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 #include <sys/time.h>
   7
   8 static const char pack_usage[] = "git-pack-objects [-q] [--non-empty] [--local] [--incremental] [--window=N] [--depth=N] {--stdout | base-name} < object-list";
   9
  10 struct object_entry {
  11         unsigned char sha1[20];
  12         unsigned long size;
  13         unsigned long offset;
  14         unsigned int depth;
  15         unsigned int hash;
  16         enum object_type type;
  17         unsigned long delta_size;
  18         struct object_entry *delta;
  19 };
  20
  21 static unsigned char object_list_sha1[20];
  22 static int non_empty = 0;
  23 static int local = 0;
  24 static int incremental = 0;
  25 static struct object_entry **sorted_by_sha, **sorted_by_type;
  26 static struct object_entry *objects = NULL;
  27 static int nr_objects = 0, nr_alloc = 0;
  28 static const char *base_name;
  29 static unsigned char pack_file_sha1[20];
  30 static int progress = 1;
  31
  32 static void *delta_against(void *buf, unsigned long size, struct object_entry *entry)
  33 {
  34         unsigned long othersize, delta_size;
  35         char type[10];
  36         void *otherbuf = read_sha1_file(entry->delta->sha1, type, &othersize);
  37         void *delta_buf;
  38
  39         if (!otherbuf)
  40                 die("unable to read %s", sha1_to_hex(entry->delta->sha1));
  41         delta_buf = diff_delta(otherbuf, othersize,
  42                                buf, size, &delta_size, 0);
  43         if (!delta_buf || delta_size != entry->delta_size)
  44                 die("delta size changed");
  45         free(buf);
  46         free(otherbuf);
  47         return delta_buf;
  48 }
  49
  50 /*
  51  * The per-object header is a pretty dense thing, which is
  52  *  - first byte: low four bits are "size", then three bits of "type",
  53  *    and the high bit is "size continues".
  54  *  - each byte afterwards: low seven bits are size continuation,
  55  *    with the high bit being "size continues"
  56  */
  57 static int encode_header(enum object_type type, unsigned long size, unsigned char *hdr)
  58 {
  59         int n = 1;
  60         unsigned char c;
  61
  62         if (type < OBJ_COMMIT || type > OBJ_DELTA)
  63                 die("bad type %d", type);
  64
  65         c = (type << 4) | (size & 15);
  66         size >>= 4;
  67         while (size) {
  68                 *hdr++ = c | 0x80;
  69                 c = size & 0x7f;
  70                 size >>= 7;
  71                 n++;
  72         }
  73         *hdr = c;
  74         return n;
  75 }
  76
  77 static unsigned long write_object(struct sha1file *f, struct object_entry *entry)
  78 {
  79         unsigned long size;
  80         char type[10];
  81         void *buf = read_sha1_file(entry->sha1, type, &size);
  82         unsigned char header[10];
  83         unsigned hdrlen, datalen;
  84         enum object_type obj_type;
  85
  86         if (!buf)
  87                 die("unable to read %s", sha1_to_hex(entry->sha1));
  88         if (size != entry->size)
  89                 die("object %s size inconsistency (%lu vs %lu)", sha1_to_hex(entry->sha1), size, entry->size);
  90
  91         /*
  92          * The object header is a byte of 'type' followed by zero or
  93          * more bytes of length.  For deltas, the 20 bytes of delta sha1
  94          * follows that.
  95          */
  96         obj_type = entry->type;
  97         if (entry->delta) {
  98                 buf = delta_against(buf, size, entry);
  99                 size = entry->delta_size;
 100                 obj_type = OBJ_DELTA;
 101         }
 102         hdrlen = encode_header(obj_type, size, header);
 103         sha1write(f, header, hdrlen);
 104         if (entry->delta) {
 105                 sha1write(f, entry->delta, 20);
 106                 hdrlen += 20;
 107         }
 108         datalen = sha1write_compressed(f, buf, size);
 109         free(buf);
 110         return hdrlen + datalen;
 111 }
 112
 113 static unsigned long write_one(struct sha1file *f,
 114                                struct object_entry *e,
 115                                unsigned long offset)
 116 {
 117         if (e->offset)
 118                 /* offset starts from header size and cannot be zero
 119                  * if it is written already.
 120                  */
 121                 return offset;
 122         e->offset = offset;
 123         offset += write_object(f, e);
 124         /* if we are deltified, write out its base object. */
 125         if (e->delta)
 126                 offset = write_one(f, e->delta, offset);
 127         return offset;
 128 }
 129
 130 static void write_pack_file(void)
 131 {
 132         int i;
 133         struct sha1file *f;
 134         unsigned long offset;
 135         unsigned long mb;
 136         struct pack_header hdr;
 137
 138         if (!base_name)
 139                 f = sha1fd(1, "<stdout>");
 140         else
 141                 f = sha1create("%s-%s.%s", base_name, sha1_to_hex(object_list_sha1), "pack");
 142         hdr.hdr_signature = htonl(PACK_SIGNATURE);
 143         hdr.hdr_version = htonl(PACK_VERSION);
 144         hdr.hdr_entries = htonl(nr_objects);
 145         sha1write(f, &hdr, sizeof(hdr));
 146         offset = sizeof(hdr);
 147         for (i = 0; i < nr_objects; i++)
 148                 offset = write_one(f, objects + i, offset);
 149
 150         sha1close(f, pack_file_sha1, 1);
 151         mb = offset >> 20;
 152         offset &= 0xfffff;
 153 }
 154
 155 static void write_index_file(void)
 156 {
 157         int i;
 158         struct sha1file *f = sha1create("%s-%s.%s", base_name, sha1_to_hex(object_list_sha1), "idx");
 159         struct object_entry **list = sorted_by_sha;
 160         struct object_entry **last = list + nr_objects;
 161         unsigned int array[256];
 162
 163         /*
 164          * Write the first-level table (the list is sorted,
 165          * but we use a 256-entry lookup to be able to avoid
 166          * having to do eight extra binary search iterations).
 167          */
 168         for (i = 0; i < 256; i++) {
 169                 struct object_entry **next = list;
 170                 while (next < last) {
 171                         struct object_entry *entry = *next;
 172                         if (entry->sha1[0] != i)
 173                                 break;
 174                         next++;
 175                 }
 176                 array[i] = htonl(next - sorted_by_sha);
 177                 list = next;
 178         }
 179         sha1write(f, array, 256 * sizeof(int));
 180
 181         /*
 182          * Write the actual SHA1 entries..
 183          */
 184         list = sorted_by_sha;
 185         for (i = 0; i < nr_objects; i++) {
 186                 struct object_entry *entry = *list++;
 187                 unsigned int offset = htonl(entry->offset);
 188                 sha1write(f, &offset, 4);
 189                 sha1write(f, entry->sha1, 20);
 190         }
 191         sha1write(f, pack_file_sha1, 20);
 192         sha1close(f, NULL, 1);
 193 }
 194
 195 static int add_object_entry(unsigned char *sha1, unsigned int hash)
 196 {
 197         unsigned int idx = nr_objects;
 198         struct object_entry *entry;
 199
 200         if (incremental || local) {
 201                 struct packed_git *p;
 202
 203                 for (p = packed_git; p; p = p->next) {
 204                         struct pack_entry e;
 205
 206                         if (find_pack_entry_one(sha1, &e, p)) {
 207                                 if (incremental)
 208                                         return 0;
 209                                 if (local && !p->pack_local)
 210                                         return 0;
 211                         }
 212                 }
 213         }
 214
 215         if (idx >= nr_alloc) {
 216                 unsigned int needed = (idx + 1024) * 3 / 2;
 217                 objects = xrealloc(objects, needed * sizeof(*entry));
 218                 nr_alloc = needed;
 219         }
 220         entry = objects + idx;
 221         memset(entry, 0, sizeof(*entry));
 222         memcpy(entry->sha1, sha1, 20);
 223         entry->hash = hash;
 224         nr_objects = idx+1;
 225         return 1;
 226 }
 227
 228 static void check_object(struct object_entry *entry)
 229 {
 230         char type[20];
 231
 232         if (!sha1_object_info(entry->sha1, type, &entry->size)) {
 233                 if (!strcmp(type, "commit")) {
 234                         entry->type = OBJ_COMMIT;
 235                 } else if (!strcmp(type, "tree")) {
 236                         entry->type = OBJ_TREE;
 237                 } else if (!strcmp(type, "blob")) {
 238                         entry->type = OBJ_BLOB;
 239                 } else if (!strcmp(type, "tag")) {
 240                         entry->type = OBJ_TAG;
 241                 } else
 242                         die("unable to pack object %s of type %s",
 243                             sha1_to_hex(entry->sha1), type);
 244         }
 245         else
 246                 die("unable to get type of object %s",
 247                     sha1_to_hex(entry->sha1));
 248 }
 249
 250 static void get_object_details(void)
 251 {
 252         int i;
 253         struct object_entry *entry = objects;
 254
 255         for (i = 0; i < nr_objects; i++)
 256                 check_object(entry++);
 257 }
 258
 259 typedef int (*entry_sort_t)(const struct object_entry *, const struct object_entry *);
 260
 261 static entry_sort_t current_sort;
 262
 263 static int sort_comparator(const void *_a, const void *_b)
 264 {
 265         struct object_entry *a = *(struct object_entry **)_a;
 266         struct object_entry *b = *(struct object_entry **)_b;
 267         return current_sort(a,b);
 268 }
 269
 270 static struct object_entry **create_sorted_list(entry_sort_t sort)
 271 {
 272         struct object_entry **list = xmalloc(nr_objects * sizeof(struct object_entry *));
 273         int i;
 274
 275         for (i = 0; i < nr_objects; i++)
 276                 list[i] = objects + i;
 277         current_sort = sort;
 278         qsort(list, nr_objects, sizeof(struct object_entry *), sort_comparator);
 279         return list;
 280 }
 281
 282 static int sha1_sort(const struct object_entry *a, const struct object_entry *b)
 283 {
 284         return memcmp(a->sha1, b->sha1, 20);
 285 }
 286
 287 static int type_size_sort(const struct object_entry *a, const struct object_entry *b)
 288 {
 289         if (a->type < b->type)
 290                 return -1;
 291         if (a->type > b->type)
 292                 return 1;
 293         if (a->hash < b->hash)
 294                 return -1;
 295         if (a->hash > b->hash)
 296                 return 1;
 297         if (a->size < b->size)
 298                 return -1;
 299         if (a->size > b->size)
 300                 return 1;
 301         return a < b ? -1 : (a > b);
 302 }
 303
 304 struct unpacked {
 305         struct object_entry *entry;
 306         void *data;
 307 };
 308
 309 /*
 310  * We search for deltas _backwards_ in a list sorted by type and
 311  * by size, so that we see progressively smaller and smaller files.
 312  * That's because we prefer deltas to be from the bigger file
 313  * to the smaller - deletes are potentially cheaper, but perhaps
 314  * more importantly, the bigger file is likely the more recent
 315  * one.
 316  */
 317 static int try_delta(struct unpacked *cur, struct unpacked *old, unsigned max_depth)
 318 {
 319         struct object_entry *cur_entry = cur->entry;
 320         struct object_entry *old_entry = old->entry;
 321         unsigned long size, oldsize, delta_size, sizediff;
 322         long max_size;
 323         void *delta_buf;
 324
 325         /* Don't bother doing diffs between different types */
 326         if (cur_entry->type != old_entry->type)
 327                 return -1;
 328
 329         size = cur_entry->size;
 330         if (size < 50)
 331                 return -1;
 332         oldsize = old_entry->size;
 333         sizediff = oldsize > size ? oldsize - size : size - oldsize;
 334         if (sizediff > size / 8)
 335                 return -1;
 336         if (old_entry->depth >= max_depth)
 337                 return 0;
 338
 339         /*
 340          * NOTE!
 341          *
 342          * We always delta from the bigger to the smaller, since that's
 343          * more space-efficient (deletes don't have to say _what_ they
 344          * delete).
 345          */
 346         max_size = size / 2 - 20;
 347         if (cur_entry->delta)
 348                 max_size = cur_entry->delta_size-1;
 349         if (sizediff >= max_size)
 350                 return -1;
 351         delta_buf = diff_delta(old->data, oldsize,
 352                                cur->data, size, &delta_size, max_size);
 353         if (!delta_buf)
 354                 return 0;
 355         cur_entry->delta = old_entry;
 356         cur_entry->delta_size = delta_size;
 357         cur_entry->depth = old_entry->depth + 1;
 358         free(delta_buf);
 359         return 0;
 360 }
 361
 362 static void find_deltas(struct object_entry **list, int window, int depth)
 363 {
 364         int i, idx;
 365         unsigned int array_size = window * sizeof(struct unpacked);
 366         struct unpacked *array = xmalloc(array_size);
 367         int eye_candy;
 368
 369         memset(array, 0, array_size);
 370         i = nr_objects;
 371         idx = 0;
 372         eye_candy = i - (nr_objects / 20);
 373
 374         while (--i >= 0) {
 375                 struct object_entry *entry = list[i];
 376                 struct unpacked *n = array + idx;
 377                 unsigned long size;
 378                 char type[10];
 379                 int j;
 380
 381                 if (progress && i <= eye_candy) {
 382                         eye_candy -= nr_objects / 20;
 383                         fputc('.', stderr);
 384                 }
 385                 free(n->data);
 386                 n->entry = entry;
 387                 n->data = read_sha1_file(entry->sha1, type, &size);
 388                 if (size != entry->size)
 389                         die("object %s inconsistent object length (%lu vs %lu)", sha1_to_hex(entry->sha1), size, entry->size);
 390                 j = window;
 391                 while (--j > 0) {
 392                         unsigned int other_idx = idx + j;
 393                         struct unpacked *m;
 394                         if (other_idx >= window)
 395                                 other_idx -= window;
 396                         m = array + other_idx;
 397                         if (!m->entry)
 398                                 break;
 399                         if (try_delta(n, m, depth) < 0)
 400                                 break;
 401                 }
 402                 idx++;
 403                 if (idx >= window)
 404                         idx = 0;
 405         }
 406
 407         for (i = 0; i < window; ++i)
 408                 free(array[i].data);
 409         free(array);
 410 }
 411
 412 static void prepare_pack(int window, int depth)
 413 {
 414         get_object_details();
 415
 416         if (progress)
 417                 fprintf(stderr, "Packing %d objects", nr_objects);
 418         sorted_by_type = create_sorted_list(type_size_sort);
 419         if (window && depth)
 420                 find_deltas(sorted_by_type, window+1, depth);
 421         if (progress)
 422                 fputc('\n', stderr);
 423         write_pack_file();
 424 }
 425
 426 static int reuse_cached_pack(unsigned char *sha1, int pack_to_stdout)
 427 {
 428         static const char cache[] = "pack-cache/pack-%s.%s";
 429         char *cached_pack, *cached_idx;
 430         int ifd, ofd, ifd_ix = -1;
 431
 432         cached_pack = git_path(cache, sha1_to_hex(sha1), "pack");
 433         ifd = open(cached_pack, O_RDONLY);
 434         if (ifd < 0)
 435                 return 0;
 436
 437         if (!pack_to_stdout) {
 438                 cached_idx = git_path(cache, sha1_to_hex(sha1), "idx");
 439                 ifd_ix = open(cached_idx, O_RDONLY);
 440                 if (ifd_ix < 0) {
 441                         close(ifd);
 442                         return 0;
 443                 }
 444         }
 445
 446         fprintf(stderr, "Reusing %d objects pack %s\n", nr_objects,
 447                 sha1_to_hex(sha1));
 448
 449         if (pack_to_stdout) {
 450                 if (copy_fd(ifd, 1))
 451                         exit(1);
 452                 close(ifd);
 453         }
 454         else {
 455                 char name[PATH_MAX];
 456                 snprintf(name, sizeof(name),
 457                          "%s-%s.%s", base_name, sha1_to_hex(sha1), "pack");
 458                 ofd = open(name, O_CREAT | O_EXCL | O_WRONLY, 0666);
 459                 if (ofd < 0)
 460                         die("unable to open %s (%s)", name, strerror(errno));
 461                 if (copy_fd(ifd, ofd))
 462                         exit(1);
 463                 close(ifd);
 464
 465                 snprintf(name, sizeof(name),
 466                          "%s-%s.%s", base_name, sha1_to_hex(sha1), "idx");
 467                 ofd = open(name, O_CREAT | O_EXCL | O_WRONLY, 0666);
 468                 if (ofd < 0)
 469                         die("unable to open %s (%s)", name, strerror(errno));
 470                 if (copy_fd(ifd_ix, ofd))
 471                         exit(1);
 472                 close(ifd_ix);
 473                 puts(sha1_to_hex(sha1));
 474         }
 475
 476         return 1;
 477 }
 478
 479 int main(int argc, char **argv)
 480 {
 481         SHA_CTX ctx;
 482         char line[PATH_MAX + 20];
 483         int window = 10, depth = 10, pack_to_stdout = 0;
 484         struct object_entry **list;
 485         int i;
 486         struct timeval prev_tv;
 487         int eye_candy = 0;
 488         int eye_candy_incr = 500;
 489
 490
 491         setup_git_directory();
 492
 493         for (i = 1; i < argc; i++) {
 494                 const char *arg = argv[i];
 495
 496                 if (*arg == '-') {
 497                         if (!strcmp("--non-empty", arg)) {
 498                                 non_empty = 1;
 499                                 continue;
 500                         }
 501                         if (!strcmp("--local", arg)) {
 502                                 local = 1;
 503                                 continue;
 504                         }
 505                         if (!strcmp("--incremental", arg)) {
 506                                 incremental = 1;
 507                                 continue;
 508                         }
 509                         if (!strncmp("--window=", arg, 9)) {
 510                                 char *end;
 511                                 window = strtoul(arg+9, &end, 0);
 512                                 if (!arg[9] || *end)
 513                                         usage(pack_usage);
 514                                 continue;
 515                         }
 516                         if (!strncmp("--depth=", arg, 8)) {
 517                                 char *end;
 518                                 depth = strtoul(arg+8, &end, 0);
 519                                 if (!arg[8] || *end)
 520                                         usage(pack_usage);
 521                                 continue;
 522                         }
 523                         if (!strcmp("-q", arg)) {
 524                                 progress = 0;
 525                                 continue;
 526                         }
 527                         if (!strcmp("--stdout", arg)) {
 528                                 pack_to_stdout = 1;
 529                                 continue;
 530                         }
 531                         usage(pack_usage);
 532                 }
 533                 if (base_name)
 534                         usage(pack_usage);
 535                 base_name = arg;
 536         }
 537
 538         if (pack_to_stdout != !base_name)
 539                 usage(pack_usage);
 540
 541         prepare_packed_git();
 542         if (progress) {
 543                 fprintf(stderr, "Generating pack...\n");
 544                 gettimeofday(&prev_tv, NULL);
 545         }
 546         while (fgets(line, sizeof(line), stdin) != NULL) {
 547                 unsigned int hash;
 548                 char *p;
 549                 unsigned char sha1[20];
 550
 551                 if (progress && (eye_candy <= nr_objects)) {
 552                         fprintf(stderr, "Counting objects...%d\r", nr_objects);
 553                         if (eye_candy && (50 <= eye_candy_incr)) {
 554                                 struct timeval tv;
 555                                 int time_diff;
 556                                 gettimeofday(&tv, NULL);
 557                                 time_diff = (tv.tv_sec - prev_tv.tv_sec);
 558                                 time_diff <<= 10;
 559                                 time_diff += (tv.tv_usec - prev_tv.tv_usec);
 560                                 if ((1 << 9) < time_diff)
 561                                         eye_candy_incr += 50;
 562                                 else if (50 < eye_candy_incr)
 563                                         eye_candy_incr -= 50;
 564                         }
 565                         eye_candy += eye_candy_incr;
 566                 }
 567                 if (get_sha1_hex(line, sha1))
 568                         die("expected sha1, got garbage:\n %s", line);
 569                 hash = 0;
 570                 p = line+40;
 571                 while (*p) {
 572                         unsigned char c = *p++;
 573                         if (isspace(c))
 574                                 continue;
 575                         hash = hash * 11 + c;
 576                 }
 577                 add_object_entry(sha1, hash);
 578         }
 579         if (progress)
 580                 fprintf(stderr, "Done counting %d objects.\n", nr_objects);
 581         if (non_empty && !nr_objects)
 582                 return 0;
 583
 584         sorted_by_sha = create_sorted_list(sha1_sort);
 585         SHA1_Init(&ctx);
 586         list = sorted_by_sha;
 587         for (i = 0; i < nr_objects; i++) {
 588                 struct object_entry *entry = *list++;
 589                 SHA1_Update(&ctx, entry->sha1, 20);
 590         }
 591         SHA1_Final(object_list_sha1, &ctx);
 592
 593         if (reuse_cached_pack(object_list_sha1, pack_to_stdout))
 594                 ;
 595         else {
 596                 prepare_pack(window, depth);
 597                 if (!pack_to_stdout) {
 598                         write_index_file();
 599                         puts(sha1_to_hex(object_list_sha1));
 600                 }
 601         }
 602         return 0;
 603 }