Merge branch 'gl/cleanup' into gl/cleanup-next
[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
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
21 struct cache_entry **active_cache;
22 static time_t index_file_timestamp;
23 unsigned int active_nr, active_alloc, active_cache_changed;
24
25 struct cache_tree *active_cache_tree;
26
27 int cache_errno;
28
29 static void *cache_mmap;
30 static 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 */
37 void 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
55 static 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
69 static 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
96 static 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
113 static 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
172 int 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
215 int 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
241 int 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
260 int 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
286 int 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.. */
308 int 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
318 int 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
328 int 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.
351 */
352 int pos = cache_name_pos(path, namelen);
353 if (pos >= 0)
354 ce->ce_mode = active_cache[pos]->ce_mode;
355 }
356
357 if (index_path(ce->sha1, path, &st, 1))
358 die("unable to index file %s", path);
359 if (add_cache_entry(ce, ADD_CACHE_OK_TO_ADD))
360 die("unable to add %s to index",path);
361 if (verbose)
362 printf("add '%s'\n", path);
363 cache_tree_invalidate_path(active_cache_tree, path);
364 return 0;
365 }
366
367 int ce_same_name(struct cache_entry *a, struct cache_entry *b)
368 {
369 int len = ce_namelen(a);
370 return ce_namelen(b) == len && !memcmp(a->name, b->name, len);
371 }
372
373 int ce_path_match(const struct cache_entry *ce, const char **pathspec)
374 {
375 const char *match, *name;
376 int len;
377
378 if (!pathspec)
379 return 1;
380
381 len = ce_namelen(ce);
382 name = ce->name;
383 while ((match = *pathspec++) != NULL) {
384 int matchlen = strlen(match);
385 if (matchlen > len)
386 continue;
387 if (memcmp(name, match, matchlen))
388 continue;
389 if (matchlen && name[matchlen-1] == '/')
390 return 1;
391 if (name[matchlen] == '/' || !name[matchlen])
392 return 1;
393 if (!matchlen)
394 return 1;
395 }
396 return 0;
397 }
398
399 /*
400 * We fundamentally don't like some paths: we don't want
401 * dot or dot-dot anywhere, and for obvious reasons don't
402 * want to recurse into ".git" either.
403 *
404 * Also, we don't want double slashes or slashes at the
405 * end that can make pathnames ambiguous.
406 */
407 static int verify_dotfile(const char *rest)
408 {
409 /*
410 * The first character was '.', but that
411 * has already been discarded, we now test
412 * the rest.
413 */
414 switch (*rest) {
415 /* "." is not allowed */
416 case '\0': case '/':
417 return 0;
418
419 /*
420 * ".git" followed by NUL or slash is bad. This
421 * shares the path end test with the ".." case.
422 */
423 case 'g':
424 if (rest[1] != 'i')
425 break;
426 if (rest[2] != 't')
427 break;
428 rest += 2;
429 /* fallthrough */
430 case '.':
431 if (rest[1] == '\0' || rest[1] == '/')
432 return 0;
433 }
434 return 1;
435 }
436
437 int verify_path(const char *path)
438 {
439 char c;
440
441 goto inside;
442 for (;;) {
443 if (!c)
444 return 1;
445 if (c == '/') {
446 inside:
447 c = *path++;
448 switch (c) {
449 default:
450 continue;
451 case '/': case '\0':
452 break;
453 case '.':
454 if (verify_dotfile(path))
455 continue;
456 }
457 return 0;
458 }
459 c = *path++;
460 }
461 }
462
463 /*
464 * Do we have another file that has the beginning components being a
465 * proper superset of the name we're trying to add?
466 */
467 static int has_file_name(const struct cache_entry *ce, int pos, int ok_to_replace)
468 {
469 int retval = 0;
470 int len = ce_namelen(ce);
471 int stage = ce_stage(ce);
472 const char *name = ce->name;
473
474 while (pos < active_nr) {
475 struct cache_entry *p = active_cache[pos++];
476
477 if (len >= ce_namelen(p))
478 break;
479 if (memcmp(name, p->name, len))
480 break;
481 if (ce_stage(p) != stage)
482 continue;
483 if (p->name[len] != '/')
484 continue;
485 retval = -1;
486 if (!ok_to_replace)
487 break;
488 remove_cache_entry_at(--pos);
489 }
490 return retval;
491 }
492
493 /*
494 * Do we have another file with a pathname that is a proper
495 * subset of the name we're trying to add?
496 */
497 static int has_dir_name(const struct cache_entry *ce, int pos, int ok_to_replace)
498 {
499 int retval = 0;
500 int stage = ce_stage(ce);
501 const char *name = ce->name;
502 const char *slash = name + ce_namelen(ce);
503
504 for (;;) {
505 int len;
506
507 for (;;) {
508 if (*--slash == '/')
509 break;
510 if (slash <= ce->name)
511 return retval;
512 }
513 len = slash - name;
514
515 pos = cache_name_pos(name, ntohs(create_ce_flags(len, stage)));
516 if (pos >= 0) {
517 retval = -1;
518 if (ok_to_replace)
519 break;
520 remove_cache_entry_at(pos);
521 continue;
522 }
523
524 /*
525 * Trivial optimization: if we find an entry that
526 * already matches the sub-directory, then we know
527 * we're ok, and we can exit.
528 */
529 pos = -pos-1;
530 while (pos < active_nr) {
531 struct cache_entry *p = active_cache[pos];
532 if ((ce_namelen(p) <= len) ||
533 (p->name[len] != '/') ||
534 memcmp(p->name, name, len))
535 break; /* not our subdirectory */
536 if (ce_stage(p) == stage)
537 /* p is at the same stage as our entry, and
538 * is a subdirectory of what we are looking
539 * at, so we cannot have conflicts at our
540 * level or anything shorter.
541 */
542 return retval;
543 pos++;
544 }
545 }
546 return retval;
547 }
548
549 /* We may be in a situation where we already have path/file and path
550 * is being added, or we already have path and path/file is being
551 * added. Either one would result in a nonsense tree that has path
552 * twice when git-write-tree tries to write it out. Prevent it.
553 *
554 * If ok-to-replace is specified, we remove the conflicting entries
555 * from the cache so the caller should recompute the insert position.
556 * When this happens, we return non-zero.
557 */
558 static int check_file_directory_conflict(const struct cache_entry *ce, int pos, int ok_to_replace)
559 {
560 /*
561 * We check if the path is a sub-path of a subsequent pathname
562 * first, since removing those will not change the position
563 * in the array
564 */
565 int retval = has_file_name(ce, pos, ok_to_replace);
566 /*
567 * Then check if the path might have a clashing sub-directory
568 * before it.
569 */
570 return retval + has_dir_name(ce, pos, ok_to_replace);
571 }
572
573 int add_cache_entry(struct cache_entry *ce, int option)
574 {
575 int pos;
576 int ok_to_add = option & ADD_CACHE_OK_TO_ADD;
577 int ok_to_replace = option & ADD_CACHE_OK_TO_REPLACE;
578 int skip_df_check = option & ADD_CACHE_SKIP_DFCHECK;
579
580 pos = cache_name_pos(ce->name, ntohs(ce->ce_flags));
581
582 /* existing match? Just replace it. */
583 if (pos >= 0) {
584 active_cache_changed = 1;
585 active_cache[pos] = ce;
586 return 0;
587 }
588 pos = -pos-1;
589
590 /*
591 * Inserting a merged entry ("stage 0") into the index
592 * will always replace all non-merged entries..
593 */
594 if (pos < active_nr && ce_stage(ce) == 0) {
595 while (ce_same_name(active_cache[pos], ce)) {
596 ok_to_add = 1;
597 if (!remove_cache_entry_at(pos))
598 break;
599 }
600 }
601
602 if (!ok_to_add)
603 return -1;
604 if (!verify_path(ce->name))
605 return -1;
606
607 if (!skip_df_check &&
608 check_file_directory_conflict(ce, pos, ok_to_replace)) {
609 if (!ok_to_replace)
610 return -1;
611 pos = cache_name_pos(ce->name, ntohs(ce->ce_flags));
612 pos = -pos-1;
613 }
614
615 /* Make sure the array is big enough .. */
616 if (active_nr == active_alloc) {
617 active_alloc = alloc_nr(active_alloc);
618 active_cache = xrealloc(active_cache, active_alloc * sizeof(struct cache_entry *));
619 }
620
621 /* Add it in.. */
622 active_nr++;
623 if (active_nr > pos)
624 memmove(active_cache + pos + 1, active_cache + pos, (active_nr - pos - 1) * sizeof(ce));
625 active_cache[pos] = ce;
626 active_cache_changed = 1;
627 return 0;
628 }
629
630 /*
631 * "refresh" does not calculate a new sha1 file or bring the
632 * cache up-to-date for mode/content changes. But what it
633 * _does_ do is to "re-match" the stat information of a file
634 * with the cache, so that you can refresh the cache for a
635 * file that hasn't been changed but where the stat entry is
636 * out of date.
637 *
638 * For example, you'd want to do this after doing a "git-read-tree",
639 * to link up the stat cache details with the proper files.
640 */
641 struct cache_entry *refresh_cache_entry(struct cache_entry *ce, int really)
642 {
643 struct stat st;
644 struct cache_entry *updated;
645 int changed, size;
646
647 if (lstat(ce->name, &st) < 0) {
648 cache_errno = errno;
649 return NULL;
650 }
651
652 changed = ce_match_stat(ce, &st, really);
653 if (!changed) {
654 if (really && assume_unchanged &&
655 !(ce->ce_flags & htons(CE_VALID)))
656 ; /* mark this one VALID again */
657 else
658 return ce;
659 }
660
661 if (ce_modified(ce, &st, really)) {
662 cache_errno = EINVAL;
663 return NULL;
664 }
665
666 size = ce_size(ce);
667 updated = xmalloc(size);
668 memcpy(updated, ce, size);
669 fill_stat_cache_info(updated, &st);
670
671 /* In this case, if really is not set, we should leave
672 * CE_VALID bit alone. Otherwise, paths marked with
673 * --no-assume-unchanged (i.e. things to be edited) will
674 * reacquire CE_VALID bit automatically, which is not
675 * really what we want.
676 */
677 if (!really && assume_unchanged && !(ce->ce_flags & htons(CE_VALID)))
678 updated->ce_flags &= ~htons(CE_VALID);
679
680 return updated;
681 }
682
683 int refresh_cache(unsigned int flags)
684 {
685 int i;
686 int has_errors = 0;
687 int really = (flags & REFRESH_REALLY) != 0;
688 int allow_unmerged = (flags & REFRESH_UNMERGED) != 0;
689 int quiet = (flags & REFRESH_QUIET) != 0;
690 int not_new = (flags & REFRESH_IGNORE_MISSING) != 0;
691
692 for (i = 0; i < active_nr; i++) {
693 struct cache_entry *ce, *new;
694 ce = active_cache[i];
695 if (ce_stage(ce)) {
696 while ((i < active_nr) &&
697 ! strcmp(active_cache[i]->name, ce->name))
698 i++;
699 i--;
700 if (allow_unmerged)
701 continue;
702 printf("%s: needs merge\n", ce->name);
703 has_errors = 1;
704 continue;
705 }
706
707 new = refresh_cache_entry(ce, really);
708 if (new == ce)
709 continue;
710 if (!new) {
711 if (not_new && cache_errno == ENOENT)
712 continue;
713 if (really && cache_errno == EINVAL) {
714 /* If we are doing --really-refresh that
715 * means the index is not valid anymore.
716 */
717 ce->ce_flags &= ~htons(CE_VALID);
718 active_cache_changed = 1;
719 }
720 if (quiet)
721 continue;
722 printf("%s: needs update\n", ce->name);
723 has_errors = 1;
724 continue;
725 }
726 active_cache_changed = 1;
727 /* You can NOT just free active_cache[i] here, since it
728 * might not be necessarily malloc()ed but can also come
729 * from mmap(). */
730 active_cache[i] = new;
731 }
732 return has_errors;
733 }
734
735 static int verify_hdr(struct cache_header *hdr, unsigned long size)
736 {
737 SHA_CTX c;
738 unsigned char sha1[20];
739
740 if (hdr->hdr_signature != htonl(CACHE_SIGNATURE))
741 return error("bad signature");
742 if (hdr->hdr_version != htonl(2))
743 return error("bad index version");
744 SHA1_Init(&c);
745 SHA1_Update(&c, hdr, size - 20);
746 SHA1_Final(sha1, &c);
747 if (hashcmp(sha1, (unsigned char *)hdr + size - 20))
748 return error("bad index file sha1 signature");
749 return 0;
750 }
751
752 static int read_index_extension(const char *ext, void *data, unsigned long sz)
753 {
754 switch (CACHE_EXT(ext)) {
755 case CACHE_EXT_TREE:
756 active_cache_tree = cache_tree_read(data, sz);
757 break;
758 default:
759 if (*ext < 'A' || 'Z' < *ext)
760 return error("index uses %.4s extension, which we do not understand",
761 ext);
762 fprintf(stderr, "ignoring %.4s extension\n", ext);
763 break;
764 }
765 return 0;
766 }
767
768 int read_cache(void)
769 {
770 return read_cache_from(get_index_file());
771 }
772
773 /* remember to discard_cache() before reading a different cache! */
774 int read_cache_from(const char *path)
775 {
776 int fd, i;
777 struct stat st;
778 unsigned long offset;
779 struct cache_header *hdr;
780
781 errno = EBUSY;
782 if (cache_mmap)
783 return active_nr;
784
785 errno = ENOENT;
786 index_file_timestamp = 0;
787 fd = open(path, O_RDONLY);
788 if (fd < 0) {
789 if (errno == ENOENT)
790 return 0;
791 die("index file open failed (%s)", strerror(errno));
792 }
793
794 cache_mmap = MAP_FAILED;
795 if (!fstat(fd, &st)) {
796 cache_mmap_size = st.st_size;
797 errno = EINVAL;
798 if (cache_mmap_size >= sizeof(struct cache_header) + 20)
799 cache_mmap = mmap(NULL, cache_mmap_size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
800 }
801 close(fd);
802 if (cache_mmap == MAP_FAILED)
803 die("index file mmap failed (%s)", strerror(errno));
804
805 hdr = cache_mmap;
806 if (verify_hdr(hdr, cache_mmap_size) < 0)
807 goto unmap;
808
809 active_nr = ntohl(hdr->hdr_entries);
810 active_alloc = alloc_nr(active_nr);
811 active_cache = xcalloc(active_alloc, sizeof(struct cache_entry *));
812
813 offset = sizeof(*hdr);
814 for (i = 0; i < active_nr; i++) {
815 struct cache_entry *ce = (struct cache_entry *) ((char *) cache_mmap + offset);
816 offset = offset + ce_size(ce);
817 active_cache[i] = ce;
818 }
819 index_file_timestamp = st.st_mtime;
820 while (offset <= cache_mmap_size - 20 - 8) {
821 /* After an array of active_nr index entries,
822 * there can be arbitrary number of extended
823 * sections, each of which is prefixed with
824 * extension name (4-byte) and section length
825 * in 4-byte network byte order.
826 */
827 unsigned long extsize;
828 memcpy(&extsize, (char *) cache_mmap + offset + 4, 4);
829 extsize = ntohl(extsize);
830 if (read_index_extension(((const char *) cache_mmap) + offset,
831 (char *) cache_mmap + offset + 8,
832 extsize) < 0)
833 goto unmap;
834 offset += 8;
835 offset += extsize;
836 }
837 return active_nr;
838
839 unmap:
840 munmap(cache_mmap, cache_mmap_size);
841 errno = EINVAL;
842 die("index file corrupt");
843 }
844
845 int discard_cache()
846 {
847 int ret;
848
849 active_nr = active_cache_changed = 0;
850 index_file_timestamp = 0;
851 cache_tree_free(&active_cache_tree);
852 if (cache_mmap == NULL)
853 return 0;
854 ret = munmap(cache_mmap, cache_mmap_size);
855 cache_mmap = NULL;
856 cache_mmap_size = 0;
857
858 /* no need to throw away allocated active_cache */
859 return ret;
860 }
861
862 #define WRITE_BUFFER_SIZE 8192
863 static unsigned char write_buffer[WRITE_BUFFER_SIZE];
864 static unsigned long write_buffer_len;
865
866 static int ce_write_flush(SHA_CTX *context, int fd)
867 {
868 unsigned int buffered = write_buffer_len;
869 if (buffered) {
870 SHA1_Update(context, write_buffer, buffered);
871 if (write(fd, write_buffer, buffered) != buffered)
872 return -1;
873 write_buffer_len = 0;
874 }
875 return 0;
876 }
877
878 static int ce_write(SHA_CTX *context, int fd, void *data, unsigned int len)
879 {
880 while (len) {
881 unsigned int buffered = write_buffer_len;
882 unsigned int partial = WRITE_BUFFER_SIZE - buffered;
883 if (partial > len)
884 partial = len;
885 memcpy(write_buffer + buffered, data, partial);
886 buffered += partial;
887 if (buffered == WRITE_BUFFER_SIZE) {
888 write_buffer_len = buffered;
889 if (ce_write_flush(context, fd))
890 return -1;
891 buffered = 0;
892 }
893 write_buffer_len = buffered;
894 len -= partial;
895 data = (char *) data + partial;
896 }
897 return 0;
898 }
899
900 static int write_index_ext_header(SHA_CTX *context, int fd,
901 unsigned int ext, unsigned int sz)
902 {
903 ext = htonl(ext);
904 sz = htonl(sz);
905 return ((ce_write(context, fd, &ext, 4) < 0) ||
906 (ce_write(context, fd, &sz, 4) < 0)) ? -1 : 0;
907 }
908
909 static int ce_flush(SHA_CTX *context, int fd)
910 {
911 unsigned int left = write_buffer_len;
912
913 if (left) {
914 write_buffer_len = 0;
915 SHA1_Update(context, write_buffer, left);
916 }
917
918 /* Flush first if not enough space for SHA1 signature */
919 if (left + 20 > WRITE_BUFFER_SIZE) {
920 if (write(fd, write_buffer, left) != left)
921 return -1;
922 left = 0;
923 }
924
925 /* Append the SHA1 signature at the end */
926 SHA1_Final(write_buffer + left, context);
927 left += 20;
928 return (write(fd, write_buffer, left) != left) ? -1 : 0;
929 }
930
931 static void ce_smudge_racily_clean_entry(struct cache_entry *ce)
932 {
933 /*
934 * The only thing we care about in this function is to smudge the
935 * falsely clean entry due to touch-update-touch race, so we leave
936 * everything else as they are. We are called for entries whose
937 * ce_mtime match the index file mtime.
938 */
939 struct stat st;
940
941 if (lstat(ce->name, &st) < 0)
942 return;
943 if (ce_match_stat_basic(ce, &st))
944 return;
945 if (ce_modified_check_fs(ce, &st)) {
946 /* This is "racily clean"; smudge it. Note that this
947 * is a tricky code. At first glance, it may appear
948 * that it can break with this sequence:
949 *
950 * $ echo xyzzy >frotz
951 * $ git-update-index --add frotz
952 * $ : >frotz
953 * $ sleep 3
954 * $ echo filfre >nitfol
955 * $ git-update-index --add nitfol
956 *
957 * but it does not. When the second update-index runs,
958 * it notices that the entry "frotz" has the same timestamp
959 * as index, and if we were to smudge it by resetting its
960 * size to zero here, then the object name recorded
961 * in index is the 6-byte file but the cached stat information
962 * becomes zero --- which would then match what we would
963 * obtain from the filesystem next time we stat("frotz").
964 *
965 * However, the second update-index, before calling
966 * this function, notices that the cached size is 6
967 * bytes and what is on the filesystem is an empty
968 * file, and never calls us, so the cached size information
969 * for "frotz" stays 6 which does not match the filesystem.
970 */
971 ce->ce_size = htonl(0);
972 }
973 }
974
975 int write_cache(int newfd, struct cache_entry **cache, int entries)
976 {
977 SHA_CTX c;
978 struct cache_header hdr;
979 int i, removed;
980
981 for (i = removed = 0; i < entries; i++)
982 if (!cache[i]->ce_mode)
983 removed++;
984
985 hdr.hdr_signature = htonl(CACHE_SIGNATURE);
986 hdr.hdr_version = htonl(2);
987 hdr.hdr_entries = htonl(entries - removed);
988
989 SHA1_Init(&c);
990 if (ce_write(&c, newfd, &hdr, sizeof(hdr)) < 0)
991 return -1;
992
993 for (i = 0; i < entries; i++) {
994 struct cache_entry *ce = cache[i];
995 if (!ce->ce_mode)
996 continue;
997 if (index_file_timestamp &&
998 index_file_timestamp <= ntohl(ce->ce_mtime.sec))
999 ce_smudge_racily_clean_entry(ce);
1000 if (ce_write(&c, newfd, ce, ce_size(ce)) < 0)
1001 return -1;
1002 }
1003
1004 /* Write extension data here */
1005 if (active_cache_tree) {
1006 unsigned long sz;
1007 void *data = cache_tree_write(active_cache_tree, &sz);
1008 if (data &&
1009 !write_index_ext_header(&c, newfd, CACHE_EXT_TREE, sz) &&
1010 !ce_write(&c, newfd, data, sz))
1011 ;
1012 else {
1013 free(data);
1014 return -1;
1015 }
1016 }
1017 return ce_flush(&c, newfd);
1018 }