read-cache.con commit update-index: make D/F conflict error a bit more verbose. (790fa0e)
   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
   9/* Index extensions.
  10 *
  11 * The first letter should be 'A'..'Z' for extensions that are not
  12 * necessary for a correct operation (i.e. optimization data).
  13 * When new extensions are added that _needs_ to be understood in
  14 * order to correctly interpret the index file, pick character that
  15 * is outside the range, to cause the reader to abort.
  16 */
  17
  18#define CACHE_EXT(s) ( (s[0]<<24)|(s[1]<<16)|(s[2]<<8)|(s[3]) )
  19#define CACHE_EXT_TREE 0x54524545       /* "TREE" */
  20
  21struct cache_entry **active_cache;
  22static time_t index_file_timestamp;
  23unsigned int active_nr, active_alloc, active_cache_changed;
  24
  25struct cache_tree *active_cache_tree;
  26
  27int cache_errno;
  28
  29static void *cache_mmap;
  30static size_t cache_mmap_size;
  31
  32/*
  33 * This only updates the "non-critical" parts of the directory
  34 * cache, ie the parts that aren't tracked by GIT, and only used
  35 * to validate the cache.
  36 */
  37void fill_stat_cache_info(struct cache_entry *ce, struct stat *st)
  38{
  39        ce->ce_ctime.sec = htonl(st->st_ctime);
  40        ce->ce_mtime.sec = htonl(st->st_mtime);
  41#ifdef USE_NSEC
  42        ce->ce_ctime.nsec = htonl(st->st_ctim.tv_nsec);
  43        ce->ce_mtime.nsec = htonl(st->st_mtim.tv_nsec);
  44#endif
  45        ce->ce_dev = htonl(st->st_dev);
  46        ce->ce_ino = htonl(st->st_ino);
  47        ce->ce_uid = htonl(st->st_uid);
  48        ce->ce_gid = htonl(st->st_gid);
  49        ce->ce_size = htonl(st->st_size);
  50
  51        if (assume_unchanged)
  52                ce->ce_flags |= htons(CE_VALID);
  53}
  54
  55static int ce_compare_data(struct cache_entry *ce, struct stat *st)
  56{
  57        int match = -1;
  58        int fd = open(ce->name, O_RDONLY);
  59
  60        if (fd >= 0) {
  61                unsigned char sha1[20];
  62                if (!index_fd(sha1, fd, st, 0, NULL))
  63                        match = hashcmp(sha1, ce->sha1);
  64                /* index_fd() closed the file descriptor already */
  65        }
  66        return match;
  67}
  68
  69static int ce_compare_link(struct cache_entry *ce, unsigned long expected_size)
  70{
  71        int match = -1;
  72        char *target;
  73        void *buffer;
  74        unsigned long size;
  75        char type[10];
  76        int len;
  77
  78        target = xmalloc(expected_size);
  79        len = readlink(ce->name, target, expected_size);
  80        if (len != expected_size) {
  81                free(target);
  82                return -1;
  83        }
  84        buffer = read_sha1_file(ce->sha1, type, &size);
  85        if (!buffer) {
  86                free(target);
  87                return -1;
  88        }
  89        if (size == expected_size)
  90                match = memcmp(buffer, target, size);
  91        free(buffer);
  92        free(target);
  93        return match;
  94}
  95
  96static int ce_modified_check_fs(struct cache_entry *ce, struct stat *st)
  97{
  98        switch (st->st_mode & S_IFMT) {
  99        case S_IFREG:
 100                if (ce_compare_data(ce, st))
 101                        return DATA_CHANGED;
 102                break;
 103        case S_IFLNK:
 104                if (ce_compare_link(ce, st->st_size))
 105                        return DATA_CHANGED;
 106                break;
 107        default:
 108                return TYPE_CHANGED;
 109        }
 110        return 0;
 111}
 112
 113static int ce_match_stat_basic(struct cache_entry *ce, struct stat *st)
 114{
 115        unsigned int changed = 0;
 116
 117        switch (ntohl(ce->ce_mode) & S_IFMT) {
 118        case S_IFREG:
 119                changed |= !S_ISREG(st->st_mode) ? TYPE_CHANGED : 0;
 120                /* We consider only the owner x bit to be relevant for
 121                 * "mode changes"
 122                 */
 123                if (trust_executable_bit &&
 124                    (0100 & (ntohl(ce->ce_mode) ^ st->st_mode)))
 125                        changed |= MODE_CHANGED;
 126                break;
 127        case S_IFLNK:
 128                changed |= !S_ISLNK(st->st_mode) ? TYPE_CHANGED : 0;
 129                break;
 130        default:
 131                die("internal error: ce_mode is %o", ntohl(ce->ce_mode));
 132        }
 133        if (ce->ce_mtime.sec != htonl(st->st_mtime))
 134                changed |= MTIME_CHANGED;
 135        if (ce->ce_ctime.sec != htonl(st->st_ctime))
 136                changed |= CTIME_CHANGED;
 137
 138#ifdef USE_NSEC
 139        /*
 140         * nsec seems unreliable - not all filesystems support it, so
 141         * as long as it is in the inode cache you get right nsec
 142         * but after it gets flushed, you get zero nsec.
 143         */
 144        if (ce->ce_mtime.nsec != htonl(st->st_mtim.tv_nsec))
 145                changed |= MTIME_CHANGED;
 146        if (ce->ce_ctime.nsec != htonl(st->st_ctim.tv_nsec))
 147                changed |= CTIME_CHANGED;
 148#endif  
 149
 150        if (ce->ce_uid != htonl(st->st_uid) ||
 151            ce->ce_gid != htonl(st->st_gid))
 152                changed |= OWNER_CHANGED;
 153        if (ce->ce_ino != htonl(st->st_ino))
 154                changed |= INODE_CHANGED;
 155
 156#ifdef USE_STDEV
 157        /*
 158         * st_dev breaks on network filesystems where different
 159         * clients will have different views of what "device"
 160         * the filesystem is on
 161         */
 162        if (ce->ce_dev != htonl(st->st_dev))
 163                changed |= INODE_CHANGED;
 164#endif
 165
 166        if (ce->ce_size != htonl(st->st_size))
 167                changed |= DATA_CHANGED;
 168
 169        return changed;
 170}
 171
 172int ce_match_stat(struct cache_entry *ce, struct stat *st, int options)
 173{
 174        unsigned int changed;
 175        int ignore_valid = options & 01;
 176        int assume_racy_is_modified = options & 02;
 177
 178        /*
 179         * If it's marked as always valid in the index, it's
 180         * valid whatever the checked-out copy says.
 181         */
 182        if (!ignore_valid && (ce->ce_flags & htons(CE_VALID)))
 183                return 0;
 184
 185        changed = ce_match_stat_basic(ce, st);
 186
 187        /*
 188         * Within 1 second of this sequence:
 189         *      echo xyzzy >file && git-update-index --add file
 190         * running this command:
 191         *      echo frotz >file
 192         * would give a falsely clean cache entry.  The mtime and
 193         * length match the cache, and other stat fields do not change.
 194         *
 195         * We could detect this at update-index time (the cache entry
 196         * being registered/updated records the same time as "now")
 197         * and delay the return from git-update-index, but that would
 198         * effectively mean we can make at most one commit per second,
 199         * which is not acceptable.  Instead, we check cache entries
 200         * whose mtime are the same as the index file timestamp more
 201         * carefully than others.
 202         */
 203        if (!changed &&
 204            index_file_timestamp &&
 205            index_file_timestamp <= ntohl(ce->ce_mtime.sec)) {
 206                if (assume_racy_is_modified)
 207                        changed |= DATA_CHANGED;
 208                else
 209                        changed |= ce_modified_check_fs(ce, st);
 210        }
 211
 212        return changed;
 213}
 214
 215int ce_modified(struct cache_entry *ce, struct stat *st, int really)
 216{
 217        int changed, changed_fs;
 218        changed = ce_match_stat(ce, st, really);
 219        if (!changed)
 220                return 0;
 221        /*
 222         * If the mode or type has changed, there's no point in trying
 223         * to refresh the entry - it's not going to match
 224         */
 225        if (changed & (MODE_CHANGED | TYPE_CHANGED))
 226                return changed;
 227
 228        /* Immediately after read-tree or update-index --cacheinfo,
 229         * the length field is zero.  For other cases the ce_size
 230         * should match the SHA1 recorded in the index entry.
 231         */
 232        if ((changed & DATA_CHANGED) && ce->ce_size != htonl(0))
 233                return changed;
 234
 235        changed_fs = ce_modified_check_fs(ce, st);
 236        if (changed_fs)
 237                return changed | changed_fs;
 238        return 0;
 239}
 240
 241int base_name_compare(const char *name1, int len1, int mode1,
 242                      const char *name2, int len2, int mode2)
 243{
 244        unsigned char c1, c2;
 245        int len = len1 < len2 ? len1 : len2;
 246        int cmp;
 247
 248        cmp = memcmp(name1, name2, len);
 249        if (cmp)
 250                return cmp;
 251        c1 = name1[len];
 252        c2 = name2[len];
 253        if (!c1 && S_ISDIR(mode1))
 254                c1 = '/';
 255        if (!c2 && S_ISDIR(mode2))
 256                c2 = '/';
 257        return (c1 < c2) ? -1 : (c1 > c2) ? 1 : 0;
 258}
 259
 260int cache_name_compare(const char *name1, int flags1, const char *name2, int flags2)
 261{
 262        int len1 = flags1 & CE_NAMEMASK;
 263        int len2 = flags2 & CE_NAMEMASK;
 264        int len = len1 < len2 ? len1 : len2;
 265        int cmp;
 266
 267        cmp = memcmp(name1, name2, len);
 268        if (cmp)
 269                return cmp;
 270        if (len1 < len2)
 271                return -1;
 272        if (len1 > len2)
 273                return 1;
 274
 275        /* Compare stages  */
 276        flags1 &= CE_STAGEMASK;
 277        flags2 &= CE_STAGEMASK;
 278
 279        if (flags1 < flags2)
 280                return -1;
 281        if (flags1 > flags2)
 282                return 1;
 283        return 0;
 284}
 285
 286int cache_name_pos(const char *name, int namelen)
 287{
 288        int first, last;
 289
 290        first = 0;
 291        last = active_nr;
 292        while (last > first) {
 293                int next = (last + first) >> 1;
 294                struct cache_entry *ce = active_cache[next];
 295                int cmp = cache_name_compare(name, namelen, ce->name, ntohs(ce->ce_flags));
 296                if (!cmp)
 297                        return next;
 298                if (cmp < 0) {
 299                        last = next;
 300                        continue;
 301                }
 302                first = next+1;
 303        }
 304        return -first-1;
 305}
 306
 307/* Remove entry, return true if there are more entries to go.. */
 308int remove_cache_entry_at(int pos)
 309{
 310        active_cache_changed = 1;
 311        active_nr--;
 312        if (pos >= active_nr)
 313                return 0;
 314        memmove(active_cache + pos, active_cache + pos + 1, (active_nr - pos) * sizeof(struct cache_entry *));
 315        return 1;
 316}
 317
 318int remove_file_from_cache(const char *path)
 319{
 320        int pos = cache_name_pos(path, strlen(path));
 321        if (pos < 0)
 322                pos = -pos-1;
 323        while (pos < active_nr && !strcmp(active_cache[pos]->name, path))
 324                remove_cache_entry_at(pos);
 325        return 0;
 326}
 327
 328int add_file_to_index(const char *path, int verbose)
 329{
 330        int size, namelen;
 331        struct stat st;
 332        struct cache_entry *ce;
 333
 334        if (lstat(path, &st))
 335                die("%s: unable to stat (%s)", path, strerror(errno));
 336
 337        if (!S_ISREG(st.st_mode) && !S_ISLNK(st.st_mode))
 338                die("%s: can only add regular files or symbolic links", path);
 339
 340        namelen = strlen(path);
 341        size = cache_entry_size(namelen);
 342        ce = xcalloc(1, size);
 343        memcpy(ce->name, path, namelen);
 344        ce->ce_flags = htons(namelen);
 345        fill_stat_cache_info(ce, &st);
 346
 347        ce->ce_mode = create_ce_mode(st.st_mode);
 348        if (!trust_executable_bit) {
 349                /* If there is an existing entry, pick the mode bits
 350                 * from it, otherwise assume unexecutable.
 351                 */
 352                int pos = cache_name_pos(path, namelen);
 353                if (pos >= 0)
 354                        ce->ce_mode = active_cache[pos]->ce_mode;
 355                else if (S_ISREG(st.st_mode))
 356                        ce->ce_mode = create_ce_mode(S_IFREG | 0666);
 357        }
 358
 359        if (index_path(ce->sha1, path, &st, 1))
 360                die("unable to index file %s", path);
 361        if (add_cache_entry(ce, ADD_CACHE_OK_TO_ADD))
 362                die("unable to add %s to index",path);
 363        if (verbose)
 364                printf("add '%s'\n", path);
 365        cache_tree_invalidate_path(active_cache_tree, path);
 366        return 0;
 367}
 368
 369int ce_same_name(struct cache_entry *a, struct cache_entry *b)
 370{
 371        int len = ce_namelen(a);
 372        return ce_namelen(b) == len && !memcmp(a->name, b->name, len);
 373}
 374
 375int ce_path_match(const struct cache_entry *ce, const char **pathspec)
 376{
 377        const char *match, *name;
 378        int len;
 379
 380        if (!pathspec)
 381                return 1;
 382
 383        len = ce_namelen(ce);
 384        name = ce->name;
 385        while ((match = *pathspec++) != NULL) {
 386                int matchlen = strlen(match);
 387                if (matchlen > len)
 388                        continue;
 389                if (memcmp(name, match, matchlen))
 390                        continue;
 391                if (matchlen && name[matchlen-1] == '/')
 392                        return 1;
 393                if (name[matchlen] == '/' || !name[matchlen])
 394                        return 1;
 395                if (!matchlen)
 396                        return 1;
 397        }
 398        return 0;
 399}
 400
 401/*
 402 * We fundamentally don't like some paths: we don't want
 403 * dot or dot-dot anywhere, and for obvious reasons don't
 404 * want to recurse into ".git" either.
 405 *
 406 * Also, we don't want double slashes or slashes at the
 407 * end that can make pathnames ambiguous.
 408 */
 409static int verify_dotfile(const char *rest)
 410{
 411        /*
 412         * The first character was '.', but that
 413         * has already been discarded, we now test
 414         * the rest.
 415         */
 416        switch (*rest) {
 417        /* "." is not allowed */
 418        case '\0': case '/':
 419                return 0;
 420
 421        /*
 422         * ".git" followed by  NUL or slash is bad. This
 423         * shares the path end test with the ".." case.
 424         */
 425        case 'g':
 426                if (rest[1] != 'i')
 427                        break;
 428                if (rest[2] != 't')
 429                        break;
 430                rest += 2;
 431        /* fallthrough */
 432        case '.':
 433                if (rest[1] == '\0' || rest[1] == '/')
 434                        return 0;
 435        }
 436        return 1;
 437}
 438
 439int verify_path(const char *path)
 440{
 441        char c;
 442
 443        goto inside;
 444        for (;;) {
 445                if (!c)
 446                        return 1;
 447                if (c == '/') {
 448inside:
 449                        c = *path++;
 450                        switch (c) {
 451                        default:
 452                                continue;
 453                        case '/': case '\0':
 454                                break;
 455                        case '.':
 456                                if (verify_dotfile(path))
 457                                        continue;
 458                        }
 459                        return 0;
 460                }
 461                c = *path++;
 462        }
 463}
 464
 465/*
 466 * Do we have another file that has the beginning components being a
 467 * proper superset of the name we're trying to add?
 468 */
 469static int has_file_name(const struct cache_entry *ce, int pos, int ok_to_replace)
 470{
 471        int retval = 0;
 472        int len = ce_namelen(ce);
 473        int stage = ce_stage(ce);
 474        const char *name = ce->name;
 475
 476        while (pos < active_nr) {
 477                struct cache_entry *p = active_cache[pos++];
 478
 479                if (len >= ce_namelen(p))
 480                        break;
 481                if (memcmp(name, p->name, len))
 482                        break;
 483                if (ce_stage(p) != stage)
 484                        continue;
 485                if (p->name[len] != '/')
 486                        continue;
 487                retval = -1;
 488                if (!ok_to_replace)
 489                        break;
 490                remove_cache_entry_at(--pos);
 491        }
 492        return retval;
 493}
 494
 495/*
 496 * Do we have another file with a pathname that is a proper
 497 * subset of the name we're trying to add?
 498 */
 499static int has_dir_name(const struct cache_entry *ce, int pos, int ok_to_replace)
 500{
 501        int retval = 0;
 502        int stage = ce_stage(ce);
 503        const char *name = ce->name;
 504        const char *slash = name + ce_namelen(ce);
 505
 506        for (;;) {
 507                int len;
 508
 509                for (;;) {
 510                        if (*--slash == '/')
 511                                break;
 512                        if (slash <= ce->name)
 513                                return retval;
 514                }
 515                len = slash - name;
 516
 517                pos = cache_name_pos(name, ntohs(create_ce_flags(len, stage)));
 518                if (pos >= 0) {
 519                        retval = -1;
 520                        if (ok_to_replace)
 521                                break;
 522                        remove_cache_entry_at(pos);
 523                        continue;
 524                }
 525
 526                /*
 527                 * Trivial optimization: if we find an entry that
 528                 * already matches the sub-directory, then we know
 529                 * we're ok, and we can exit.
 530                 */
 531                pos = -pos-1;
 532                while (pos < active_nr) {
 533                        struct cache_entry *p = active_cache[pos];
 534                        if ((ce_namelen(p) <= len) ||
 535                            (p->name[len] != '/') ||
 536                            memcmp(p->name, name, len))
 537                                break; /* not our subdirectory */
 538                        if (ce_stage(p) == stage)
 539                                /* p is at the same stage as our entry, and
 540                                 * is a subdirectory of what we are looking
 541                                 * at, so we cannot have conflicts at our
 542                                 * level or anything shorter.
 543                                 */
 544                                return retval;
 545                        pos++;
 546                }
 547        }
 548        return retval;
 549}
 550
 551/* We may be in a situation where we already have path/file and path
 552 * is being added, or we already have path and path/file is being
 553 * added.  Either one would result in a nonsense tree that has path
 554 * twice when git-write-tree tries to write it out.  Prevent it.
 555 * 
 556 * If ok-to-replace is specified, we remove the conflicting entries
 557 * from the cache so the caller should recompute the insert position.
 558 * When this happens, we return non-zero.
 559 */
 560static int check_file_directory_conflict(const struct cache_entry *ce, int pos, int ok_to_replace)
 561{
 562        /*
 563         * We check if the path is a sub-path of a subsequent pathname
 564         * first, since removing those will not change the position
 565         * in the array
 566         */
 567        int retval = has_file_name(ce, pos, ok_to_replace);
 568        /*
 569         * Then check if the path might have a clashing sub-directory
 570         * before it.
 571         */
 572        return retval + has_dir_name(ce, pos, ok_to_replace);
 573}
 574
 575int add_cache_entry(struct cache_entry *ce, int option)
 576{
 577        int pos;
 578        int ok_to_add = option & ADD_CACHE_OK_TO_ADD;
 579        int ok_to_replace = option & ADD_CACHE_OK_TO_REPLACE;
 580        int skip_df_check = option & ADD_CACHE_SKIP_DFCHECK;
 581
 582        pos = cache_name_pos(ce->name, ntohs(ce->ce_flags));
 583
 584        /* existing match? Just replace it. */
 585        if (pos >= 0) {
 586                active_cache_changed = 1;
 587                active_cache[pos] = ce;
 588                return 0;
 589        }
 590        pos = -pos-1;
 591
 592        /*
 593         * Inserting a merged entry ("stage 0") into the index
 594         * will always replace all non-merged entries..
 595         */
 596        if (pos < active_nr && ce_stage(ce) == 0) {
 597                while (ce_same_name(active_cache[pos], ce)) {
 598                        ok_to_add = 1;
 599                        if (!remove_cache_entry_at(pos))
 600                                break;
 601                }
 602        }
 603
 604        if (!ok_to_add)
 605                return -1;
 606        if (!verify_path(ce->name))
 607                return -1;
 608
 609        if (!skip_df_check &&
 610            check_file_directory_conflict(ce, pos, ok_to_replace)) {
 611                if (!ok_to_replace)
 612                        return error("'%s' appears as both a file and as a directory", ce->name);
 613                pos = cache_name_pos(ce->name, ntohs(ce->ce_flags));
 614                pos = -pos-1;
 615        }
 616
 617        /* Make sure the array is big enough .. */
 618        if (active_nr == active_alloc) {
 619                active_alloc = alloc_nr(active_alloc);
 620                active_cache = xrealloc(active_cache, active_alloc * sizeof(struct cache_entry *));
 621        }
 622
 623        /* Add it in.. */
 624        active_nr++;
 625        if (active_nr > pos)
 626                memmove(active_cache + pos + 1, active_cache + pos, (active_nr - pos - 1) * sizeof(ce));
 627        active_cache[pos] = ce;
 628        active_cache_changed = 1;
 629        return 0;
 630}
 631
 632/*
 633 * "refresh" does not calculate a new sha1 file or bring the
 634 * cache up-to-date for mode/content changes. But what it
 635 * _does_ do is to "re-match" the stat information of a file
 636 * with the cache, so that you can refresh the cache for a
 637 * file that hasn't been changed but where the stat entry is
 638 * out of date.
 639 *
 640 * For example, you'd want to do this after doing a "git-read-tree",
 641 * to link up the stat cache details with the proper files.
 642 */
 643struct cache_entry *refresh_cache_entry(struct cache_entry *ce, int really)
 644{
 645        struct stat st;
 646        struct cache_entry *updated;
 647        int changed, size;
 648
 649        if (lstat(ce->name, &st) < 0) {
 650                cache_errno = errno;
 651                return NULL;
 652        }
 653
 654        changed = ce_match_stat(ce, &st, really);
 655        if (!changed) {
 656                if (really && assume_unchanged &&
 657                    !(ce->ce_flags & htons(CE_VALID)))
 658                        ; /* mark this one VALID again */
 659                else
 660                        return ce;
 661        }
 662
 663        if (ce_modified(ce, &st, really)) {
 664                cache_errno = EINVAL;
 665                return NULL;
 666        }
 667
 668        size = ce_size(ce);
 669        updated = xmalloc(size);
 670        memcpy(updated, ce, size);
 671        fill_stat_cache_info(updated, &st);
 672
 673        /* In this case, if really is not set, we should leave
 674         * CE_VALID bit alone.  Otherwise, paths marked with
 675         * --no-assume-unchanged (i.e. things to be edited) will
 676         * reacquire CE_VALID bit automatically, which is not
 677         * really what we want.
 678         */
 679        if (!really && assume_unchanged && !(ce->ce_flags & htons(CE_VALID)))
 680                updated->ce_flags &= ~htons(CE_VALID);
 681
 682        return updated;
 683}
 684
 685int refresh_cache(unsigned int flags)
 686{
 687        int i;
 688        int has_errors = 0;
 689        int really = (flags & REFRESH_REALLY) != 0;
 690        int allow_unmerged = (flags & REFRESH_UNMERGED) != 0;
 691        int quiet = (flags & REFRESH_QUIET) != 0;
 692        int not_new = (flags & REFRESH_IGNORE_MISSING) != 0;
 693
 694        for (i = 0; i < active_nr; i++) {
 695                struct cache_entry *ce, *new;
 696                ce = active_cache[i];
 697                if (ce_stage(ce)) {
 698                        while ((i < active_nr) &&
 699                               ! strcmp(active_cache[i]->name, ce->name))
 700                                i++;
 701                        i--;
 702                        if (allow_unmerged)
 703                                continue;
 704                        printf("%s: needs merge\n", ce->name);
 705                        has_errors = 1;
 706                        continue;
 707                }
 708
 709                new = refresh_cache_entry(ce, really);
 710                if (new == ce)
 711                        continue;
 712                if (!new) {
 713                        if (not_new && cache_errno == ENOENT)
 714                                continue;
 715                        if (really && cache_errno == EINVAL) {
 716                                /* If we are doing --really-refresh that
 717                                 * means the index is not valid anymore.
 718                                 */
 719                                ce->ce_flags &= ~htons(CE_VALID);
 720                                active_cache_changed = 1;
 721                        }
 722                        if (quiet)
 723                                continue;
 724                        printf("%s: needs update\n", ce->name);
 725                        has_errors = 1;
 726                        continue;
 727                }
 728                active_cache_changed = 1;
 729                /* You can NOT just free active_cache[i] here, since it
 730                 * might not be necessarily malloc()ed but can also come
 731                 * from mmap(). */
 732                active_cache[i] = new;
 733        }
 734        return has_errors;
 735}
 736
 737static int verify_hdr(struct cache_header *hdr, unsigned long size)
 738{
 739        SHA_CTX c;
 740        unsigned char sha1[20];
 741
 742        if (hdr->hdr_signature != htonl(CACHE_SIGNATURE))
 743                return error("bad signature");
 744        if (hdr->hdr_version != htonl(2))
 745                return error("bad index version");
 746        SHA1_Init(&c);
 747        SHA1_Update(&c, hdr, size - 20);
 748        SHA1_Final(sha1, &c);
 749        if (hashcmp(sha1, (unsigned char *)hdr + size - 20))
 750                return error("bad index file sha1 signature");
 751        return 0;
 752}
 753
 754static int read_index_extension(const char *ext, void *data, unsigned long sz)
 755{
 756        switch (CACHE_EXT(ext)) {
 757        case CACHE_EXT_TREE:
 758                active_cache_tree = cache_tree_read(data, sz);
 759                break;
 760        default:
 761                if (*ext < 'A' || 'Z' < *ext)
 762                        return error("index uses %.4s extension, which we do not understand",
 763                                     ext);
 764                fprintf(stderr, "ignoring %.4s extension\n", ext);
 765                break;
 766        }
 767        return 0;
 768}
 769
 770int read_cache(void)
 771{
 772        return read_cache_from(get_index_file());
 773}
 774
 775/* remember to discard_cache() before reading a different cache! */
 776int read_cache_from(const char *path)
 777{
 778        int fd, i;
 779        struct stat st;
 780        unsigned long offset;
 781        struct cache_header *hdr;
 782
 783        errno = EBUSY;
 784        if (cache_mmap)
 785                return active_nr;
 786
 787        errno = ENOENT;
 788        index_file_timestamp = 0;
 789        fd = open(path, O_RDONLY);
 790        if (fd < 0) {
 791                if (errno == ENOENT)
 792                        return 0;
 793                die("index file open failed (%s)", strerror(errno));
 794        }
 795
 796        cache_mmap = MAP_FAILED;
 797        if (!fstat(fd, &st)) {
 798                cache_mmap_size = st.st_size;
 799                errno = EINVAL;
 800                if (cache_mmap_size >= sizeof(struct cache_header) + 20)
 801                        cache_mmap = mmap(NULL, cache_mmap_size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
 802        }
 803        close(fd);
 804        if (cache_mmap == MAP_FAILED)
 805                die("index file mmap failed (%s)", strerror(errno));
 806
 807        hdr = cache_mmap;
 808        if (verify_hdr(hdr, cache_mmap_size) < 0)
 809                goto unmap;
 810
 811        active_nr = ntohl(hdr->hdr_entries);
 812        active_alloc = alloc_nr(active_nr);
 813        active_cache = xcalloc(active_alloc, sizeof(struct cache_entry *));
 814
 815        offset = sizeof(*hdr);
 816        for (i = 0; i < active_nr; i++) {
 817                struct cache_entry *ce = (struct cache_entry *) ((char *) cache_mmap + offset);
 818                offset = offset + ce_size(ce);
 819                active_cache[i] = ce;
 820        }
 821        index_file_timestamp = st.st_mtime;
 822        while (offset <= cache_mmap_size - 20 - 8) {
 823                /* After an array of active_nr index entries,
 824                 * there can be arbitrary number of extended
 825                 * sections, each of which is prefixed with
 826                 * extension name (4-byte) and section length
 827                 * in 4-byte network byte order.
 828                 */
 829                unsigned long extsize;
 830                memcpy(&extsize, (char *) cache_mmap + offset + 4, 4);
 831                extsize = ntohl(extsize);
 832                if (read_index_extension(((const char *) cache_mmap) + offset,
 833                                         (char *) cache_mmap + offset + 8,
 834                                         extsize) < 0)
 835                        goto unmap;
 836                offset += 8;
 837                offset += extsize;
 838        }
 839        return active_nr;
 840
 841unmap:
 842        munmap(cache_mmap, cache_mmap_size);
 843        errno = EINVAL;
 844        die("index file corrupt");
 845}
 846
 847int discard_cache(void)
 848{
 849        int ret;
 850
 851        active_nr = active_cache_changed = 0;
 852        index_file_timestamp = 0;
 853        cache_tree_free(&active_cache_tree);
 854        if (cache_mmap == NULL)
 855                return 0;
 856        ret = munmap(cache_mmap, cache_mmap_size);
 857        cache_mmap = NULL;
 858        cache_mmap_size = 0;
 859
 860        /* no need to throw away allocated active_cache */
 861        return ret;
 862}
 863
 864#define WRITE_BUFFER_SIZE 8192
 865static unsigned char write_buffer[WRITE_BUFFER_SIZE];
 866static unsigned long write_buffer_len;
 867
 868static int ce_write_flush(SHA_CTX *context, int fd)
 869{
 870        unsigned int buffered = write_buffer_len;
 871        if (buffered) {
 872                SHA1_Update(context, write_buffer, buffered);
 873                if (write(fd, write_buffer, buffered) != buffered)
 874                        return -1;
 875                write_buffer_len = 0;
 876        }
 877        return 0;
 878}
 879
 880static int ce_write(SHA_CTX *context, int fd, void *data, unsigned int len)
 881{
 882        while (len) {
 883                unsigned int buffered = write_buffer_len;
 884                unsigned int partial = WRITE_BUFFER_SIZE - buffered;
 885                if (partial > len)
 886                        partial = len;
 887                memcpy(write_buffer + buffered, data, partial);
 888                buffered += partial;
 889                if (buffered == WRITE_BUFFER_SIZE) {
 890                        write_buffer_len = buffered;
 891                        if (ce_write_flush(context, fd))
 892                                return -1;
 893                        buffered = 0;
 894                }
 895                write_buffer_len = buffered;
 896                len -= partial;
 897                data = (char *) data + partial;
 898        }
 899        return 0;
 900}
 901
 902static int write_index_ext_header(SHA_CTX *context, int fd,
 903                                  unsigned int ext, unsigned int sz)
 904{
 905        ext = htonl(ext);
 906        sz = htonl(sz);
 907        return ((ce_write(context, fd, &ext, 4) < 0) ||
 908                (ce_write(context, fd, &sz, 4) < 0)) ? -1 : 0;
 909}
 910
 911static int ce_flush(SHA_CTX *context, int fd)
 912{
 913        unsigned int left = write_buffer_len;
 914
 915        if (left) {
 916                write_buffer_len = 0;
 917                SHA1_Update(context, write_buffer, left);
 918        }
 919
 920        /* Flush first if not enough space for SHA1 signature */
 921        if (left + 20 > WRITE_BUFFER_SIZE) {
 922                if (write(fd, write_buffer, left) != left)
 923                        return -1;
 924                left = 0;
 925        }
 926
 927        /* Append the SHA1 signature at the end */
 928        SHA1_Final(write_buffer + left, context);
 929        left += 20;
 930        return (write(fd, write_buffer, left) != left) ? -1 : 0;
 931}
 932
 933static void ce_smudge_racily_clean_entry(struct cache_entry *ce)
 934{
 935        /*
 936         * The only thing we care about in this function is to smudge the
 937         * falsely clean entry due to touch-update-touch race, so we leave
 938         * everything else as they are.  We are called for entries whose
 939         * ce_mtime match the index file mtime.
 940         */
 941        struct stat st;
 942
 943        if (lstat(ce->name, &st) < 0)
 944                return;
 945        if (ce_match_stat_basic(ce, &st))
 946                return;
 947        if (ce_modified_check_fs(ce, &st)) {
 948                /* This is "racily clean"; smudge it.  Note that this
 949                 * is a tricky code.  At first glance, it may appear
 950                 * that it can break with this sequence:
 951                 *
 952                 * $ echo xyzzy >frotz
 953                 * $ git-update-index --add frotz
 954                 * $ : >frotz
 955                 * $ sleep 3
 956                 * $ echo filfre >nitfol
 957                 * $ git-update-index --add nitfol
 958                 *
 959                 * but it does not.  When the second update-index runs,
 960                 * it notices that the entry "frotz" has the same timestamp
 961                 * as index, and if we were to smudge it by resetting its
 962                 * size to zero here, then the object name recorded
 963                 * in index is the 6-byte file but the cached stat information
 964                 * becomes zero --- which would then match what we would
 965                 * obtain from the filesystem next time we stat("frotz"). 
 966                 *
 967                 * However, the second update-index, before calling
 968                 * this function, notices that the cached size is 6
 969                 * bytes and what is on the filesystem is an empty
 970                 * file, and never calls us, so the cached size information
 971                 * for "frotz" stays 6 which does not match the filesystem.
 972                 */
 973                ce->ce_size = htonl(0);
 974        }
 975}
 976
 977int write_cache(int newfd, struct cache_entry **cache, int entries)
 978{
 979        SHA_CTX c;
 980        struct cache_header hdr;
 981        int i, removed;
 982
 983        for (i = removed = 0; i < entries; i++)
 984                if (!cache[i]->ce_mode)
 985                        removed++;
 986
 987        hdr.hdr_signature = htonl(CACHE_SIGNATURE);
 988        hdr.hdr_version = htonl(2);
 989        hdr.hdr_entries = htonl(entries - removed);
 990
 991        SHA1_Init(&c);
 992        if (ce_write(&c, newfd, &hdr, sizeof(hdr)) < 0)
 993                return -1;
 994
 995        for (i = 0; i < entries; i++) {
 996                struct cache_entry *ce = cache[i];
 997                if (!ce->ce_mode)
 998                        continue;
 999                if (index_file_timestamp &&
1000                    index_file_timestamp <= ntohl(ce->ce_mtime.sec))
1001                        ce_smudge_racily_clean_entry(ce);
1002                if (ce_write(&c, newfd, ce, ce_size(ce)) < 0)
1003                        return -1;
1004        }
1005
1006        /* Write extension data here */
1007        if (active_cache_tree) {
1008                unsigned long sz;
1009                void *data = cache_tree_write(active_cache_tree, &sz);
1010                if (data &&
1011                    !write_index_ext_header(&c, newfd, CACHE_EXT_TREE, sz) &&
1012                    !ce_write(&c, newfd, data, sz))
1013                        ;
1014                else {
1015                        free(data);
1016                        return -1;
1017                }
1018        }
1019        return ce_flush(&c, newfd);
1020}