9b4385ea5cfd23ac07b460557cf296650983794d
[git/git.git] / read-cache.c
1 /*
2 * GIT - The information manager from hell
3 *
4 * Copyright (C) Linus Torvalds, 2005
5 */
6 #include "cache.h"
7 #include "cache-tree.h"
8 #include "refs.h"
9
10 /* Index extensions.
11 *
12 * The first letter should be 'A'..'Z' for extensions that are not
13 * necessary for a correct operation (i.e. optimization data).
14 * When new extensions are added that _needs_ to be understood in
15 * order to correctly interpret the index file, pick character that
16 * is outside the range, to cause the reader to abort.
17 */
18
19 #define CACHE_EXT(s) ( (s[0]<<24)|(s[1]<<16)|(s[2]<<8)|(s[3]) )
20 #define CACHE_EXT_TREE 0x54524545 /* "TREE" */
21
22 struct index_state the_index;
23 #define index_file_timestamp (the_index.timestamp)
24 #define cache_mmap (the_index.mmap)
25 #define cache_mmap_size (the_index.mmap_size)
26
27 /*
28 * This only updates the "non-critical" parts of the directory
29 * cache, ie the parts that aren't tracked by GIT, and only used
30 * to validate the cache.
31 */
32 void fill_stat_cache_info(struct cache_entry *ce, struct stat *st)
33 {
34 ce->ce_ctime.sec = htonl(st->st_ctime);
35 ce->ce_mtime.sec = htonl(st->st_mtime);
36 #ifdef USE_NSEC
37 ce->ce_ctime.nsec = htonl(st->st_ctim.tv_nsec);
38 ce->ce_mtime.nsec = htonl(st->st_mtim.tv_nsec);
39 #endif
40 ce->ce_dev = htonl(st->st_dev);
41 ce->ce_ino = htonl(st->st_ino);
42 ce->ce_uid = htonl(st->st_uid);
43 ce->ce_gid = htonl(st->st_gid);
44 ce->ce_size = htonl(st->st_size);
45
46 if (assume_unchanged)
47 ce->ce_flags |= htons(CE_VALID);
48 }
49
50 static int ce_compare_data(struct cache_entry *ce, struct stat *st)
51 {
52 int match = -1;
53 int fd = open(ce->name, O_RDONLY);
54
55 if (fd >= 0) {
56 unsigned char sha1[20];
57 if (!index_fd(sha1, fd, st, 0, OBJ_BLOB, ce->name))
58 match = hashcmp(sha1, ce->sha1);
59 /* index_fd() closed the file descriptor already */
60 }
61 return match;
62 }
63
64 static int ce_compare_link(struct cache_entry *ce, size_t expected_size)
65 {
66 int match = -1;
67 char *target;
68 void *buffer;
69 unsigned long size;
70 enum object_type type;
71 int len;
72
73 target = xmalloc(expected_size);
74 len = readlink(ce->name, target, expected_size);
75 if (len != expected_size) {
76 free(target);
77 return -1;
78 }
79 buffer = read_sha1_file(ce->sha1, &type, &size);
80 if (!buffer) {
81 free(target);
82 return -1;
83 }
84 if (size == expected_size)
85 match = memcmp(buffer, target, size);
86 free(buffer);
87 free(target);
88 return match;
89 }
90
91 static int ce_compare_gitlink(struct cache_entry *ce)
92 {
93 unsigned char sha1[20];
94
95 /*
96 * We don't actually require that the .git directory
97 * under DIRLNK directory be a valid git directory. It
98 * might even be missing (in case nobody populated that
99 * sub-project).
100 *
101 * If so, we consider it always to match.
102 */
103 if (resolve_gitlink_ref(ce->name, "HEAD", sha1) < 0)
104 return 0;
105 return hashcmp(sha1, ce->sha1);
106 }
107
108 static int ce_modified_check_fs(struct cache_entry *ce, struct stat *st)
109 {
110 switch (st->st_mode & S_IFMT) {
111 case S_IFREG:
112 if (ce_compare_data(ce, st))
113 return DATA_CHANGED;
114 break;
115 case S_IFLNK:
116 if (ce_compare_link(ce, xsize_t(st->st_size)))
117 return DATA_CHANGED;
118 break;
119 case S_IFDIR:
120 if (S_ISDIRLNK(ntohl(ce->ce_mode)))
121 return 0;
122 default:
123 return TYPE_CHANGED;
124 }
125 return 0;
126 }
127
128 static int ce_match_stat_basic(struct cache_entry *ce, struct stat *st)
129 {
130 unsigned int changed = 0;
131
132 switch (ntohl(ce->ce_mode) & S_IFMT) {
133 case S_IFREG:
134 changed |= !S_ISREG(st->st_mode) ? TYPE_CHANGED : 0;
135 /* We consider only the owner x bit to be relevant for
136 * "mode changes"
137 */
138 if (trust_executable_bit &&
139 (0100 & (ntohl(ce->ce_mode) ^ st->st_mode)))
140 changed |= MODE_CHANGED;
141 break;
142 case S_IFLNK:
143 if (!S_ISLNK(st->st_mode) &&
144 (has_symlinks || !S_ISREG(st->st_mode)))
145 changed |= TYPE_CHANGED;
146 break;
147 case S_IFDIRLNK:
148 if (!S_ISDIR(st->st_mode))
149 changed |= TYPE_CHANGED;
150 else if (ce_compare_gitlink(ce))
151 changed |= DATA_CHANGED;
152 return changed;
153 default:
154 die("internal error: ce_mode is %o", ntohl(ce->ce_mode));
155 }
156 if (ce->ce_mtime.sec != htonl(st->st_mtime))
157 changed |= MTIME_CHANGED;
158 if (ce->ce_ctime.sec != htonl(st->st_ctime))
159 changed |= CTIME_CHANGED;
160
161 #ifdef USE_NSEC
162 /*
163 * nsec seems unreliable - not all filesystems support it, so
164 * as long as it is in the inode cache you get right nsec
165 * but after it gets flushed, you get zero nsec.
166 */
167 if (ce->ce_mtime.nsec != htonl(st->st_mtim.tv_nsec))
168 changed |= MTIME_CHANGED;
169 if (ce->ce_ctime.nsec != htonl(st->st_ctim.tv_nsec))
170 changed |= CTIME_CHANGED;
171 #endif
172
173 if (ce->ce_uid != htonl(st->st_uid) ||
174 ce->ce_gid != htonl(st->st_gid))
175 changed |= OWNER_CHANGED;
176 if (ce->ce_ino != htonl(st->st_ino))
177 changed |= INODE_CHANGED;
178
179 #ifdef USE_STDEV
180 /*
181 * st_dev breaks on network filesystems where different
182 * clients will have different views of what "device"
183 * the filesystem is on
184 */
185 if (ce->ce_dev != htonl(st->st_dev))
186 changed |= INODE_CHANGED;
187 #endif
188
189 if (ce->ce_size != htonl(st->st_size))
190 changed |= DATA_CHANGED;
191
192 return changed;
193 }
194
195 int ce_match_stat(struct cache_entry *ce, struct stat *st, int options)
196 {
197 unsigned int changed;
198 int ignore_valid = options & 01;
199 int assume_racy_is_modified = options & 02;
200
201 /*
202 * If it's marked as always valid in the index, it's
203 * valid whatever the checked-out copy says.
204 */
205 if (!ignore_valid && (ce->ce_flags & htons(CE_VALID)))
206 return 0;
207
208 changed = ce_match_stat_basic(ce, st);
209
210 /*
211 * Within 1 second of this sequence:
212 * echo xyzzy >file && git-update-index --add file
213 * running this command:
214 * echo frotz >file
215 * would give a falsely clean cache entry. The mtime and
216 * length match the cache, and other stat fields do not change.
217 *
218 * We could detect this at update-index time (the cache entry
219 * being registered/updated records the same time as "now")
220 * and delay the return from git-update-index, but that would
221 * effectively mean we can make at most one commit per second,
222 * which is not acceptable. Instead, we check cache entries
223 * whose mtime are the same as the index file timestamp more
224 * carefully than others.
225 */
226 if (!changed &&
227 index_file_timestamp &&
228 index_file_timestamp <= ntohl(ce->ce_mtime.sec)) {
229 if (assume_racy_is_modified)
230 changed |= DATA_CHANGED;
231 else
232 changed |= ce_modified_check_fs(ce, st);
233 }
234
235 return changed;
236 }
237
238 int ce_modified(struct cache_entry *ce, struct stat *st, int really)
239 {
240 int changed, changed_fs;
241 changed = ce_match_stat(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 cache_name_pos(const char *name, int namelen)
310 {
311 int first, last;
312
313 first = 0;
314 last = active_nr;
315 while (last > first) {
316 int next = (last + first) >> 1;
317 struct cache_entry *ce = active_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_cache_entry_at(int pos)
332 {
333 active_cache_changed = 1;
334 active_nr--;
335 if (pos >= active_nr)
336 return 0;
337 memmove(active_cache + pos, active_cache + pos + 1, (active_nr - pos) * sizeof(struct cache_entry *));
338 return 1;
339 }
340
341 int remove_file_from_cache(const char *path)
342 {
343 int pos = cache_name_pos(path, strlen(path));
344 if (pos < 0)
345 pos = -pos-1;
346 while (pos < active_nr && !strcmp(active_cache[pos]->name, path))
347 remove_cache_entry_at(pos);
348 return 0;
349 }
350
351 int add_file_to_cache(const char *path, int verbose)
352 {
353 int size, namelen;
354 struct stat st;
355 struct cache_entry *ce;
356
357 if (lstat(path, &st))
358 die("%s: unable to stat (%s)", path, strerror(errno));
359
360 if (!S_ISREG(st.st_mode) && !S_ISLNK(st.st_mode) && !S_ISDIR(st.st_mode))
361 die("%s: can only add regular files, symbolic links or git-directories", path);
362
363 namelen = strlen(path);
364 if (S_ISDIR(st.st_mode)) {
365 while (namelen && path[namelen-1] == '/')
366 namelen--;
367 }
368 size = cache_entry_size(namelen);
369 ce = xcalloc(1, size);
370 memcpy(ce->name, path, namelen);
371 ce->ce_flags = htons(namelen);
372 fill_stat_cache_info(ce, &st);
373
374 if (trust_executable_bit && has_symlinks)
375 ce->ce_mode = create_ce_mode(st.st_mode);
376 else {
377 /* If there is an existing entry, pick the mode bits and type
378 * from it, otherwise assume unexecutable regular file.
379 */
380 struct cache_entry *ent;
381 int pos = cache_name_pos(path, namelen);
382
383 ent = (0 <= pos) ? active_cache[pos] : NULL;
384 ce->ce_mode = ce_mode_from_stat(ent, st.st_mode);
385 }
386
387 if (index_path(ce->sha1, path, &st, 1))
388 die("unable to index file %s", path);
389 if (add_cache_entry(ce, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE))
390 die("unable to add %s to index",path);
391 if (verbose)
392 printf("add '%s'\n", path);
393 cache_tree_invalidate_path(active_cache_tree, path);
394 return 0;
395 }
396
397 int ce_same_name(struct cache_entry *a, struct cache_entry *b)
398 {
399 int len = ce_namelen(a);
400 return ce_namelen(b) == len && !memcmp(a->name, b->name, len);
401 }
402
403 int ce_path_match(const struct cache_entry *ce, const char **pathspec)
404 {
405 const char *match, *name;
406 int len;
407
408 if (!pathspec)
409 return 1;
410
411 len = ce_namelen(ce);
412 name = ce->name;
413 while ((match = *pathspec++) != NULL) {
414 int matchlen = strlen(match);
415 if (matchlen > len)
416 continue;
417 if (memcmp(name, match, matchlen))
418 continue;
419 if (matchlen && name[matchlen-1] == '/')
420 return 1;
421 if (name[matchlen] == '/' || !name[matchlen])
422 return 1;
423 if (!matchlen)
424 return 1;
425 }
426 return 0;
427 }
428
429 /*
430 * We fundamentally don't like some paths: we don't want
431 * dot or dot-dot anywhere, and for obvious reasons don't
432 * want to recurse into ".git" either.
433 *
434 * Also, we don't want double slashes or slashes at the
435 * end that can make pathnames ambiguous.
436 */
437 static int verify_dotfile(const char *rest)
438 {
439 /*
440 * The first character was '.', but that
441 * has already been discarded, we now test
442 * the rest.
443 */
444 switch (*rest) {
445 /* "." is not allowed */
446 case '\0': case '/':
447 return 0;
448
449 /*
450 * ".git" followed by NUL or slash is bad. This
451 * shares the path end test with the ".." case.
452 */
453 case 'g':
454 if (rest[1] != 'i')
455 break;
456 if (rest[2] != 't')
457 break;
458 rest += 2;
459 /* fallthrough */
460 case '.':
461 if (rest[1] == '\0' || rest[1] == '/')
462 return 0;
463 }
464 return 1;
465 }
466
467 int verify_path(const char *path)
468 {
469 char c;
470
471 goto inside;
472 for (;;) {
473 if (!c)
474 return 1;
475 if (c == '/') {
476 inside:
477 c = *path++;
478 switch (c) {
479 default:
480 continue;
481 case '/': case '\0':
482 break;
483 case '.':
484 if (verify_dotfile(path))
485 continue;
486 }
487 return 0;
488 }
489 c = *path++;
490 }
491 }
492
493 /*
494 * Do we have another file that has the beginning components being a
495 * proper superset of the name we're trying to add?
496 */
497 static int has_file_name(const struct cache_entry *ce, int pos, int ok_to_replace)
498 {
499 int retval = 0;
500 int len = ce_namelen(ce);
501 int stage = ce_stage(ce);
502 const char *name = ce->name;
503
504 while (pos < active_nr) {
505 struct cache_entry *p = active_cache[pos++];
506
507 if (len >= ce_namelen(p))
508 break;
509 if (memcmp(name, p->name, len))
510 break;
511 if (ce_stage(p) != stage)
512 continue;
513 if (p->name[len] != '/')
514 continue;
515 if (!ce_stage(p) && !p->ce_mode)
516 continue;
517 retval = -1;
518 if (!ok_to_replace)
519 break;
520 remove_cache_entry_at(--pos);
521 }
522 return retval;
523 }
524
525 /*
526 * Do we have another file with a pathname that is a proper
527 * subset of the name we're trying to add?
528 */
529 static int has_dir_name(const struct cache_entry *ce, int pos, int ok_to_replace)
530 {
531 int retval = 0;
532 int stage = ce_stage(ce);
533 const char *name = ce->name;
534 const char *slash = name + ce_namelen(ce);
535
536 for (;;) {
537 int len;
538
539 for (;;) {
540 if (*--slash == '/')
541 break;
542 if (slash <= ce->name)
543 return retval;
544 }
545 len = slash - name;
546
547 pos = cache_name_pos(name, ntohs(create_ce_flags(len, stage)));
548 if (pos >= 0) {
549 /*
550 * Found one, but not so fast. This could
551 * be a marker that says "I was here, but
552 * I am being removed". Such an entry is
553 * not a part of the resulting tree, and
554 * it is Ok to have a directory at the same
555 * path.
556 */
557 if (stage || active_cache[pos]->ce_mode) {
558 retval = -1;
559 if (!ok_to_replace)
560 break;
561 remove_cache_entry_at(pos);
562 continue;
563 }
564 }
565 else
566 pos = -pos-1;
567
568 /*
569 * Trivial optimization: if we find an entry that
570 * already matches the sub-directory, then we know
571 * we're ok, and we can exit.
572 */
573 while (pos < active_nr) {
574 struct cache_entry *p = active_cache[pos];
575 if ((ce_namelen(p) <= len) ||
576 (p->name[len] != '/') ||
577 memcmp(p->name, name, len))
578 break; /* not our subdirectory */
579 if (ce_stage(p) == stage && (stage || p->ce_mode))
580 /* p is at the same stage as our entry, and
581 * is a subdirectory of what we are looking
582 * at, so we cannot have conflicts at our
583 * level or anything shorter.
584 */
585 return retval;
586 pos++;
587 }
588 }
589 return retval;
590 }
591
592 /* We may be in a situation where we already have path/file and path
593 * is being added, or we already have path and path/file is being
594 * added. Either one would result in a nonsense tree that has path
595 * twice when git-write-tree tries to write it out. Prevent it.
596 *
597 * If ok-to-replace is specified, we remove the conflicting entries
598 * from the cache so the caller should recompute the insert position.
599 * When this happens, we return non-zero.
600 */
601 static int check_file_directory_conflict(const struct cache_entry *ce, int pos, int ok_to_replace)
602 {
603 int retval;
604
605 /*
606 * When ce is an "I am going away" entry, we allow it to be added
607 */
608 if (!ce_stage(ce) && !ce->ce_mode)
609 return 0;
610
611 /*
612 * We check if the path is a sub-path of a subsequent pathname
613 * first, since removing those will not change the position
614 * in the array.
615 */
616 retval = has_file_name(ce, pos, ok_to_replace);
617
618 /*
619 * Then check if the path might have a clashing sub-directory
620 * before it.
621 */
622 return retval + has_dir_name(ce, pos, ok_to_replace);
623 }
624
625 int add_cache_entry(struct cache_entry *ce, int option)
626 {
627 int pos;
628 int ok_to_add = option & ADD_CACHE_OK_TO_ADD;
629 int ok_to_replace = option & ADD_CACHE_OK_TO_REPLACE;
630 int skip_df_check = option & ADD_CACHE_SKIP_DFCHECK;
631
632 pos = cache_name_pos(ce->name, ntohs(ce->ce_flags));
633
634 /* existing match? Just replace it. */
635 if (pos >= 0) {
636 active_cache_changed = 1;
637 active_cache[pos] = ce;
638 return 0;
639 }
640 pos = -pos-1;
641
642 /*
643 * Inserting a merged entry ("stage 0") into the index
644 * will always replace all non-merged entries..
645 */
646 if (pos < active_nr && ce_stage(ce) == 0) {
647 while (ce_same_name(active_cache[pos], ce)) {
648 ok_to_add = 1;
649 if (!remove_cache_entry_at(pos))
650 break;
651 }
652 }
653
654 if (!ok_to_add)
655 return -1;
656 if (!verify_path(ce->name))
657 return -1;
658
659 if (!skip_df_check &&
660 check_file_directory_conflict(ce, pos, ok_to_replace)) {
661 if (!ok_to_replace)
662 return error("'%s' appears as both a file and as a directory", ce->name);
663 pos = cache_name_pos(ce->name, ntohs(ce->ce_flags));
664 pos = -pos-1;
665 }
666
667 /* Make sure the array is big enough .. */
668 if (active_nr == active_alloc) {
669 active_alloc = alloc_nr(active_alloc);
670 active_cache = xrealloc(active_cache, active_alloc * sizeof(struct cache_entry *));
671 }
672
673 /* Add it in.. */
674 active_nr++;
675 if (active_nr > pos)
676 memmove(active_cache + pos + 1, active_cache + pos, (active_nr - pos - 1) * sizeof(ce));
677 active_cache[pos] = ce;
678 active_cache_changed = 1;
679 return 0;
680 }
681
682 /*
683 * "refresh" does not calculate a new sha1 file or bring the
684 * cache up-to-date for mode/content changes. But what it
685 * _does_ do is to "re-match" the stat information of a file
686 * with the cache, so that you can refresh the cache for a
687 * file that hasn't been changed but where the stat entry is
688 * out of date.
689 *
690 * For example, you'd want to do this after doing a "git-read-tree",
691 * to link up the stat cache details with the proper files.
692 */
693 static struct cache_entry *refresh_cache_ent(struct cache_entry *ce, int really, int *err)
694 {
695 struct stat st;
696 struct cache_entry *updated;
697 int changed, size;
698
699 if (lstat(ce->name, &st) < 0) {
700 if (err)
701 *err = errno;
702 return NULL;
703 }
704
705 changed = ce_match_stat(ce, &st, really);
706 if (!changed) {
707 if (really && assume_unchanged &&
708 !(ce->ce_flags & htons(CE_VALID)))
709 ; /* mark this one VALID again */
710 else
711 return ce;
712 }
713
714 if (ce_modified(ce, &st, really)) {
715 if (err)
716 *err = EINVAL;
717 return NULL;
718 }
719
720 size = ce_size(ce);
721 updated = xmalloc(size);
722 memcpy(updated, ce, size);
723 fill_stat_cache_info(updated, &st);
724
725 /* In this case, if really is not set, we should leave
726 * CE_VALID bit alone. Otherwise, paths marked with
727 * --no-assume-unchanged (i.e. things to be edited) will
728 * reacquire CE_VALID bit automatically, which is not
729 * really what we want.
730 */
731 if (!really && assume_unchanged && !(ce->ce_flags & htons(CE_VALID)))
732 updated->ce_flags &= ~htons(CE_VALID);
733
734 return updated;
735 }
736
737 int refresh_cache(unsigned int flags)
738 {
739 int i;
740 int has_errors = 0;
741 int really = (flags & REFRESH_REALLY) != 0;
742 int allow_unmerged = (flags & REFRESH_UNMERGED) != 0;
743 int quiet = (flags & REFRESH_QUIET) != 0;
744 int not_new = (flags & REFRESH_IGNORE_MISSING) != 0;
745
746 for (i = 0; i < active_nr; i++) {
747 struct cache_entry *ce, *new;
748 int cache_errno = 0;
749
750 ce = active_cache[i];
751 if (ce_stage(ce)) {
752 while ((i < active_nr) &&
753 ! strcmp(active_cache[i]->name, ce->name))
754 i++;
755 i--;
756 if (allow_unmerged)
757 continue;
758 printf("%s: needs merge\n", ce->name);
759 has_errors = 1;
760 continue;
761 }
762
763 new = refresh_cache_ent(ce, really, &cache_errno);
764 if (new == ce)
765 continue;
766 if (!new) {
767 if (not_new && cache_errno == ENOENT)
768 continue;
769 if (really && cache_errno == EINVAL) {
770 /* If we are doing --really-refresh that
771 * means the index is not valid anymore.
772 */
773 ce->ce_flags &= ~htons(CE_VALID);
774 active_cache_changed = 1;
775 }
776 if (quiet)
777 continue;
778 printf("%s: needs update\n", ce->name);
779 has_errors = 1;
780 continue;
781 }
782 active_cache_changed = 1;
783 /* You can NOT just free active_cache[i] here, since it
784 * might not be necessarily malloc()ed but can also come
785 * from mmap(). */
786 active_cache[i] = new;
787 }
788 return has_errors;
789 }
790
791 struct cache_entry *refresh_cache_entry(struct cache_entry *ce, int really)
792 {
793 return refresh_cache_ent(ce, really, NULL);
794 }
795
796 static int verify_hdr(struct cache_header *hdr, unsigned long size)
797 {
798 SHA_CTX c;
799 unsigned char sha1[20];
800
801 if (hdr->hdr_signature != htonl(CACHE_SIGNATURE))
802 return error("bad signature");
803 if (hdr->hdr_version != htonl(2))
804 return error("bad index version");
805 SHA1_Init(&c);
806 SHA1_Update(&c, hdr, size - 20);
807 SHA1_Final(sha1, &c);
808 if (hashcmp(sha1, (unsigned char *)hdr + size - 20))
809 return error("bad index file sha1 signature");
810 return 0;
811 }
812
813 static int read_index_extension(const char *ext, void *data, unsigned long sz)
814 {
815 switch (CACHE_EXT(ext)) {
816 case CACHE_EXT_TREE:
817 active_cache_tree = cache_tree_read(data, sz);
818 break;
819 default:
820 if (*ext < 'A' || 'Z' < *ext)
821 return error("index uses %.4s extension, which we do not understand",
822 ext);
823 fprintf(stderr, "ignoring %.4s extension\n", ext);
824 break;
825 }
826 return 0;
827 }
828
829 int read_cache(void)
830 {
831 return read_cache_from(get_index_file());
832 }
833
834 /* remember to discard_cache() before reading a different cache! */
835 int read_cache_from(const char *path)
836 {
837 int fd, i;
838 struct stat st;
839 unsigned long offset;
840 struct cache_header *hdr;
841
842 errno = EBUSY;
843 if (cache_mmap)
844 return active_nr;
845
846 errno = ENOENT;
847 index_file_timestamp = 0;
848 fd = open(path, O_RDONLY);
849 if (fd < 0) {
850 if (errno == ENOENT)
851 return 0;
852 die("index file open failed (%s)", strerror(errno));
853 }
854
855 if (!fstat(fd, &st)) {
856 cache_mmap_size = xsize_t(st.st_size);
857 errno = EINVAL;
858 if (cache_mmap_size >= sizeof(struct cache_header) + 20)
859 cache_mmap = xmmap(NULL, cache_mmap_size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
860 else
861 die("index file smaller than expected");
862 } else
863 die("cannot stat the open index (%s)", strerror(errno));
864 close(fd);
865
866 hdr = cache_mmap;
867 if (verify_hdr(hdr, cache_mmap_size) < 0)
868 goto unmap;
869
870 active_nr = ntohl(hdr->hdr_entries);
871 active_alloc = alloc_nr(active_nr);
872 active_cache = xcalloc(active_alloc, sizeof(struct cache_entry *));
873
874 offset = sizeof(*hdr);
875 for (i = 0; i < active_nr; i++) {
876 struct cache_entry *ce = (struct cache_entry *) ((char *) cache_mmap + offset);
877 offset = offset + ce_size(ce);
878 active_cache[i] = ce;
879 }
880 index_file_timestamp = st.st_mtime;
881 while (offset <= cache_mmap_size - 20 - 8) {
882 /* After an array of active_nr index entries,
883 * there can be arbitrary number of extended
884 * sections, each of which is prefixed with
885 * extension name (4-byte) and section length
886 * in 4-byte network byte order.
887 */
888 unsigned long extsize;
889 memcpy(&extsize, (char *) cache_mmap + offset + 4, 4);
890 extsize = ntohl(extsize);
891 if (read_index_extension(((const char *) cache_mmap) + offset,
892 (char *) cache_mmap + offset + 8,
893 extsize) < 0)
894 goto unmap;
895 offset += 8;
896 offset += extsize;
897 }
898 return active_nr;
899
900 unmap:
901 munmap(cache_mmap, cache_mmap_size);
902 errno = EINVAL;
903 die("index file corrupt");
904 }
905
906 int discard_cache(void)
907 {
908 int ret;
909
910 active_nr = active_cache_changed = 0;
911 index_file_timestamp = 0;
912 cache_tree_free(&active_cache_tree);
913 if (cache_mmap == NULL)
914 return 0;
915 ret = munmap(cache_mmap, cache_mmap_size);
916 cache_mmap = NULL;
917 cache_mmap_size = 0;
918
919 /* no need to throw away allocated active_cache */
920 return ret;
921 }
922
923 #define WRITE_BUFFER_SIZE 8192
924 static unsigned char write_buffer[WRITE_BUFFER_SIZE];
925 static unsigned long write_buffer_len;
926
927 static int ce_write_flush(SHA_CTX *context, int fd)
928 {
929 unsigned int buffered = write_buffer_len;
930 if (buffered) {
931 SHA1_Update(context, write_buffer, buffered);
932 if (write_in_full(fd, write_buffer, buffered) != buffered)
933 return -1;
934 write_buffer_len = 0;
935 }
936 return 0;
937 }
938
939 static int ce_write(SHA_CTX *context, int fd, void *data, unsigned int len)
940 {
941 while (len) {
942 unsigned int buffered = write_buffer_len;
943 unsigned int partial = WRITE_BUFFER_SIZE - buffered;
944 if (partial > len)
945 partial = len;
946 memcpy(write_buffer + buffered, data, partial);
947 buffered += partial;
948 if (buffered == WRITE_BUFFER_SIZE) {
949 write_buffer_len = buffered;
950 if (ce_write_flush(context, fd))
951 return -1;
952 buffered = 0;
953 }
954 write_buffer_len = buffered;
955 len -= partial;
956 data = (char *) data + partial;
957 }
958 return 0;
959 }
960
961 static int write_index_ext_header(SHA_CTX *context, int fd,
962 unsigned int ext, unsigned int sz)
963 {
964 ext = htonl(ext);
965 sz = htonl(sz);
966 return ((ce_write(context, fd, &ext, 4) < 0) ||
967 (ce_write(context, fd, &sz, 4) < 0)) ? -1 : 0;
968 }
969
970 static int ce_flush(SHA_CTX *context, int fd)
971 {
972 unsigned int left = write_buffer_len;
973
974 if (left) {
975 write_buffer_len = 0;
976 SHA1_Update(context, write_buffer, left);
977 }
978
979 /* Flush first if not enough space for SHA1 signature */
980 if (left + 20 > WRITE_BUFFER_SIZE) {
981 if (write_in_full(fd, write_buffer, left) != left)
982 return -1;
983 left = 0;
984 }
985
986 /* Append the SHA1 signature at the end */
987 SHA1_Final(write_buffer + left, context);
988 left += 20;
989 return (write_in_full(fd, write_buffer, left) != left) ? -1 : 0;
990 }
991
992 static void ce_smudge_racily_clean_entry(struct cache_entry *ce)
993 {
994 /*
995 * The only thing we care about in this function is to smudge the
996 * falsely clean entry due to touch-update-touch race, so we leave
997 * everything else as they are. We are called for entries whose
998 * ce_mtime match the index file mtime.
999 */
1000 struct stat st;
1001
1002 if (lstat(ce->name, &st) < 0)
1003 return;
1004 if (ce_match_stat_basic(ce, &st))
1005 return;
1006 if (ce_modified_check_fs(ce, &st)) {
1007 /* This is "racily clean"; smudge it. Note that this
1008 * is a tricky code. At first glance, it may appear
1009 * that it can break with this sequence:
1010 *
1011 * $ echo xyzzy >frotz
1012 * $ git-update-index --add frotz
1013 * $ : >frotz
1014 * $ sleep 3
1015 * $ echo filfre >nitfol
1016 * $ git-update-index --add nitfol
1017 *
1018 * but it does not. When the second update-index runs,
1019 * it notices that the entry "frotz" has the same timestamp
1020 * as index, and if we were to smudge it by resetting its
1021 * size to zero here, then the object name recorded
1022 * in index is the 6-byte file but the cached stat information
1023 * becomes zero --- which would then match what we would
1024 * obtain from the filesystem next time we stat("frotz").
1025 *
1026 * However, the second update-index, before calling
1027 * this function, notices that the cached size is 6
1028 * bytes and what is on the filesystem is an empty
1029 * file, and never calls us, so the cached size information
1030 * for "frotz" stays 6 which does not match the filesystem.
1031 */
1032 ce->ce_size = htonl(0);
1033 }
1034 }
1035
1036 int write_cache(int newfd, struct cache_entry **cache, int entries)
1037 {
1038 SHA_CTX c;
1039 struct cache_header hdr;
1040 int i, removed;
1041
1042 for (i = removed = 0; i < entries; i++)
1043 if (!cache[i]->ce_mode)
1044 removed++;
1045
1046 hdr.hdr_signature = htonl(CACHE_SIGNATURE);
1047 hdr.hdr_version = htonl(2);
1048 hdr.hdr_entries = htonl(entries - removed);
1049
1050 SHA1_Init(&c);
1051 if (ce_write(&c, newfd, &hdr, sizeof(hdr)) < 0)
1052 return -1;
1053
1054 for (i = 0; i < entries; i++) {
1055 struct cache_entry *ce = cache[i];
1056 if (!ce->ce_mode)
1057 continue;
1058 if (index_file_timestamp &&
1059 index_file_timestamp <= ntohl(ce->ce_mtime.sec))
1060 ce_smudge_racily_clean_entry(ce);
1061 if (ce_write(&c, newfd, ce, ce_size(ce)) < 0)
1062 return -1;
1063 }
1064
1065 /* Write extension data here */
1066 if (active_cache_tree) {
1067 unsigned long sz;
1068 void *data = cache_tree_write(active_cache_tree, &sz);
1069 if (data &&
1070 !write_index_ext_header(&c, newfd, CACHE_EXT_TREE, sz) &&
1071 !ce_write(&c, newfd, data, sz))
1072 free(data);
1073 else {
1074 free(data);
1075 return -1;
1076 }
1077 }
1078 return ce_flush(&c, newfd);
1079 }