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

   1 #include "cache.h"
   2 #include "delta.h"
   3 #include "pack.h"
   4 #include "csum-file.h"
   5 #include "blob.h"
   6 #include "commit.h"
   7 #include "tag.h"
   8 #include "tree.h"
   9
  10 static const char index_pack_usage[] =
  11 "git-index-pack [-o index-file] pack-file";
  12
  13 struct object_entry
  14 {
  15         unsigned long offset;
  16         enum object_type type;
  17         enum object_type real_type;
  18         unsigned char sha1[20];
  19 };
  20
  21 struct delta_entry
  22 {
  23         struct object_entry *obj;
  24         unsigned char base_sha1[20];
  25 };
  26
  27 static const char *pack_name;
  28 static unsigned char *pack_base;
  29 static unsigned long pack_size;
  30 static struct object_entry *objects;
  31 static struct delta_entry *deltas;
  32 static int nr_objects;
  33 static int nr_deltas;
  34
  35 static void open_pack_file(void)
  36 {
  37         int fd;
  38         struct stat st;
  39
  40         fd = open(pack_name, O_RDONLY);
  41         if (fd < 0)
  42                 die("cannot open packfile '%s': %s", pack_name,
  43                     strerror(errno));
  44         if (fstat(fd, &st)) {
  45                 int err = errno;
  46                 close(fd);
  47                 die("cannot fstat packfile '%s': %s", pack_name,
  48                     strerror(err));
  49         }
  50         pack_size = st.st_size;
  51         pack_base = mmap(NULL, pack_size, PROT_READ, MAP_PRIVATE, fd, 0);
  52         if (pack_base == MAP_FAILED) {
  53                 int err = errno;
  54                 close(fd);
  55                 die("cannot mmap packfile '%s': %s", pack_name,
  56                     strerror(err));
  57         }
  58         close(fd);
  59 }
  60
  61 static void parse_pack_header(void)
  62 {
  63         const struct pack_header *hdr;
  64         unsigned char sha1[20];
  65         SHA_CTX ctx;
  66
  67         /* Ensure there are enough bytes for the header and final SHA1 */
  68         if (pack_size < sizeof(struct pack_header) + 20)
  69                 die("packfile '%s' is too small", pack_name);
  70
  71         /* Header consistency check */
  72         hdr = (void *)pack_base;
  73         if (hdr->hdr_signature != htonl(PACK_SIGNATURE))
  74                 die("packfile '%s' signature mismatch", pack_name);
  75         if (!pack_version_ok(hdr->hdr_version))
  76                 die("packfile '%s' version %d unsupported",
  77                     pack_name, ntohl(hdr->hdr_version));
  78
  79         nr_objects = ntohl(hdr->hdr_entries);
  80
  81         /* Check packfile integrity */
  82         SHA1_Init(&ctx);
  83         SHA1_Update(&ctx, pack_base, pack_size - 20);
  84         SHA1_Final(sha1, &ctx);
  85         if (memcmp(sha1, pack_base + pack_size - 20, 20))
  86                 die("packfile '%s' SHA1 mismatch", pack_name);
  87 }
  88
  89 static void bad_object(unsigned long offset, const char *format,
  90                        ...) NORETURN __attribute__((format (printf, 2, 3)));
  91
  92 static void bad_object(unsigned long offset, const char *format, ...)
  93 {
  94         va_list params;
  95         char buf[1024];
  96
  97         va_start(params, format);
  98         vsnprintf(buf, sizeof(buf), format, params);
  99         va_end(params);
 100         die("packfile '%s': bad object at offset %lu: %s",
 101             pack_name, offset, buf);
 102 }
 103
 104 static void *unpack_entry_data(unsigned long offset,
 105                                unsigned long *current_pos, unsigned long size)
 106 {
 107         unsigned long pack_limit = pack_size - 20;
 108         unsigned long pos = *current_pos;
 109         z_stream stream;
 110         void *buf = xmalloc(size);
 111
 112         memset(&stream, 0, sizeof(stream));
 113         stream.next_out = buf;
 114         stream.avail_out = size;
 115         stream.next_in = pack_base + pos;
 116         stream.avail_in = pack_limit - pos;
 117         inflateInit(&stream);
 118
 119         for (;;) {
 120                 int ret = inflate(&stream, 0);
 121                 if (ret == Z_STREAM_END)
 122                         break;
 123                 if (ret != Z_OK)
 124                         bad_object(offset, "inflate returned %d", ret);
 125         }
 126         inflateEnd(&stream);
 127         if (stream.total_out != size)
 128                 bad_object(offset, "size mismatch (expected %lu, got %lu)",
 129                            size, stream.total_out);
 130         *current_pos = pack_limit - stream.avail_in;
 131         return buf;
 132 }
 133
 134 static void *unpack_raw_entry(unsigned long offset,
 135                               enum object_type *obj_type,
 136                               unsigned long *obj_size,
 137                               unsigned char *delta_base,
 138                               unsigned long *next_obj_offset)
 139 {
 140         unsigned long pack_limit = pack_size - 20;
 141         unsigned long pos = offset;
 142         unsigned char c;
 143         unsigned long size;
 144         unsigned shift;
 145         enum object_type type;
 146         void *data;
 147
 148         c = pack_base[pos++];
 149         type = (c >> 4) & 7;
 150         size = (c & 15);
 151         shift = 4;
 152         while (c & 0x80) {
 153                 if (pos >= pack_limit)
 154                         bad_object(offset, "object extends past end of pack");
 155                 c = pack_base[pos++];
 156                 size += (c & 0x7fUL) << shift;
 157                 shift += 7;
 158         }
 159
 160         switch (type) {
 161         case OBJ_DELTA:
 162                 if (pos + 20 >= pack_limit)
 163                         bad_object(offset, "object extends past end of pack");
 164                 memcpy(delta_base, pack_base + pos, 20);
 165                 pos += 20;
 166                 /* fallthru */
 167         case OBJ_COMMIT:
 168         case OBJ_TREE:
 169         case OBJ_BLOB:
 170         case OBJ_TAG:
 171                 data = unpack_entry_data(offset, &pos, size);
 172                 break;
 173         default:
 174                 bad_object(offset, "bad object type %d", type);
 175         }
 176
 177         *obj_type = type;
 178         *obj_size = size;
 179         *next_obj_offset = pos;
 180         return data;
 181 }
 182
 183 static int find_delta(const unsigned char *base_sha1)
 184 {
 185         int first = 0, last = nr_deltas;
 186
 187         while (first < last) {
 188                 int next = (first + last) / 2;
 189                 struct delta_entry *delta = &deltas[next];
 190                 int cmp;
 191
 192                 cmp = memcmp(base_sha1, delta->base_sha1, 20);
 193                 if (!cmp)
 194                         return next;
 195                 if (cmp < 0) {
 196                         last = next;
 197                         continue;
 198                 }
 199                 first = next+1;
 200         }
 201         return -first-1;
 202 }
 203
 204 static int find_deltas_based_on_sha1(const unsigned char *base_sha1,
 205                                      int *first_index, int *last_index)
 206 {
 207         int first = find_delta(base_sha1);
 208         int last = first;
 209         int end = nr_deltas - 1;
 210
 211         if (first < 0)
 212                 return -1;
 213         while (first > 0 && !memcmp(deltas[first-1].base_sha1, base_sha1, 20))
 214                 --first;
 215         while (last < end && !memcmp(deltas[last+1].base_sha1, base_sha1, 20))
 216                 ++last;
 217         *first_index = first;
 218         *last_index = last;
 219         return 0;
 220 }
 221
 222 static void sha1_object(const void *data, unsigned long size,
 223                         enum object_type type, unsigned char *sha1)
 224 {
 225         SHA_CTX ctx;
 226         char header[50];
 227         int header_size;
 228         const char *type_str;
 229
 230         switch (type) {
 231         case OBJ_COMMIT: type_str = commit_type; break;
 232         case OBJ_TREE:   type_str = tree_type; break;
 233         case OBJ_BLOB:   type_str = blob_type; break;
 234         case OBJ_TAG:    type_str = tag_type; break;
 235         default:
 236                 die("bad type %d", type);
 237         }
 238
 239         header_size = sprintf(header, "%s %lu", type_str, size) + 1;
 240
 241         SHA1_Init(&ctx);
 242         SHA1_Update(&ctx, header, header_size);
 243         SHA1_Update(&ctx, data, size);
 244         SHA1_Final(sha1, &ctx);
 245 }
 246
 247 static void resolve_delta(struct delta_entry *delta, void *base_data,
 248                           unsigned long base_size, enum object_type type)
 249 {
 250         struct object_entry *obj = delta->obj;
 251         void *delta_data;
 252         unsigned long delta_size;
 253         void *result;
 254         unsigned long result_size;
 255         enum object_type delta_type;
 256         unsigned char base_sha1[20];
 257         unsigned long next_obj_offset;
 258         int j, first, last;
 259
 260         obj->real_type = type;
 261         delta_data = unpack_raw_entry(obj->offset, &delta_type,
 262                                       &delta_size, base_sha1,
 263                                       &next_obj_offset);
 264         result = patch_delta(base_data, base_size, delta_data, delta_size,
 265                              &result_size);
 266         free(delta_data);
 267         if (!result)
 268                 bad_object(obj->offset, "failed to apply delta");
 269         sha1_object(result, result_size, type, obj->sha1);
 270         if (!find_deltas_based_on_sha1(obj->sha1, &first, &last)) {
 271                 for (j = first; j <= last; j++)
 272                         resolve_delta(&deltas[j], result, result_size, type);
 273         }
 274         free(result);
 275 }
 276
 277 static int compare_delta_entry(const void *a, const void *b)
 278 {
 279         const struct delta_entry *delta_a = a;
 280         const struct delta_entry *delta_b = b;
 281         return memcmp(delta_a->base_sha1, delta_b->base_sha1, 20);
 282 }
 283
 284 static void parse_pack_objects(void)
 285 {
 286         int i;
 287         unsigned long offset = sizeof(struct pack_header);
 288         unsigned char base_sha1[20];
 289         void *data;
 290         unsigned long data_size;
 291
 292         /*
 293          * First pass:
 294          * - find locations of all objects;
 295          * - calculate SHA1 of all non-delta objects;
 296          * - remember base SHA1 for all deltas.
 297          */
 298         for (i = 0; i < nr_objects; i++) {
 299                 struct object_entry *obj = &objects[i];
 300                 obj->offset = offset;
 301                 data = unpack_raw_entry(offset, &obj->type, &data_size,
 302                                         base_sha1, &offset);
 303                 obj->real_type = obj->type;
 304                 if (obj->type == OBJ_DELTA) {
 305                         struct delta_entry *delta = &deltas[nr_deltas++];
 306                         delta->obj = obj;
 307                         memcpy(delta->base_sha1, base_sha1, 20);
 308                 } else
 309                         sha1_object(data, data_size, obj->type, obj->sha1);
 310                 free(data);
 311         }
 312         if (offset != pack_size - 20)
 313                 die("packfile '%s' has junk at the end", pack_name);
 314
 315         /* Sort deltas by base SHA1 for fast searching */
 316         qsort(deltas, nr_deltas, sizeof(struct delta_entry),
 317               compare_delta_entry);
 318
 319         /*
 320          * Second pass:
 321          * - for all non-delta objects, look if it is used as a base for
 322          *   deltas;
 323          * - if used as a base, uncompress the object and apply all deltas,
 324          *   recursively checking if the resulting object is used as a base
 325          *   for some more deltas.
 326          */
 327         for (i = 0; i < nr_objects; i++) {
 328                 struct object_entry *obj = &objects[i];
 329                 int j, first, last;
 330
 331                 if (obj->type == OBJ_DELTA)
 332                         continue;
 333                 if (find_deltas_based_on_sha1(obj->sha1, &first, &last))
 334                         continue;
 335                 data = unpack_raw_entry(obj->offset, &obj->type, &data_size,
 336                                         base_sha1, &offset);
 337                 for (j = first; j <= last; j++)
 338                         resolve_delta(&deltas[j], data, data_size, obj->type);
 339                 free(data);
 340         }
 341
 342         /* Check for unresolved deltas */
 343         for (i = 0; i < nr_deltas; i++) {
 344                 if (deltas[i].obj->real_type == OBJ_DELTA)
 345                         die("packfile '%s' has unresolved deltas",  pack_name);
 346         }
 347 }
 348
 349 static int sha1_compare(const void *_a, const void *_b)
 350 {
 351         struct object_entry *a = *(struct object_entry **)_a;
 352         struct object_entry *b = *(struct object_entry **)_b;
 353         return memcmp(a->sha1, b->sha1, 20);
 354 }
 355
 356 static void write_index_file(const char *index_name, unsigned char *sha1)
 357 {
 358         struct sha1file *f;
 359         struct object_entry **sorted_by_sha, **list, **last;
 360         unsigned int array[256];
 361         int i;
 362         SHA_CTX ctx;
 363
 364         if (nr_objects) {
 365                 sorted_by_sha =
 366                         xcalloc(nr_objects, sizeof(struct object_entry *));
 367                 list = sorted_by_sha;
 368                 last = sorted_by_sha + nr_objects;
 369                 for (i = 0; i < nr_objects; ++i)
 370                         sorted_by_sha[i] = &objects[i];
 371                 qsort(sorted_by_sha, nr_objects, sizeof(sorted_by_sha[0]),
 372                       sha1_compare);
 373
 374         }
 375         else
 376                 sorted_by_sha = list = last = NULL;
 377
 378         unlink(index_name);
 379         f = sha1create("%s", index_name);
 380
 381         /*
 382          * Write the first-level table (the list is sorted,
 383          * but we use a 256-entry lookup to be able to avoid
 384          * having to do eight extra binary search iterations).
 385          */
 386         for (i = 0; i < 256; i++) {
 387                 struct object_entry **next = list;
 388                 while (next < last) {
 389                         struct object_entry *obj = *next;
 390                         if (obj->sha1[0] != i)
 391                                 break;
 392                         next++;
 393                 }
 394                 array[i] = htonl(next - sorted_by_sha);
 395                 list = next;
 396         }
 397         sha1write(f, array, 256 * sizeof(int));
 398
 399         /* recompute the SHA1 hash of sorted object names.
 400          * currently pack-objects does not do this, but that
 401          * can be fixed.
 402          */
 403         SHA1_Init(&ctx);
 404         /*
 405          * Write the actual SHA1 entries..
 406          */
 407         list = sorted_by_sha;
 408         for (i = 0; i < nr_objects; i++) {
 409                 struct object_entry *obj = *list++;
 410                 unsigned int offset = htonl(obj->offset);
 411                 sha1write(f, &offset, 4);
 412                 sha1write(f, obj->sha1, 20);
 413                 SHA1_Update(&ctx, obj->sha1, 20);
 414         }
 415         sha1write(f, pack_base + pack_size - 20, 20);
 416         sha1close(f, NULL, 1);
 417         free(sorted_by_sha);
 418         SHA1_Final(sha1, &ctx);
 419 }
 420
 421 int main(int argc, char **argv)
 422 {
 423         int i;
 424         char *index_name = NULL;
 425         char *index_name_buf = NULL;
 426         unsigned char sha1[20];
 427
 428         for (i = 1; i < argc; i++) {
 429                 const char *arg = argv[i];
 430
 431                 if (*arg == '-') {
 432                         if (!strcmp(arg, "-o")) {
 433                                 if (index_name || (i+1) >= argc)
 434                                         usage(index_pack_usage);
 435                                 index_name = argv[++i];
 436                         } else
 437                                 usage(index_pack_usage);
 438                         continue;
 439                 }
 440
 441                 if (pack_name)
 442                         usage(index_pack_usage);
 443                 pack_name = arg;
 444         }
 445
 446         if (!pack_name)
 447                 usage(index_pack_usage);
 448         if (!index_name) {
 449                 int len = strlen(pack_name);
 450                 if (!has_extension(pack_name, ".pack"))
 451                         die("packfile name '%s' does not end with '.pack'",
 452                             pack_name);
 453                 index_name_buf = xmalloc(len);
 454                 memcpy(index_name_buf, pack_name, len - 5);
 455                 strcpy(index_name_buf + len - 5, ".idx");
 456                 index_name = index_name_buf;
 457         }
 458
 459         open_pack_file();
 460         parse_pack_header();
 461         objects = xcalloc(nr_objects, sizeof(struct object_entry));
 462         deltas = xcalloc(nr_objects, sizeof(struct delta_entry));
 463         parse_pack_objects();
 464         free(deltas);
 465         write_index_file(index_name, sha1);
 466         free(objects);
 467         free(index_name_buf);
 468
 469         printf("%s\n", sha1_to_hex(sha1));
 470
 471         return 0;
 472 }