other_idx -= window;
 387                         m = array + other_idx;
 388                         if (!m->entry)
 389                                 break;
 390                         if (try_delta(n, m, depth) < 0)
 391                                 break;
 392                 }
 393                 idx++;
 394                 if (idx >= window)
 395                         idx = 0;
 396         }
 397
 398         for (i = 0; i < window; ++i)
 399                 free(array[i].data);
 400         free(array);
 401 }
 402
 403 static void prepare_pack(int window, int depth)
 404 {
 405         get_object_details();
 406
 407         fprintf(stderr, "Packing %d objects\n", nr_objects);
 408
 409         sorted_by_type = create_sorted_list(type_size_sort);
 410         if (window && depth)
 411                 find_deltas(sorted_by_type, window+1, depth);
 412         write_pack_file();
 413 }
 414
 415 static int reuse_cached_pack(unsigned char *sha1, int pack_to_stdout)
 416 {
 417         static const char cache[] = "pack-cache/pack-%s.%s";
 418         char *cached_pack, *cached_idx;
 419         int ifd, ofd, ifd_ix = -1;
 420
 421         cached_pack = git_path(cache, sha1_to_hex(sha1), "pack");
 422         ifd = open(cached_pack, O_RDONLY);
 423         if (ifd < 0)
 424                 return 0;
 425
 426         if (!pack_to_stdout) {
 427                 cached_idx = git_path(cache, sha1_to_hex(sha1), "idx");
 428                 ifd_ix = open(cached_idx, O_RDONLY);
 429                 if (ifd_ix < 0) {
 430                         close(ifd);
 431                         return 0;
 432                 }
 433         }
 434
 435         fprintf(stderr, "Reusing %d objects pack %s\n", nr_objects,
 436                 sha1_to_hex(sha1));
 437
 438         if (pack_to_stdout) {
 439                 if (copy_fd(ifd, 1))
 440                         exit(1);
 441                 close(ifd);
 442         }
 443         else {
 444                 char name[PATH_MAX];
 445                 snprintf(name, sizeof(name),
 446                          "%s-%s.%s", base_name, sha1_to_hex(sha1), "pack");
 447                 ofd = open(name, O_CREAT | O_EXCL | O_WRONLY, 0666);
 448                 if (ofd < 0)
 449                         die("unable to open %s (%s)", name, strerror(errno));
 450                 if (copy_fd(ifd, ofd))
 451                         exit(1);
 452                 close(ifd);
 453
 454                 snprintf(name, sizeof(name),
 455                          "%s-%s.%s", base_name, sha1_to_hex(sha1), "idx");
 456                 ofd = open(name, O_CREAT | O_EXCL | O_WRONLY, 0666);
 457                 if (ofd < 0)
 458                         die("unable to open %s (%s)", name, strerror(errno));
 459                 if (copy_fd(ifd_ix, ofd))
 460                         exit(1);
 461                 close(ifd_ix);
 462                 puts(sha1_to_hex(sha1));
 463         }
 464
 465         return 1;
 466 }
 467
 468 int main(int argc, char **argv)
 469 {
 470         SHA_CTX ctx;
 471         char line[PATH_MAX + 20];
 472         int window = 10, depth = 10, pack_to_stdout = 0;
 473         struct object_entry **list;
 474         int i;
 475
 476         setup_git_directory();
 477
 478         for (i = 1; i < argc; i++) {
 479                 const char *arg = argv[i];
 480
 481                 if (*arg == '-') {
 482                         if (!strcmp("--non-empty", arg)) {
 483                                 non_empty = 1;
 484                                 continue;
 485                         }
 486                         if (!strcmp("--local", arg)) {
 487                                 local = 1;
 488                                 continue;
 489                         }
 490                         if (!strcmp("--incremental", arg)) {
 491                                 incremental = 1;
 492                                 continue;
 493                         }
 494                         if (!strncmp("--window=", arg, 9)) {
 495                                 char *end;
 496                                 window = strtoul(arg+9, &end, 0);
 497                                 if (!arg[9] || *end)
 498                                         usage(pack_usage);
 499                                 continue;
 500                         }
 501                         if (!strncmp("--depth=", arg, 8)) {
 502                                 char *end;
 503                                 depth = strtoul(arg+8, &end, 0);
 504                                 if (!arg[8] || *end)
 505                                         usage(pack_usage);
 506                                 continue;
 507                         }
 508                         if (!strcmp("--stdout", arg)) {
 509                                 pack_to_stdout = 1;
 510                                 continue;
 511                         }
 512                         usage(pack_usage);
 513                 }
 514                 if (base_name)
 515                         usage(pack_usage);
 516                 base_name = arg;
 517         }
 518
 519         if (pack_to_stdout != !base_name)
 520                 usage(pack_usage);
 521
 522         prepare_packed_git();
 523         while (fgets(line, sizeof(line), stdin) != NULL) {
 524                 unsigned int hash;
 525                 char *p;
 526                 unsigned char sha1[20];
 527
 528                 if (get_sha1_hex(line, sha1))
 529                         die("expected sha1, got garbage:\n %s", line);
 530                 hash = 0;
 531                 p = line+40;
 532                 while (*p) {
 533                         unsigned char c = *p++;
 534                         if (isspace(c))
 535                                 continue;
 536                         hash = hash * 11 + c;
 537                 }
 538                 add_object_entry(sha1, hash);
 539         }
 540         if (non_empty && !nr_objects)
 541                 return 0;
 542
 543         sorted_by_sha = create_sorted_list(sha1_sort);
 544         SHA1_Init(&ctx);
 545         list = sorted_by_sha;
 546         for (i = 0; i < nr_objects; i++) {
 547                 struct object_entry *entry = *list++;
 548                 SHA1_Update(&ctx, entry->sha1, 20);
 549         }
 550         SHA1_Final(object_list_sha1, &ctx);
 551
 552         if (reuse_cached_pack(object_list_sha1, pack_to_stdout))
 553                 ;
 554         else {
 555                 prepare_pack(window, depth);
 556                 if (!pack_to_stdout) {
 557                         write_index_file();
 558                         puts(sha1_to_hex(object_list_sha1));
 559                 }
 560         }
 561         return 0;
 562 }