read-cache.c

   1 /*
   2  * GIT - The information manager from hell
   3  *
   4  * Copyright (C) Linus Torvalds, 2005
   5  */
   6 #include "cache.h"
   7 #include "cache-tree.h"
   8 #include "refs.h"
   9
  10 /* Index extensions.
  11  *
  12  * The first letter should be 'A'..'Z' for extensions that are not
  13  * necessary for a correct operation (i.e. optimization data).
  14  * When new extensions are added that _needs_ to be understood in
  15  * order to correctly interpret the index file, pick character that
  16  * is outside the range, to cause the reader to abort.
  17  */
  18
  19 #define CACHE_EXT(s) ( (s[0]<<24)|(s[1]<<16)|(s[2]<<8)|(s[3]) )
  20 #define CACHE_EXT_TREE 0x54524545       /* "TREE" */
  21
  22 struct cache_entry **active_cache;
  23 static time_t index_file_timestamp;
  24 unsigned int active_nr, active_alloc, active_cache_changed;
  25
  26 struct cache_tree *active_cache_tree;
  27
  28 static void *cache_mmap;
  29 static size_t cache_mmap_size;
  30
  31 /*
  32  * This only updates the "non-critical" parts of the directory
  33  * cache, ie the parts that aren't tracked by GIT, and only used
  34  * to validate the cache.
  35  */
  36 void fill_stat_cache_info(struct cache_entry *ce, struct stat *st)
  37 {
  38         ce->ce_ctime.sec = htonl(st->st_ctime);
  39         ce->ce_mtime.sec = htonl(st->st_mtime);
  40 #ifdef USE_NSEC
  41         ce->ce_ctime.nsec = htonl(st->st_ctim.tv_nsec);
  42         ce->ce_mtime.nsec = htonl(st->st_mtim.tv_nsec);
  43 #endif
  44         ce->ce_dev = htonl(st->st_dev);
  45         ce->ce_ino = htonl(st->st_ino);
  46         ce->ce_uid = htonl(st->st_uid);
  47         ce->ce_gid = htonl(st->st_gid);
  48         ce->ce_size = htonl(st->st_size);
  49
  50         if (assume_unchanged)
  51                 ce->ce_flags |= htons(CE_VALID);
  52 }
  53
  54 static int ce_compare_data(struct cache_entry *ce, struct stat *st)
  55 {
  56         int match = -1;
  57         int fd = open(ce->name, O_RDONLY);
  58
  59         if (fd >= 0) {
  60                 unsigned char sha1[20];
  61                 if (!index_fd(sha1, fd, st, 0, OBJ_BLOB, ce->name))
  62                         match = hashcmp(sha1, ce->sha1);
  63                 /* index_fd() closed the file descriptor already */
  64         }
  65         return match;
  66 }
  67
  68 static int ce_compare_link(struct cache_entry *ce, size_t expected_size)
  69 {
  70         int match = -1;
  71         char *target;
  72         void *buffer;
  73         unsigned long size;
  74         enum object_type type;
  75         int len;
  76
  77         target = xmalloc(expected_size);
  78         len = readlink(ce->name, target, expected_size);
  79         if (len != expected_size) {
  80                 free(target);
  81                 return -1;
  82         }
  83         buffer = read_sha1_file(ce->sha1, &type, &size);
  84         if (!buffer) {
  85                 free(target);
  86                 return -1;
  87         }
  88         if (size == expected_size)
  89                 match = memcmp(buffer, target, size);
  90         free(buffer);
  91         free(target);
  92         return match;
  93 }
  94
  95 static int ce_compare_gitlink(struct cache_entry *ce)
  96 {
  97         unsigned char sha1[20];
  98
  99         /*
 100          * We don't actually require that the .git directory
 101          * under DIRLNK directory be a valid git directory. It
 102          * might even be missing (in case nobody populated that
 103          * sub-project).
 104          *
 105          * If so, we consider it always to match.
 106          */
 107         if (resolve_gitlink_ref(ce->name, "HEAD", sha1) < 0)
 108                 return 0;
 109         return hashcmp(sha1, ce->sha1);
 110 }
 111
 112 static int ce_modified_check_fs(struct cache_entry *ce, struct stat *st)
 113 {
 114         switch (st->st_mode & S_IFMT) {
 115         case S_IFREG:
 116                 if (ce_compare_data(ce, st))
 117                         return DATA_CHANGED;
 118                 break;
 119         case S_IFLNK:
 120                 if (ce_compare_link(ce, xsize_t(st->st_size)))
 121                         return DATA_CHANGED;
 122                 break;
 123         case S_IFDIR:
 124                 if (S_ISDIRLNK(ntohl(ce->ce_mode)))
 125                         return 0;
 126         default:
 127                 return TYPE_CHANGED;
 128         }
 129         return 0;
 130 }
 131
 132 static int ce_match_stat_basic(struct cache_entry *ce, struct stat *st)
 133 {
 134         unsigned int changed = 0;
 135
 136         switch (ntohl(ce->ce_mode) & S_IFMT) {
 137         case S_IFREG:
 138                 changed |= !S_ISREG(st->st_mode) ? TYPE_CHANGED : 0;
 139                 /* We consider only the owner x bit to be relevant for
 140                  * "mode changes"
 141                  */
 142                 if (trust_executable_bit &&
 143                     (0100 & (ntohl(ce->ce_mode) ^ st->st_mode)))
 144                         changed |= MODE_CHANGED;
 145                 break;
 146         case S_IFLNK:
 147                 if (!S_ISLNK(st->st_mode) &&
 148                     (has_symlinks || !S_ISREG(st->st_mode)))
 149                         changed |= TYPE_CHANGED;
 150                 break;
 151         case S_IFDIRLNK:
 152                 if (!S_ISDIR(st->st_mode))
 153                         changed |= TYPE_CHANGED;
 154                 else if (ce_compare_gitlink(ce))
 155                         changed |= DATA_CHANGED;
 156                 return changed;
 157         default:
 158                 die("internal error: ce_mode is %o", ntohl(ce->ce_mode));
 159         }
 160         if (ce->ce_mtime.sec != htonl(st->st_mtime))
 161                 changed |= MTIME_CHANGED;
 162         if (ce->ce_ctime.sec != htonl(st->st_ctime))
 163                 changed |= CTIME_CHANGED;
 164
 165 #ifdef USE_NSEC
 166         /*
 167          * nsec seems unreliable - not all filesystems support it, so
 168          * as long as it is in the inode cache you get right nsec
 169          * but after it gets flushed, you get zero nsec.
 170          */
 171         if (ce->ce_mtime.nsec != htonl(st->st_mtim.tv_nsec))
 172                 changed |= MTIME_CHANGED;
 173         if (ce->ce_ctime.nsec != htonl(st->st_ctim.tv_nsec))
 174                 changed |= CTIME_CHANGED;
 175 #endif
 176
 177         if (ce->ce_uid != htonl(st->st_uid) ||
 178             ce->ce_gid != htonl(st->st_gid))
 179                 changed |= OWNER_CHANGED;
 180         if (ce->ce_ino != htonl(st->st_ino))
 181                 changed |= INODE_CHANGED;
 182
 183 #ifdef USE_STDEV
 184         /*
 185          * st_dev breaks on network filesystems where different
 186          * clients will have different views of what "device"
 187          * the filesystem is on
 188          */
 189         if (ce->ce_dev != htonl(st->st_dev))
 190                 changed |= INODE_CHANGED;
 191 #endif
 192
 193         if (ce->ce_size != htonl(st->st_size))
 194                 changed |= DATA_CHANGED;
 195
 196         return changed;
 197 }
 198
 199 int ce_match_stat(struct cache_entry *ce, struct stat *st, int options)
 200 {
 201         unsigned int changed;
 202         int ignore_valid = options & 01;
 203         int assume_racy_is_modified = options & 02;
 204
 205         /*
 206          * If it's marked as always valid in the index, it's
 207          * valid whatever the checked-out copy says.
 208          */
 209         if (!ignore_valid && (ce->ce_flags & htons(CE_VALID)))
 210                 return 0;
 211
 212         changed = ce_match_stat_basic(ce, st);
 213
 214         /*
 215          * Within 1 second of this sequence:
 216          *      echo xyzzy >file && git-update-index --add file
 217          * running this command:
 218          *      echo frotz >file
 219          * would give a falsely clean cache entry.  The mtime and
 220          * length match the cache, and other stat fields do not change.
 221          *
 222          * We could detect this at update-index time (the cache entry
 223          * being registered/updated records the same time as "now")
 224          * and delay the return from git-update-index, but that would
 225          * effectively mean we can make at most one commit per second,
 226          * which is not acceptable.  Instead, we check cache entries
 227          * whose mtime are the same as the index file timestamp more
 228          * carefully than others.
 229          */
 230         if (!changed &&
 231             index_file_timestamp &&
 232             index_file_timestamp <= ntohl(ce->ce_mtime.sec)) {
 233                 if (assume_racy_is_modified)
 234                         changed |= DATA_CHANGED;
 235                 else
 236                         changed |= ce_modified_check_fs(ce, st);
 237         }
 238
 239         return changed;
 240 }
 241
 242 int ce_modified(struct cache_entry *ce, struct stat *st, int really)
 243 {
 244         int changed, changed_fs;
 245         changed = ce_match_stat(ce, st, really);
 246         if (!changed)
 247                 return 0;
 248         /*
 249          * If the mode or type has changed, there's no point in trying
 250          * to refresh the entry - it's not going to match
 251          */
 252         if (changed & (MODE_CHANGED | TYPE_CHANGED))
 253                 return changed;
 254
 255         /* Immediately after read-tree or update-index --cacheinfo,
 256          * the length field is zero.  For other cases the ce_size
 257          * should match the SHA1 recorded in the index entry.
 258          */
 259         if ((changed & DATA_CHANGED) && ce->ce_size != htonl(0))
 260                 return changed;
 261
 262         changed_fs = ce_modified_check_fs(ce, st);
 263         if (changed_fs)
 264                 return changed | changed_fs;
 265         return 0;
 266 }
 267
 268 int base_name_compare(const char *name1, int len1, int mode1,
 269                       const char *name2, int len2, int mode2)
 270 {
 271         unsigned char c1, c2;
 272         int len = len1 < len2 ? len1 : len2;
 273         int cmp;
 274
 275         cmp = memcmp(name1, name2, len);
 276         if (cmp)
 277                 return cmp;
 278         c1 = name1[len];
 279         c2 = name2[len];
 280         if (!c1 && S_ISDIR(mode1))
 281                 c1 = '/';
 282         if (!c2 && S_ISDIR(mode2))
 283                 c2 = '/';
 284         return (c1 < c2) ? -1 : (c1 > c2) ? 1 : 0;
 285 }
 286
 287 int cache_name_compare(const char *name1, int flags1, const char *name2, int flags2)
 288 {
 289         int len1 = flags1 & CE_NAMEMASK;
 290         int len2 = flags2 & CE_NAMEMASK;
 291         int len = len1 < len2 ? len1 : len2;
 292         int cmp;
 293
 294         cmp = memcmp(name1, name2, len);
 295         if (cmp)
 296                 return cmp;
 297         if (len1 < len2)
 298                 return -1;
 299         if (len1 > len2)
 300                 return 1;
 301
 302         /* Compare stages  */
 303         flags1 &= CE_STAGEMASK;
 304         flags2 &= CE_STAGEMASK;
 305
 306         if (flags1 < flags2)
 307                 return -1;
 308         if (flags1 > flags2)
 309                 return 1;
 310         return 0;
 311 }
 312
 313 int cache_name_pos(const char *name, int namelen)
 314 {
 315         int first, last;
 316
 317         first = 0;
 318         last = active_nr;
 319         while (last > first) {
 320                 int next = (last + first) >> 1;
 321                 struct cache_entry *ce = active_cache[next];
 322                 int cmp = cache_name_compare(name, namelen, ce->name, ntohs(ce->ce_flags));
 323                 if (!cmp)
 324                         return next;
 325                 if (cmp < 0) {
 326                         last = next;
 327                         continue;
 328                 }
 329                 first = next+1;
 330         }
 331         return -first-1;
 332 }
 333
 334 /* Remove entry, return true if there are more entries to go.. */
 335 int remove_cache_entry_at(int pos)
 336 {
 337         active_cache_changed = 1;
 338         active_nr--;
 339         if (pos >= active_nr)
 340                 return 0;
 341         memmove(active_cache + pos, active_cache + pos + 1, (active_nr - pos) * sizeof(struct cache_entry *));
 342         return 1;
 343 }
 344
 345 int remove_file_from_cache(const char *path)
 346 {
 347         int pos = cache_name_pos(path, strlen(path));
 348         if (pos < 0)
 349                 pos = -pos-1;
 350         while (pos < active_nr && !strcmp(active_cache[pos]->name, path))
 351                 remove_cache_entry_at(pos);
 352         return 0;
 353 }
 354
 355 int add_file_to_cache(const char *path, int verbose)
 356 {
 357         int size, namelen;
 358         struct stat st;
 359         struct cache_entry *ce;
 360
 361         if (lstat(path, &st))
 362                 die("%s: unable to stat (%s)", path, strerror(errno));
 363
 364         if (!S_ISREG(st.st_mode) && !S_ISLNK(st.st_mode) && !S_ISDIR(st.st_mode))
 365                 die("%s: can only add regular files, symbolic links or git-directories", path);
 366
 367         namelen = strlen(path);
 368         if (S_ISDIR(st.st_mode)) {
 369                 while (namelen && path[namelen-1] == '/')
 370                         namelen--;
 371         }
 372         size = cache_entry_size(namelen);
 373         ce = xcalloc(1, size);
 374         memcpy(ce->name, path, namelen);
 375         ce->ce_flags = htons(namelen);
 376         fill_stat_cache_info(ce, &st);
 377
 378         if (trust_executable_bit && has_symlinks)
 379                 ce->ce_mode = create_ce_mode(st.st_mode);
 380         else {
 381                 /* If there is an existing entry, pick the mode bits and type
 382                  * from it, otherwise assume unexecutable regular file.
 383                  */
 384                 struct cache_entry *ent;
 385                 int pos = cache_name_pos(path, namelen);
 386
 387                 ent = (0 <= pos) ? active_cache[pos] : NULL;
 388                 ce->ce_mode = ce_mode_from_stat(ent, st.st_mode);
 389         }
 390
 391         if (index_path(ce->sha1, path, &st, 1))
 392                 die("unable to index file %s", path);
 393         if (add_cache_entry(ce, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE))
 394                 die("unable to add %s to index",path);
 395         if (verbose)
 396                 printf("add '%s'\n", path);
 397         cache_tree_invalidate_path(active_cache_tree, path);
 398         return 0;
 399 }
 400
 401 int ce_same_name(struct cache_entry *a, struct cache_entry *b)
 402 {
 403         int len = ce_namelen(a);
 404         return ce_namelen(b) == len && !memcmp(a->name, b->name, len);
 405 }
 406
 407 int ce_path_match(const struct cache_entry *ce, const char **pathspec)
 408 {
 409         const char *match, *name;
 410         int len;
 411
 412         if (!pathspec)
 413                 return 1;
 414
 415         len = ce_namelen(ce);
 416         name = ce->name;
 417         while ((match = *pathspec++) != NULL) {
 418                 int matchlen = strlen(match);
 419                 if (matchlen > len)
 420                         continue;
 421                 if (memcmp(name, match, matchlen))
 422                         continue;
 423                 if (matchlen && name[matchlen-1] == '/')
 424                         return 1;
 425                 if (name[matchlen] == '/' || !name[matchlen])
 426                         return 1;
 427                 if (!matchlen)
 428                         return 1;
 429         }
 430         return 0;
 431 }
 432
 433 /*
 434  * We fundamentally don't like some paths: we don't want
 435  * dot or dot-dot anywhere, and for obvious reasons don't
 436  * want to recurse into ".git" either.
 437  *
 438  * Also, we don't want double slashes or slashes at the
 439  * end that can make pathnames ambiguous.
 440  */
 441 static int verify_dotfile(const char *rest)
 442 {
 443         /*
 444          * The first character was '.', but that
 445          * has already been discarded, we now test
 446          * the rest.
 447          */
 448         switch (*rest) {
 449         /* "." is not allowed */
 450         case '\0': case '/':
 451                 return 0;
 452
 453         /*
 454          * ".git" followed by  NUL or slash is bad. This
 455          * shares the path end test with the ".." case.
 456          */
 457         case 'g':
 458                 if (rest[1] != 'i')
 459                         break;
 460                 if (rest[2] != 't')
 461                         break;
 462                 rest += 2;
 463         /* fallthrough */
 464         case '.':
 465                 if (rest[1] == '\0' || rest[1] == '/')
 466                         return 0;
 467         }
 468         return 1;
 469 }
 470
 471 int verify_path(const char *path)
 472 {
 473         char c;
 474
 475         goto inside;
 476         for (;;) {
 477                 if (!c)
 478                         return 1;
 479                 if (c == '/') {
 480 inside:
 481                         c = *path++;
 482                         switch (c) {
 483                         default:
 484                                 continue;
 485                         case '/': case '\0':
 486                                 break;
 487                         case '.':
 488                                 if (verify_dotfile(path))
 489                                         continue;
 490                         }
 491                         return 0;
 492                 }
 493                 c = *path++;
 494         }
 495 }
 496
 497 /*
 498  * Do we have another file that has the beginning components being a
 499  * proper superset of the name we're trying to add?
 500  */
 501 static int has_file_name(const struct cache_entry *ce, int pos, int ok_to_replace)
 502 {
 503         int retval = 0;
 504         int len = ce_namelen(ce);
 505         int stage = ce_stage(ce);
 506         const char *name = ce->name;
 507
 508         while (pos < active_nr) {
 509                 struct cache_entry *p = active_cache[pos++];
 510
 511                 if (len >= ce_namelen(p))
 512                         break;
 513                 if (memcmp(name, p->name, len))
 514                         break;
 515                 if (ce_stage(p) != stage)
 516                         continue;
 517                 if (p->name[len] != '/')
 518                         continue;
 519                 if (!ce_stage(p) && !p->ce_mode)
 520                         continue;
 521                 retval = -1;
 522                 if (!ok_to_replace)
 523                         break;
 524                 remove_cache_entry_at(--pos);
 525         }
 526         return retval;
 527 }
 528
 529 /*
 530  * Do we have another file with a pathname that is a proper
 531  * subset of the name we're trying to add?
 532  */
 533 static int has_dir_name(const struct cache_entry *ce, int pos, int ok_to_replace)
 534 {
 535         int retval = 0;
 536         int stage = ce_stage(ce);
 537         const char *name = ce->name;
 538         const char *slash = name + ce_namelen(ce);
 539
 540         for (;;) {
 541                 int len;
 542
 543                 for (;;) {
 544                         if (*--slash == '/')
 545                                 break;
 546                         if (slash <= ce->name)
 547                                 return retval;
 548                 }
 549                 len = slash - name;
 550
 551                 pos = cache_name_pos(name, ntohs(create_ce_flags(len, stage)));
 552                 if (pos >= 0) {
 553                         /*
 554                          * Found one, but not so fast.  This could
 555                          * be a marker that says "I was here, but
 556                          * I am being removed".  Such an entry is
 557                          * not a part of the resulting tree, and
 558                          * it is Ok to have a directory at the same
 559                          * path.
 560                          */
 561                         if (stage || active_cache[pos]->ce_mode) {
 562                                 retval = -1;
 563                                 if (!ok_to_replace)
 564                                         break;
 565                                 remove_cache_entry_at(pos);
 566                                 continue;
 567                         }
 568                 }
 569                 else
 570                         pos = -pos-1;
 571
 572                 /*
 573                  * Trivial optimization: if we find an entry that
 574                  * already matches the sub-directory, then we know
 575                  * we're ok, and we can exit.
 576                  */
 577                 while (pos < active_nr) {
 578                         struct cache_entry *p = active_cache[pos];
 579                         if ((ce_namelen(p) <= len) ||
 580                             (p->name[len] != '/') ||
 581                             memcmp(p->name, name, len))
 582                                 break; /* not our subdirectory */
 583                         if (ce_stage(p) == stage && (stage || p->ce_mode))
 584                                 /* p is at the same stage as our entry, and
 585                                  * is a subdirectory of what we are looking
 586                                  * at, so we cannot have conflicts at our
 587                                  * level or anything shorter.
 588                                  */
 589                                 return retval;
 590                         pos++;
 591                 }
 592         }
 593         return retval;
 594 }
 595
 596 /* We may be in a situation where we already have path/file and path
 597  * is being added, or we already have path and path/file is being
 598  * added.  Either one would result in a nonsense tree that has path
 599  * twice when git-write-tree tries to write it out.  Prevent it.
 600  *
 601  * If ok-to-replace is specified, we remove the conflicting entries
 602  * from the cache so the caller should recompute the insert position.
 603  * When this happens, we return non-zero.
 604  */
 605 static int check_file_directory_conflict(const struct cache_entry *ce, int pos, int ok_to_replace)
 606 {
 607         int retval;
 608
 609         /*
 610          * When ce is an "I am going away" entry, we allow it to be added
 611          */
 612         if (!ce_stage(ce) && !ce->ce_mode)
 613                 return 0;
 614
 615         /*
 616          * We check if the path is a sub-path of a subsequent pathname
 617          * first, since removing those will not change the position
 618          * in the array.
 619          */
 620         retval = has_file_name(ce, pos, ok_to_replace);
 621
 622         /*
 623          * Then check if the path might have a clashing sub-directory
 624          * before it.
 625          */
 626         return retval + has_dir_name(ce, pos, ok_to_replace);
 627 }
 628
 629 int add_cache_entry(struct cache_entry *ce, int option)
 630 {
 631         int pos;
 632         int ok_to_add = option & ADD_CACHE_OK_TO_ADD;
 633         int ok_to_replace = option & ADD_CACHE_OK_TO_REPLACE;
 634         int skip_df_check = option & ADD_CACHE_SKIP_DFCHECK;
 635
 636         pos = cache_name_pos(ce->name, ntohs(ce->ce_flags));
 637
 638         /* existing match? Just replace it. */
 639         if (pos >= 0) {
 640                 active_cache_changed = 1;
 641                 active_cache[pos] = ce;
 642                 return 0;
 643         }
 644         pos = -pos-1;
 645
 646         /*
 647          * Inserting a merged entry ("stage 0") into the index
 648          * will always replace all non-merged entries..
 649          */
 650         if (pos < active_nr && ce_stage(ce) == 0) {
 651                 while (ce_same_name(active_cache[pos], ce)) {
 652                         ok_to_add = 1;
 653                         if (!remove_cache_entry_at(pos))
 654                                 break;
 655                 }
 656         }
 657
 658         if (!ok_to_add)
 659                 return -1;
 660         if (!verify_path(ce->name))
 661                 return -1;
 662
 663         if (!skip_df_check &&
 664             check_file_directory_conflict(ce, pos, ok_to_replace)) {
 665                 if (!ok_to_replace)
 666                         return error("'%s' appears as both a file and as a directory", ce->name);
 667                 pos = cache_name_pos(ce->name, ntohs(ce->ce_flags));
 668                 pos = -pos-1;
 669         }
 670
 671         /* Make sure the array is big enough .. */
 672         if (active_nr == active_alloc) {
 673                 active_alloc = alloc_nr(active_alloc);
 674                 active_cache = xrealloc(active_cache, active_alloc * sizeof(struct cache_entry *));
 675         }
 676
 677         /* Add it in.. */
 678         active_nr++;
 679         if (active_nr > pos)
 680                 memmove(active_cache + pos + 1, active_cache + pos, (active_nr - pos - 1) * sizeof(ce));
 681         active_cache[pos] = ce;
 682         active_cache_changed = 1;
 683         return 0;
 684 }
 685
 686 /*
 687  * "refresh" does not calculate a new sha1 file or bring the
 688  * cache up-to-date for mode/content changes. But what it
 689  * _does_ do is to "re-match" the stat information of a file
 690  * with the cache, so that you can refresh the cache for a
 691  * file that hasn't been changed but where the stat entry is
 692  * out of date.
 693  *
 694  * For example, you'd want to do this after doing a "git-read-tree",
 695  * to link up the stat cache details with the proper files.
 696  */
 697 static struct cache_entry *refresh_cache_ent(struct cache_entry *ce, int really, int *err)
 698 {
 699         struct stat st;
 700         struct cache_entry *updated;
 701         int changed, size;
 702
 703         if (lstat(ce->name, &st) < 0) {
 704                 if (err)
 705                         *err = errno;
 706                 return NULL;
 707         }
 708
 709         changed = ce_match_stat(ce, &st, really);
 710         if (!changed) {
 711                 if (really && assume_unchanged &&
 712                     !(ce->ce_flags & htons(CE_VALID)))
 713                         ; /* mark this one VALID again */
 714                 else
 715                         return ce;
 716         }
 717
 718         if (ce_modified(ce, &st, really)) {
 719                 if (err)
 720                         *err = EINVAL;
 721                 return NULL;
 722         }
 723
 724         size = ce_size(ce);
 725         updated = xmalloc(size);
 726         memcpy(updated, ce, size);
 727         fill_stat_cache_info(updated, &st);
 728
 729         /* In this case, if really is not set, we should leave
 730          * CE_VALID bit alone.  Otherwise, paths marked with
 731          * --no-assume-unchanged (i.e. things to be edited) will
 732          * reacquire CE_VALID bit automatically, which is not
 733          * really what we want.
 734          */
 735         if (!really && assume_unchanged && !(ce->ce_flags & htons(CE_VALID)))
 736                 updated->ce_flags &= ~htons(CE_VALID);
 737
 738         return updated;
 739 }
 740
 741 int refresh_cache(unsigned int flags)
 742 {
 743         int i;
 744         int has_errors = 0;
 745         int really = (flags & REFRESH_REALLY) != 0;
 746         int allow_unmerged = (flags & REFRESH_UNMERGED) != 0;
 747         int quiet = (flags & REFRESH_QUIET) != 0;
 748         int not_new = (flags & REFRESH_IGNORE_MISSING) != 0;
 749
 750         for (i = 0; i < active_nr; i++) {
 751                 struct cache_entry *ce, *new;
 752                 int cache_errno = 0;
 753
 754                 ce = active_cache[i];
 755                 if (ce_stage(ce)) {
 756                         while ((i < active_nr) &&
 757                                ! strcmp(active_cache[i]->name, ce->name))
 758                                 i++;
 759                         i--;
 760                         if (allow_unmerged)
 761                                 continue;
 762                         printf("%s: needs merge\n", ce->name);
 763                         has_errors = 1;
 764                         continue;
 765                 }
 766
 767                 new = refresh_cache_ent(ce, really, &cache_errno);
 768                 if (new == ce)
 769                         continue;
 770                 if (!new) {
 771                         if (not_new && cache_errno == ENOENT)
 772                                 continue;
 773                         if (really && cache_errno == EINVAL) {
 774                                 /* If we are doing --really-refresh that
 775                                  * means the index is not valid anymore.
 776                                  */
 777                                 ce->ce_flags &= ~htons(CE_VALID);
 778                                 active_cache_changed = 1;
 779                         }
 780                         if (quiet)
 781                                 continue;
 782                         printf("%s: needs update\n", ce->name);
 783                         has_errors = 1;
 784                         continue;
 785                 }
 786                 active_cache_changed = 1;
 787                 /* You can NOT just free active_cache[i] here, since it
 788                  * might not be necessarily malloc()ed but can also come
 789                  * from mmap(). */
 790                 active_cache[i] = new;
 791         }
 792         return has_errors;
 793 }
 794
 795 struct cache_entry *refresh_cache_entry(struct cache_entry *ce, int really)
 796 {
 797         return refresh_cache_ent(ce, really, NULL);
 798 }
 799
 800 static int verify_hdr(struct cache_header *hdr, unsigned long size)
 801 {
 802         SHA_CTX c;
 803         unsigned char sha1[20];
 804
 805         if (hdr->hdr_signature != htonl(CACHE_SIGNATURE))
 806                 return error("bad signature");
 807         if (hdr->hdr_version != htonl(2))
 808                 return error("bad index version");
 809         SHA1_Init(&c);
 810         SHA1_Update(&c, hdr, size - 20);
 811         SHA1_Final(sha1, &c);
 812         if (hashcmp(sha1, (unsigned char *)hdr + size - 20))
 813                 return error("bad index file sha1 signature");
 814         return 0;
 815 }
 816
 817 static int read_index_extension(const char *ext, void *data, unsigned long sz)
 818 {
 819         switch (CACHE_EXT(ext)) {
 820         case CACHE_EXT_TREE:
 821                 active_cache_tree = cache_tree_read(data, sz);
 822                 break;
 823         default:
 824                 if (*ext < 'A' || 'Z' < *ext)
 825                         return error("index uses %.4s extension, which we do not understand",
 826                                      ext);
 827                 fprintf(stderr, "ignoring %.4s extension\n", ext);
 828                 break;
 829         }
 830         return 0;
 831 }
 832
 833 int read_cache(void)
 834 {
 835         return read_cache_from(get_index_file());
 836 }
 837
 838 /* remember to discard_cache() before reading a different cache! */
 839 int read_cache_from(const char *path)
 840 {
 841         int fd, i;
 842         struct stat st;
 843         unsigned long offset;
 844         struct cache_header *hdr;
 845
 846         errno = EBUSY;
 847         if (cache_mmap)
 848                 return active_nr;
 849
 850         errno = ENOENT;
 851         index_file_timestamp = 0;
 852         fd = open(path, O_RDONLY);
 853         if (fd < 0) {
 854                 if (errno == ENOENT)
 855                         return 0;
 856                 die("index file open failed (%s)", strerror(errno));
 857         }
 858
 859         if (!fstat(fd, &st)) {
 860                 cache_mmap_size = xsize_t(st.st_size);
 861                 errno = EINVAL;
 862                 if (cache_mmap_size >= sizeof(struct cache_header) + 20)
 863                         cache_mmap = xmmap(NULL, cache_mmap_size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
 864                 else
 865                         die("index file smaller than expected");
 866         } else
 867                 die("cannot stat the open index (%s)", strerror(errno));
 868         close(fd);
 869
 870         hdr = cache_mmap;
 871         if (verify_hdr(hdr, cache_mmap_size) < 0)
 872                 goto unmap;
 873
 874         active_nr = ntohl(hdr->hdr_entries);
 875         active_alloc = alloc_nr(active_nr);
 876         active_cache = xcalloc(active_alloc, sizeof(struct cache_entry *));
 877
 878         offset = sizeof(*hdr);
 879         for (i = 0; i < active_nr; i++) {
 880                 struct cache_entry *ce = (struct cache_entry *) ((char *) cache_mmap + offset);
 881                 offset = offset + ce_size(ce);
 882                 active_cache[i] = ce;
 883         }
 884         index_file_timestamp = st.st_mtime;
 885         while (offset <= cache_mmap_size - 20 - 8) {
 886                 /* After an array of active_nr index entries,
 887                  * there can be arbitrary number of extended
 888                  * sections, each of which is prefixed with
 889                  * extension name (4-byte) and section length
 890                  * in 4-byte network byte order.
 891                  */
 892                 unsigned long extsize;
 893                 memcpy(&extsize, (char *) cache_mmap + offset + 4, 4);
 894                 extsize = ntohl(extsize);
 895                 if (read_index_extension(((const char *) cache_mmap) + offset,
 896                                          (char *) cache_mmap + offset + 8,
 897                                          extsize) < 0)
 898                         goto unmap;
 899                 offset += 8;
 900                 offset += extsize;
 901         }
 902         return active_nr;
 903
 904 unmap:
 905         munmap(cache_mmap, cache_mmap_size);
 906         errno = EINVAL;
 907         die("index file corrupt");
 908 }
 909
 910 int discard_cache(void)
 911 {
 912         int ret;
 913
 914         active_nr = active_cache_changed = 0;
 915         index_file_timestamp = 0;
 916         cache_tree_free(&active_cache_tree);
 917         if (cache_mmap == NULL)
 918                 return 0;
 919         ret = munmap(cache_mmap, cache_mmap_size);
 920         cache_mmap = NULL;
 921         cache_mmap_size = 0;
 922
 923         /* no need to throw away allocated active_cache */
 924         return ret;
 925 }
 926
 927 #define WRITE_BUFFER_SIZE 8192
 928 static unsigned char write_buffer[WRITE_BUFFER_SIZE];
 929 static unsigned long write_buffer_len;
 930
 931 static int ce_write_flush(SHA_CTX *context, int fd)
 932 {
 933         unsigned int buffered = write_buffer_len;
 934         if (buffered) {
 935                 SHA1_Update(context, write_buffer, buffered);
 936                 if (write_in_full(fd, write_buffer, buffered) != buffered)
 937                         return -1;
 938                 write_buffer_len = 0;
 939         }
 940         return 0;
 941 }
 942
 943 static int ce_write(SHA_CTX *context, int fd, void *data, unsigned int len)
 944 {
 945         while (len) {
 946                 unsigned int buffered = write_buffer_len;
 947                 unsigned int partial = WRITE_BUFFER_SIZE - buffered;
 948                 if (partial > len)
 949                         partial = len;
 950                 memcpy(write_buffer + buffered, data, partial);
 951                 buffered += partial;
 952                 if (buffered == WRITE_BUFFER_SIZE) {
 953                         write_buffer_len = buffered;
 954                         if (ce_write_flush(context, fd))
 955                                 return -1;
 956                         buffered = 0;
 957                 }
 958                 write_buffer_len = buffered;
 959                 len -= partial;
 960                 data = (char *) data + partial;
 961         }
 962         return 0;
 963 }
 964
 965 static int write_index_ext_header(SHA_CTX *context, int fd,
 966                                   unsigned int ext, unsigned int sz)
 967 {
 968         ext = htonl(ext);
 969         sz = htonl(sz);
 970         return ((ce_write(context, fd, &ext, 4) < 0) ||
 971                 (ce_write(context, fd, &sz, 4) < 0)) ? -1 : 0;
 972 }
 973
 974 static int ce_flush(SHA_CTX *context, int fd)
 975 {
 976         unsigned int left = write_buffer_len;
 977
 978         if (left) {
 979                 write_buffer_len = 0;
 980                 SHA1_Update(context, write_buffer, left);
 981         }
 982
 983         /* Flush first if not enough space for SHA1 signature */
 984         if (left + 20 > WRITE_BUFFER_SIZE) {
 985                 if (write_in_full(fd, write_buffer, left) != left)
 986                         return -1;
 987                 left = 0;
 988         }
 989
 990         /* Append the SHA1 signature at the end */
 991         SHA1_Final(write_buffer + left, context);
 992         left += 20;
 993         return (write_in_full(fd, write_buffer, left) != left) ? -1 : 0;
 994 }
 995
 996 static void ce_smudge_racily_clean_entry(struct cache_entry *ce)
 997 {
 998         /*
 999          * The only thing we care about in this function is to smudge the
1000          * falsely clean entry due to touch-update-touch race, so we leave
1001          * everything else as they are.  We are called for entries whose
1002          * ce_mtime match the index file mtime.
1003          */
1004         struct stat st;
1005
1006         if (lstat(ce->name, &st) < 0)
1007                 return;
1008         if (ce_match_stat_basic(ce, &st))
1009                 return;
1010         if (ce_modified_check_fs(ce, &st)) {
1011                 /* This is "racily clean"; smudge it.  Note that this
1012                  * is a tricky code.  At first glance, it may appear
1013                  * that it can break with this sequence:
1014                  *
1015                  * $ echo xyzzy >frotz
1016                  * $ git-update-index --add frotz
1017                  * $ : >frotz
1018                  * $ sleep 3
1019                  * $ echo filfre >nitfol
1020                  * $ git-update-index --add nitfol
1021                  *
1022                  * but it does not.  When the second update-index runs,
1023                  * it notices that the entry "frotz" has the same timestamp
1024                  * as index, and if we were to smudge it by resetting its
1025                  * size to zero here, then the object name recorded
1026                  * in index is the 6-byte file but the cached stat information
1027                  * becomes zero --- which would then match what we would
1028                  * obtain from the filesystem next time we stat("frotz").
1029                  *
1030                  * However, the second update-index, before calling
1031                  * this function, notices that the cached size is 6
1032                  * bytes and what is on the filesystem is an empty
1033                  * file, and never calls us, so the cached size information
1034                  * for "frotz" stays 6 which does not match the filesystem.
1035                  */
1036                 ce->ce_size = htonl(0);
1037         }
1038 }
1039
1040 int write_cache(int newfd, struct cache_entry **cache, int entries)
1041 {
1042         SHA_CTX c;
1043         struct cache_header hdr;
1044         int i, removed;
1045
1046         for (i = removed = 0; i < entries; i++)
1047                 if (!cache[i]->ce_mode)
1048                         removed++;
1049
1050         hdr.hdr_signature = htonl(CACHE_SIGNATURE);
1051         hdr.hdr_version = htonl(2);
1052         hdr.hdr_entries = htonl(entries - removed);
1053
1054         SHA1_Init(&c);
1055         if (ce_write(&c, newfd, &hdr, sizeof(hdr)) < 0)
1056                 return -1;
1057
1058         for (i = 0; i < entries; i++) {
1059                 struct cache_entry *ce = cache[i];
1060                 if (!ce->ce_mode)
1061                         continue;
1062                 if (index_file_timestamp &&
1063                     index_file_timestamp <= ntohl(ce->ce_mtime.sec))
1064                         ce_smudge_racily_clean_entry(ce);
1065                 if (ce_write(&c, newfd, ce, ce_size(ce)) < 0)
1066                         return -1;
1067         }
1068
1069         /* Write extension data here */
1070         if (active_cache_tree) {
1071                 unsigned long sz;
1072                 void *data = cache_tree_write(active_cache_tree, &sz);
1073                 if (data &&
1074                     !write_index_ext_header(&c, newfd, CACHE_EXT_TREE, sz) &&
1075                     !ce_write(&c, newfd, data, sz))
1076                         free(data);
1077                 else {
1078                         free(data);
1079                         return -1;
1080                 }
1081         }
1082         return ce_flush(&c, newfd);
1083 }