pack-write.c

   1 #include "cache.h"
   2 #include "pack.h"
   3 #include "csum-file.h"
   4
   5 void reset_pack_idx_option(struct pack_idx_option *opts)
   6 {
   7         memset(opts, 0, sizeof(*opts));
   8         opts->version = 2;
   9         opts->off32_limit = 0x7fffffff;
  10 }
  11
  12 static int sha1_compare(const void *_a, const void *_b)
  13 {
  14         struct pack_idx_entry *a = *(struct pack_idx_entry **)_a;
  15         struct pack_idx_entry *b = *(struct pack_idx_entry **)_b;
  16         return hashcmp(a->sha1, b->sha1);
  17 }
  18
  19 static int cmp_uint32(const void *a_, const void *b_)
  20 {
  21         uint32_t a = *((uint32_t *)a_);
  22         uint32_t b = *((uint32_t *)b_);
  23
  24         return (a < b) ? -1 : (a != b);
  25 }
  26
  27 static int need_large_offset(off_t offset, const struct pack_idx_option *opts)
  28 {
  29         uint32_t ofsval;
  30
  31         if ((offset >> 31) || (opts->off32_limit < offset))
  32                 return 1;
  33         if (!opts->anomaly_nr)
  34                 return 0;
  35         ofsval = offset;
  36         return !!bsearch(&ofsval, opts->anomaly, opts->anomaly_nr,
  37                          sizeof(ofsval), cmp_uint32);
  38 }
  39
  40 /*
  41  * On entry *sha1 contains the pack content SHA1 hash, on exit it is
  42  * the SHA1 hash of sorted object names. The objects array passed in
  43  * will be sorted by SHA1 on exit.
  44  */
  45 const char *write_idx_file(const char *index_name, struct pack_idx_entry **objects,
  46                            int nr_objects, const struct pack_idx_option *opts,
  47                            unsigned char *sha1)
  48 {
  49         struct sha1file *f;
  50         struct pack_idx_entry **sorted_by_sha, **list, **last;
  51         off_t last_obj_offset = 0;
  52         uint32_t array[256];
  53         int i, fd;
  54         git_SHA_CTX ctx;
  55         uint32_t index_version;
  56
  57         if (nr_objects) {
  58                 sorted_by_sha = objects;
  59                 list = sorted_by_sha;
  60                 last = sorted_by_sha + nr_objects;
  61                 for (i = 0; i < nr_objects; ++i) {
  62                         if (objects[i]->offset > last_obj_offset)
  63                                 last_obj_offset = objects[i]->offset;
  64                 }
  65                 qsort(sorted_by_sha, nr_objects, sizeof(sorted_by_sha[0]),
  66                       sha1_compare);
  67         }
  68         else
  69                 sorted_by_sha = list = last = NULL;
  70
  71         if (opts->flags & WRITE_IDX_VERIFY) {
  72                 assert(index_name);
  73                 f = sha1fd_check(index_name);
  74         } else {
  75                 if (!index_name) {
  76                         static char tmp_file[PATH_MAX];
  77                         fd = odb_mkstemp(tmp_file, sizeof(tmp_file), "pack/tmp_idx_XXXXXX");
  78                         index_name = xstrdup(tmp_file);
  79                 } else {
  80                         unlink(index_name);
  81                         fd = open(index_name, O_CREAT|O_EXCL|O_WRONLY, 0600);
  82                 }
  83                 if (fd < 0)
  84                         die_errno("unable to create '%s'", index_name);
  85                 f = sha1fd(fd, index_name);
  86         }
  87
  88         /* if last object's offset is >= 2^31 we should use index V2 */
  89         index_version = need_large_offset(last_obj_offset, opts) ? 2 : opts->version;
  90
  91         /* index versions 2 and above need a header */
  92         if (index_version >= 2) {
  93                 struct pack_idx_header hdr;
  94                 hdr.idx_signature = htonl(PACK_IDX_SIGNATURE);
  95                 hdr.idx_version = htonl(index_version);
  96                 sha1write(f, &hdr, sizeof(hdr));
  97         }
  98
  99         /*
 100          * Write the first-level table (the list is sorted,
 101          * but we use a 256-entry lookup to be able to avoid
 102          * having to do eight extra binary search iterations).
 103          */
 104         for (i = 0; i < 256; i++) {
 105                 struct pack_idx_entry **next = list;
 106                 while (next < last) {
 107                         struct pack_idx_entry *obj = *next;
 108                         if (obj->sha1[0] != i)
 109                                 break;
 110                         next++;
 111                 }
 112                 array[i] = htonl(next - sorted_by_sha);
 113                 list = next;
 114         }
 115         sha1write(f, array, 256 * 4);
 116
 117         /* compute the SHA1 hash of sorted object names. */
 118         git_SHA1_Init(&ctx);
 119
 120         /*
 121          * Write the actual SHA1 entries..
 122          */
 123         list = sorted_by_sha;
 124         for (i = 0; i < nr_objects; i++) {
 125                 struct pack_idx_entry *obj = *list++;
 126                 if (index_version < 2) {
 127                         uint32_t offset = htonl(obj->offset);
 128                         sha1write(f, &offset, 4);
 129                 }
 130                 sha1write(f, obj->sha1, 20);
 131                 git_SHA1_Update(&ctx, obj->sha1, 20);
 132                 if ((opts->flags & WRITE_IDX_STRICT) &&
 133                     (i && !hashcmp(list[-2]->sha1, obj->sha1)))
 134                         die("The same object %s appears twice in the pack",
 135                             sha1_to_hex(obj->sha1));
 136         }
 137
 138         if (index_version >= 2) {
 139                 unsigned int nr_large_offset = 0;
 140
 141                 /* write the crc32 table */
 142                 list = sorted_by_sha;
 143                 for (i = 0; i < nr_objects; i++) {
 144                         struct pack_idx_entry *obj = *list++;
 145                         uint32_t crc32_val = htonl(obj->crc32);
 146                         sha1write(f, &crc32_val, 4);
 147                 }
 148
 149                 /* write the 32-bit offset table */
 150                 list = sorted_by_sha;
 151                 for (i = 0; i < nr_objects; i++) {
 152                         struct pack_idx_entry *obj = *list++;
 153                         uint32_t offset;
 154
 155                         offset = (need_large_offset(obj->offset, opts)
 156                                   ? (0x80000000 | nr_large_offset++)
 157                                   : obj->offset);
 158                         offset = htonl(offset);
 159                         sha1write(f, &offset, 4);
 160                 }
 161
 162                 /* write the large offset table */
 163                 list = sorted_by_sha;
 164                 while (nr_large_offset) {
 165                         struct pack_idx_entry *obj = *list++;
 166                         uint64_t offset = obj->offset;
 167                         uint32_t split[2];
 168
 169                         if (!need_large_offset(offset, opts))
 170                                 continue;
 171                         split[0] = htonl(offset >> 32);
 172                         split[1] = htonl(offset & 0xffffffff);
 173                         sha1write(f, split, 8);
 174                         nr_large_offset--;
 175                 }
 176         }
 177
 178         sha1write(f, sha1, 20);
 179         sha1close(f, NULL, ((opts->flags & WRITE_IDX_VERIFY)
 180                             ? CSUM_CLOSE : CSUM_FSYNC));
 181         git_SHA1_Final(sha1, &ctx);
 182         return index_name;
 183 }
 184
 185 off_t write_pack_header(struct sha1file *f, uint32_t nr_entries)
 186 {
 187         struct pack_header hdr;
 188
 189         hdr.hdr_signature = htonl(PACK_SIGNATURE);
 190         hdr.hdr_version = htonl(PACK_VERSION);
 191         hdr.hdr_entries = htonl(nr_entries);
 192         if (sha1write(f, &hdr, sizeof(hdr)))
 193                 return 0;
 194         return sizeof(hdr);
 195 }
 196
 197 /*
 198  * Update pack header with object_count and compute new SHA1 for pack data
 199  * associated to pack_fd, and write that SHA1 at the end.  That new SHA1
 200  * is also returned in new_pack_sha1.
 201  *
 202  * If partial_pack_sha1 is non null, then the SHA1 of the existing pack
 203  * (without the header update) is computed and validated against the
 204  * one provided in partial_pack_sha1.  The validation is performed at
 205  * partial_pack_offset bytes in the pack file.  The SHA1 of the remaining
 206  * data (i.e. from partial_pack_offset to the end) is then computed and
 207  * returned in partial_pack_sha1.
 208  *
 209  * Note that new_pack_sha1 is updated last, so both new_pack_sha1 and
 210  * partial_pack_sha1 can refer to the same buffer if the caller is not
 211  * interested in the resulting SHA1 of pack data above partial_pack_offset.
 212  */
 213 void fixup_pack_header_footer(int pack_fd,
 214                          unsigned char *new_pack_sha1,
 215                          const char *pack_name,
 216                          uint32_t object_count,
 217                          unsigned char *partial_pack_sha1,
 218                          off_t partial_pack_offset)
 219 {
 220         int aligned_sz, buf_sz = 8 * 1024;
 221         git_SHA_CTX old_sha1_ctx, new_sha1_ctx;
 222         struct pack_header hdr;
 223         char *buf;
 224
 225         git_SHA1_Init(&old_sha1_ctx);
 226         git_SHA1_Init(&new_sha1_ctx);
 227
 228         if (lseek(pack_fd, 0, SEEK_SET) != 0)
 229                 die_errno("Failed seeking to start of '%s'", pack_name);
 230         if (read_in_full(pack_fd, &hdr, sizeof(hdr)) != sizeof(hdr))
 231                 die_errno("Unable to reread header of '%s'", pack_name);
 232         if (lseek(pack_fd, 0, SEEK_SET) != 0)
 233                 die_errno("Failed seeking to start of '%s'", pack_name);
 234         git_SHA1_Update(&old_sha1_ctx, &hdr, sizeof(hdr));
 235         hdr.hdr_entries = htonl(object_count);
 236         git_SHA1_Update(&new_sha1_ctx, &hdr, sizeof(hdr));
 237         write_or_die(pack_fd, &hdr, sizeof(hdr));
 238         partial_pack_offset -= sizeof(hdr);
 239
 240         buf = xmalloc(buf_sz);
 241         aligned_sz = buf_sz - sizeof(hdr);
 242         for (;;) {
 243                 ssize_t m, n;
 244                 m = (partial_pack_sha1 && partial_pack_offset < aligned_sz) ?
 245                         partial_pack_offset : aligned_sz;
 246                 n = xread(pack_fd, buf, m);
 247                 if (!n)
 248                         break;
 249                 if (n < 0)
 250                         die_errno("Failed to checksum '%s'", pack_name);
 251                 git_SHA1_Update(&new_sha1_ctx, buf, n);
 252
 253                 aligned_sz -= n;
 254                 if (!aligned_sz)
 255                         aligned_sz = buf_sz;
 256
 257                 if (!partial_pack_sha1)
 258                         continue;
 259
 260                 git_SHA1_Update(&old_sha1_ctx, buf, n);
 261                 partial_pack_offset -= n;
 262                 if (partial_pack_offset == 0) {
 263                         unsigned char sha1[20];
 264                         git_SHA1_Final(sha1, &old_sha1_ctx);
 265                         if (hashcmp(sha1, partial_pack_sha1) != 0)
 266                                 die("Unexpected checksum for %s "
 267                                     "(disk corruption?)", pack_name);
 268                         /*
 269                          * Now let's compute the SHA1 of the remainder of the
 270                          * pack, which also means making partial_pack_offset
 271                          * big enough not to matter anymore.
 272                          */
 273                         git_SHA1_Init(&old_sha1_ctx);
 274                         partial_pack_offset = ~partial_pack_offset;
 275                         partial_pack_offset -= MSB(partial_pack_offset, 1);
 276                 }
 277         }
 278         free(buf);
 279
 280         if (partial_pack_sha1)
 281                 git_SHA1_Final(partial_pack_sha1, &old_sha1_ctx);
 282         git_SHA1_Final(new_pack_sha1, &new_sha1_ctx);
 283         write_or_die(pack_fd, new_pack_sha1, 20);
 284         fsync_or_die(pack_fd, pack_name);
 285 }
 286
 287 char *index_pack_lockfile(int ip_out)
 288 {
 289         char packname[46];
 290
 291         /*
 292          * The first thing we expect from index-pack's output
 293          * is "pack\t%40s\n" or "keep\t%40s\n" (46 bytes) where
 294          * %40s is the newly created pack SHA1 name.  In the "keep"
 295          * case, we need it to remove the corresponding .keep file
 296          * later on.  If we don't get that then tough luck with it.
 297          */
 298         if (read_in_full(ip_out, packname, 46) == 46 && packname[45] == '\n' &&
 299             memcmp(packname, "keep\t", 5) == 0) {
 300                 char path[PATH_MAX];
 301                 packname[45] = 0;
 302                 snprintf(path, sizeof(path), "%s/pack/pack-%s.keep",
 303                          get_object_directory(), packname + 5);
 304                 return xstrdup(path);
 305         }
 306         return NULL;
 307 }
 308
 309 /*
 310  * The per-object header is a pretty dense thing, which is
 311  *  - first byte: low four bits are "size", then three bits of "type",
 312  *    and the high bit is "size continues".
 313  *  - each byte afterwards: low seven bits are size continuation,
 314  *    with the high bit being "size continues"
 315  */
 316 int encode_in_pack_object_header(enum object_type type, uintmax_t size, unsigned char *hdr)
 317 {
 318         int n = 1;
 319         unsigned char c;
 320
 321         if (type < OBJ_COMMIT || type > OBJ_REF_DELTA)
 322                 die("bad type %d", type);
 323
 324         c = (type << 4) | (size & 15);
 325         size >>= 4;
 326         while (size) {
 327                 *hdr++ = c | 0x80;
 328                 c = size & 0x7f;
 329                 size >>= 7;
 330                 n++;
 331         }
 332         *hdr = c;
 333         return n;
 334 }
 335
 336 struct sha1file *create_tmp_packfile(char **pack_tmp_name)
 337 {
 338         char tmpname[PATH_MAX];
 339         int fd;
 340
 341         fd = odb_mkstemp(tmpname, sizeof(tmpname), "pack/tmp_pack_XXXXXX");
 342         *pack_tmp_name = xstrdup(tmpname);
 343         return sha1fd(fd, *pack_tmp_name);
 344 }
 345
 346 void finish_tmp_packfile(char *name_buffer,
 347                          const char *pack_tmp_name,
 348                          struct pack_idx_entry **written_list,
 349                          uint32_t nr_written,
 350                          struct pack_idx_option *pack_idx_opts,
 351                          unsigned char sha1[])
 352 {
 353         const char *idx_tmp_name;
 354         char *end_of_name_prefix = strrchr(name_buffer, 0);
 355
 356         if (adjust_shared_perm(pack_tmp_name))
 357                 die_errno("unable to make temporary pack file readable");
 358
 359         idx_tmp_name = write_idx_file(NULL, written_list, nr_written,
 360                                       pack_idx_opts, sha1);
 361         if (adjust_shared_perm(idx_tmp_name))
 362                 die_errno("unable to make temporary index file readable");
 363
 364         sprintf(end_of_name_prefix, "%s.pack", sha1_to_hex(sha1));
 365         free_pack_by_name(name_buffer);
 366
 367         if (rename(pack_tmp_name, name_buffer))
 368                 die_errno("unable to rename temporary pack file");
 369
 370         sprintf(end_of_name_prefix, "%s.idx", sha1_to_hex(sha1));
 371         if (rename(idx_tmp_name, name_buffer))
 372                 die_errno("unable to rename temporary index file");
 373
 374         free((void *)idx_tmp_name);
 375 }