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