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 tmpfile[PATH_MAX];
  77                         fd = odb_mkstemp(tmpfile, sizeof(tmpfile), "pack/tmp_idx_XXXXXX");
  78                         index_name = xstrdup(tmpfile);
  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         }
 133
 134         if (index_version >= 2) {
 135                 unsigned int nr_large_offset = 0;
 136
 137                 /* write the crc32 table */
 138                 list = sorted_by_sha;
 139                 for (i = 0; i < nr_objects; i++) {
 140                         struct pack_idx_entry *obj = *list++;
 141                         uint32_t crc32_val = htonl(obj->crc32);
 142                         sha1write(f, &crc32_val, 4);
 143                 }
 144
 145                 /* write the 32-bit offset table */
 146                 list = sorted_by_sha;
 147                 for (i = 0; i < nr_objects; i++) {
 148                         struct pack_idx_entry *obj = *list++;
 149                         uint32_t offset;
 150
 151                         offset = (need_large_offset(obj->offset, opts)
 152                                   ? (0x80000000 | nr_large_offset++)
 153                                   : obj->offset);
 154                         offset = htonl(offset);
 155                         sha1write(f, &offset, 4);
 156                 }
 157
 158                 /* write the large offset table */
 159                 list = sorted_by_sha;
 160                 while (nr_large_offset) {
 161                         struct pack_idx_entry *obj = *list++;
 162                         uint64_t offset = obj->offset;
 163                         uint32_t split[2];
 164
 165                         if (!need_large_offset(offset, opts))
 166                                 continue;
 167                         split[0] = htonl(offset >> 32);
 168                         split[1] = htonl(offset & 0xffffffff);
 169                         sha1write(f, split, 8);
 170                         nr_large_offset--;
 171                 }
 172         }
 173
 174         sha1write(f, sha1, 20);
 175         sha1close(f, NULL, ((opts->flags & WRITE_IDX_VERIFY)
 176                             ? CSUM_CLOSE : CSUM_FSYNC));
 177         git_SHA1_Final(sha1, &ctx);
 178         return index_name;
 179 }
 180
 181 off_t write_pack_header(struct sha1file *f, uint32_t nr_entries)
 182 {
 183         struct pack_header hdr;
 184
 185         hdr.hdr_signature = htonl(PACK_SIGNATURE);
 186         hdr.hdr_version = htonl(PACK_VERSION);
 187         hdr.hdr_entries = htonl(nr_entries);
 188         if (sha1write(f, &hdr, sizeof(hdr)))
 189                 return 0;
 190         return sizeof(hdr);
 191 }
 192
 193 /*
 194  * Update pack header with object_count and compute new SHA1 for pack data
 195  * associated to pack_fd, and write that SHA1 at the end.  That new SHA1
 196  * is also returned in new_pack_sha1.
 197  *
 198  * If partial_pack_sha1 is non null, then the SHA1 of the existing pack
 199  * (without the header update) is computed and validated against the
 200  * one provided in partial_pack_sha1.  The validation is performed at
 201  * partial_pack_offset bytes in the pack file.  The SHA1 of the remaining
 202  * data (i.e. from partial_pack_offset to the end) is then computed and
 203  * returned in partial_pack_sha1.
 204  *
 205  * Note that new_pack_sha1 is updated last, so both new_pack_sha1 and
 206  * partial_pack_sha1 can refer to the same buffer if the caller is not
 207  * interested in the resulting SHA1 of pack data above partial_pack_offset.
 208  */
 209 void fixup_pack_header_footer(int pack_fd,
 210                          unsigned char *new_pack_sha1,
 211                          const char *pack_name,
 212                          uint32_t object_count,
 213                          unsigned char *partial_pack_sha1,
 214                          off_t partial_pack_offset)
 215 {
 216         int aligned_sz, buf_sz = 8 * 1024;
 217         git_SHA_CTX old_sha1_ctx, new_sha1_ctx;
 218         struct pack_header hdr;
 219         char *buf;
 220
 221         git_SHA1_Init(&old_sha1_ctx);
 222         git_SHA1_Init(&new_sha1_ctx);
 223
 224         if (lseek(pack_fd, 0, SEEK_SET) != 0)
 225                 die_errno("Failed seeking to start of '%s'", pack_name);
 226         if (read_in_full(pack_fd, &hdr, sizeof(hdr)) != sizeof(hdr))
 227                 die_errno("Unable to reread header of '%s'", pack_name);
 228         if (lseek(pack_fd, 0, SEEK_SET) != 0)
 229                 die_errno("Failed seeking to start of '%s'", pack_name);
 230         git_SHA1_Update(&old_sha1_ctx, &hdr, sizeof(hdr));
 231         hdr.hdr_entries = htonl(object_count);
 232         git_SHA1_Update(&new_sha1_ctx, &hdr, sizeof(hdr));
 233         write_or_die(pack_fd, &hdr, sizeof(hdr));
 234         partial_pack_offset -= sizeof(hdr);
 235
 236         buf = xmalloc(buf_sz);
 237         aligned_sz = buf_sz - sizeof(hdr);
 238         for (;;) {
 239                 ssize_t m, n;
 240                 m = (partial_pack_sha1 && partial_pack_offset < aligned_sz) ?
 241                         partial_pack_offset : aligned_sz;
 242                 n = xread(pack_fd, buf, m);
 243                 if (!n)
 244                         break;
 245                 if (n < 0)
 246                         die_errno("Failed to checksum '%s'", pack_name);
 247                 git_SHA1_Update(&new_sha1_ctx, buf, n);
 248
 249                 aligned_sz -= n;
 250                 if (!aligned_sz)
 251                         aligned_sz = buf_sz;
 252
 253                 if (!partial_pack_sha1)
 254                         continue;
 255
 256                 git_SHA1_Update(&old_sha1_ctx, buf, n);
 257                 partial_pack_offset -= n;
 258                 if (partial_pack_offset == 0) {
 259                         unsigned char sha1[20];
 260                         git_SHA1_Final(sha1, &old_sha1_ctx);
 261                         if (hashcmp(sha1, partial_pack_sha1) != 0)
 262                                 die("Unexpected checksum for %s "
 263                                     "(disk corruption?)", pack_name);
 264                         /*
 265                          * Now let's compute the SHA1 of the remainder of the
 266                          * pack, which also means making partial_pack_offset
 267                          * big enough not to matter anymore.
 268                          */
 269                         git_SHA1_Init(&old_sha1_ctx);
 270                         partial_pack_offset = ~partial_pack_offset;
 271                         partial_pack_offset -= MSB(partial_pack_offset, 1);
 272                 }
 273         }
 274         free(buf);
 275
 276         if (partial_pack_sha1)
 277                 git_SHA1_Final(partial_pack_sha1, &old_sha1_ctx);
 278         git_SHA1_Final(new_pack_sha1, &new_sha1_ctx);
 279         write_or_die(pack_fd, new_pack_sha1, 20);
 280         fsync_or_die(pack_fd, pack_name);
 281 }
 282
 283 char *index_pack_lockfile(int ip_out)
 284 {
 285         char packname[46];
 286
 287         /*
 288          * The first thing we expect from index-pack's output
 289          * is "pack\t%40s\n" or "keep\t%40s\n" (46 bytes) where
 290          * %40s is the newly created pack SHA1 name.  In the "keep"
 291          * case, we need it to remove the corresponding .keep file
 292          * later on.  If we don't get that then tough luck with it.
 293          */
 294         if (read_in_full(ip_out, packname, 46) == 46 && packname[45] == '\n' &&
 295             memcmp(packname, "keep\t", 5) == 0) {
 296                 char path[PATH_MAX];
 297                 packname[45] = 0;
 298                 snprintf(path, sizeof(path), "%s/pack/pack-%s.keep",
 299                          get_object_directory(), packname + 5);
 300                 return xstrdup(path);
 301         }
 302         return NULL;
 303 }
 304
 305 /*
 306  * The per-object header is a pretty dense thing, which is
 307  *  - first byte: low four bits are "size", then three bits of "type",
 308  *    and the high bit is "size continues".
 309  *  - each byte afterwards: low seven bits are size continuation,
 310  *    with the high bit being "size continues"
 311  */
 312 int encode_in_pack_object_header(enum object_type type, uintmax_t size, unsigned char *hdr)
 313 {
 314         int n = 1;
 315         unsigned char c;
 316
 317         if (type < OBJ_COMMIT || type > OBJ_REF_DELTA)
 318                 die("bad type %d", type);
 319
 320         c = (type << 4) | (size & 15);
 321         size >>= 4;
 322         while (size) {
 323                 *hdr++ = c | 0x80;
 324                 c = size & 0x7f;
 325                 size >>= 7;
 326                 n++;
 327         }
 328         *hdr = c;
 329         return n;
 330 }
 331
 332 struct sha1file *create_tmp_packfile(char **pack_tmp_name)
 333 {
 334         char tmpname[PATH_MAX];
 335         int fd;
 336
 337         fd = odb_mkstemp(tmpname, sizeof(tmpname), "pack/tmp_pack_XXXXXX");
 338         *pack_tmp_name = xstrdup(tmpname);
 339         return sha1fd(fd, *pack_tmp_name);
 340 }
 341
 342 void finish_tmp_packfile(char *name_buffer,
 343                          const char *pack_tmp_name,
 344                          struct pack_idx_entry **written_list,
 345                          uint32_t nr_written,
 346                          struct pack_idx_option *pack_idx_opts,
 347                          unsigned char sha1[])
 348 {
 349         const char *idx_tmp_name;
 350         char *end_of_name_prefix = strrchr(name_buffer, 0);
 351
 352         if (adjust_shared_perm(pack_tmp_name))
 353                 die_errno("unable to make temporary pack file readable");
 354
 355         idx_tmp_name = write_idx_file(NULL, written_list, nr_written,
 356                                       pack_idx_opts, sha1);
 357         if (adjust_shared_perm(idx_tmp_name))
 358                 die_errno("unable to make temporary index file readable");
 359
 360         sprintf(end_of_name_prefix, "%s.pack", sha1_to_hex(sha1));
 361         free_pack_by_name(name_buffer);
 362
 363         if (rename(pack_tmp_name, name_buffer))
 364                 die_errno("unable to rename temporary pack file");
 365
 366         sprintf(end_of_name_prefix, "%s.idx", sha1_to_hex(sha1));
 367         if (rename(idx_tmp_name, name_buffer))
 368                 die_errno("unable to rename temporary index file");
 369
 370         free((void *)idx_tmp_name);
 371 }