git/read-cache.c

   1 /*
   2  * GIT - The information manager from hell
   3  *
   4  * Copyright (C) Linus Torvalds, 2005
   5  */
   6 #define NO_THE_INDEX_COMPATIBILITY_MACROS
   7 #include "cache.h"
   8 #include "cache-tree.h"
   9 #include "refs.h"
  10
  11 /* Index extensions.
  12  *
  13  * The first letter should be 'A'..'Z' for extensions that are not
  14  * necessary for a correct operation (i.e. optimization data).
  15  * When new extensions are added that _needs_ to be understood in
  16  * order to correctly interpret the index file, pick character that
  17  * is outside the range, to cause the reader to abort.
  18  */
  19
  20 #define CACHE_EXT(s) ( (s[0]<<24)|(s[1]<<16)|(s[2]<<8)|(s[3]) )
  21 #define CACHE_EXT_TREE 0x54524545       /* "TREE" */
  22
  23 struct index_state the_index;
  24
  25 /*
  26  * This only updates the "non-critical" parts of the directory
  27  * cache, ie the parts that aren't tracked by GIT, and only used
  28  * to validate the cache.
  29  */
  30 void fill_stat_cache_info(struct cache_entry *ce, struct stat *st)
  31 {
  32         ce->ce_ctime.sec = htonl(st->st_ctime);
  33         ce->ce_mtime.sec = htonl(st->st_mtime);
  34 #ifdef USE_NSEC
  35         ce->ce_ctime.nsec = htonl(st->st_ctim.tv_nsec);
  36         ce->ce_mtime.nsec = htonl(st->st_mtim.tv_nsec);
  37 #endif
  38         ce->ce_dev = htonl(st->st_dev);
  39         ce->ce_ino = htonl(st->st_ino);
  40         ce->ce_uid = htonl(st->st_uid);
  41         ce->ce_gid = htonl(st->st_gid);
  42         ce->ce_size = htonl(st->st_size);
  43
  44         if (assume_unchanged)
  45                 ce->ce_flags |= htons(CE_VALID);
  46 }
  47
  48 static int ce_compare_data(struct cache_entry *ce, struct stat *st)
  49 {
  50         int match = -1;
  51         int fd = open(ce->name, O_RDONLY);
  52
  53         if (fd >= 0) {
  54                 unsigned char sha1[20];
  55                 if (!index_fd(sha1, fd, st, 0, OBJ_BLOB, ce->name))
  56                         match = hashcmp(sha1, ce->sha1);
  57                 /* index_fd() closed the file descriptor already */
  58         }
  59         return match;
  60 }
  61
  62 static int ce_compare_link(struct cache_entry *ce, size_t expected_size)
  63 {
  64         int match = -1;
  65         char *target;
  66         void *buffer;
  67         unsigned long size;
  68         enum object_type type;
  69         int len;
  70
  71         target = xmalloc(expected_size);
  72         len = readlink(ce->name, target, expected_size);
  73         if (len != expected_size) {
  74                 free(target);
  75                 return -1;
  76         }
  77         buffer = read_sha1_file(ce->sha1, &type, &size);
  78         if (!buffer) {
  79                 free(target);
  80                 return -1;
  81         }
  82         if (size == expected_size)
  83                 match = memcmp(buffer, target, size);
  84         free(buffer);
  85         free(target);
  86         return match;
  87 }
  88
  89 static int ce_compare_gitlink(struct cache_entry *ce)
  90 {
  91         unsigned char sha1[20];
  92
  93         /*
  94          * We don't actually require that the .git directory
  95          * under GITLINK directory be a valid git directory. It
  96          * might even be missing (in case nobody populated that
  97          * sub-project).
  98          *
  99          * If so, we consider it always to match.
 100          */
 101         if (resolve_gitlink_ref(ce->name, "HEAD", sha1) < 0)
 102                 return 0;
 103         return hashcmp(sha1, ce->sha1);
 104 }
 105
 106 static int ce_modified_check_fs(struct cache_entry *ce, struct stat *st)
 107 {
 108         switch (st->st_mode & S_IFMT) {
 109         case S_IFREG:
 110                 if (ce_compare_data(ce, st))
 111                         return DATA_CHANGED;
 112                 break;
 113         case S_IFLNK:
 114                 if (ce_compare_link(ce, xsize_t(st->st_size)))
 115                         return DATA_CHANGED;
 116                 break;
 117         case S_IFDIR:
 118                 if (S_ISGITLINK(ntohl(ce->ce_mode)))
 119                         return 0;
 120         default:
 121                 return TYPE_CHANGED;
 122         }
 123         return 0;
 124 }
 125
 126 static int ce_match_stat_basic(struct cache_entry *ce, struct stat *st)
 127 {
 128         unsigned int changed = 0;
 129
 130         switch (ntohl(ce->ce_mode) & S_IFMT) {
 131         case S_IFREG:
 132                 changed |= !S_ISREG(st->st_mode) ? TYPE_CHANGED : 0;
 133                 /* We consider only the owner x bit to be relevant for
 134                  * "mode changes"
 135                  */
 136                 if (trust_executable_bit &&
 137                     (0100 & (ntohl(ce->ce_mode) ^ st->st_mode)))
 138                         changed |= MODE_CHANGED;
 139                 break;
 140         case S_IFLNK:
 141                 if (!S_ISLNK(st->st_mode) &&
 142                     (has_symlinks || !S_ISREG(st->st_mode)))
 143                         changed |= TYPE_CHANGED;
 144                 break;
 145         case S_IFGITLINK:
 146                 if (!S_ISDIR(st->st_mode))
 147                         changed |= TYPE_CHANGED;
 148                 else if (ce_compare_gitlink(ce))
 149                         changed |= DATA_CHANGED;
 150                 return changed;
 151         default:
 152                 die("internal error: ce_mode is %o", ntohl(ce->ce_mode));
 153         }
 154         if (ce->ce_mtime.sec != htonl(st->st_mtime))
 155                 changed |= MTIME_CHANGED;
 156         if (ce->ce_ctime.sec != htonl(st->st_ctime))
 157                 changed |= CTIME_CHANGED;
 158
 159 #ifdef USE_NSEC
 160         /*
 161          * nsec seems unreliable - not all filesystems support it, so
 162          * as long as it is in the inode cache you get right nsec
 163          * but after it gets flushed, you get zero nsec.
 164          */
 165         if (ce->ce_mtime.nsec != htonl(st->st_mtim.tv_nsec))
 166                 changed |= MTIME_CHANGED;
 167         if (ce->ce_ctime.nsec != htonl(st->st_ctim.tv_nsec))
 168                 changed |= CTIME_CHANGED;
 169 #endif
 170
 171         if (ce->ce_uid != htonl(st->st_uid) ||
 172             ce->ce_gid != htonl(st->st_gid))
 173                 changed |= OWNER_CHANGED;
 174         if (ce->ce_ino != htonl(st->st_ino))
 175                 changed |= INODE_CHANGED;
 176
 177 #ifdef USE_STDEV
 178         /*
 179          * st_dev breaks on network filesystems where different
 180          * clients will have different views of what "device"
 181          * the filesystem is on
 182          */
 183         if (ce->ce_dev != htonl(st->st_dev))
 184                 changed |= INODE_CHANGED;
 185 #endif
 186
 187         if (ce->ce_size != htonl(st->st_size))
 188                 changed |= DATA_CHANGED;
 189
 190         return changed;
 191 }
 192
 193 int ie_match_stat(struct index_state *istate,
 194                   struct cache_entry *ce, struct stat *st, int options)
 195 {
 196         unsigned int changed;
 197         int ignore_valid = options & 01;
 198         int assume_racy_is_modified = options & 02;
 199
 200         /*
 201          * If it's marked as always valid in the index, it's
 202          * valid whatever the checked-out copy says.
 203          */
 204         if (!ignore_valid && (ce->ce_flags & htons(CE_VALID)))
 205                 return 0;
 206
 207         changed = ce_match_stat_basic(ce, st);
 208
 209         /*
 210          * Within 1 second of this sequence:
 211          *      echo xyzzy >file && git-update-index --add file
 212          * running this command:
 213          *      echo frotz >file
 214          * would give a falsely clean cache entry.  The mtime and
 215          * length match the cache, and other stat fields do not change.
 216          *
 217          * We could detect this at update-index time (the cache entry
 218          * being registered/updated records the same time as "now")
 219          * and delay the return from git-update-index, but that would
 220          * effectively mean we can make at most one commit per second,
 221          * which is not acceptable.  Instead, we check cache entries
 222          * whose mtime are the same as the index file timestamp more
 223          * carefully than others.
 224          */
 225         if (!changed &&
 226             istate->timestamp &&
 227             istate->timestamp <= ntohl(ce->ce_mtime.sec)) {
 228                 if (assume_racy_is_modified)
 229                         changed |= DATA_CHANGED;
 230                 else
 231                         changed |= ce_modified_check_fs(ce, st);
 232         }
 233
 234         return changed;
 235 }
 236
 237 int ie_modified(struct index_state *istate,
 238                 struct cache_entry *ce, struct stat *st, int really)
 239 {
 240         int changed, changed_fs;
 241         changed = ie_match_stat(istate, ce, st, really);
 242         if (!changed)
 243                 return 0;
 244         /*
 245          * If the mode or type has changed, there's no point in trying
 246          * to refresh the entry - it's not going to match
 247          */
 248         if (changed & (MODE_CHANGED | TYPE_CHANGED))
 249                 return changed;
 250
 251         /* Immediately after read-tree or update-index --cacheinfo,
 252          * the length field is zero.  For other cases the ce_size
 253          * should match the SHA1 recorded in the index entry.
 254          */
 255         if ((changed & DATA_CHANGED) && ce->ce_size != htonl(0))
 256                 return changed;
 257
 258         changed_fs = ce_modified_check_fs(ce, st);
 259         if (changed_fs)
 260                 return changed | changed_fs;
 261         return 0;
 262 }
 263
 264 int base_name_compare(const char *name1, int len1, int mode1,
 265                       const char *name2, int len2, int mode2)
 266 {
 267         unsigned char c1, c2;
 268         int len = len1 < len2 ? len1 : len2;
 269         int cmp;
 270
 271         cmp = memcmp(name1, name2, len);
 272         if (cmp)
 273                 return cmp;
 274         c1 = name1[len];
 275         c2 = name2[len];
 276         if (!c1 && S_ISDIR(mode1))
 277                 c1 = '/';
 278         if (!c2 && S_ISDIR(mode2))
 279                 c2 = '/';
 280         return (c1 < c2) ? -1 : (c1 > c2) ? 1 : 0;
 281 }
 282
 283 int cache_name_compare(const char *name1, int flags1, const char *name2, int flags2)
 284 {
 285         int len1 = flags1 & CE_NAMEMASK;
 286         int len2 = flags2 & CE_NAMEMASK;
 287         int len = len1 < len2 ? len1 : len2;
 288         int cmp;
 289
 290         cmp = memcmp(name1, name2, len);
 291         if (cmp)
 292                 return cmp;
 293         if (len1 < len2)
 294                 return -1;
 295         if (len1 > len2)
 296                 return 1;
 297
 298         /* Compare stages  */
 299         flags1 &= CE_STAGEMASK;
 300         flags2 &= CE_STAGEMASK;
 301
 302         if (flags1 < flags2)
 303                 return -1;
 304         if (flags1 > flags2)
 305                 return 1;
 306         return 0;
 307 }
 308
 309 int index_name_pos(struct index_state *istate, const char *name, int namelen)
 310 {
 311         int first, last;
 312
 313         first = 0;
 314         last = istate->cache_nr;
 315         while (last > first) {
 316                 int next = (last + first) >> 1;
 317                 struct cache_entry *ce = istate->cache[next];
 318                 int cmp = cache_name_compare(name, namelen, ce->name, ntohs(ce->ce_flags));
 319                 if (!cmp)
 320                         return next;
 321                 if (cmp < 0) {
 322                         last = next;
 323                         continue;
 324                 }
 325                 first = next+1;
 326         }
 327         return -first-1;
 328 }
 329
 330 /* Remove entry, return true if there are more entries to go.. */
 331 int remove_index_entry_at(struct index_state *istate, int pos)
 332 {
 333         istate->cache_changed = 1;
 334         istate->cache_nr--;
 335         if (pos >= istate->cache_nr)
 336                 return 0;
 337         memmove(istate->cache + pos,
 338                 istate->cache + pos + 1,
 339                 (istate->cache_nr - pos) * sizeof(struct cache_entry *));
 340         return 1;
 341 }
 342
 343 int remove_file_from_index(struct index_state *istate, const char *path)
 344 {
 345         int pos = index_name_pos(istate, path, strlen(path));
 346         if (pos < 0)
 347                 pos = -pos-1;
 348         while (pos < istate->cache_nr && !strcmp(istate->cache[pos]->name, path))
 349                 remove_index_entry_at(istate, pos);
 350         return 0;
 351 }
 352
 353 static int compare_name(struct cache_entry *ce, const char *path, int namelen)
 354 {
 355         return namelen != ce_namelen(ce) || memcmp(path, ce->name, namelen);
 356 }
 357
 358 static int index_name_pos_also_unmerged(struct index_state *istate,
 359         const char *path, int namelen)
 360 {
 361         int pos = index_name_pos(istate, path, namelen);
 362         struct cache_entry *ce;
 363
 364         if (pos >= 0)
 365                 return pos;
 366
 367         /* maybe unmerged? */
 368         pos = -1 - pos;
 369         if (pos >= istate->cache_nr ||
 370                         compare_name((ce = istate->cache[pos]), path, namelen))
 371                 return -1;
 372
 373         /* order of preference: stage 2, 1, 3 */
 374         if (ce_stage(ce) == 1 && pos + 1 < istate->cache_nr &&
 375                         ce_stage((ce = istate->cache[pos + 1])) == 2 &&
 376                         !compare_name(ce, path, namelen))
 377                 pos++;
 378         return pos;
 379 }
 380
 381 int add_file_to_index(struct index_state *istate, const char *path, int verbose)
 382 {
 383         int size, namelen;
 384         struct stat st;
 385         struct cache_entry *ce;
 386
 387         if (lstat(path, &st))
 388                 die("%s: unable to stat (%s)", path, strerror(errno));
 389
 390         if (!S_ISREG(st.st_mode) && !S_ISLNK(st.st_mode) && !S_ISDIR(st.st_mode))
 391                 die("%s: can only add regular files, symbolic links or git-directories", path);
 392
 393         namelen = strlen(path);
 394         if (S_ISDIR(st.st_mode)) {
 395                 while (namelen && path[namelen-1] == '/')
 396                         namelen--;
 397         }
 398         size = cache_entry_size(namelen);
 399         ce = xcalloc(1, size);
 400         memcpy(ce->name, path, namelen);
 401         ce->ce_flags = htons(namelen);
 402         fill_stat_cache_info(ce, &st);
 403
 404         if (trust_executable_bit && has_symlinks)
 405                 ce->ce_mode = create_ce_mode(st.st_mode);
 406         else {
 407                 /* If there is an existing entry, pick the mode bits and type
 408                  * from it, otherwise assume unexecutable regular file.
 409                  */
 410                 struct cache_entry *ent;
 411                 int pos = index_name_pos_also_unmerged(istate, path, namelen);
 412
 413                 ent = (0 <= pos) ? istate->cache[pos] : NULL;
 414                 ce->ce_mode = ce_mode_from_stat(ent, st.st_mode);
 415         }
 416
 417         if (index_path(ce->sha1, path, &st, 1))
 418                 die("unable to index file %s", path);
 419         if (add_index_entry(istate, ce, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE))
 420                 die("unable to add %s to index",path);
 421         if (verbose)
 422                 printf("add '%s'\n", path);
 423         cache_tree_invalidate_path(istate->cache_tree, path);
 424         return 0;
 425 }
 426
 427 int ce_same_name(struct cache_entry *a, struct cache_entry *b)
 428 {
 429         int len = ce_namelen(a);
 430         return ce_namelen(b) == len && !memcmp(a->name, b->name, len);
 431 }
 432
 433 int ce_path_match(const struct cache_entry *ce, const char **pathspec)
 434 {
 435         const char *match, *name;
 436         int len;
 437
 438         if (!pathspec)
 439                 return 1;
 440
 441         len = ce_namelen(ce);
 442         name = ce->name;
 443         while ((match = *pathspec++) != NULL) {
 444                 int matchlen = strlen(match);
 445                 if (matchlen > len)
 446                         continue;
 447                 if (memcmp(name, match, matchlen))
 448                         continue;
 449                 if (matchlen && name[matchlen-1] == '/')
 450                         return 1;
 451                 if (name[matchlen] == '/' || !name[matchlen])
 452                         return 1;
 453                 if (!matchlen)
 454                         return 1;
 455         }
 456         return 0;
 457 }
 458
 459 /*
 460  * We fundamentally don't like some paths: we don't want
 461  * dot or dot-dot anywhere, and for obvious reasons don't
 462  * want to recurse into ".git" either.
 463  *
 464  * Also, we don't want double slashes or slashes at the
 465  * end that can make pathnames ambiguous.
 466  */
 467 static int verify_dotfile(const char *rest)
 468 {
 469         /*
 470          * The first character was '.', but that
 471          * has already been discarded, we now test
 472          * the rest.
 473          */
 474         switch (*rest) {
 475         /* "." is not allowed */
 476         case '\0': case '/':
 477                 return 0;
 478
 479         /*
 480          * ".git" followed by  NUL or slash is bad. This
 481          * shares the path end test with the ".." case.
 482          */
 483         case 'g':
 484                 if (rest[1] != 'i')
 485                         break;
 486                 if (rest[2] != 't')
 487                         break;
 488                 rest += 2;
 489         /* fallthrough */
 490         case '.':
 491                 if (rest[1] == '\0' || rest[1] == '/')
 492                         return 0;
 493         }
 494         return 1;
 495 }
 496
 497 int verify_path(const char *path)
 498 {
 499         char c;
 500
 501         goto inside;
 502         for (;;) {
 503                 if (!c)
 504                         return 1;
 505                 if (c == '/') {
 506 inside:
 507                         c = *path++;
 508                         switch (c) {
 509                         default:
 510                                 continue;
 511                         case '/': case '\0':
 512                                 break;
 513                         case '.':
 514                                 if (verify_dotfile(path))
 515                                         continue;
 516                         }
 517                         return 0;
 518                 }
 519                 c = *path++;
 520         }
 521 }
 522
 523 /*
 524  * Do we have another file that has the beginning components being a
 525  * proper superset of the name we're trying to add?
 526  */
 527 static int has_file_name(struct index_state *istate,
 528                          const struct cache_entry *ce, int pos, int ok_to_replace)
 529 {
 530         int retval = 0;
 531         int len = ce_namelen(ce);
 532         int stage = ce_stage(ce);
 533         const char *name = ce->name;
 534
 535         while (pos < istate->cache_nr) {
 536                 struct cache_entry *p = istate->cache[pos++];
 537
 538                 if (len >= ce_namelen(p))
 539                         break;
 540                 if (memcmp(name, p->name, len))
 541                         break;
 542                 if (ce_stage(p) != stage)
 543                         continue;
 544                 if (p->name[len] != '/')
 545                         continue;
 546                 if (!ce_stage(p) && !p->ce_mode)
 547                         continue;
 548                 retval = -1;
 549                 if (!ok_to_replace)
 550                         break;
 551                 remove_index_entry_at(istate, --pos);
 552         }
 553         return retval;
 554 }
 555
 556 /*
 557  * Do we have another file with a pathname that is a proper
 558  * subset of the name we're trying to add?
 559  */
 560 static int has_dir_name(struct index_state *istate,
 561                         const struct cache_entry *ce, int pos, int ok_to_replace)
 562 {
 563         int retval = 0;
 564         int stage = ce_stage(ce);
 565         const char *name = ce->name;
 566         const char *slash = name + ce_namelen(ce);
 567
 568         for (;;) {
 569                 int len;
 570
 571                 for (;;) {
 572                         if (*--slash == '/')
 573                                 break;
 574                         if (slash <= ce->name)
 575                                 return retval;
 576                 }
 577                 len = slash - name;
 578
 579                 pos = index_name_pos(istate, name, ntohs(create_ce_flags(len, stage)));
 580                 if (pos >= 0) {
 581                         /*
 582                          * Found one, but not so fast.  This could
 583                          * be a marker that says "I was here, but
 584                          * I am being removed".  Such an entry is
 585                          * not a part of the resulting tree, and
 586                          * it is Ok to have a directory at the same
 587                          * path.
 588                          */
 589                         if (stage || istate->cache[pos]->ce_mode) {
 590                                 retval = -1;
 591                                 if (!ok_to_replace)
 592                                         break;
 593                                 remove_index_entry_at(istate, pos);
 594                                 continue;
 595                         }
 596                 }
 597                 else
 598                         pos = -pos-1;
 599
 600                 /*
 601                  * Trivial optimization: if we find an entry that
 602                  * already matches the sub-directory, then we know
 603                  * we're ok, and we can exit.
 604                  */
 605                 while (pos < istate->cache_nr) {
 606                         struct cache_entry *p = istate->cache[pos];
 607                         if ((ce_namelen(p) <= len) ||
 608                             (p->name[len] != '/') ||
 609                             memcmp(p->name, name, len))
 610                                 break; /* not our subdirectory */
 611                         if (ce_stage(p) == stage && (stage || p->ce_mode))
 612                                 /* p is at the same stage as our entry, and
 613                                  * is a subdirectory of what we are looking
 614                                  * at, so we cannot have conflicts at our
 615                                  * level or anything shorter.
 616                                  */
 617                                 return retval;
 618                         pos++;
 619                 }
 620         }
 621         return retval;
 622 }
 623
 624 /* We may be in a situation where we already have path/file and path
 625  * is being added, or we already have path and path/file is being
 626  * added.  Either one would result in a nonsense tree that has path
 627  * twice when git-write-tree tries to write it out.  Prevent it.
 628  *
 629  * If ok-to-replace is specified, we remove the conflicting entries
 630  * from the cache so the caller should recompute the insert position.
 631  * When this happens, we return non-zero.
 632  */
 633 static int check_file_directory_conflict(struct index_state *istate,
 634                                          const struct cache_entry *ce,
 635                                          int pos, int ok_to_replace)
 636 {
 637         int retval;
 638
 639         /*
 640          * When ce is an "I am going away" entry, we allow it to be added
 641          */
 642         if (!ce_stage(ce) && !ce->ce_mode)
 643                 return 0;
 644
 645         /*
 646          * We check if the path is a sub-path of a subsequent pathname
 647          * first, since removing those will not change the position
 648          * in the array.
 649          */
 650         retval = has_file_name(istate, ce, pos, ok_to_replace);
 651
 652         /*
 653          * Then check if the path might have a clashing sub-directory
 654          * before it.
 655          */
 656         return retval + has_dir_name(istate, ce, pos, ok_to_replace);
 657 }
 658
 659 int add_index_entry(struct index_state *istate, struct cache_entry *ce, int option)
 660 {
 661         int pos;
 662         int ok_to_add = option & ADD_CACHE_OK_TO_ADD;
 663         int ok_to_replace = option & ADD_CACHE_OK_TO_REPLACE;
 664         int skip_df_check = option & ADD_CACHE_SKIP_DFCHECK;
 665
 666         pos = index_name_pos(istate, ce->name, ntohs(ce->ce_flags));
 667
 668         /* existing match? Just replace it. */
 669         if (pos >= 0) {
 670                 istate->cache_changed = 1;
 671                 istate->cache[pos] = ce;
 672                 return 0;
 673         }
 674         pos = -pos-1;
 675
 676         /*
 677          * Inserting a merged entry ("stage 0") into the index
 678          * will always replace all non-merged entries..
 679          */
 680         if (pos < istate->cache_nr && ce_stage(ce) == 0) {
 681                 while (ce_same_name(istate->cache[pos], ce)) {
 682                         ok_to_add = 1;
 683                         if (!remove_index_entry_at(istate, pos))
 684                                 break;
 685                 }
 686         }
 687
 688         if (!ok_to_add)
 689                 return -1;
 690         if (!verify_path(ce->name))
 691                 return -1;
 692
 693         if (!skip_df_check &&
 694             check_file_directory_conflict(istate, ce, pos, ok_to_replace)) {
 695                 if (!ok_to_replace)
 696                         return error("'%s' appears as both a file and as a directory",
 697                                      ce->name);
 698                 pos = index_name_pos(istate, ce->name, ntohs(ce->ce_flags));
 699                 pos = -pos-1;
 700         }
 701
 702         /* Make sure the array is big enough .. */
 703         if (istate->cache_nr == istate->cache_alloc) {
 704                 istate->cache_alloc = alloc_nr(istate->cache_alloc);
 705                 istate->cache = xrealloc(istate->cache,
 706                                         istate->cache_alloc * sizeof(struct cache_entry *));
 707         }
 708
 709         /* Add it in.. */
 710         istate->cache_nr++;
 711         if (istate->cache_nr > pos)
 712                 memmove(istate->cache + pos + 1,
 713                         istate->cache + pos,
 714                         (istate->cache_nr - pos - 1) * sizeof(ce));
 715         istate->cache[pos] = ce;
 716         istate->cache_changed = 1;
 717         return 0;
 718 }
 719
 720 /*
 721  * "refresh" does not calculate a new sha1 file or bring the
 722  * cache up-to-date for mode/content changes. But what it
 723  * _does_ do is to "re-match" the stat information of a file
 724  * with the cache, so that you can refresh the cache for a
 725  * file that hasn't been changed but where the stat entry is
 726  * out of date.
 727  *
 728  * For example, you'd want to do this after doing a "git-read-tree",
 729  * to link up the stat cache details with the proper files.
 730  */
 731 static struct cache_entry *refresh_cache_ent(struct index_state *istate,
 732                                              struct cache_entry *ce, int really, int *err)
 733 {
 734         struct stat st;
 735         struct cache_entry *updated;
 736         int changed, size;
 737
 738         if (lstat(ce->name, &st) < 0) {
 739                 if (err)
 740                         *err = errno;
 741                 return NULL;
 742         }
 743
 744         changed = ie_match_stat(istate, ce, &st, really);
 745         if (!changed) {
 746                 if (really && assume_unchanged &&
 747                     !(ce->ce_flags & htons(CE_VALID)))
 748                         ; /* mark this one VALID again */
 749                 else
 750                         return ce;
 751         }
 752
 753         if (ie_modified(istate, ce, &st, really)) {
 754                 if (err)
 755                         *err = EINVAL;
 756                 return NULL;
 757         }
 758
 759         size = ce_size(ce);
 760         updated = xmalloc(size);
 761         memcpy(updated, ce, size);
 762         fill_stat_cache_info(updated, &st);
 763
 764         /* In this case, if really is not set, we should leave
 765          * CE_VALID bit alone.  Otherwise, paths marked with
 766          * --no-assume-unchanged (i.e. things to be edited) will
 767          * reacquire CE_VALID bit automatically, which is not
 768          * really what we want.
 769          */
 770         if (!really && assume_unchanged && !(ce->ce_flags & htons(CE_VALID)))
 771                 updated->ce_flags &= ~htons(CE_VALID);
 772
 773         return updated;
 774 }
 775
 776 int refresh_index(struct index_state *istate, unsigned int flags)
 777 {
 778         int i;
 779         int has_errors = 0;
 780         int really = (flags & REFRESH_REALLY) != 0;
 781         int allow_unmerged = (flags & REFRESH_UNMERGED) != 0;
 782         int quiet = (flags & REFRESH_QUIET) != 0;
 783         int not_new = (flags & REFRESH_IGNORE_MISSING) != 0;
 784
 785         for (i = 0; i < istate->cache_nr; i++) {
 786                 struct cache_entry *ce, *new;
 787                 int cache_errno = 0;
 788
 789                 ce = istate->cache[i];
 790                 if (ce_stage(ce)) {
 791                         while ((i < istate->cache_nr) &&
 792                                ! strcmp(istate->cache[i]->name, ce->name))
 793                                 i++;
 794                         i--;
 795                         if (allow_unmerged)
 796                                 continue;
 797                         printf("%s: needs merge\n", ce->name);
 798                         has_errors = 1;
 799                         continue;
 800                 }
 801
 802                 new = refresh_cache_ent(istate, ce, really, &cache_errno);
 803                 if (new == ce)
 804                         continue;
 805                 if (!new) {
 806                         if (not_new && cache_errno == ENOENT)
 807                                 continue;
 808                         if (really && cache_errno == EINVAL) {
 809                                 /* If we are doing --really-refresh that
 810                                  * means the index is not valid anymore.
 811                                  */
 812                                 ce->ce_flags &= ~htons(CE_VALID);
 813                                 istate->cache_changed = 1;
 814                         }
 815                         if (quiet)
 816                                 continue;
 817                         printf("%s: needs update\n", ce->name);
 818                         has_errors = 1;
 819                         continue;
 820                 }
 821                 istate->cache_changed = 1;
 822                 /* You can NOT just free istate->cache[i] here, since it
 823                  * might not be necessarily malloc()ed but can also come
 824                  * from mmap(). */
 825                 istate->cache[i] = new;
 826         }
 827         return has_errors;
 828 }
 829
 830 struct cache_entry *refresh_cache_entry(struct cache_entry *ce, int really)
 831 {
 832         return refresh_cache_ent(&the_index, ce, really, NULL);
 833 }
 834
 835 static int verify_hdr(struct cache_header *hdr, unsigned long size)
 836 {
 837         SHA_CTX c;
 838         unsigned char sha1[20];
 839
 840         if (hdr->hdr_signature != htonl(CACHE_SIGNATURE))
 841                 return error("bad signature");
 842         if (hdr->hdr_version != htonl(2))
 843                 return error("bad index version");
 844         SHA1_Init(&c);
 845         SHA1_Update(&c, hdr, size - 20);
 846         SHA1_Final(sha1, &c);
 847         if (hashcmp(sha1, (unsigned char *)hdr + size - 20))
 848                 return error("bad index file sha1 signature");
 849         return 0;
 850 }
 851
 852 static int read_index_extension(struct index_state *istate,
 853                                 const char *ext, void *data, unsigned long sz)
 854 {
 855         switch (CACHE_EXT(ext)) {
 856         case CACHE_EXT_TREE:
 857                 istate->cache_tree = cache_tree_read(data, sz);
 858                 break;
 859         default:
 860                 if (*ext < 'A' || 'Z' < *ext)
 861                         return error("index uses %.4s extension, which we do not understand",
 862                                      ext);
 863                 fprintf(stderr, "ignoring %.4s extension\n", ext);
 864                 break;
 865         }
 866         return 0;
 867 }
 868
 869 int read_index(struct index_state *istate)
 870 {
 871         return read_index_from(istate, get_index_file());
 872 }
 873
 874 /* remember to discard_cache() before reading a different cache! */
 875 int read_index_from(struct index_state *istate, const char *path)
 876 {
 877         int fd, i;
 878         struct stat st;
 879         unsigned long offset;
 880         struct cache_header *hdr;
 881
 882         errno = EBUSY;
 883         if (istate->mmap)
 884                 return istate->cache_nr;
 885
 886         errno = ENOENT;
 887         istate->timestamp = 0;
 888         fd = open(path, O_RDONLY);
 889         if (fd < 0) {
 890                 if (errno == ENOENT)
 891                         return 0;
 892                 die("index file open failed (%s)", strerror(errno));
 893         }
 894
 895         if (fstat(fd, &st))
 896                 die("cannot stat the open index (%s)", strerror(errno));
 897
 898         errno = EINVAL;
 899         istate->mmap_size = xsize_t(st.st_size);
 900         if (istate->mmap_size < sizeof(struct cache_header) + 20)
 901                 die("index file smaller than expected");
 902
 903         istate->mmap = xmmap(NULL, istate->mmap_size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
 904         close(fd);
 905
 906         hdr = istate->mmap;
 907         if (verify_hdr(hdr, istate->mmap_size) < 0)
 908                 goto unmap;
 909
 910         istate->cache_nr = ntohl(hdr->hdr_entries);
 911         istate->cache_alloc = alloc_nr(istate->cache_nr);
 912         istate->cache = xcalloc(istate->cache_alloc, sizeof(struct cache_entry *));
 913
 914         offset = sizeof(*hdr);
 915         for (i = 0; i < istate->cache_nr; i++) {
 916                 struct cache_entry *ce;
 917
 918                 ce = (struct cache_entry *)((char *)(istate->mmap) + offset);
 919                 offset = offset + ce_size(ce);
 920                 istate->cache[i] = ce;
 921         }
 922         istate->timestamp = st.st_mtime;
 923         while (offset <= istate->mmap_size - 20 - 8) {
 924                 /* After an array of active_nr index entries,
 925                  * there can be arbitrary number of extended
 926                  * sections, each of which is prefixed with
 927                  * extension name (4-byte) and section length
 928                  * in 4-byte network byte order.
 929                  */
 930                 unsigned long extsize;
 931                 memcpy(&extsize, (char *)(istate->mmap) + offset + 4, 4);
 932                 extsize = ntohl(extsize);
 933                 if (read_index_extension(istate,
 934                                          ((const char *) (istate->mmap)) + offset,
 935                                          (char *) (istate->mmap) + offset + 8,
 936                                          extsize) < 0)
 937                         goto unmap;
 938                 offset += 8;
 939                 offset += extsize;
 940         }
 941         return istate->cache_nr;
 942
 943 unmap:
 944         munmap(istate->mmap, istate->mmap_size);
 945         errno = EINVAL;
 946         die("index file corrupt");
 947 }
 948
 949 int discard_index(struct index_state *istate)
 950 {
 951         int ret;
 952
 953         istate->cache_nr = 0;
 954         istate->cache_changed = 0;
 955         istate->timestamp = 0;
 956         cache_tree_free(&(istate->cache_tree));
 957         if (istate->mmap == NULL)
 958                 return 0;
 959         ret = munmap(istate->mmap, istate->mmap_size);
 960         istate->mmap = NULL;
 961         istate->mmap_size = 0;
 962
 963         /* no need to throw away allocated active_cache */
 964         return ret;
 965 }
 966
 967 #define WRITE_BUFFER_SIZE 8192
 968 static unsigned char write_buffer[WRITE_BUFFER_SIZE];
 969 static unsigned long write_buffer_len;
 970
 971 static int ce_write_flush(SHA_CTX *context, int fd)
 972 {
 973         unsigned int buffered = write_buffer_len;
 974         if (buffered) {
 975                 SHA1_Update(context, write_buffer, buffered);
 976                 if (write_in_full(fd, write_buffer, buffered) != buffered)
 977                         return -1;
 978                 write_buffer_len = 0;
 979         }
 980         return 0;
 981 }
 982
 983 static int ce_write(SHA_CTX *context, int fd, void *data, unsigned int len)
 984 {
 985         while (len) {
 986                 unsigned int buffered = write_buffer_len;
 987                 unsigned int partial = WRITE_BUFFER_SIZE - buffered;
 988                 if (partial > len)
 989                         partial = len;
 990                 memcpy(write_buffer + buffered, data, partial);
 991                 buffered += partial;
 992                 if (buffered == WRITE_BUFFER_SIZE) {
 993                         write_buffer_len = buffered;
 994                         if (ce_write_flush(context, fd))
 995                                 return -1;
 996                         buffered = 0;
 997                 }
 998                 write_buffer_len = buffered;
 999                 len -= partial;
1000                 data = (char *) data + partial;
1001         }
1002         return 0;
1003 }
1004
1005 static int write_index_ext_header(SHA_CTX *context, int fd,
1006                                   unsigned int ext, unsigned int sz)
1007 {
1008         ext = htonl(ext);
1009         sz = htonl(sz);
1010         return ((ce_write(context, fd, &ext, 4) < 0) ||
1011                 (ce_write(context, fd, &sz, 4) < 0)) ? -1 : 0;
1012 }
1013
1014 static int ce_flush(SHA_CTX *context, int fd)
1015 {
1016         unsigned int left = write_buffer_len;
1017
1018         if (left) {
1019                 write_buffer_len = 0;
1020                 SHA1_Update(context, write_buffer, left);
1021         }
1022
1023         /* Flush first if not enough space for SHA1 signature */
1024         if (left + 20 > WRITE_BUFFER_SIZE) {
1025                 if (write_in_full(fd, write_buffer, left) != left)
1026                         return -1;
1027                 left = 0;
1028         }
1029
1030         /* Append the SHA1 signature at the end */
1031         SHA1_Final(write_buffer + left, context);
1032         left += 20;
1033         return (write_in_full(fd, write_buffer, left) != left) ? -1 : 0;
1034 }
1035
1036 static void ce_smudge_racily_clean_entry(struct cache_entry *ce)
1037 {
1038         /*
1039          * The only thing we care about in this function is to smudge the
1040          * falsely clean entry due to touch-update-touch race, so we leave
1041          * everything else as they are.  We are called for entries whose
1042          * ce_mtime match the index file mtime.
1043          */
1044         struct stat st;
1045
1046         if (lstat(ce->name, &st) < 0)
1047                 return;
1048         if (ce_match_stat_basic(ce, &st))
1049                 return;
1050         if (ce_modified_check_fs(ce, &st)) {
1051                 /* This is "racily clean"; smudge it.  Note that this
1052                  * is a tricky code.  At first glance, it may appear
1053                  * that it can break with this sequence:
1054                  *
1055                  * $ echo xyzzy >frotz
1056                  * $ git-update-index --add frotz
1057                  * $ : >frotz
1058                  * $ sleep 3
1059                  * $ echo filfre >nitfol
1060                  * $ git-update-index --add nitfol
1061                  *
1062                  * but it does not.  When the second update-index runs,
1063                  * it notices that the entry "frotz" has the same timestamp
1064                  * as index, and if we were to smudge it by resetting its
1065                  * size to zero here, then the object name recorded
1066                  * in index is the 6-byte file but the cached stat information
1067                  * becomes zero --- which would then match what we would
1068                  * obtain from the filesystem next time we stat("frotz").
1069                  *
1070                  * However, the second update-index, before calling
1071                  * this function, notices that the cached size is 6
1072                  * bytes and what is on the filesystem is an empty
1073                  * file, and never calls us, so the cached size information
1074                  * for "frotz" stays 6 which does not match the filesystem.
1075                  */
1076                 ce->ce_size = htonl(0);
1077         }
1078 }
1079
1080 int write_index(struct index_state *istate, int newfd)
1081 {
1082         SHA_CTX c;
1083         struct cache_header hdr;
1084         int i, removed;
1085         struct cache_entry **cache = istate->cache;
1086         int entries = istate->cache_nr;
1087
1088         for (i = removed = 0; i < entries; i++)
1089                 if (!cache[i]->ce_mode)
1090                         removed++;
1091
1092         hdr.hdr_signature = htonl(CACHE_SIGNATURE);
1093         hdr.hdr_version = htonl(2);
1094         hdr.hdr_entries = htonl(entries - removed);
1095
1096         SHA1_Init(&c);
1097         if (ce_write(&c, newfd, &hdr, sizeof(hdr)) < 0)
1098                 return -1;
1099
1100         for (i = 0; i < entries; i++) {
1101                 struct cache_entry *ce = cache[i];
1102                 if (!ce->ce_mode)
1103                         continue;
1104                 if (istate->timestamp &&
1105                     istate->timestamp <= ntohl(ce->ce_mtime.sec))
1106                         ce_smudge_racily_clean_entry(ce);
1107                 if (ce_write(&c, newfd, ce, ce_size(ce)) < 0)
1108                         return -1;
1109         }
1110
1111         /* Write extension data here */
1112         if (istate->cache_tree) {
1113                 unsigned long sz;
1114                 void *data = cache_tree_write(istate->cache_tree, &sz);
1115                 if (data &&
1116                     !write_index_ext_header(&c, newfd, CACHE_EXT_TREE, sz) &&
1117                     !ce_write(&c, newfd, data, sz))
1118                         free(data);
1119                 else {
1120                         free(data);
1121                         return -1;
1122                 }
1123         }
1124         return ce_flush(&c, newfd);
1125 }