cherry-pick/revert: transparently refresh index
[git] / sha1_file.c
1 /*
2  * GIT - The information manager from hell
3  *
4  * Copyright (C) Linus Torvalds, 2005
5  *
6  * This handles basic git sha1 object files - packing, unpacking,
7  * creation etc.
8  */
9 #include "cache.h"
10 #include "delta.h"
11 #include "pack.h"
12 #include "blob.h"
13 #include "commit.h"
14 #include "tag.h"
15 #include "tree.h"
16 #include "refs.h"
17 #include "pack-revindex.h"
18 #include "sha1-lookup.h"
19
20 #ifndef O_NOATIME
21 #if defined(__linux__) && (defined(__i386__) || defined(__PPC__))
22 #define O_NOATIME 01000000
23 #else
24 #define O_NOATIME 0
25 #endif
26 #endif
27
28 #ifdef NO_C99_FORMAT
29 #define SZ_FMT "lu"
30 static unsigned long sz_fmt(size_t s) { return (unsigned long)s; }
31 #else
32 #define SZ_FMT "zu"
33 static size_t sz_fmt(size_t s) { return s; }
34 #endif
35
36 const unsigned char null_sha1[20];
37
38 int safe_create_leading_directories(char *path)
39 {
40         char *pos = path + offset_1st_component(path);
41         struct stat st;
42
43         while (pos) {
44                 pos = strchr(pos, '/');
45                 if (!pos)
46                         break;
47                 while (*++pos == '/')
48                         ;
49                 if (!*pos)
50                         break;
51                 *--pos = '\0';
52                 if (!stat(path, &st)) {
53                         /* path exists */
54                         if (!S_ISDIR(st.st_mode)) {
55                                 *pos = '/';
56                                 return -3;
57                         }
58                 }
59                 else if (mkdir(path, 0777)) {
60                         *pos = '/';
61                         return -1;
62                 }
63                 else if (adjust_shared_perm(path)) {
64                         *pos = '/';
65                         return -2;
66                 }
67                 *pos++ = '/';
68         }
69         return 0;
70 }
71
72 int safe_create_leading_directories_const(const char *path)
73 {
74         /* path points to cache entries, so xstrdup before messing with it */
75         char *buf = xstrdup(path);
76         int result = safe_create_leading_directories(buf);
77         free(buf);
78         return result;
79 }
80
81 static void fill_sha1_path(char *pathbuf, const unsigned char *sha1)
82 {
83         int i;
84         for (i = 0; i < 20; i++) {
85                 static char hex[] = "0123456789abcdef";
86                 unsigned int val = sha1[i];
87                 char *pos = pathbuf + i*2 + (i > 0);
88                 *pos++ = hex[val >> 4];
89                 *pos = hex[val & 0xf];
90         }
91 }
92
93 /*
94  * NOTE! This returns a statically allocated buffer, so you have to be
95  * careful about using it. Do an "xstrdup()" if you need to save the
96  * filename.
97  *
98  * Also note that this returns the location for creating.  Reading
99  * SHA1 file can happen from any alternate directory listed in the
100  * DB_ENVIRONMENT environment variable if it is not found in
101  * the primary object database.
102  */
103 char *sha1_file_name(const unsigned char *sha1)
104 {
105         static char buf[PATH_MAX];
106         const char *objdir;
107         int len;
108
109         objdir = get_object_directory();
110         len = strlen(objdir);
111
112         /* '/' + sha1(2) + '/' + sha1(38) + '\0' */
113         if (len + 43 > PATH_MAX)
114                 die("insanely long object directory %s", objdir);
115         memcpy(buf, objdir, len);
116         buf[len] = '/';
117         buf[len+3] = '/';
118         buf[len+42] = '\0';
119         fill_sha1_path(buf + len + 1, sha1);
120         return buf;
121 }
122
123 static char *sha1_get_pack_name(const unsigned char *sha1,
124                                 char **name, char **base, const char *which)
125 {
126         static const char hex[] = "0123456789abcdef";
127         char *buf;
128         int i;
129
130         if (!*base) {
131                 const char *sha1_file_directory = get_object_directory();
132                 int len = strlen(sha1_file_directory);
133                 *base = xmalloc(len + 60);
134                 sprintf(*base, "%s/pack/pack-1234567890123456789012345678901234567890.%s",
135                         sha1_file_directory, which);
136                 *name = *base + len + 11;
137         }
138
139         buf = *name;
140
141         for (i = 0; i < 20; i++) {
142                 unsigned int val = *sha1++;
143                 *buf++ = hex[val >> 4];
144                 *buf++ = hex[val & 0xf];
145         }
146
147         return *base;
148 }
149
150 char *sha1_pack_name(const unsigned char *sha1)
151 {
152         static char *name, *base;
153
154         return sha1_get_pack_name(sha1, &name, &base, "pack");
155 }
156
157 char *sha1_pack_index_name(const unsigned char *sha1)
158 {
159         static char *name, *base;
160
161         return sha1_get_pack_name(sha1, &name, &base, "idx");
162 }
163
164 struct alternate_object_database *alt_odb_list;
165 static struct alternate_object_database **alt_odb_tail;
166
167 static void read_info_alternates(const char * alternates, int depth);
168
169 /*
170  * Prepare alternate object database registry.
171  *
172  * The variable alt_odb_list points at the list of struct
173  * alternate_object_database.  The elements on this list come from
174  * non-empty elements from colon separated ALTERNATE_DB_ENVIRONMENT
175  * environment variable, and $GIT_OBJECT_DIRECTORY/info/alternates,
176  * whose contents is similar to that environment variable but can be
177  * LF separated.  Its base points at a statically allocated buffer that
178  * contains "/the/directory/corresponding/to/.git/objects/...", while
179  * its name points just after the slash at the end of ".git/objects/"
180  * in the example above, and has enough space to hold 40-byte hex
181  * SHA1, an extra slash for the first level indirection, and the
182  * terminating NUL.
183  */
184 static int link_alt_odb_entry(const char * entry, int len, const char * relative_base, int depth)
185 {
186         const char *objdir = get_object_directory();
187         struct alternate_object_database *ent;
188         struct alternate_object_database *alt;
189         /* 43 = 40-byte + 2 '/' + terminating NUL */
190         int pfxlen = len;
191         int entlen = pfxlen + 43;
192         int base_len = -1;
193
194         if (!is_absolute_path(entry) && relative_base) {
195                 /* Relative alt-odb */
196                 if (base_len < 0)
197                         base_len = strlen(relative_base) + 1;
198                 entlen += base_len;
199                 pfxlen += base_len;
200         }
201         ent = xmalloc(sizeof(*ent) + entlen);
202
203         if (!is_absolute_path(entry) && relative_base) {
204                 memcpy(ent->base, relative_base, base_len - 1);
205                 ent->base[base_len - 1] = '/';
206                 memcpy(ent->base + base_len, entry, len);
207         }
208         else
209                 memcpy(ent->base, entry, pfxlen);
210
211         ent->name = ent->base + pfxlen + 1;
212         ent->base[pfxlen + 3] = '/';
213         ent->base[pfxlen] = ent->base[entlen-1] = 0;
214
215         /* Detect cases where alternate disappeared */
216         if (!is_directory(ent->base)) {
217                 error("object directory %s does not exist; "
218                       "check .git/objects/info/alternates.",
219                       ent->base);
220                 free(ent);
221                 return -1;
222         }
223
224         /* Prevent the common mistake of listing the same
225          * thing twice, or object directory itself.
226          */
227         for (alt = alt_odb_list; alt; alt = alt->next) {
228                 if (!memcmp(ent->base, alt->base, pfxlen)) {
229                         free(ent);
230                         return -1;
231                 }
232         }
233         if (!memcmp(ent->base, objdir, pfxlen)) {
234                 free(ent);
235                 return -1;
236         }
237
238         /* add the alternate entry */
239         *alt_odb_tail = ent;
240         alt_odb_tail = &(ent->next);
241         ent->next = NULL;
242
243         /* recursively add alternates */
244         read_info_alternates(ent->base, depth + 1);
245
246         ent->base[pfxlen] = '/';
247
248         return 0;
249 }
250
251 static void link_alt_odb_entries(const char *alt, const char *ep, int sep,
252                                  const char *relative_base, int depth)
253 {
254         const char *cp, *last;
255
256         if (depth > 5) {
257                 error("%s: ignoring alternate object stores, nesting too deep.",
258                                 relative_base);
259                 return;
260         }
261
262         last = alt;
263         while (last < ep) {
264                 cp = last;
265                 if (cp < ep && *cp == '#') {
266                         while (cp < ep && *cp != sep)
267                                 cp++;
268                         last = cp + 1;
269                         continue;
270                 }
271                 while (cp < ep && *cp != sep)
272                         cp++;
273                 if (last != cp) {
274                         if (!is_absolute_path(last) && depth) {
275                                 error("%s: ignoring relative alternate object store %s",
276                                                 relative_base, last);
277                         } else {
278                                 link_alt_odb_entry(last, cp - last,
279                                                 relative_base, depth);
280                         }
281                 }
282                 while (cp < ep && *cp == sep)
283                         cp++;
284                 last = cp;
285         }
286 }
287
288 static void read_info_alternates(const char * relative_base, int depth)
289 {
290         char *map;
291         size_t mapsz;
292         struct stat st;
293         const char alt_file_name[] = "info/alternates";
294         /* Given that relative_base is no longer than PATH_MAX,
295            ensure that "path" has enough space to append "/", the
296            file name, "info/alternates", and a trailing NUL.  */
297         char path[PATH_MAX + 1 + sizeof alt_file_name];
298         int fd;
299
300         sprintf(path, "%s/%s", relative_base, alt_file_name);
301         fd = open(path, O_RDONLY);
302         if (fd < 0)
303                 return;
304         if (fstat(fd, &st) || (st.st_size == 0)) {
305                 close(fd);
306                 return;
307         }
308         mapsz = xsize_t(st.st_size);
309         map = xmmap(NULL, mapsz, PROT_READ, MAP_PRIVATE, fd, 0);
310         close(fd);
311
312         link_alt_odb_entries(map, map + mapsz, '\n', relative_base, depth);
313
314         munmap(map, mapsz);
315 }
316
317 void add_to_alternates_file(const char *reference)
318 {
319         struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
320         int fd = hold_lock_file_for_append(lock, git_path("objects/info/alternates"), LOCK_DIE_ON_ERROR);
321         char *alt = mkpath("%s/objects\n", reference);
322         write_or_die(fd, alt, strlen(alt));
323         if (commit_lock_file(lock))
324                 die("could not close alternates file");
325         if (alt_odb_tail)
326                 link_alt_odb_entries(alt, alt + strlen(alt), '\n', NULL, 0);
327 }
328
329 void foreach_alt_odb(alt_odb_fn fn, void *cb)
330 {
331         struct alternate_object_database *ent;
332
333         prepare_alt_odb();
334         for (ent = alt_odb_list; ent; ent = ent->next)
335                 if (fn(ent, cb))
336                         return;
337 }
338
339 void prepare_alt_odb(void)
340 {
341         const char *alt;
342
343         if (alt_odb_tail)
344                 return;
345
346         alt = getenv(ALTERNATE_DB_ENVIRONMENT);
347         if (!alt) alt = "";
348
349         alt_odb_tail = &alt_odb_list;
350         link_alt_odb_entries(alt, alt + strlen(alt), PATH_SEP, NULL, 0);
351
352         read_info_alternates(get_object_directory(), 0);
353 }
354
355 static int has_loose_object_local(const unsigned char *sha1)
356 {
357         char *name = sha1_file_name(sha1);
358         return !access(name, F_OK);
359 }
360
361 int has_loose_object_nonlocal(const unsigned char *sha1)
362 {
363         struct alternate_object_database *alt;
364         prepare_alt_odb();
365         for (alt = alt_odb_list; alt; alt = alt->next) {
366                 fill_sha1_path(alt->name, sha1);
367                 if (!access(alt->base, F_OK))
368                         return 1;
369         }
370         return 0;
371 }
372
373 static int has_loose_object(const unsigned char *sha1)
374 {
375         return has_loose_object_local(sha1) ||
376                has_loose_object_nonlocal(sha1);
377 }
378
379 static unsigned int pack_used_ctr;
380 static unsigned int pack_mmap_calls;
381 static unsigned int peak_pack_open_windows;
382 static unsigned int pack_open_windows;
383 static size_t peak_pack_mapped;
384 static size_t pack_mapped;
385 struct packed_git *packed_git;
386
387 void pack_report(void)
388 {
389         fprintf(stderr,
390                 "pack_report: getpagesize()            = %10" SZ_FMT "\n"
391                 "pack_report: core.packedGitWindowSize = %10" SZ_FMT "\n"
392                 "pack_report: core.packedGitLimit      = %10" SZ_FMT "\n",
393                 sz_fmt(getpagesize()),
394                 sz_fmt(packed_git_window_size),
395                 sz_fmt(packed_git_limit));
396         fprintf(stderr,
397                 "pack_report: pack_used_ctr            = %10u\n"
398                 "pack_report: pack_mmap_calls          = %10u\n"
399                 "pack_report: pack_open_windows        = %10u / %10u\n"
400                 "pack_report: pack_mapped              = "
401                         "%10" SZ_FMT " / %10" SZ_FMT "\n",
402                 pack_used_ctr,
403                 pack_mmap_calls,
404                 pack_open_windows, peak_pack_open_windows,
405                 sz_fmt(pack_mapped), sz_fmt(peak_pack_mapped));
406 }
407
408 static int check_packed_git_idx(const char *path,  struct packed_git *p)
409 {
410         void *idx_map;
411         struct pack_idx_header *hdr;
412         size_t idx_size;
413         uint32_t version, nr, i, *index;
414         int fd = open(path, O_RDONLY);
415         struct stat st;
416
417         if (fd < 0)
418                 return -1;
419         if (fstat(fd, &st)) {
420                 close(fd);
421                 return -1;
422         }
423         idx_size = xsize_t(st.st_size);
424         if (idx_size < 4 * 256 + 20 + 20) {
425                 close(fd);
426                 return error("index file %s is too small", path);
427         }
428         idx_map = xmmap(NULL, idx_size, PROT_READ, MAP_PRIVATE, fd, 0);
429         close(fd);
430
431         hdr = idx_map;
432         if (hdr->idx_signature == htonl(PACK_IDX_SIGNATURE)) {
433                 version = ntohl(hdr->idx_version);
434                 if (version < 2 || version > 2) {
435                         munmap(idx_map, idx_size);
436                         return error("index file %s is version %"PRIu32
437                                      " and is not supported by this binary"
438                                      " (try upgrading GIT to a newer version)",
439                                      path, version);
440                 }
441         } else
442                 version = 1;
443
444         nr = 0;
445         index = idx_map;
446         if (version > 1)
447                 index += 2;  /* skip index header */
448         for (i = 0; i < 256; i++) {
449                 uint32_t n = ntohl(index[i]);
450                 if (n < nr) {
451                         munmap(idx_map, idx_size);
452                         return error("non-monotonic index %s", path);
453                 }
454                 nr = n;
455         }
456
457         if (version == 1) {
458                 /*
459                  * Total size:
460                  *  - 256 index entries 4 bytes each
461                  *  - 24-byte entries * nr (20-byte sha1 + 4-byte offset)
462                  *  - 20-byte SHA1 of the packfile
463                  *  - 20-byte SHA1 file checksum
464                  */
465                 if (idx_size != 4*256 + nr * 24 + 20 + 20) {
466                         munmap(idx_map, idx_size);
467                         return error("wrong index v1 file size in %s", path);
468                 }
469         } else if (version == 2) {
470                 /*
471                  * Minimum size:
472                  *  - 8 bytes of header
473                  *  - 256 index entries 4 bytes each
474                  *  - 20-byte sha1 entry * nr
475                  *  - 4-byte crc entry * nr
476                  *  - 4-byte offset entry * nr
477                  *  - 20-byte SHA1 of the packfile
478                  *  - 20-byte SHA1 file checksum
479                  * And after the 4-byte offset table might be a
480                  * variable sized table containing 8-byte entries
481                  * for offsets larger than 2^31.
482                  */
483                 unsigned long min_size = 8 + 4*256 + nr*(20 + 4 + 4) + 20 + 20;
484                 unsigned long max_size = min_size;
485                 if (nr)
486                         max_size += (nr - 1)*8;
487                 if (idx_size < min_size || idx_size > max_size) {
488                         munmap(idx_map, idx_size);
489                         return error("wrong index v2 file size in %s", path);
490                 }
491                 if (idx_size != min_size &&
492                     /*
493                      * make sure we can deal with large pack offsets.
494                      * 31-bit signed offset won't be enough, neither
495                      * 32-bit unsigned one will be.
496                      */
497                     (sizeof(off_t) <= 4)) {
498                         munmap(idx_map, idx_size);
499                         return error("pack too large for current definition of off_t in %s", path);
500                 }
501         }
502
503         p->index_version = version;
504         p->index_data = idx_map;
505         p->index_size = idx_size;
506         p->num_objects = nr;
507         return 0;
508 }
509
510 int open_pack_index(struct packed_git *p)
511 {
512         char *idx_name;
513         int ret;
514
515         if (p->index_data)
516                 return 0;
517
518         idx_name = xstrdup(p->pack_name);
519         strcpy(idx_name + strlen(idx_name) - strlen(".pack"), ".idx");
520         ret = check_packed_git_idx(idx_name, p);
521         free(idx_name);
522         return ret;
523 }
524
525 static void scan_windows(struct packed_git *p,
526         struct packed_git **lru_p,
527         struct pack_window **lru_w,
528         struct pack_window **lru_l)
529 {
530         struct pack_window *w, *w_l;
531
532         for (w_l = NULL, w = p->windows; w; w = w->next) {
533                 if (!w->inuse_cnt) {
534                         if (!*lru_w || w->last_used < (*lru_w)->last_used) {
535                                 *lru_p = p;
536                                 *lru_w = w;
537                                 *lru_l = w_l;
538                         }
539                 }
540                 w_l = w;
541         }
542 }
543
544 static int unuse_one_window(struct packed_git *current, int keep_fd)
545 {
546         struct packed_git *p, *lru_p = NULL;
547         struct pack_window *lru_w = NULL, *lru_l = NULL;
548
549         if (current)
550                 scan_windows(current, &lru_p, &lru_w, &lru_l);
551         for (p = packed_git; p; p = p->next)
552                 scan_windows(p, &lru_p, &lru_w, &lru_l);
553         if (lru_p) {
554                 munmap(lru_w->base, lru_w->len);
555                 pack_mapped -= lru_w->len;
556                 if (lru_l)
557                         lru_l->next = lru_w->next;
558                 else {
559                         lru_p->windows = lru_w->next;
560                         if (!lru_p->windows && lru_p->pack_fd != keep_fd) {
561                                 close(lru_p->pack_fd);
562                                 lru_p->pack_fd = -1;
563                         }
564                 }
565                 free(lru_w);
566                 pack_open_windows--;
567                 return 1;
568         }
569         return 0;
570 }
571
572 void release_pack_memory(size_t need, int fd)
573 {
574         size_t cur = pack_mapped;
575         while (need >= (cur - pack_mapped) && unuse_one_window(NULL, fd))
576                 ; /* nothing */
577 }
578
579 void close_pack_windows(struct packed_git *p)
580 {
581         while (p->windows) {
582                 struct pack_window *w = p->windows;
583
584                 if (w->inuse_cnt)
585                         die("pack '%s' still has open windows to it",
586                             p->pack_name);
587                 munmap(w->base, w->len);
588                 pack_mapped -= w->len;
589                 pack_open_windows--;
590                 p->windows = w->next;
591                 free(w);
592         }
593 }
594
595 void unuse_pack(struct pack_window **w_cursor)
596 {
597         struct pack_window *w = *w_cursor;
598         if (w) {
599                 w->inuse_cnt--;
600                 *w_cursor = NULL;
601         }
602 }
603
604 void close_pack_index(struct packed_git *p)
605 {
606         if (p->index_data) {
607                 munmap((void *)p->index_data, p->index_size);
608                 p->index_data = NULL;
609         }
610 }
611
612 /*
613  * This is used by git-repack in case a newly created pack happens to
614  * contain the same set of objects as an existing one.  In that case
615  * the resulting file might be different even if its name would be the
616  * same.  It is best to close any reference to the old pack before it is
617  * replaced on disk.  Of course no index pointers nor windows for given pack
618  * must subsist at this point.  If ever objects from this pack are requested
619  * again, the new version of the pack will be reinitialized through
620  * reprepare_packed_git().
621  */
622 void free_pack_by_name(const char *pack_name)
623 {
624         struct packed_git *p, **pp = &packed_git;
625
626         while (*pp) {
627                 p = *pp;
628                 if (strcmp(pack_name, p->pack_name) == 0) {
629                         clear_delta_base_cache();
630                         close_pack_windows(p);
631                         if (p->pack_fd != -1)
632                                 close(p->pack_fd);
633                         close_pack_index(p);
634                         free(p->bad_object_sha1);
635                         *pp = p->next;
636                         free(p);
637                         return;
638                 }
639                 pp = &p->next;
640         }
641 }
642
643 /*
644  * Do not call this directly as this leaks p->pack_fd on error return;
645  * call open_packed_git() instead.
646  */
647 static int open_packed_git_1(struct packed_git *p)
648 {
649         struct stat st;
650         struct pack_header hdr;
651         unsigned char sha1[20];
652         unsigned char *idx_sha1;
653         long fd_flag;
654
655         if (!p->index_data && open_pack_index(p))
656                 return error("packfile %s index unavailable", p->pack_name);
657
658         p->pack_fd = open(p->pack_name, O_RDONLY);
659         while (p->pack_fd < 0 && errno == EMFILE && unuse_one_window(p, -1))
660                 p->pack_fd = open(p->pack_name, O_RDONLY);
661         if (p->pack_fd < 0 || fstat(p->pack_fd, &st))
662                 return -1;
663
664         /* If we created the struct before we had the pack we lack size. */
665         if (!p->pack_size) {
666                 if (!S_ISREG(st.st_mode))
667                         return error("packfile %s not a regular file", p->pack_name);
668                 p->pack_size = st.st_size;
669         } else if (p->pack_size != st.st_size)
670                 return error("packfile %s size changed", p->pack_name);
671
672         /* We leave these file descriptors open with sliding mmap;
673          * there is no point keeping them open across exec(), though.
674          */
675         fd_flag = fcntl(p->pack_fd, F_GETFD, 0);
676         if (fd_flag < 0)
677                 return error("cannot determine file descriptor flags");
678         fd_flag |= FD_CLOEXEC;
679         if (fcntl(p->pack_fd, F_SETFD, fd_flag) == -1)
680                 return error("cannot set FD_CLOEXEC");
681
682         /* Verify we recognize this pack file format. */
683         if (read_in_full(p->pack_fd, &hdr, sizeof(hdr)) != sizeof(hdr))
684                 return error("file %s is far too short to be a packfile", p->pack_name);
685         if (hdr.hdr_signature != htonl(PACK_SIGNATURE))
686                 return error("file %s is not a GIT packfile", p->pack_name);
687         if (!pack_version_ok(hdr.hdr_version))
688                 return error("packfile %s is version %"PRIu32" and not"
689                         " supported (try upgrading GIT to a newer version)",
690                         p->pack_name, ntohl(hdr.hdr_version));
691
692         /* Verify the pack matches its index. */
693         if (p->num_objects != ntohl(hdr.hdr_entries))
694                 return error("packfile %s claims to have %"PRIu32" objects"
695                              " while index indicates %"PRIu32" objects",
696                              p->pack_name, ntohl(hdr.hdr_entries),
697                              p->num_objects);
698         if (lseek(p->pack_fd, p->pack_size - sizeof(sha1), SEEK_SET) == -1)
699                 return error("end of packfile %s is unavailable", p->pack_name);
700         if (read_in_full(p->pack_fd, sha1, sizeof(sha1)) != sizeof(sha1))
701                 return error("packfile %s signature is unavailable", p->pack_name);
702         idx_sha1 = ((unsigned char *)p->index_data) + p->index_size - 40;
703         if (hashcmp(sha1, idx_sha1))
704                 return error("packfile %s does not match index", p->pack_name);
705         return 0;
706 }
707
708 static int open_packed_git(struct packed_git *p)
709 {
710         if (!open_packed_git_1(p))
711                 return 0;
712         if (p->pack_fd != -1) {
713                 close(p->pack_fd);
714                 p->pack_fd = -1;
715         }
716         return -1;
717 }
718
719 static int in_window(struct pack_window *win, off_t offset)
720 {
721         /* We must promise at least 20 bytes (one hash) after the
722          * offset is available from this window, otherwise the offset
723          * is not actually in this window and a different window (which
724          * has that one hash excess) must be used.  This is to support
725          * the object header and delta base parsing routines below.
726          */
727         off_t win_off = win->offset;
728         return win_off <= offset
729                 && (offset + 20) <= (win_off + win->len);
730 }
731
732 unsigned char *use_pack(struct packed_git *p,
733                 struct pack_window **w_cursor,
734                 off_t offset,
735                 unsigned int *left)
736 {
737         struct pack_window *win = *w_cursor;
738
739         if (p->pack_fd == -1 && open_packed_git(p))
740                 die("packfile %s cannot be accessed", p->pack_name);
741
742         /* Since packfiles end in a hash of their content and it's
743          * pointless to ask for an offset into the middle of that
744          * hash, and the in_window function above wouldn't match
745          * don't allow an offset too close to the end of the file.
746          */
747         if (offset > (p->pack_size - 20))
748                 die("offset beyond end of packfile (truncated pack?)");
749
750         if (!win || !in_window(win, offset)) {
751                 if (win)
752                         win->inuse_cnt--;
753                 for (win = p->windows; win; win = win->next) {
754                         if (in_window(win, offset))
755                                 break;
756                 }
757                 if (!win) {
758                         size_t window_align = packed_git_window_size / 2;
759                         off_t len;
760                         win = xcalloc(1, sizeof(*win));
761                         win->offset = (offset / window_align) * window_align;
762                         len = p->pack_size - win->offset;
763                         if (len > packed_git_window_size)
764                                 len = packed_git_window_size;
765                         win->len = (size_t)len;
766                         pack_mapped += win->len;
767                         while (packed_git_limit < pack_mapped
768                                 && unuse_one_window(p, p->pack_fd))
769                                 ; /* nothing */
770                         win->base = xmmap(NULL, win->len,
771                                 PROT_READ, MAP_PRIVATE,
772                                 p->pack_fd, win->offset);
773                         if (win->base == MAP_FAILED)
774                                 die("packfile %s cannot be mapped: %s",
775                                         p->pack_name,
776                                         strerror(errno));
777                         pack_mmap_calls++;
778                         pack_open_windows++;
779                         if (pack_mapped > peak_pack_mapped)
780                                 peak_pack_mapped = pack_mapped;
781                         if (pack_open_windows > peak_pack_open_windows)
782                                 peak_pack_open_windows = pack_open_windows;
783                         win->next = p->windows;
784                         p->windows = win;
785                 }
786         }
787         if (win != *w_cursor) {
788                 win->last_used = pack_used_ctr++;
789                 win->inuse_cnt++;
790                 *w_cursor = win;
791         }
792         offset -= win->offset;
793         if (left)
794                 *left = win->len - xsize_t(offset);
795         return win->base + offset;
796 }
797
798 static struct packed_git *alloc_packed_git(int extra)
799 {
800         struct packed_git *p = xmalloc(sizeof(*p) + extra);
801         memset(p, 0, sizeof(*p));
802         p->pack_fd = -1;
803         return p;
804 }
805
806 struct packed_git *add_packed_git(const char *path, int path_len, int local)
807 {
808         struct stat st;
809         struct packed_git *p = alloc_packed_git(path_len + 2);
810
811         /*
812          * Make sure a corresponding .pack file exists and that
813          * the index looks sane.
814          */
815         path_len -= strlen(".idx");
816         if (path_len < 1) {
817                 free(p);
818                 return NULL;
819         }
820         memcpy(p->pack_name, path, path_len);
821
822         strcpy(p->pack_name + path_len, ".keep");
823         if (!access(p->pack_name, F_OK))
824                 p->pack_keep = 1;
825
826         strcpy(p->pack_name + path_len, ".pack");
827         if (stat(p->pack_name, &st) || !S_ISREG(st.st_mode)) {
828                 free(p);
829                 return NULL;
830         }
831
832         /* ok, it looks sane as far as we can check without
833          * actually mapping the pack file.
834          */
835         p->pack_size = st.st_size;
836         p->pack_local = local;
837         p->mtime = st.st_mtime;
838         if (path_len < 40 || get_sha1_hex(path + path_len - 40, p->sha1))
839                 hashclr(p->sha1);
840         return p;
841 }
842
843 struct packed_git *parse_pack_index(unsigned char *sha1, const char *idx_path)
844 {
845         const char *path = sha1_pack_name(sha1);
846         struct packed_git *p = alloc_packed_git(strlen(path) + 1);
847
848         strcpy(p->pack_name, path);
849         hashcpy(p->sha1, sha1);
850         if (check_packed_git_idx(idx_path, p)) {
851                 free(p);
852                 return NULL;
853         }
854
855         return p;
856 }
857
858 void install_packed_git(struct packed_git *pack)
859 {
860         pack->next = packed_git;
861         packed_git = pack;
862 }
863
864 static void prepare_packed_git_one(char *objdir, int local)
865 {
866         /* Ensure that this buffer is large enough so that we can
867            append "/pack/" without clobbering the stack even if
868            strlen(objdir) were PATH_MAX.  */
869         char path[PATH_MAX + 1 + 4 + 1 + 1];
870         int len;
871         DIR *dir;
872         struct dirent *de;
873
874         sprintf(path, "%s/pack", objdir);
875         len = strlen(path);
876         dir = opendir(path);
877         while (!dir && errno == EMFILE && unuse_one_window(packed_git, -1))
878                 dir = opendir(path);
879         if (!dir) {
880                 if (errno != ENOENT)
881                         error("unable to open object pack directory: %s: %s",
882                               path, strerror(errno));
883                 return;
884         }
885         path[len++] = '/';
886         while ((de = readdir(dir)) != NULL) {
887                 int namelen = strlen(de->d_name);
888                 struct packed_git *p;
889
890                 if (!has_extension(de->d_name, ".idx"))
891                         continue;
892
893                 if (len + namelen + 1 > sizeof(path))
894                         continue;
895
896                 /* Don't reopen a pack we already have. */
897                 strcpy(path + len, de->d_name);
898                 for (p = packed_git; p; p = p->next) {
899                         if (!memcmp(path, p->pack_name, len + namelen - 4))
900                                 break;
901                 }
902                 if (p)
903                         continue;
904                 /* See if it really is a valid .idx file with corresponding
905                  * .pack file that we can map.
906                  */
907                 p = add_packed_git(path, len + namelen, local);
908                 if (!p)
909                         continue;
910                 install_packed_git(p);
911         }
912         closedir(dir);
913 }
914
915 static int sort_pack(const void *a_, const void *b_)
916 {
917         struct packed_git *a = *((struct packed_git **)a_);
918         struct packed_git *b = *((struct packed_git **)b_);
919         int st;
920
921         /*
922          * Local packs tend to contain objects specific to our
923          * variant of the project than remote ones.  In addition,
924          * remote ones could be on a network mounted filesystem.
925          * Favor local ones for these reasons.
926          */
927         st = a->pack_local - b->pack_local;
928         if (st)
929                 return -st;
930
931         /*
932          * Younger packs tend to contain more recent objects,
933          * and more recent objects tend to get accessed more
934          * often.
935          */
936         if (a->mtime < b->mtime)
937                 return 1;
938         else if (a->mtime == b->mtime)
939                 return 0;
940         return -1;
941 }
942
943 static void rearrange_packed_git(void)
944 {
945         struct packed_git **ary, *p;
946         int i, n;
947
948         for (n = 0, p = packed_git; p; p = p->next)
949                 n++;
950         if (n < 2)
951                 return;
952
953         /* prepare an array of packed_git for easier sorting */
954         ary = xcalloc(n, sizeof(struct packed_git *));
955         for (n = 0, p = packed_git; p; p = p->next)
956                 ary[n++] = p;
957
958         qsort(ary, n, sizeof(struct packed_git *), sort_pack);
959
960         /* link them back again */
961         for (i = 0; i < n - 1; i++)
962                 ary[i]->next = ary[i + 1];
963         ary[n - 1]->next = NULL;
964         packed_git = ary[0];
965
966         free(ary);
967 }
968
969 static int prepare_packed_git_run_once = 0;
970 void prepare_packed_git(void)
971 {
972         struct alternate_object_database *alt;
973
974         if (prepare_packed_git_run_once)
975                 return;
976         prepare_packed_git_one(get_object_directory(), 1);
977         prepare_alt_odb();
978         for (alt = alt_odb_list; alt; alt = alt->next) {
979                 alt->name[-1] = 0;
980                 prepare_packed_git_one(alt->base, 0);
981                 alt->name[-1] = '/';
982         }
983         rearrange_packed_git();
984         prepare_packed_git_run_once = 1;
985 }
986
987 void reprepare_packed_git(void)
988 {
989         discard_revindex();
990         prepare_packed_git_run_once = 0;
991         prepare_packed_git();
992 }
993
994 static void mark_bad_packed_object(struct packed_git *p,
995                                    const unsigned char *sha1)
996 {
997         unsigned i;
998         for (i = 0; i < p->num_bad_objects; i++)
999                 if (!hashcmp(sha1, p->bad_object_sha1 + 20 * i))
1000                         return;
1001         p->bad_object_sha1 = xrealloc(p->bad_object_sha1, 20 * (p->num_bad_objects + 1));
1002         hashcpy(p->bad_object_sha1 + 20 * p->num_bad_objects, sha1);
1003         p->num_bad_objects++;
1004 }
1005
1006 static int has_packed_and_bad(const unsigned char *sha1)
1007 {
1008         struct packed_git *p;
1009         unsigned i;
1010
1011         for (p = packed_git; p; p = p->next)
1012                 for (i = 0; i < p->num_bad_objects; i++)
1013                         if (!hashcmp(sha1, p->bad_object_sha1 + 20 * i))
1014                                 return 1;
1015         return 0;
1016 }
1017
1018 int check_sha1_signature(const unsigned char *sha1, void *map, unsigned long size, const char *type)
1019 {
1020         unsigned char real_sha1[20];
1021         hash_sha1_file(map, size, type, real_sha1);
1022         return hashcmp(sha1, real_sha1) ? -1 : 0;
1023 }
1024
1025 static int git_open_noatime(const char *name)
1026 {
1027         static int sha1_file_open_flag = O_NOATIME;
1028         int fd = open(name, O_RDONLY | sha1_file_open_flag);
1029
1030         /* Might the failure be due to O_NOATIME? */
1031         if (fd < 0 && errno != ENOENT && sha1_file_open_flag) {
1032                 fd = open(name, O_RDONLY);
1033                 if (fd >= 0)
1034                         sha1_file_open_flag = 0;
1035         }
1036         return fd;
1037 }
1038
1039 static int open_sha1_file(const unsigned char *sha1)
1040 {
1041         int fd;
1042         char *name = sha1_file_name(sha1);
1043         struct alternate_object_database *alt;
1044
1045         fd = git_open_noatime(name);
1046         if (fd >= 0)
1047                 return fd;
1048
1049         prepare_alt_odb();
1050         errno = ENOENT;
1051         for (alt = alt_odb_list; alt; alt = alt->next) {
1052                 name = alt->name;
1053                 fill_sha1_path(name, sha1);
1054                 fd = git_open_noatime(alt->base);
1055                 if (fd >= 0)
1056                         return fd;
1057         }
1058         return -1;
1059 }
1060
1061 static void *map_sha1_file(const unsigned char *sha1, unsigned long *size)
1062 {
1063         void *map;
1064         int fd;
1065
1066         fd = open_sha1_file(sha1);
1067         map = NULL;
1068         if (fd >= 0) {
1069                 struct stat st;
1070
1071                 if (!fstat(fd, &st)) {
1072                         *size = xsize_t(st.st_size);
1073                         map = xmmap(NULL, *size, PROT_READ, MAP_PRIVATE, fd, 0);
1074                 }
1075                 close(fd);
1076         }
1077         return map;
1078 }
1079
1080 static int legacy_loose_object(unsigned char *map)
1081 {
1082         unsigned int word;
1083
1084         /*
1085          * Is it a zlib-compressed buffer? If so, the first byte
1086          * must be 0x78 (15-bit window size, deflated), and the
1087          * first 16-bit word is evenly divisible by 31
1088          */
1089         word = (map[0] << 8) + map[1];
1090         if (map[0] == 0x78 && !(word % 31))
1091                 return 1;
1092         else
1093                 return 0;
1094 }
1095
1096 unsigned long unpack_object_header_buffer(const unsigned char *buf,
1097                 unsigned long len, enum object_type *type, unsigned long *sizep)
1098 {
1099         unsigned shift;
1100         unsigned long size, c;
1101         unsigned long used = 0;
1102
1103         c = buf[used++];
1104         *type = (c >> 4) & 7;
1105         size = c & 15;
1106         shift = 4;
1107         while (c & 0x80) {
1108                 if (len <= used || bitsizeof(long) <= shift) {
1109                         error("bad object header");
1110                         return 0;
1111                 }
1112                 c = buf[used++];
1113                 size += (c & 0x7f) << shift;
1114                 shift += 7;
1115         }
1116         *sizep = size;
1117         return used;
1118 }
1119
1120 static int unpack_sha1_header(z_stream *stream, unsigned char *map, unsigned long mapsize, void *buffer, unsigned long bufsiz)
1121 {
1122         unsigned long size, used;
1123         static const char valid_loose_object_type[8] = {
1124                 0, /* OBJ_EXT */
1125                 1, 1, 1, 1, /* "commit", "tree", "blob", "tag" */
1126                 0, /* "delta" and others are invalid in a loose object */
1127         };
1128         enum object_type type;
1129
1130         /* Get the data stream */
1131         memset(stream, 0, sizeof(*stream));
1132         stream->next_in = map;
1133         stream->avail_in = mapsize;
1134         stream->next_out = buffer;
1135         stream->avail_out = bufsiz;
1136
1137         if (legacy_loose_object(map)) {
1138                 git_inflate_init(stream);
1139                 return git_inflate(stream, 0);
1140         }
1141
1142
1143         /*
1144          * There used to be a second loose object header format which
1145          * was meant to mimic the in-pack format, allowing for direct
1146          * copy of the object data.  This format turned up not to be
1147          * really worth it and we don't write it any longer.  But we
1148          * can still read it.
1149          */
1150         used = unpack_object_header_buffer(map, mapsize, &type, &size);
1151         if (!used || !valid_loose_object_type[type])
1152                 return -1;
1153         map += used;
1154         mapsize -= used;
1155
1156         /* Set up the stream for the rest.. */
1157         stream->next_in = map;
1158         stream->avail_in = mapsize;
1159         git_inflate_init(stream);
1160
1161         /* And generate the fake traditional header */
1162         stream->total_out = 1 + snprintf(buffer, bufsiz, "%s %lu",
1163                                          typename(type), size);
1164         return 0;
1165 }
1166
1167 static void *unpack_sha1_rest(z_stream *stream, void *buffer, unsigned long size, const unsigned char *sha1)
1168 {
1169         int bytes = strlen(buffer) + 1;
1170         unsigned char *buf = xmallocz(size);
1171         unsigned long n;
1172         int status = Z_OK;
1173
1174         n = stream->total_out - bytes;
1175         if (n > size)
1176                 n = size;
1177         memcpy(buf, (char *) buffer + bytes, n);
1178         bytes = n;
1179         if (bytes <= size) {
1180                 /*
1181                  * The above condition must be (bytes <= size), not
1182                  * (bytes < size).  In other words, even though we
1183                  * expect no more output and set avail_out to zer0,
1184                  * the input zlib stream may have bytes that express
1185                  * "this concludes the stream", and we *do* want to
1186                  * eat that input.
1187                  *
1188                  * Otherwise we would not be able to test that we
1189                  * consumed all the input to reach the expected size;
1190                  * we also want to check that zlib tells us that all
1191                  * went well with status == Z_STREAM_END at the end.
1192                  */
1193                 stream->next_out = buf + bytes;
1194                 stream->avail_out = size - bytes;
1195                 while (status == Z_OK)
1196                         status = git_inflate(stream, Z_FINISH);
1197         }
1198         if (status == Z_STREAM_END && !stream->avail_in) {
1199                 git_inflate_end(stream);
1200                 return buf;
1201         }
1202
1203         if (status < 0)
1204                 error("corrupt loose object '%s'", sha1_to_hex(sha1));
1205         else if (stream->avail_in)
1206                 error("garbage at end of loose object '%s'",
1207                       sha1_to_hex(sha1));
1208         free(buf);
1209         return NULL;
1210 }
1211
1212 /*
1213  * We used to just use "sscanf()", but that's actually way
1214  * too permissive for what we want to check. So do an anal
1215  * object header parse by hand.
1216  */
1217 static int parse_sha1_header(const char *hdr, unsigned long *sizep)
1218 {
1219         char type[10];
1220         int i;
1221         unsigned long size;
1222
1223         /*
1224          * The type can be at most ten bytes (including the
1225          * terminating '\0' that we add), and is followed by
1226          * a space.
1227          */
1228         i = 0;
1229         for (;;) {
1230                 char c = *hdr++;
1231                 if (c == ' ')
1232                         break;
1233                 type[i++] = c;
1234                 if (i >= sizeof(type))
1235                         return -1;
1236         }
1237         type[i] = 0;
1238
1239         /*
1240          * The length must follow immediately, and be in canonical
1241          * decimal format (ie "010" is not valid).
1242          */
1243         size = *hdr++ - '0';
1244         if (size > 9)
1245                 return -1;
1246         if (size) {
1247                 for (;;) {
1248                         unsigned long c = *hdr - '0';
1249                         if (c > 9)
1250                                 break;
1251                         hdr++;
1252                         size = size * 10 + c;
1253                 }
1254         }
1255         *sizep = size;
1256
1257         /*
1258          * The length must be followed by a zero byte
1259          */
1260         return *hdr ? -1 : type_from_string(type);
1261 }
1262
1263 static void *unpack_sha1_file(void *map, unsigned long mapsize, enum object_type *type, unsigned long *size, const unsigned char *sha1)
1264 {
1265         int ret;
1266         z_stream stream;
1267         char hdr[8192];
1268
1269         ret = unpack_sha1_header(&stream, map, mapsize, hdr, sizeof(hdr));
1270         if (ret < Z_OK || (*type = parse_sha1_header(hdr, size)) < 0)
1271                 return NULL;
1272
1273         return unpack_sha1_rest(&stream, hdr, *size, sha1);
1274 }
1275
1276 unsigned long get_size_from_delta(struct packed_git *p,
1277                                   struct pack_window **w_curs,
1278                                   off_t curpos)
1279 {
1280         const unsigned char *data;
1281         unsigned char delta_head[20], *in;
1282         z_stream stream;
1283         int st;
1284
1285         memset(&stream, 0, sizeof(stream));
1286         stream.next_out = delta_head;
1287         stream.avail_out = sizeof(delta_head);
1288
1289         git_inflate_init(&stream);
1290         do {
1291                 in = use_pack(p, w_curs, curpos, &stream.avail_in);
1292                 stream.next_in = in;
1293                 st = git_inflate(&stream, Z_FINISH);
1294                 curpos += stream.next_in - in;
1295         } while ((st == Z_OK || st == Z_BUF_ERROR) &&
1296                  stream.total_out < sizeof(delta_head));
1297         git_inflate_end(&stream);
1298         if ((st != Z_STREAM_END) && stream.total_out != sizeof(delta_head)) {
1299                 error("delta data unpack-initial failed");
1300                 return 0;
1301         }
1302
1303         /* Examine the initial part of the delta to figure out
1304          * the result size.
1305          */
1306         data = delta_head;
1307
1308         /* ignore base size */
1309         get_delta_hdr_size(&data, delta_head+sizeof(delta_head));
1310
1311         /* Read the result size */
1312         return get_delta_hdr_size(&data, delta_head+sizeof(delta_head));
1313 }
1314
1315 static off_t get_delta_base(struct packed_git *p,
1316                                     struct pack_window **w_curs,
1317                                     off_t *curpos,
1318                                     enum object_type type,
1319                                     off_t delta_obj_offset)
1320 {
1321         unsigned char *base_info = use_pack(p, w_curs, *curpos, NULL);
1322         off_t base_offset;
1323
1324         /* use_pack() assured us we have [base_info, base_info + 20)
1325          * as a range that we can look at without walking off the
1326          * end of the mapped window.  Its actually the hash size
1327          * that is assured.  An OFS_DELTA longer than the hash size
1328          * is stupid, as then a REF_DELTA would be smaller to store.
1329          */
1330         if (type == OBJ_OFS_DELTA) {
1331                 unsigned used = 0;
1332                 unsigned char c = base_info[used++];
1333                 base_offset = c & 127;
1334                 while (c & 128) {
1335                         base_offset += 1;
1336                         if (!base_offset || MSB(base_offset, 7))
1337                                 return 0;  /* overflow */
1338                         c = base_info[used++];
1339                         base_offset = (base_offset << 7) + (c & 127);
1340                 }
1341                 base_offset = delta_obj_offset - base_offset;
1342                 if (base_offset <= 0 || base_offset >= delta_obj_offset)
1343                         return 0;  /* out of bound */
1344                 *curpos += used;
1345         } else if (type == OBJ_REF_DELTA) {
1346                 /* The base entry _must_ be in the same pack */
1347                 base_offset = find_pack_entry_one(base_info, p);
1348                 *curpos += 20;
1349         } else
1350                 die("I am totally screwed");
1351         return base_offset;
1352 }
1353
1354 /* forward declaration for a mutually recursive function */
1355 static int packed_object_info(struct packed_git *p, off_t offset,
1356                               unsigned long *sizep);
1357
1358 static int packed_delta_info(struct packed_git *p,
1359                              struct pack_window **w_curs,
1360                              off_t curpos,
1361                              enum object_type type,
1362                              off_t obj_offset,
1363                              unsigned long *sizep)
1364 {
1365         off_t base_offset;
1366
1367         base_offset = get_delta_base(p, w_curs, &curpos, type, obj_offset);
1368         if (!base_offset)
1369                 return OBJ_BAD;
1370         type = packed_object_info(p, base_offset, NULL);
1371         if (type <= OBJ_NONE) {
1372                 struct revindex_entry *revidx;
1373                 const unsigned char *base_sha1;
1374                 revidx = find_pack_revindex(p, base_offset);
1375                 if (!revidx)
1376                         return OBJ_BAD;
1377                 base_sha1 = nth_packed_object_sha1(p, revidx->nr);
1378                 mark_bad_packed_object(p, base_sha1);
1379                 type = sha1_object_info(base_sha1, NULL);
1380                 if (type <= OBJ_NONE)
1381                         return OBJ_BAD;
1382         }
1383
1384         /* We choose to only get the type of the base object and
1385          * ignore potentially corrupt pack file that expects the delta
1386          * based on a base with a wrong size.  This saves tons of
1387          * inflate() calls.
1388          */
1389         if (sizep) {
1390                 *sizep = get_size_from_delta(p, w_curs, curpos);
1391                 if (*sizep == 0)
1392                         type = OBJ_BAD;
1393         }
1394
1395         return type;
1396 }
1397
1398 static int unpack_object_header(struct packed_git *p,
1399                                 struct pack_window **w_curs,
1400                                 off_t *curpos,
1401                                 unsigned long *sizep)
1402 {
1403         unsigned char *base;
1404         unsigned int left;
1405         unsigned long used;
1406         enum object_type type;
1407
1408         /* use_pack() assures us we have [base, base + 20) available
1409          * as a range that we can look at at.  (Its actually the hash
1410          * size that is assured.)  With our object header encoding
1411          * the maximum deflated object size is 2^137, which is just
1412          * insane, so we know won't exceed what we have been given.
1413          */
1414         base = use_pack(p, w_curs, *curpos, &left);
1415         used = unpack_object_header_buffer(base, left, &type, sizep);
1416         if (!used) {
1417                 type = OBJ_BAD;
1418         } else
1419                 *curpos += used;
1420
1421         return type;
1422 }
1423
1424 const char *packed_object_info_detail(struct packed_git *p,
1425                                       off_t obj_offset,
1426                                       unsigned long *size,
1427                                       unsigned long *store_size,
1428                                       unsigned int *delta_chain_length,
1429                                       unsigned char *base_sha1)
1430 {
1431         struct pack_window *w_curs = NULL;
1432         off_t curpos;
1433         unsigned long dummy;
1434         unsigned char *next_sha1;
1435         enum object_type type;
1436         struct revindex_entry *revidx;
1437
1438         *delta_chain_length = 0;
1439         curpos = obj_offset;
1440         type = unpack_object_header(p, &w_curs, &curpos, size);
1441
1442         revidx = find_pack_revindex(p, obj_offset);
1443         *store_size = revidx[1].offset - obj_offset;
1444
1445         for (;;) {
1446                 switch (type) {
1447                 default:
1448                         die("pack %s contains unknown object type %d",
1449                             p->pack_name, type);
1450                 case OBJ_COMMIT:
1451                 case OBJ_TREE:
1452                 case OBJ_BLOB:
1453                 case OBJ_TAG:
1454                         unuse_pack(&w_curs);
1455                         return typename(type);
1456                 case OBJ_OFS_DELTA:
1457                         obj_offset = get_delta_base(p, &w_curs, &curpos, type, obj_offset);
1458                         if (!obj_offset)
1459                                 die("pack %s contains bad delta base reference of type %s",
1460                                     p->pack_name, typename(type));
1461                         if (*delta_chain_length == 0) {
1462                                 revidx = find_pack_revindex(p, obj_offset);
1463                                 hashcpy(base_sha1, nth_packed_object_sha1(p, revidx->nr));
1464                         }
1465                         break;
1466                 case OBJ_REF_DELTA:
1467                         next_sha1 = use_pack(p, &w_curs, curpos, NULL);
1468                         if (*delta_chain_length == 0)
1469                                 hashcpy(base_sha1, next_sha1);
1470                         obj_offset = find_pack_entry_one(next_sha1, p);
1471                         break;
1472                 }
1473                 (*delta_chain_length)++;
1474                 curpos = obj_offset;
1475                 type = unpack_object_header(p, &w_curs, &curpos, &dummy);
1476         }
1477 }
1478
1479 static int packed_object_info(struct packed_git *p, off_t obj_offset,
1480                               unsigned long *sizep)
1481 {
1482         struct pack_window *w_curs = NULL;
1483         unsigned long size;
1484         off_t curpos = obj_offset;
1485         enum object_type type;
1486
1487         type = unpack_object_header(p, &w_curs, &curpos, &size);
1488
1489         switch (type) {
1490         case OBJ_OFS_DELTA:
1491         case OBJ_REF_DELTA:
1492                 type = packed_delta_info(p, &w_curs, curpos,
1493                                          type, obj_offset, sizep);
1494                 break;
1495         case OBJ_COMMIT:
1496         case OBJ_TREE:
1497         case OBJ_BLOB:
1498         case OBJ_TAG:
1499                 if (sizep)
1500                         *sizep = size;
1501                 break;
1502         default:
1503                 error("unknown object type %i at offset %"PRIuMAX" in %s",
1504                       type, (uintmax_t)obj_offset, p->pack_name);
1505                 type = OBJ_BAD;
1506         }
1507         unuse_pack(&w_curs);
1508         return type;
1509 }
1510
1511 static void *unpack_compressed_entry(struct packed_git *p,
1512                                     struct pack_window **w_curs,
1513                                     off_t curpos,
1514                                     unsigned long size)
1515 {
1516         int st;
1517         z_stream stream;
1518         unsigned char *buffer, *in;
1519
1520         buffer = xmallocz(size);
1521         memset(&stream, 0, sizeof(stream));
1522         stream.next_out = buffer;
1523         stream.avail_out = size + 1;
1524
1525         git_inflate_init(&stream);
1526         do {
1527                 in = use_pack(p, w_curs, curpos, &stream.avail_in);
1528                 stream.next_in = in;
1529                 st = git_inflate(&stream, Z_FINISH);
1530                 if (!stream.avail_out)
1531                         break; /* the payload is larger than it should be */
1532                 curpos += stream.next_in - in;
1533         } while (st == Z_OK || st == Z_BUF_ERROR);
1534         git_inflate_end(&stream);
1535         if ((st != Z_STREAM_END) || stream.total_out != size) {
1536                 free(buffer);
1537                 return NULL;
1538         }
1539
1540         return buffer;
1541 }
1542
1543 #define MAX_DELTA_CACHE (256)
1544
1545 static size_t delta_base_cached;
1546
1547 static struct delta_base_cache_lru_list {
1548         struct delta_base_cache_lru_list *prev;
1549         struct delta_base_cache_lru_list *next;
1550 } delta_base_cache_lru = { &delta_base_cache_lru, &delta_base_cache_lru };
1551
1552 static struct delta_base_cache_entry {
1553         struct delta_base_cache_lru_list lru;
1554         void *data;
1555         struct packed_git *p;
1556         off_t base_offset;
1557         unsigned long size;
1558         enum object_type type;
1559 } delta_base_cache[MAX_DELTA_CACHE];
1560
1561 static unsigned long pack_entry_hash(struct packed_git *p, off_t base_offset)
1562 {
1563         unsigned long hash;
1564
1565         hash = (unsigned long)p + (unsigned long)base_offset;
1566         hash += (hash >> 8) + (hash >> 16);
1567         return hash % MAX_DELTA_CACHE;
1568 }
1569
1570 static void *cache_or_unpack_entry(struct packed_git *p, off_t base_offset,
1571         unsigned long *base_size, enum object_type *type, int keep_cache)
1572 {
1573         void *ret;
1574         unsigned long hash = pack_entry_hash(p, base_offset);
1575         struct delta_base_cache_entry *ent = delta_base_cache + hash;
1576
1577         ret = ent->data;
1578         if (!ret || ent->p != p || ent->base_offset != base_offset)
1579                 return unpack_entry(p, base_offset, type, base_size);
1580
1581         if (!keep_cache) {
1582                 ent->data = NULL;
1583                 ent->lru.next->prev = ent->lru.prev;
1584                 ent->lru.prev->next = ent->lru.next;
1585                 delta_base_cached -= ent->size;
1586         } else {
1587                 ret = xmemdupz(ent->data, ent->size);
1588         }
1589         *type = ent->type;
1590         *base_size = ent->size;
1591         return ret;
1592 }
1593
1594 static inline void release_delta_base_cache(struct delta_base_cache_entry *ent)
1595 {
1596         if (ent->data) {
1597                 free(ent->data);
1598                 ent->data = NULL;
1599                 ent->lru.next->prev = ent->lru.prev;
1600                 ent->lru.prev->next = ent->lru.next;
1601                 delta_base_cached -= ent->size;
1602         }
1603 }
1604
1605 void clear_delta_base_cache(void)
1606 {
1607         unsigned long p;
1608         for (p = 0; p < MAX_DELTA_CACHE; p++)
1609                 release_delta_base_cache(&delta_base_cache[p]);
1610 }
1611
1612 static void add_delta_base_cache(struct packed_git *p, off_t base_offset,
1613         void *base, unsigned long base_size, enum object_type type)
1614 {
1615         unsigned long hash = pack_entry_hash(p, base_offset);
1616         struct delta_base_cache_entry *ent = delta_base_cache + hash;
1617         struct delta_base_cache_lru_list *lru;
1618
1619         release_delta_base_cache(ent);
1620         delta_base_cached += base_size;
1621
1622         for (lru = delta_base_cache_lru.next;
1623              delta_base_cached > delta_base_cache_limit
1624              && lru != &delta_base_cache_lru;
1625              lru = lru->next) {
1626                 struct delta_base_cache_entry *f = (void *)lru;
1627                 if (f->type == OBJ_BLOB)
1628                         release_delta_base_cache(f);
1629         }
1630         for (lru = delta_base_cache_lru.next;
1631              delta_base_cached > delta_base_cache_limit
1632              && lru != &delta_base_cache_lru;
1633              lru = lru->next) {
1634                 struct delta_base_cache_entry *f = (void *)lru;
1635                 release_delta_base_cache(f);
1636         }
1637
1638         ent->p = p;
1639         ent->base_offset = base_offset;
1640         ent->type = type;
1641         ent->data = base;
1642         ent->size = base_size;
1643         ent->lru.next = &delta_base_cache_lru;
1644         ent->lru.prev = delta_base_cache_lru.prev;
1645         delta_base_cache_lru.prev->next = &ent->lru;
1646         delta_base_cache_lru.prev = &ent->lru;
1647 }
1648
1649 static void *read_object(const unsigned char *sha1, enum object_type *type,
1650                          unsigned long *size);
1651
1652 static void *unpack_delta_entry(struct packed_git *p,
1653                                 struct pack_window **w_curs,
1654                                 off_t curpos,
1655                                 unsigned long delta_size,
1656                                 off_t obj_offset,
1657                                 enum object_type *type,
1658                                 unsigned long *sizep)
1659 {
1660         void *delta_data, *result, *base;
1661         unsigned long base_size;
1662         off_t base_offset;
1663
1664         base_offset = get_delta_base(p, w_curs, &curpos, *type, obj_offset);
1665         if (!base_offset) {
1666                 error("failed to validate delta base reference "
1667                       "at offset %"PRIuMAX" from %s",
1668                       (uintmax_t)curpos, p->pack_name);
1669                 return NULL;
1670         }
1671         unuse_pack(w_curs);
1672         base = cache_or_unpack_entry(p, base_offset, &base_size, type, 0);
1673         if (!base) {
1674                 /*
1675                  * We're probably in deep shit, but let's try to fetch
1676                  * the required base anyway from another pack or loose.
1677                  * This is costly but should happen only in the presence
1678                  * of a corrupted pack, and is better than failing outright.
1679                  */
1680                 struct revindex_entry *revidx;
1681                 const unsigned char *base_sha1;
1682                 revidx = find_pack_revindex(p, base_offset);
1683                 if (!revidx)
1684                         return NULL;
1685                 base_sha1 = nth_packed_object_sha1(p, revidx->nr);
1686                 error("failed to read delta base object %s"
1687                       " at offset %"PRIuMAX" from %s",
1688                       sha1_to_hex(base_sha1), (uintmax_t)base_offset,
1689                       p->pack_name);
1690                 mark_bad_packed_object(p, base_sha1);
1691                 base = read_object(base_sha1, type, &base_size);
1692                 if (!base)
1693                         return NULL;
1694         }
1695
1696         delta_data = unpack_compressed_entry(p, w_curs, curpos, delta_size);
1697         if (!delta_data) {
1698                 error("failed to unpack compressed delta "
1699                       "at offset %"PRIuMAX" from %s",
1700                       (uintmax_t)curpos, p->pack_name);
1701                 free(base);
1702                 return NULL;
1703         }
1704         result = patch_delta(base, base_size,
1705                              delta_data, delta_size,
1706                              sizep);
1707         if (!result)
1708                 die("failed to apply delta");
1709         free(delta_data);
1710         add_delta_base_cache(p, base_offset, base, base_size, *type);
1711         return result;
1712 }
1713
1714 int do_check_packed_object_crc;
1715
1716 void *unpack_entry(struct packed_git *p, off_t obj_offset,
1717                    enum object_type *type, unsigned long *sizep)
1718 {
1719         struct pack_window *w_curs = NULL;
1720         off_t curpos = obj_offset;
1721         void *data;
1722
1723         if (do_check_packed_object_crc && p->index_version > 1) {
1724                 struct revindex_entry *revidx = find_pack_revindex(p, obj_offset);
1725                 unsigned long len = revidx[1].offset - obj_offset;
1726                 if (check_pack_crc(p, &w_curs, obj_offset, len, revidx->nr)) {
1727                         const unsigned char *sha1 =
1728                                 nth_packed_object_sha1(p, revidx->nr);
1729                         error("bad packed object CRC for %s",
1730                               sha1_to_hex(sha1));
1731                         mark_bad_packed_object(p, sha1);
1732                         unuse_pack(&w_curs);
1733                         return NULL;
1734                 }
1735         }
1736
1737         *type = unpack_object_header(p, &w_curs, &curpos, sizep);
1738         switch (*type) {
1739         case OBJ_OFS_DELTA:
1740         case OBJ_REF_DELTA:
1741                 data = unpack_delta_entry(p, &w_curs, curpos, *sizep,
1742                                           obj_offset, type, sizep);
1743                 break;
1744         case OBJ_COMMIT:
1745         case OBJ_TREE:
1746         case OBJ_BLOB:
1747         case OBJ_TAG:
1748                 data = unpack_compressed_entry(p, &w_curs, curpos, *sizep);
1749                 break;
1750         default:
1751                 data = NULL;
1752                 error("unknown object type %i at offset %"PRIuMAX" in %s",
1753                       *type, (uintmax_t)obj_offset, p->pack_name);
1754         }
1755         unuse_pack(&w_curs);
1756         return data;
1757 }
1758
1759 const unsigned char *nth_packed_object_sha1(struct packed_git *p,
1760                                             uint32_t n)
1761 {
1762         const unsigned char *index = p->index_data;
1763         if (!index) {
1764                 if (open_pack_index(p))
1765                         return NULL;
1766                 index = p->index_data;
1767         }
1768         if (n >= p->num_objects)
1769                 return NULL;
1770         index += 4 * 256;
1771         if (p->index_version == 1) {
1772                 return index + 24 * n + 4;
1773         } else {
1774                 index += 8;
1775                 return index + 20 * n;
1776         }
1777 }
1778
1779 off_t nth_packed_object_offset(const struct packed_git *p, uint32_t n)
1780 {
1781         const unsigned char *index = p->index_data;
1782         index += 4 * 256;
1783         if (p->index_version == 1) {
1784                 return ntohl(*((uint32_t *)(index + 24 * n)));
1785         } else {
1786                 uint32_t off;
1787                 index += 8 + p->num_objects * (20 + 4);
1788                 off = ntohl(*((uint32_t *)(index + 4 * n)));
1789                 if (!(off & 0x80000000))
1790                         return off;
1791                 index += p->num_objects * 4 + (off & 0x7fffffff) * 8;
1792                 return (((uint64_t)ntohl(*((uint32_t *)(index + 0)))) << 32) |
1793                                    ntohl(*((uint32_t *)(index + 4)));
1794         }
1795 }
1796
1797 off_t find_pack_entry_one(const unsigned char *sha1,
1798                                   struct packed_git *p)
1799 {
1800         const uint32_t *level1_ofs = p->index_data;
1801         const unsigned char *index = p->index_data;
1802         unsigned hi, lo, stride;
1803         static int use_lookup = -1;
1804         static int debug_lookup = -1;
1805
1806         if (debug_lookup < 0)
1807                 debug_lookup = !!getenv("GIT_DEBUG_LOOKUP");
1808
1809         if (!index) {
1810                 if (open_pack_index(p))
1811                         return 0;
1812                 level1_ofs = p->index_data;
1813                 index = p->index_data;
1814         }
1815         if (p->index_version > 1) {
1816                 level1_ofs += 2;
1817                 index += 8;
1818         }
1819         index += 4 * 256;
1820         hi = ntohl(level1_ofs[*sha1]);
1821         lo = ((*sha1 == 0x0) ? 0 : ntohl(level1_ofs[*sha1 - 1]));
1822         if (p->index_version > 1) {
1823                 stride = 20;
1824         } else {
1825                 stride = 24;
1826                 index += 4;
1827         }
1828
1829         if (debug_lookup)
1830                 printf("%02x%02x%02x... lo %u hi %u nr %"PRIu32"\n",
1831                        sha1[0], sha1[1], sha1[2], lo, hi, p->num_objects);
1832
1833         if (use_lookup < 0)
1834                 use_lookup = !!getenv("GIT_USE_LOOKUP");
1835         if (use_lookup) {
1836                 int pos = sha1_entry_pos(index, stride, 0,
1837                                          lo, hi, p->num_objects, sha1);
1838                 if (pos < 0)
1839                         return 0;
1840                 return nth_packed_object_offset(p, pos);
1841         }
1842
1843         do {
1844                 unsigned mi = (lo + hi) / 2;
1845                 int cmp = hashcmp(index + mi * stride, sha1);
1846
1847                 if (debug_lookup)
1848                         printf("lo %u hi %u rg %u mi %u\n",
1849                                lo, hi, hi - lo, mi);
1850                 if (!cmp)
1851                         return nth_packed_object_offset(p, mi);
1852                 if (cmp > 0)
1853                         hi = mi;
1854                 else
1855                         lo = mi+1;
1856         } while (lo < hi);
1857         return 0;
1858 }
1859
1860 static int find_pack_entry(const unsigned char *sha1, struct pack_entry *e)
1861 {
1862         static struct packed_git *last_found = (void *)1;
1863         struct packed_git *p;
1864         off_t offset;
1865
1866         prepare_packed_git();
1867         if (!packed_git)
1868                 return 0;
1869         p = (last_found == (void *)1) ? packed_git : last_found;
1870
1871         do {
1872                 if (p->num_bad_objects) {
1873                         unsigned i;
1874                         for (i = 0; i < p->num_bad_objects; i++)
1875                                 if (!hashcmp(sha1, p->bad_object_sha1 + 20 * i))
1876                                         goto next;
1877                 }
1878
1879                 offset = find_pack_entry_one(sha1, p);
1880                 if (offset) {
1881                         /*
1882                          * We are about to tell the caller where they can
1883                          * locate the requested object.  We better make
1884                          * sure the packfile is still here and can be
1885                          * accessed before supplying that answer, as
1886                          * it may have been deleted since the index
1887                          * was loaded!
1888                          */
1889                         if (p->pack_fd == -1 && open_packed_git(p)) {
1890                                 error("packfile %s cannot be accessed", p->pack_name);
1891                                 goto next;
1892                         }
1893                         e->offset = offset;
1894                         e->p = p;
1895                         hashcpy(e->sha1, sha1);
1896                         last_found = p;
1897                         return 1;
1898                 }
1899
1900                 next:
1901                 if (p == last_found)
1902                         p = packed_git;
1903                 else
1904                         p = p->next;
1905                 if (p == last_found)
1906                         p = p->next;
1907         } while (p);
1908         return 0;
1909 }
1910
1911 struct packed_git *find_sha1_pack(const unsigned char *sha1,
1912                                   struct packed_git *packs)
1913 {
1914         struct packed_git *p;
1915
1916         for (p = packs; p; p = p->next) {
1917                 if (find_pack_entry_one(sha1, p))
1918                         return p;
1919         }
1920         return NULL;
1921
1922 }
1923
1924 static int sha1_loose_object_info(const unsigned char *sha1, unsigned long *sizep)
1925 {
1926         int status;
1927         unsigned long mapsize, size;
1928         void *map;
1929         z_stream stream;
1930         char hdr[32];
1931
1932         map = map_sha1_file(sha1, &mapsize);
1933         if (!map)
1934                 return error("unable to find %s", sha1_to_hex(sha1));
1935         if (unpack_sha1_header(&stream, map, mapsize, hdr, sizeof(hdr)) < 0)
1936                 status = error("unable to unpack %s header",
1937                                sha1_to_hex(sha1));
1938         else if ((status = parse_sha1_header(hdr, &size)) < 0)
1939                 status = error("unable to parse %s header", sha1_to_hex(sha1));
1940         else if (sizep)
1941                 *sizep = size;
1942         git_inflate_end(&stream);
1943         munmap(map, mapsize);
1944         return status;
1945 }
1946
1947 int sha1_object_info(const unsigned char *sha1, unsigned long *sizep)
1948 {
1949         struct pack_entry e;
1950         int status;
1951
1952         if (!find_pack_entry(sha1, &e)) {
1953                 /* Most likely it's a loose object. */
1954                 status = sha1_loose_object_info(sha1, sizep);
1955                 if (status >= 0)
1956                         return status;
1957
1958                 /* Not a loose object; someone else may have just packed it. */
1959                 reprepare_packed_git();
1960                 if (!find_pack_entry(sha1, &e))
1961                         return status;
1962         }
1963
1964         status = packed_object_info(e.p, e.offset, sizep);
1965         if (status < 0) {
1966                 mark_bad_packed_object(e.p, sha1);
1967                 status = sha1_object_info(sha1, sizep);
1968         }
1969
1970         return status;
1971 }
1972
1973 static void *read_packed_sha1(const unsigned char *sha1,
1974                               enum object_type *type, unsigned long *size)
1975 {
1976         struct pack_entry e;
1977         void *data;
1978
1979         if (!find_pack_entry(sha1, &e))
1980                 return NULL;
1981         data = cache_or_unpack_entry(e.p, e.offset, size, type, 1);
1982         if (!data) {
1983                 /*
1984                  * We're probably in deep shit, but let's try to fetch
1985                  * the required object anyway from another pack or loose.
1986                  * This should happen only in the presence of a corrupted
1987                  * pack, and is better than failing outright.
1988                  */
1989                 error("failed to read object %s at offset %"PRIuMAX" from %s",
1990                       sha1_to_hex(sha1), (uintmax_t)e.offset, e.p->pack_name);
1991                 mark_bad_packed_object(e.p, sha1);
1992                 data = read_object(sha1, type, size);
1993         }
1994         return data;
1995 }
1996
1997 /*
1998  * This is meant to hold a *small* number of objects that you would
1999  * want read_sha1_file() to be able to return, but yet you do not want
2000  * to write them into the object store (e.g. a browse-only
2001  * application).
2002  */
2003 static struct cached_object {
2004         unsigned char sha1[20];
2005         enum object_type type;
2006         void *buf;
2007         unsigned long size;
2008 } *cached_objects;
2009 static int cached_object_nr, cached_object_alloc;
2010
2011 static struct cached_object empty_tree = {
2012         EMPTY_TREE_SHA1_BIN,
2013         OBJ_TREE,
2014         "",
2015         0
2016 };
2017
2018 static struct cached_object *find_cached_object(const unsigned char *sha1)
2019 {
2020         int i;
2021         struct cached_object *co = cached_objects;
2022
2023         for (i = 0; i < cached_object_nr; i++, co++) {
2024                 if (!hashcmp(co->sha1, sha1))
2025                         return co;
2026         }
2027         if (!hashcmp(sha1, empty_tree.sha1))
2028                 return &empty_tree;
2029         return NULL;
2030 }
2031
2032 int pretend_sha1_file(void *buf, unsigned long len, enum object_type type,
2033                       unsigned char *sha1)
2034 {
2035         struct cached_object *co;
2036
2037         hash_sha1_file(buf, len, typename(type), sha1);
2038         if (has_sha1_file(sha1) || find_cached_object(sha1))
2039                 return 0;
2040         if (cached_object_alloc <= cached_object_nr) {
2041                 cached_object_alloc = alloc_nr(cached_object_alloc);
2042                 cached_objects = xrealloc(cached_objects,
2043                                           sizeof(*cached_objects) *
2044                                           cached_object_alloc);
2045         }
2046         co = &cached_objects[cached_object_nr++];
2047         co->size = len;
2048         co->type = type;
2049         co->buf = xmalloc(len);
2050         memcpy(co->buf, buf, len);
2051         hashcpy(co->sha1, sha1);
2052         return 0;
2053 }
2054
2055 static void *read_object(const unsigned char *sha1, enum object_type *type,
2056                          unsigned long *size)
2057 {
2058         unsigned long mapsize;
2059         void *map, *buf;
2060         struct cached_object *co;
2061
2062         co = find_cached_object(sha1);
2063         if (co) {
2064                 *type = co->type;
2065                 *size = co->size;
2066                 return xmemdupz(co->buf, co->size);
2067         }
2068
2069         buf = read_packed_sha1(sha1, type, size);
2070         if (buf)
2071                 return buf;
2072         map = map_sha1_file(sha1, &mapsize);
2073         if (map) {
2074                 buf = unpack_sha1_file(map, mapsize, type, size, sha1);
2075                 munmap(map, mapsize);
2076                 return buf;
2077         }
2078         reprepare_packed_git();
2079         return read_packed_sha1(sha1, type, size);
2080 }
2081
2082 void *read_sha1_file_repl(const unsigned char *sha1,
2083                           enum object_type *type,
2084                           unsigned long *size,
2085                           const unsigned char **replacement)
2086 {
2087         const unsigned char *repl = lookup_replace_object(sha1);
2088         void *data = read_object(repl, type, size);
2089         char *path;
2090
2091         /* die if we replaced an object with one that does not exist */
2092         if (!data && repl != sha1)
2093                 die("replacement %s not found for %s",
2094                     sha1_to_hex(repl), sha1_to_hex(sha1));
2095
2096         /* legacy behavior is to die on corrupted objects */
2097         if (!data) {
2098                 if (has_loose_object(repl)) {
2099                         path = sha1_file_name(sha1);
2100                         die("loose object %s (stored in %s) is corrupted", sha1_to_hex(repl), path);
2101                 }
2102                 if (has_packed_and_bad(repl)) {
2103                         path = sha1_pack_name(sha1);
2104                         die("packed object %s (stored in %s) is corrupted", sha1_to_hex(repl), path);
2105                 }
2106         }
2107
2108         if (replacement)
2109                 *replacement = repl;
2110
2111         return data;
2112 }
2113
2114 void *read_object_with_reference(const unsigned char *sha1,
2115                                  const char *required_type_name,
2116                                  unsigned long *size,
2117                                  unsigned char *actual_sha1_return)
2118 {
2119         enum object_type type, required_type;
2120         void *buffer;
2121         unsigned long isize;
2122         unsigned char actual_sha1[20];
2123
2124         required_type = type_from_string(required_type_name);
2125         hashcpy(actual_sha1, sha1);
2126         while (1) {
2127                 int ref_length = -1;
2128                 const char *ref_type = NULL;
2129
2130                 buffer = read_sha1_file(actual_sha1, &type, &isize);
2131                 if (!buffer)
2132                         return NULL;
2133                 if (type == required_type) {
2134                         *size = isize;
2135                         if (actual_sha1_return)
2136                                 hashcpy(actual_sha1_return, actual_sha1);
2137                         return buffer;
2138                 }
2139                 /* Handle references */
2140                 else if (type == OBJ_COMMIT)
2141                         ref_type = "tree ";
2142                 else if (type == OBJ_TAG)
2143                         ref_type = "object ";
2144                 else {
2145                         free(buffer);
2146                         return NULL;
2147                 }
2148                 ref_length = strlen(ref_type);
2149
2150                 if (ref_length + 40 > isize ||
2151                     memcmp(buffer, ref_type, ref_length) ||
2152                     get_sha1_hex((char *) buffer + ref_length, actual_sha1)) {
2153                         free(buffer);
2154                         return NULL;
2155                 }
2156                 free(buffer);
2157                 /* Now we have the ID of the referred-to object in
2158                  * actual_sha1.  Check again. */
2159         }
2160 }
2161
2162 static void write_sha1_file_prepare(const void *buf, unsigned long len,
2163                                     const char *type, unsigned char *sha1,
2164                                     char *hdr, int *hdrlen)
2165 {
2166         git_SHA_CTX c;
2167
2168         /* Generate the header */
2169         *hdrlen = sprintf(hdr, "%s %lu", type, len)+1;
2170
2171         /* Sha1.. */
2172         git_SHA1_Init(&c);
2173         git_SHA1_Update(&c, hdr, *hdrlen);
2174         git_SHA1_Update(&c, buf, len);
2175         git_SHA1_Final(sha1, &c);
2176 }
2177
2178 /*
2179  * Move the just written object into its final resting place.
2180  * NEEDSWORK: this should be renamed to finalize_temp_file() as
2181  * "moving" is only a part of what it does, when no patch between
2182  * master to pu changes the call sites of this function.
2183  */
2184 int move_temp_to_file(const char *tmpfile, const char *filename)
2185 {
2186         int ret = 0;
2187
2188         if (object_creation_mode == OBJECT_CREATION_USES_RENAMES)
2189                 goto try_rename;
2190         else if (link(tmpfile, filename))
2191                 ret = errno;
2192
2193         /*
2194          * Coda hack - coda doesn't like cross-directory links,
2195          * so we fall back to a rename, which will mean that it
2196          * won't be able to check collisions, but that's not a
2197          * big deal.
2198          *
2199          * The same holds for FAT formatted media.
2200          *
2201          * When this succeeds, we just return.  We have nothing
2202          * left to unlink.
2203          */
2204         if (ret && ret != EEXIST) {
2205         try_rename:
2206                 if (!rename(tmpfile, filename))
2207                         goto out;
2208                 ret = errno;
2209         }
2210         unlink_or_warn(tmpfile);
2211         if (ret) {
2212                 if (ret != EEXIST) {
2213                         return error("unable to write sha1 filename %s: %s\n", filename, strerror(ret));
2214                 }
2215                 /* FIXME!!! Collision check here ? */
2216         }
2217
2218 out:
2219         if (adjust_shared_perm(filename))
2220                 return error("unable to set permission to '%s'", filename);
2221         return 0;
2222 }
2223
2224 static int write_buffer(int fd, const void *buf, size_t len)
2225 {
2226         if (write_in_full(fd, buf, len) < 0)
2227                 return error("file write error (%s)", strerror(errno));
2228         return 0;
2229 }
2230
2231 int hash_sha1_file(const void *buf, unsigned long len, const char *type,
2232                    unsigned char *sha1)
2233 {
2234         char hdr[32];
2235         int hdrlen;
2236         write_sha1_file_prepare(buf, len, type, sha1, hdr, &hdrlen);
2237         return 0;
2238 }
2239
2240 /* Finalize a file on disk, and close it. */
2241 static void close_sha1_file(int fd)
2242 {
2243         if (fsync_object_files)
2244                 fsync_or_die(fd, "sha1 file");
2245         if (close(fd) != 0)
2246                 die_errno("error when closing sha1 file");
2247 }
2248
2249 /* Size of directory component, including the ending '/' */
2250 static inline int directory_size(const char *filename)
2251 {
2252         const char *s = strrchr(filename, '/');
2253         if (!s)
2254                 return 0;
2255         return s - filename + 1;
2256 }
2257
2258 /*
2259  * This creates a temporary file in the same directory as the final
2260  * 'filename'
2261  *
2262  * We want to avoid cross-directory filename renames, because those
2263  * can have problems on various filesystems (FAT, NFS, Coda).
2264  */
2265 static int create_tmpfile(char *buffer, size_t bufsiz, const char *filename)
2266 {
2267         int fd, dirlen = directory_size(filename);
2268
2269         if (dirlen + 20 > bufsiz) {
2270                 errno = ENAMETOOLONG;
2271                 return -1;
2272         }
2273         memcpy(buffer, filename, dirlen);
2274         strcpy(buffer + dirlen, "tmp_obj_XXXXXX");
2275         fd = git_mkstemp_mode(buffer, 0444);
2276         if (fd < 0 && dirlen && errno == ENOENT) {
2277                 /* Make sure the directory exists */
2278                 memcpy(buffer, filename, dirlen);
2279                 buffer[dirlen-1] = 0;
2280                 if (mkdir(buffer, 0777) || adjust_shared_perm(buffer))
2281                         return -1;
2282
2283                 /* Try again */
2284                 strcpy(buffer + dirlen - 1, "/tmp_obj_XXXXXX");
2285                 fd = git_mkstemp_mode(buffer, 0444);
2286         }
2287         return fd;
2288 }
2289
2290 static int write_loose_object(const unsigned char *sha1, char *hdr, int hdrlen,
2291                               const void *buf, unsigned long len, time_t mtime)
2292 {
2293         int fd, ret;
2294         unsigned char compressed[4096];
2295         z_stream stream;
2296         git_SHA_CTX c;
2297         unsigned char parano_sha1[20];
2298         char *filename;
2299         static char tmpfile[PATH_MAX];
2300
2301         filename = sha1_file_name(sha1);
2302         fd = create_tmpfile(tmpfile, sizeof(tmpfile), filename);
2303         while (fd < 0 && errno == EMFILE && unuse_one_window(packed_git, -1))
2304                 fd = create_tmpfile(tmpfile, sizeof(tmpfile), filename);
2305         if (fd < 0) {
2306                 if (errno == EACCES)
2307                         return error("insufficient permission for adding an object to repository database %s\n", get_object_directory());
2308                 else
2309                         return error("unable to create temporary sha1 filename %s: %s\n", tmpfile, strerror(errno));
2310         }
2311
2312         /* Set it up */
2313         memset(&stream, 0, sizeof(stream));
2314         deflateInit(&stream, zlib_compression_level);
2315         stream.next_out = compressed;
2316         stream.avail_out = sizeof(compressed);
2317         git_SHA1_Init(&c);
2318
2319         /* First header.. */
2320         stream.next_in = (unsigned char *)hdr;
2321         stream.avail_in = hdrlen;
2322         while (deflate(&stream, 0) == Z_OK)
2323                 /* nothing */;
2324         git_SHA1_Update(&c, hdr, hdrlen);
2325
2326         /* Then the data itself.. */
2327         stream.next_in = (void *)buf;
2328         stream.avail_in = len;
2329         do {
2330                 unsigned char *in0 = stream.next_in;
2331                 ret = deflate(&stream, Z_FINISH);
2332                 git_SHA1_Update(&c, in0, stream.next_in - in0);
2333                 if (write_buffer(fd, compressed, stream.next_out - compressed) < 0)
2334                         die("unable to write sha1 file");
2335                 stream.next_out = compressed;
2336                 stream.avail_out = sizeof(compressed);
2337         } while (ret == Z_OK);
2338
2339         if (ret != Z_STREAM_END)
2340                 die("unable to deflate new object %s (%d)", sha1_to_hex(sha1), ret);
2341         ret = deflateEnd(&stream);
2342         if (ret != Z_OK)
2343                 die("deflateEnd on object %s failed (%d)", sha1_to_hex(sha1), ret);
2344         git_SHA1_Final(parano_sha1, &c);
2345         if (hashcmp(sha1, parano_sha1) != 0)
2346                 die("confused by unstable object source data for %s", sha1_to_hex(sha1));
2347
2348         close_sha1_file(fd);
2349
2350         if (mtime) {
2351                 struct utimbuf utb;
2352                 utb.actime = mtime;
2353                 utb.modtime = mtime;
2354                 if (utime(tmpfile, &utb) < 0)
2355                         warning("failed utime() on %s: %s",
2356                                 tmpfile, strerror(errno));
2357         }
2358
2359         return move_temp_to_file(tmpfile, filename);
2360 }
2361
2362 int write_sha1_file(const void *buf, unsigned long len, const char *type, unsigned char *returnsha1)
2363 {
2364         unsigned char sha1[20];
2365         char hdr[32];
2366         int hdrlen;
2367
2368         /* Normally if we have it in the pack then we do not bother writing
2369          * it out into .git/objects/??/?{38} file.
2370          */
2371         write_sha1_file_prepare(buf, len, type, sha1, hdr, &hdrlen);
2372         if (returnsha1)
2373                 hashcpy(returnsha1, sha1);
2374         if (has_sha1_file(sha1))
2375                 return 0;
2376         return write_loose_object(sha1, hdr, hdrlen, buf, len, 0);
2377 }
2378
2379 int force_object_loose(const unsigned char *sha1, time_t mtime)
2380 {
2381         void *buf;
2382         unsigned long len;
2383         enum object_type type;
2384         char hdr[32];
2385         int hdrlen;
2386         int ret;
2387
2388         if (has_loose_object(sha1))
2389                 return 0;
2390         buf = read_packed_sha1(sha1, &type, &len);
2391         if (!buf)
2392                 return error("cannot read sha1_file for %s", sha1_to_hex(sha1));
2393         hdrlen = sprintf(hdr, "%s %lu", typename(type), len) + 1;
2394         ret = write_loose_object(sha1, hdr, hdrlen, buf, len, mtime);
2395         free(buf);
2396
2397         return ret;
2398 }
2399
2400 int has_pack_index(const unsigned char *sha1)
2401 {
2402         struct stat st;
2403         if (stat(sha1_pack_index_name(sha1), &st))
2404                 return 0;
2405         return 1;
2406 }
2407
2408 int has_sha1_pack(const unsigned char *sha1)
2409 {
2410         struct pack_entry e;
2411         return find_pack_entry(sha1, &e);
2412 }
2413
2414 int has_sha1_file(const unsigned char *sha1)
2415 {
2416         struct pack_entry e;
2417
2418         if (find_pack_entry(sha1, &e))
2419                 return 1;
2420         return has_loose_object(sha1);
2421 }
2422
2423 static int index_mem(unsigned char *sha1, void *buf, size_t size,
2424                      int write_object, enum object_type type, const char *path)
2425 {
2426         int ret, re_allocated = 0;
2427
2428         if (!type)
2429                 type = OBJ_BLOB;
2430
2431         /*
2432          * Convert blobs to git internal format
2433          */
2434         if ((type == OBJ_BLOB) && path) {
2435                 struct strbuf nbuf = STRBUF_INIT;
2436                 if (convert_to_git(path, buf, size, &nbuf,
2437                                    write_object ? safe_crlf : 0)) {
2438                         buf = strbuf_detach(&nbuf, &size);
2439                         re_allocated = 1;
2440                 }
2441         }
2442
2443         if (write_object)
2444                 ret = write_sha1_file(buf, size, typename(type), sha1);
2445         else
2446                 ret = hash_sha1_file(buf, size, typename(type), sha1);
2447         if (re_allocated)
2448                 free(buf);
2449         return ret;
2450 }
2451
2452 #define SMALL_FILE_SIZE (32*1024)
2453
2454 int index_fd(unsigned char *sha1, int fd, struct stat *st, int write_object,
2455              enum object_type type, const char *path)
2456 {
2457         int ret;
2458         size_t size = xsize_t(st->st_size);
2459
2460         if (!S_ISREG(st->st_mode)) {
2461                 struct strbuf sbuf = STRBUF_INIT;
2462                 if (strbuf_read(&sbuf, fd, 4096) >= 0)
2463                         ret = index_mem(sha1, sbuf.buf, sbuf.len, write_object,
2464                                         type, path);
2465                 else
2466                         ret = -1;
2467                 strbuf_release(&sbuf);
2468         } else if (!size) {
2469                 ret = index_mem(sha1, NULL, size, write_object, type, path);
2470         } else if (size <= SMALL_FILE_SIZE) {
2471                 char *buf = xmalloc(size);
2472                 if (size == read_in_full(fd, buf, size))
2473                         ret = index_mem(sha1, buf, size, write_object, type,
2474                                         path);
2475                 else
2476                         ret = error("short read %s", strerror(errno));
2477                 free(buf);
2478         } else {
2479                 void *buf = xmmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
2480                 ret = index_mem(sha1, buf, size, write_object, type, path);
2481                 munmap(buf, size);
2482         }
2483         close(fd);
2484         return ret;
2485 }
2486
2487 int index_path(unsigned char *sha1, const char *path, struct stat *st, int write_object)
2488 {
2489         int fd;
2490         struct strbuf sb = STRBUF_INIT;
2491
2492         switch (st->st_mode & S_IFMT) {
2493         case S_IFREG:
2494                 fd = open(path, O_RDONLY);
2495                 if (fd < 0)
2496                         return error("open(\"%s\"): %s", path,
2497                                      strerror(errno));
2498                 if (index_fd(sha1, fd, st, write_object, OBJ_BLOB, path) < 0)
2499                         return error("%s: failed to insert into database",
2500                                      path);
2501                 break;
2502         case S_IFLNK:
2503                 if (strbuf_readlink(&sb, path, st->st_size)) {
2504                         char *errstr = strerror(errno);
2505                         return error("readlink(\"%s\"): %s", path,
2506                                      errstr);
2507                 }
2508                 if (!write_object)
2509                         hash_sha1_file(sb.buf, sb.len, blob_type, sha1);
2510                 else if (write_sha1_file(sb.buf, sb.len, blob_type, sha1))
2511                         return error("%s: failed to insert into database",
2512                                      path);
2513                 strbuf_release(&sb);
2514                 break;
2515         case S_IFDIR:
2516                 return resolve_gitlink_ref(path, "HEAD", sha1);
2517         default:
2518                 return error("%s: unsupported file type", path);
2519         }
2520         return 0;
2521 }
2522
2523 int read_pack_header(int fd, struct pack_header *header)
2524 {
2525         if (read_in_full(fd, header, sizeof(*header)) < sizeof(*header))
2526                 /* "eof before pack header was fully read" */
2527                 return PH_ERROR_EOF;
2528
2529         if (header->hdr_signature != htonl(PACK_SIGNATURE))
2530                 /* "protocol error (pack signature mismatch detected)" */
2531                 return PH_ERROR_PACK_SIGNATURE;
2532         if (!pack_version_ok(header->hdr_version))
2533                 /* "protocol error (pack version unsupported)" */
2534                 return PH_ERROR_PROTOCOL;
2535         return 0;
2536 }
2537
2538 void assert_sha1_type(const unsigned char *sha1, enum object_type expect)
2539 {
2540         enum object_type type = sha1_object_info(sha1, NULL);
2541         if (type < 0)
2542                 die("%s is not a valid object", sha1_to_hex(sha1));
2543         if (type != expect)
2544                 die("%s is not a valid '%s' object", sha1_to_hex(sha1),
2545                     typename(expect));
2546 }