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 DIRLNK 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_ISDIRLNK(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_IFDIRLNK:
 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 int add_file_to_index(struct index_state *istate, const char *path, int verbose)
 354 {
 355         int size, namelen;
 356         struct stat st;
 357         struct cache_entry *ce;
 358
 359         if (lstat(path, &st))
 360                 die("%s: unable to stat (%s)", path, strerror(errno));
 361
 362         if (!S_ISREG(st.st_mode) && !S_ISLNK(st.st_mode) && !S_ISDIR(st.st_mode))
 363                 die("%s: can only add regular files, symbolic links or git-directories", path);
 364
 365         namelen = strlen(path);
 366         if (S_ISDIR(st.st_mode)) {
 367                 while (namelen && path[namelen-1] == '/')
 368                         namelen--;
 369         }
 370         size = cache_entry_size(namelen);
 371         ce = xcalloc(1, size);
 372         memcpy(ce->name, path, namelen);
 373         ce->ce_flags = htons(namelen);
 374         fill_stat_cache_info(ce, &st);
 375
 376         if (trust_executable_bit && has_symlinks)
 377                 ce->ce_mode = create_ce_mode(st.st_mode);
 378         else {
 379                 /* If there is an existing entry, pick the mode bits and type
 380                  * from it, otherwise assume unexecutable regular file.
 381                  */
 382                 struct cache_entry *ent;
 383                 int pos = index_name_pos(istate, path, namelen);
 384
 385                 ent = (0 <= pos) ? istate->cache[pos] : NULL;
 386                 ce->ce_mode = ce_mode_from_stat(ent, st.st_mode);
 387         }
 388
 389         if (index_path(ce->sha1, path, &st, 1))
 390                 die("unable to index file %s", path);
 391         if (add_index_entry(istate, ce, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE))
 392                 die("unable to add %s to index",path);
 393         if (verbose)
 394                 printf("add '%s'\n", path);
 395         cache_tree_invalidate_path(istate->cache_tree, path);
 396         return 0;
 397 }
 398
 399 int ce_same_name(struct cache_entry *a, struct cache_entry *b)
 400 {
 401         int len = ce_namelen(a);
 402         return ce_namelen(b) == len && !memcmp(a->name, b->name, len);
 403 }
 404
 405 int ce_path_match(const struct cache_entry *ce, const char **pathspec)
 406 {
 407         const char *match, *name;
 408         int len;
 409
 410         if (!pathspec)
 411                 return 1;
 412
 413         len = ce_namelen(ce);
 414         name = ce->name;
 415         while ((match = *pathspec++) != NULL) {
 416                 int matchlen = strlen(match);
 417                 if (matchlen > len)
 418                         continue;
 419                 if (memcmp(name, match, matchlen))
 420                         continue;
 421                 if (matchlen && name[matchlen-1] == '/')
 422                         return 1;
 423                 if (name[matchlen] == '/' || !name[matchlen])
 424                         return 1;
 425                 if (!matchlen)
 426                         return 1;
 427         }
 428         return 0;
 429 }
 430
 431 /*
 432  * We fundamentally don't like some paths: we don't want
 433  * dot or dot-dot anywhere, and for obvious reasons don't
 434  * want to recurse into ".git" either.
 435  *
 436  * Also, we don't want double slashes or slashes at the
 437  * end that can make pathnames ambiguous.
 438  */
 439 static int verify_dotfile(const char *rest)
 440 {
 441         /*
 442          * The first character was '.', but that
 443          * has already been discarded, we now test
 444          * the rest.
 445          */
 446         switch (*rest) {
 447         /* "." is not allowed */
 448         case '\0': case '/':
 449                 return 0;
 450
 451         /*
 452          * ".git" followed by  NUL or slash is bad. This
 453          * shares the path end test with the ".." case.
 454          */
 455         case 'g':
 456                 if (rest[1] != 'i')
 457                         break;
 458                 if (rest[2] != 't')
 459                         break;
 460                 rest += 2;
 461         /* fallthrough */
 462         case '.':
 463                 if (rest[1] == '\0' || rest[1] == '/')
 464                         return 0;
 465         }
 466         return 1;
 467 }
 468
 469 int verify_path(const char *path)
 470 {
 471         char c;
 472
 473         goto inside;
 474         for (;;) {
 475                 if (!c)
 476                         return 1;
 477                 if (c == '/') {
 478 inside:
 479                         c = *path++;
 480                         switch (c) {
 481                         default:
 482                                 continue;
 483                         case '/': case '\0':
 484                                 break;
 485                         case '.':
 486                                 if (verify_dotfile(path))
 487                                         continue;
 488                         }
 489                         return 0;
 490                 }
 491                 c = *path++;
 492         }
 493 }
 494
 495 /*
 496  * Do we have another file that has the beginning components being a
 497  * proper superset of the name we're trying to add?
 498  */
 499 static int has_file_name(struct index_state *istate,
 500                          const struct cache_entry *ce, int pos, int ok_to_replace)
 501 {
 502         int retval = 0;
 503         int len = ce_namelen(ce);
 504         int stage = ce_stage(ce);
 505         const char *name = ce->name;
 506
 507         while (pos < istate->cache_nr) {
 508                 struct cache_entry *p = istate->cache[pos++];
 509
 510                 if (len >= ce_namelen(p))
 511                         break;
 512                 if (memcmp(name, p->name, len))
 513                         break;
 514                 if (ce_stage(p) != stage)
 515                         continue;
 516                 if (p->name[len] != '/')
 517                         continue;
 518                 if (!ce_stage(p) && !p->ce_mode)
 519                         continue;
 520                 retval = -1;
 521                 if (!ok_to_replace)
 522                         break;
 523                 remove_index_entry_at(istate, --pos);
 524         }
 525         return retval;
 526 }
 527
 528 /*
 529  * Do we have another file with a pathname that is a proper
 530  * subset of the name we're trying to add?
 531  */
 532 static int has_dir_name(struct index_state *istate,
 533                         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 = index_name_pos(istate, 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 || istate->cache[pos]->ce_mode) {
 562                                 retval = -1;
 563                                 if (!ok_to_replace)
 564                                         break;
 565                                 remove_index_entry_at(istate, 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 < istate->cache_nr) {
 578                         struct cache_entry *p = istate->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(struct index_state *istate,
 606                                          const struct cache_entry *ce,
 607                                          int pos, int ok_to_replace)
 608 {
 609         int retval;
 610
 611         /*
 612          * When ce is an "I am going away" entry, we allow it to be added
 613          */
 614         if (!ce_stage(ce) && !ce->ce_mode)
 615                 return 0;
 616
 617         /*
 618          * We check if the path is a sub-path of a subsequent pathname
 619          * first, since removing those will not change the position
 620          * in the array.
 621          */
 622         retval = has_file_name(istate, ce, pos, ok_to_replace);
 623
 624         /*
 625          * Then check if the path might have a clashing sub-directory
 626          * before it.
 627          */
 628         return retval + has_dir_name(istate, ce, pos, ok_to_replace);
 629 }
 630
 631 int add_index_entry(struct index_state *istate, struct cache_entry *ce, int option)
 632 {
 633         int pos;
 634         int ok_to_add = option & ADD_CACHE_OK_TO_ADD;
 635         int ok_to_replace = option & ADD_CACHE_OK_TO_REPLACE;
 636         int skip_df_check = option & ADD_CACHE_SKIP_DFCHECK;
 637
 638         pos = index_name_pos(istate, ce->name, ntohs(ce->ce_flags));
 639
 640         /* existing match? Just replace it. */
 641         if (pos >= 0) {
 642                 istate->cache_changed = 1;
 643                 istate->cache[pos] = ce;
 644                 return 0;
 645         }
 646         pos = -pos-1;
 647
 648         /*
 649          * Inserting a merged entry ("stage 0") into the index
 650          * will always replace all non-merged entries..
 651          */
 652         if (pos < istate->cache_nr && ce_stage(ce) == 0) {
 653                 while (ce_same_name(istate->cache[pos], ce)) {
 654                         ok_to_add = 1;
 655                         if (!remove_index_entry_at(istate, pos))
 656                                 break;
 657                 }
 658         }
 659
 660         if (!ok_to_add)
 661                 return -1;
 662         if (!verify_path(ce->name))
 663                 return -1;
 664
 665         if (!skip_df_check &&
 666             check_file_directory_conflict(istate, ce, pos, ok_to_replace)) {
 667                 if (!ok_to_replace)
 668                         return error("'%s' appears as both a file and as a directory",
 669                                      ce->name);
 670                 pos = index_name_pos(istate, ce->name, ntohs(ce->ce_flags));
 671                 pos = -pos-1;
 672         }
 673
 674         /* Make sure the array is big enough .. */
 675         if (istate->cache_nr == istate->cache_alloc) {
 676                 istate->cache_alloc = alloc_nr(istate->cache_alloc);
 677                 istate->cache = xrealloc(istate->cache,
 678                                         istate->cache_alloc * sizeof(struct cache_entry *));
 679         }
 680
 681         /* Add it in.. */
 682         istate->cache_nr++;
 683         if (istate->cache_nr > pos)
 684                 memmove(istate->cache + pos + 1,
 685                         istate->cache + pos,
 686                         (istate->cache_nr - pos - 1) * sizeof(ce));
 687         istate->cache[pos] = ce;
 688         istate->cache_changed = 1;
 689         return 0;
 690 }
 691
 692 /*
 693  * "refresh" does not calculate a new sha1 file or bring the
 694  * cache up-to-date for mode/content changes. But what it
 695  * _does_ do is to "re-match" the stat information of a file
 696  * with the cache, so that you can refresh the cache for a
 697  * file that hasn't been changed but where the stat entry is
 698  * out of date.
 699  *
 700  * For example, you'd want to do this after doing a "git-read-tree",
 701  * to link up the stat cache details with the proper files.
 702  */
 703 static struct cache_entry *refresh_cache_ent(struct index_state *istate,
 704                                              struct cache_entry *ce, int really, int *err)
 705 {
 706         struct stat st;
 707         struct cache_entry *updated;
 708         int changed, size;
 709
 710         if (lstat(ce->name, &st) < 0) {
 711                 if (err)
 712                         *err = errno;
 713                 return NULL;
 714         }
 715
 716         changed = ie_match_stat(istate, ce, &st, really);
 717         if (!changed) {
 718                 if (really && assume_unchanged &&
 719                     !(ce->ce_flags & htons(CE_VALID)))
 720                         ; /* mark this one VALID again */
 721                 else
 722                         return ce;
 723         }
 724
 725         if (ie_modified(istate, ce, &st, really)) {
 726                 if (err)
 727                         *err = EINVAL;
 728                 return NULL;
 729         }
 730
 731         size = ce_size(ce);
 732         updated = xmalloc(size);
 733         memcpy(updated, ce, size);
 734         fill_stat_cache_info(updated, &st);
 735
 736         /* In this case, if really is not set, we should leave
 737          * CE_VALID bit alone.  Otherwise, paths marked with
 738          * --no-assume-unchanged (i.e. things to be edited) will
 739          * reacquire CE_VALID bit automatically, which is not
 740          * really what we want.
 741          */
 742         if (!really && assume_unchanged && !(ce->ce_flags & htons(CE_VALID)))
 743                 updated->ce_flags &= ~htons(CE_VALID);
 744
 745         return updated;
 746 }
 747
 748 int refresh_index(struct index_state *istate, unsigned int flags)
 749 {
 750         int i;
 751         int has_errors = 0;
 752         int really = (flags & REFRESH_REALLY) != 0;
 753         int allow_unmerged = (flags & REFRESH_UNMERGED) != 0;
 754         int quiet = (flags & REFRESH_QUIET) != 0;
 755         int not_new = (flags & REFRESH_IGNORE_MISSING) != 0;
 756
 757         for (i = 0; i < istate->cache_nr; i++) {
 758                 struct cache_entry *ce, *new;
 759                 int cache_errno = 0;
 760
 761                 ce = istate->cache[i];
 762                 if (ce_stage(ce)) {
 763                         while ((i < istate->cache_nr) &&
 764                                ! strcmp(istate->cache[i]->name, ce->name))
 765                                 i++;
 766                         i--;
 767                         if (allow_unmerged)
 768                                 continue;
 769                         printf("%s: needs merge\n", ce->name);
 770                         has_errors = 1;
 771                         continue;
 772                 }
 773
 774                 new = refresh_cache_ent(istate, ce, really, &cache_errno);
 775                 if (new == ce)
 776                         continue;
 777                 if (!new) {
 778                         if (not_new && cache_errno == ENOENT)
 779                                 continue;
 780                         if (really && cache_errno == EINVAL) {
 781                                 /* If we are doing --really-refresh that
 782                                  * means the index is not valid anymore.
 783                                  */
 784                                 ce->ce_flags &= ~htons(CE_VALID);
 785                                 istate->cache_changed = 1;
 786                         }
 787                         if (quiet)
 788                                 continue;
 789                         printf("%s: needs update\n", ce->name);
 790                         has_errors = 1;
 791                         continue;
 792                 }
 793                 istate->cache_changed = 1;
 794                 /* You can NOT just free istate->cache[i] here, since it
 795                  * might not be necessarily malloc()ed but can also come
 796                  * from mmap(). */
 797                 istate->cache[i] = new;
 798         }
 799         return has_errors;
 800 }
 801
 802 struct cache_entry *refresh_cache_entry(struct cache_entry *ce, int really)
 803 {
 804         return refresh_cache_ent(&the_index, ce, really, NULL);
 805 }
 806
 807 static int verify_hdr(struct cache_header *hdr, unsigned long size)
 808 {
 809         SHA_CTX c;
 810         unsigned char sha1[20];
 811
 812         if (hdr->hdr_signature != htonl(CACHE_SIGNATURE))
 813                 return error("bad signature");
 814         if (hdr->hdr_version != htonl(2))
 815                 return error("bad index version");
 816         SHA1_Init(&c);
 817         SHA1_Update(&c, hdr, size - 20);
 818         SHA1_Final(sha1, &c);
 819         if (hashcmp(sha1, (unsigned char *)hdr + size - 20))
 820                 return error("bad index file sha1 signature");
 821         return 0;
 822 }
 823
 824 static int read_index_extension(struct index_state *istate,
 825                                 const char *ext, void *data, unsigned long sz)
 826 {
 827         switch (CACHE_EXT(ext)) {
 828         case CACHE_EXT_TREE:
 829                 istate->cache_tree = cache_tree_read(data, sz);
 830                 break;
 831         default:
 832                 if (*ext < 'A' || 'Z' < *ext)
 833                         return error("index uses %.4s extension, which we do not understand",
 834                                      ext);
 835                 fprintf(stderr, "ignoring %.4s extension\n", ext);
 836                 break;
 837         }
 838         return 0;
 839 }
 840
 841 int read_index(struct index_state *istate)
 842 {
 843         return read_index_from(istate, get_index_file());
 844 }
 845
 846 /* remember to discard_cache() before reading a different cache! */
 847 int read_index_from(struct index_state *istate, const char *path)
 848 {
 849         int fd, i;
 850         struct stat st;
 851         unsigned long offset;
 852         struct cache_header *hdr;
 853
 854         errno = EBUSY;
 855         if (istate->mmap)
 856                 return istate->cache_nr;
 857
 858         errno = ENOENT;
 859         istate->timestamp = 0;
 860         fd = open(path, O_RDONLY);
 861         if (fd < 0) {
 862                 if (errno == ENOENT)
 863                         return 0;
 864                 die("index file open failed (%s)", strerror(errno));
 865         }
 866
 867         if (!fstat(fd, &st)) {
 868                 istate->mmap_size = xsize_t(st.st_size);
 869                 errno = EINVAL;
 870                 if (istate->mmap_size >= sizeof(struct cache_header) + 20)
 871                         istate->mmap = xmmap(NULL, istate->mmap_size,
 872                                             PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
 873                 else
 874                         die("index file smaller than expected");
 875         } else
 876                 die("cannot stat the open index (%s)", strerror(errno));
 877         close(fd);
 878
 879         hdr = istate->mmap;
 880         if (verify_hdr(hdr, istate->mmap_size) < 0)
 881                 goto unmap;
 882
 883         istate->cache_nr = ntohl(hdr->hdr_entries);
 884         istate->cache_alloc = alloc_nr(istate->cache_nr);
 885         istate->cache = xcalloc(istate->cache_alloc, sizeof(struct cache_entry *));
 886
 887         offset = sizeof(*hdr);
 888         for (i = 0; i < istate->cache_nr; i++) {
 889                 struct cache_entry *ce;
 890
 891                 ce = (struct cache_entry *)((char *)(istate->mmap) + offset);
 892                 offset = offset + ce_size(ce);
 893                 istate->cache[i] = ce;
 894         }
 895         istate->timestamp = st.st_mtime;
 896         while (offset <= istate->mmap_size - 20 - 8) {
 897                 /* After an array of active_nr index entries,
 898                  * there can be arbitrary number of extended
 899                  * sections, each of which is prefixed with
 900                  * extension name (4-byte) and section length
 901                  * in 4-byte network byte order.
 902                  */
 903                 unsigned long extsize;
 904                 memcpy(&extsize, (char *)(istate->mmap) + offset + 4, 4);
 905                 extsize = ntohl(extsize);
 906                 if (read_index_extension(istate,
 907                                          ((const char *) (istate->mmap)) + offset,
 908                                          (char *) (istate->mmap) + offset + 8,
 909                                          extsize) < 0)
 910                         goto unmap;
 911                 offset += 8;
 912                 offset += extsize;
 913         }
 914         return istate->cache_nr;
 915
 916 unmap:
 917         munmap(istate->mmap, istate->mmap_size);
 918         errno = EINVAL;
 919         die("index file corrupt");
 920 }
 921
 922 int discard_index(struct index_state *istate)
 923 {
 924         int ret;
 925
 926         istate->cache_nr = 0;
 927         istate->cache_changed = 0;
 928         istate->timestamp = 0;
 929         cache_tree_free(&(istate->cache_tree));
 930         if (istate->mmap == NULL)
 931                 return 0;
 932         ret = munmap(istate->mmap, istate->mmap_size);
 933         istate->mmap = NULL;
 934         istate->mmap_size = 0;
 935
 936         /* no need to throw away allocated active_cache */
 937         return ret;
 938 }
 939
 940 #define WRITE_BUFFER_SIZE 8192
 941 static unsigned char write_buffer[WRITE_BUFFER_SIZE];
 942 static unsigned long write_buffer_len;
 943
 944 static int ce_write_flush(SHA_CTX *context, int fd)
 945 {
 946         unsigned int buffered = write_buffer_len;
 947         if (buffered) {
 948                 SHA1_Update(context, write_buffer, buffered);
 949                 if (write_in_full(fd, write_buffer, buffered) != buffered)
 950                         return -1;
 951                 write_buffer_len = 0;
 952         }
 953         return 0;
 954 }
 955
 956 static int ce_write(SHA_CTX *context, int fd, void *data, unsigned int len)
 957 {
 958         while (len) {
 959                 unsigned int buffered = write_buffer_len;
 960                 unsigned int partial = WRITE_BUFFER_SIZE - buffered;
 961                 if (partial > len)
 962                         partial = len;
 963                 memcpy(write_buffer + buffered, data, partial);
 964                 buffered += partial;
 965                 if (buffered == WRITE_BUFFER_SIZE) {
 966                         write_buffer_len = buffered;
 967                         if (ce_write_flush(context, fd))
 968                                 return -1;
 969                         buffered = 0;
 970                 }
 971                 write_buffer_len = buffered;
 972                 len -= partial;
 973                 data = (char *) data + partial;
 974         }
 975         return 0;
 976 }
 977
 978 static int write_index_ext_header(SHA_CTX *context, int fd,
 979                                   unsigned int ext, unsigned int sz)
 980 {
 981         ext = htonl(ext);
 982         sz = htonl(sz);
 983         return ((ce_write(context, fd, &ext, 4) < 0) ||
 984                 (ce_write(context, fd, &sz, 4) < 0)) ? -1 : 0;
 985 }
 986
 987 static int ce_flush(SHA_CTX *context, int fd)
 988 {
 989         unsigned int left = write_buffer_len;
 990
 991         if (left) {
 992                 write_buffer_len = 0;
 993                 SHA1_Update(context, write_buffer, left);
 994         }
 995
 996         /* Flush first if not enough space for SHA1 signature */
 997         if (left + 20 > WRITE_BUFFER_SIZE) {
 998                 if (write_in_full(fd, write_buffer, left) != left)
 999                         return -1;
1000                 left = 0;
1001         }
1002
1003         /* Append the SHA1 signature at the end */
1004         SHA1_Final(write_buffer + left, context);
1005         left += 20;
1006         return (write_in_full(fd, write_buffer, left) != left) ? -1 : 0;
1007 }
1008
1009 static void ce_smudge_racily_clean_entry(struct cache_entry *ce)
1010 {
1011         /*
1012          * The only thing we care about in this function is to smudge the
1013          * falsely clean entry due to touch-update-touch race, so we leave
1014          * everything else as they are.  We are called for entries whose
1015          * ce_mtime match the index file mtime.
1016          */
1017         struct stat st;
1018
1019         if (lstat(ce->name, &st) < 0)
1020                 return;
1021         if (ce_match_stat_basic(ce, &st))
1022                 return;
1023         if (ce_modified_check_fs(ce, &st)) {
1024                 /* This is "racily clean"; smudge it.  Note that this
1025                  * is a tricky code.  At first glance, it may appear
1026                  * that it can break with this sequence:
1027                  *
1028                  * $ echo xyzzy >frotz
1029                  * $ git-update-index --add frotz
1030                  * $ : >frotz
1031                  * $ sleep 3
1032                  * $ echo filfre >nitfol
1033                  * $ git-update-index --add nitfol
1034                  *
1035                  * but it does not.  When the second update-index runs,
1036                  * it notices that the entry "frotz" has the same timestamp
1037                  * as index, and if we were to smudge it by resetting its
1038                  * size to zero here, then the object name recorded
1039                  * in index is the 6-byte file but the cached stat information
1040                  * becomes zero --- which would then match what we would
1041                  * obtain from the filesystem next time we stat("frotz").
1042                  *
1043                  * However, the second update-index, before calling
1044                  * this function, notices that the cached size is 6
1045                  * bytes and what is on the filesystem is an empty
1046                  * file, and never calls us, so the cached size information
1047                  * for "frotz" stays 6 which does not match the filesystem.
1048                  */
1049                 ce->ce_size = htonl(0);
1050         }
1051 }
1052
1053 int write_index(struct index_state *istate, int newfd)
1054 {
1055         SHA_CTX c;
1056         struct cache_header hdr;
1057         int i, removed;
1058         struct cache_entry **cache = istate->cache;
1059         int entries = istate->cache_nr;
1060
1061         for (i = removed = 0; i < entries; i++)
1062                 if (!cache[i]->ce_mode)
1063                         removed++;
1064
1065         hdr.hdr_signature = htonl(CACHE_SIGNATURE);
1066         hdr.hdr_version = htonl(2);
1067         hdr.hdr_entries = htonl(entries - removed);
1068
1069         SHA1_Init(&c);
1070         if (ce_write(&c, newfd, &hdr, sizeof(hdr)) < 0)
1071                 return -1;
1072
1073         for (i = 0; i < entries; i++) {
1074                 struct cache_entry *ce = cache[i];
1075                 if (!ce->ce_mode)
1076                         continue;
1077                 if (istate->timestamp &&
1078                     istate->timestamp <= ntohl(ce->ce_mtime.sec))
1079                         ce_smudge_racily_clean_entry(ce);
1080                 if (ce_write(&c, newfd, ce, ce_size(ce)) < 0)
1081                         return -1;
1082         }
1083
1084         /* Write extension data here */
1085         if (istate->cache_tree) {
1086                 unsigned long sz;
1087                 void *data = cache_tree_write(istate->cache_tree, &sz);
1088                 if (data &&
1089                     !write_index_ext_header(&c, newfd, CACHE_EXT_TREE, sz) &&
1090                     !ce_write(&c, newfd, data, sz))
1091                         free(data);
1092                 else {
1093                         free(data);
1094                         return -1;
1095                 }
1096         }
1097         return ce_flush(&c, newfd);
1098 }