read-cache.c

   1 /*
   2  * GIT - The information manager from hell
   3  *
   4  * Copyright (C) Linus Torvalds, 2005
   5  */
   6 #include "cache.h"
   7
   8 struct cache_entry **active_cache = NULL;
   9 unsigned int active_nr = 0, active_alloc = 0, active_cache_changed = 0;
  10
  11 /*
  12  * This only updates the "non-critical" parts of the directory
  13  * cache, ie the parts that aren't tracked by GIT, and only used
  14  * to validate the cache.
  15  */
  16 void fill_stat_cache_info(struct cache_entry *ce, struct stat *st)
  17 {
  18         ce->ce_ctime.sec = htonl(st->st_ctime);
  19         ce->ce_mtime.sec = htonl(st->st_mtime);
  20 #ifdef NSEC
  21         ce->ce_ctime.nsec = htonl(st->st_ctim.tv_nsec);
  22         ce->ce_mtime.nsec = htonl(st->st_mtim.tv_nsec);
  23 #endif
  24         ce->ce_dev = htonl(st->st_dev);
  25         ce->ce_ino = htonl(st->st_ino);
  26         ce->ce_uid = htonl(st->st_uid);
  27         ce->ce_gid = htonl(st->st_gid);
  28         ce->ce_size = htonl(st->st_size);
  29 }
  30
  31 int ce_match_stat(struct cache_entry *ce, struct stat *st)
  32 {
  33         unsigned int changed = 0;
  34
  35         switch (ntohl(ce->ce_mode) & S_IFMT) {
  36         case S_IFREG:
  37                 changed |= !S_ISREG(st->st_mode) ? TYPE_CHANGED : 0;
  38                 /* We consider only the owner x bit to be relevant for "mode changes" */
  39                 if (0100 & (ntohl(ce->ce_mode) ^ st->st_mode))
  40                         changed |= MODE_CHANGED;
  41                 break;
  42         case S_IFLNK:
  43                 changed |= !S_ISLNK(st->st_mode) ? TYPE_CHANGED : 0;
  44                 break;
  45         default:
  46                 die("internal error: ce_mode is %o", ntohl(ce->ce_mode));
  47         }
  48         if (ce->ce_mtime.sec != htonl(st->st_mtime))
  49                 changed |= MTIME_CHANGED;
  50         if (ce->ce_ctime.sec != htonl(st->st_ctime))
  51                 changed |= CTIME_CHANGED;
  52
  53 #ifdef NSEC
  54         /*
  55          * nsec seems unreliable - not all filesystems support it, so
  56          * as long as it is in the inode cache you get right nsec
  57          * but after it gets flushed, you get zero nsec.
  58          */
  59         if (ce->ce_mtime.nsec != htonl(st->st_mtim.tv_nsec))
  60                 changed |= MTIME_CHANGED;
  61         if (ce->ce_ctime.nsec != htonl(st->st_ctim.tv_nsec))
  62                 changed |= CTIME_CHANGED;
  63 #endif
  64
  65         if (ce->ce_uid != htonl(st->st_uid) ||
  66             ce->ce_gid != htonl(st->st_gid))
  67                 changed |= OWNER_CHANGED;
  68         if (ce->ce_dev != htonl(st->st_dev) ||
  69             ce->ce_ino != htonl(st->st_ino))
  70                 changed |= INODE_CHANGED;
  71         if (ce->ce_size != htonl(st->st_size))
  72                 changed |= DATA_CHANGED;
  73         return changed;
  74 }
  75
  76 int base_name_compare(const char *name1, int len1, int mode1,
  77                       const char *name2, int len2, int mode2)
  78 {
  79         unsigned char c1, c2;
  80         int len = len1 < len2 ? len1 : len2;
  81         int cmp;
  82
  83         cmp = memcmp(name1, name2, len);
  84         if (cmp)
  85                 return cmp;
  86         c1 = name1[len];
  87         c2 = name2[len];
  88         if (!c1 && S_ISDIR(mode1))
  89                 c1 = '/';
  90         if (!c2 && S_ISDIR(mode2))
  91                 c2 = '/';
  92         return (c1 < c2) ? -1 : (c1 > c2) ? 1 : 0;
  93 }
  94
  95 int cache_name_compare(const char *name1, int flags1, const char *name2, int flags2)
  96 {
  97         int len1 = flags1 & CE_NAMEMASK;
  98         int len2 = flags2 & CE_NAMEMASK;
  99         int len = len1 < len2 ? len1 : len2;
 100         int cmp;
 101
 102         cmp = memcmp(name1, name2, len);
 103         if (cmp)
 104                 return cmp;
 105         if (len1 < len2)
 106                 return -1;
 107         if (len1 > len2)
 108                 return 1;
 109         if (flags1 < flags2)
 110                 return -1;
 111         if (flags1 > flags2)
 112                 return 1;
 113         return 0;
 114 }
 115
 116 int cache_name_pos(const char *name, int namelen)
 117 {
 118         int first, last;
 119
 120         first = 0;
 121         last = active_nr;
 122         while (last > first) {
 123                 int next = (last + first) >> 1;
 124                 struct cache_entry *ce = active_cache[next];
 125                 int cmp = cache_name_compare(name, namelen, ce->name, htons(ce->ce_flags));
 126                 if (!cmp)
 127                         return next;
 128                 if (cmp < 0) {
 129                         last = next;
 130                         continue;
 131                 }
 132                 first = next+1;
 133         }
 134         return -first-1;
 135 }
 136
 137 /* Remove entry, return true if there are more entries to go.. */
 138 int remove_cache_entry_at(int pos)
 139 {
 140         active_cache_changed = 1;
 141         active_nr--;
 142         if (pos >= active_nr)
 143                 return 0;
 144         memmove(active_cache + pos, active_cache + pos + 1, (active_nr - pos) * sizeof(struct cache_entry *));
 145         return 1;
 146 }
 147
 148 int remove_file_from_cache(char *path)
 149 {
 150         int pos = cache_name_pos(path, strlen(path));
 151         if (pos < 0)
 152                 pos = -pos-1;
 153         while (pos < active_nr && !strcmp(active_cache[pos]->name, path))
 154                 remove_cache_entry_at(pos);
 155         return 0;
 156 }
 157
 158 int ce_same_name(struct cache_entry *a, struct cache_entry *b)
 159 {
 160         int len = ce_namelen(a);
 161         return ce_namelen(b) == len && !memcmp(a->name, b->name, len);
 162 }
 163
 164 /* We may be in a situation where we already have path/file and path
 165  * is being added, or we already have path and path/file is being
 166  * added.  Either one would result in a nonsense tree that has path
 167  * twice when git-write-tree tries to write it out.  Prevent it.
 168  *
 169  * If ok-to-replace is specified, we remove the conflicting entries
 170  * from the cache so the caller should recompute the insert position.
 171  * When this happens, we return non-zero.
 172  */
 173 static int check_file_directory_conflict(const struct cache_entry *ce,
 174                                          int ok_to_replace)
 175 {
 176         int pos, replaced = 0;
 177         const char *path = ce->name;
 178         int namelen = strlen(path);
 179         int stage = ce_stage(ce);
 180         char *pathbuf = xmalloc(namelen + 1);
 181         char *cp;
 182
 183         memcpy(pathbuf, path, namelen + 1);
 184
 185         /*
 186          * We are inserting path/file.  Do they have path registered at
 187          * the same stage?  We need to do this for all the levels of our
 188          * subpath.
 189          */
 190         cp = pathbuf;
 191         while (1) {
 192                 char *ep = strchr(cp, '/');
 193                 if (!ep)
 194                         break;
 195                 *ep = 0;    /* first cut it at slash */
 196                 pos = cache_name_pos(pathbuf,
 197                                      htons(create_ce_flags(ep-cp, stage)));
 198                 if (0 <= pos) {
 199                         /* Our leading path component is registered as a file,
 200                          * and we are trying to make it a directory.  This is
 201                          * bad.
 202                          */
 203                         if (!ok_to_replace) {
 204                                 free(pathbuf);
 205                                 return -1;
 206                         }
 207                         fprintf(stderr, "removing file '%s' to replace it with a directory to create '%s'.\n", pathbuf, path);
 208                         remove_cache_entry_at(pos);
 209                         replaced = 1;
 210                 }
 211                 *ep = '/';  /* then restore it and go downwards */
 212                 cp = ep + 1;
 213         }
 214         free(pathbuf);
 215
 216         /* Do we have an entry in the cache that makes our path a prefix
 217          * of it?  That is, are we creating a file where they already expect
 218          * a directory there?
 219          */
 220         pos = cache_name_pos(path,
 221                              htons(create_ce_flags(namelen, stage)));
 222
 223         /* (0 <= pos) cannot happen because add_cache_entry()
 224          * should have taken care of that case.
 225          */
 226         pos = -pos-1;
 227
 228         /* pos would point at an existing entry that would come immediately
 229          * after our path.  It could be the same as our path in higher stage,
 230          * or different path but in a lower stage.
 231          *
 232          * E.g. when we are inserting path at stage 2,
 233          *
 234          *        1 path
 235          * pos->  3 path
 236          *        2 path/file1
 237          *        3 path/file1
 238          *        2 path/file2
 239          *        2 patho
 240          *
 241          * We need to examine pos, ignore it because it is at different
 242          * stage, examine next to find the path/file at stage 2, and
 243          * complain.  We need to do this until we are not the leading
 244          * path of an existing entry anymore.
 245          */
 246
 247         while (pos < active_nr) {
 248                 struct cache_entry *other = active_cache[pos];
 249                 if (strncmp(other->name, path, namelen))
 250                         break; /* it is not our "subdirectory" anymore */
 251                 if ((ce_stage(other) == stage) &&
 252                     other->name[namelen] == '/') {
 253                         if (!ok_to_replace)
 254                                 return -1;
 255                         fprintf(stderr, "removing file '%s' under '%s' to be replaced with a file\n", other->name, path);
 256                         remove_cache_entry_at(pos);
 257                         replaced = 1;
 258                         continue; /* cycle without updating pos */
 259                 }
 260                 pos++;
 261         }
 262         return replaced;
 263 }
 264
 265 int add_cache_entry(struct cache_entry *ce, int option)
 266 {
 267         int pos;
 268         int ok_to_add = option & ADD_CACHE_OK_TO_ADD;
 269         int ok_to_replace = option & ADD_CACHE_OK_TO_REPLACE;
 270         pos = cache_name_pos(ce->name, htons(ce->ce_flags));
 271
 272         /* existing match? Just replace it */
 273         if (pos >= 0) {
 274                 active_cache_changed = 1;
 275                 active_cache[pos] = ce;
 276                 return 0;
 277         }
 278         pos = -pos-1;
 279
 280         /*
 281          * Inserting a merged entry ("stage 0") into the index
 282          * will always replace all non-merged entries..
 283          */
 284         if (pos < active_nr && ce_stage(ce) == 0) {
 285                 while (ce_same_name(active_cache[pos], ce)) {
 286                         ok_to_add = 1;
 287                         if (!remove_cache_entry_at(pos))
 288                                 break;
 289                 }
 290         }
 291
 292         if (!ok_to_add)
 293                 return -1;
 294
 295         if (check_file_directory_conflict(ce, ok_to_replace)) {
 296                 if (!ok_to_replace)
 297                         return -1;
 298                 pos = cache_name_pos(ce->name, htons(ce->ce_flags));
 299                 pos = -pos-1;
 300         }
 301
 302         /* Make sure the array is big enough .. */
 303         if (active_nr == active_alloc) {
 304                 active_alloc = alloc_nr(active_alloc);
 305                 active_cache = xrealloc(active_cache, active_alloc * sizeof(struct cache_entry *));
 306         }
 307
 308         /* Add it in.. */
 309         active_nr++;
 310         if (active_nr > pos)
 311                 memmove(active_cache + pos + 1, active_cache + pos, (active_nr - pos - 1) * sizeof(ce));
 312         active_cache[pos] = ce;
 313         active_cache_changed = 1;
 314         return 0;
 315 }
 316
 317 static int verify_hdr(struct cache_header *hdr, unsigned long size)
 318 {
 319         SHA_CTX c;
 320         unsigned char sha1[20];
 321
 322         if (hdr->hdr_signature != htonl(CACHE_SIGNATURE))
 323                 return error("bad signature");
 324         if (hdr->hdr_version != htonl(2))
 325                 return error("bad index version");
 326         SHA1_Init(&c);
 327         SHA1_Update(&c, hdr, size - 20);
 328         SHA1_Final(sha1, &c);
 329         if (memcmp(sha1, (void *)hdr + size - 20, 20))
 330                 return error("bad index file sha1 signature");
 331         return 0;
 332 }
 333
 334 int read_cache(void)
 335 {
 336         int fd, i;
 337         struct stat st;
 338         unsigned long size, offset;
 339         void *map;
 340         struct cache_header *hdr;
 341
 342         errno = EBUSY;
 343         if (active_cache)
 344                 return error("more than one cachefile");
 345         errno = ENOENT;
 346         fd = open(get_index_file(), O_RDONLY);
 347         if (fd < 0)
 348                 return (errno == ENOENT) ? 0 : error("open failed");
 349
 350         size = 0; // avoid gcc warning
 351         map = (void *)-1;
 352         if (!fstat(fd, &st)) {
 353                 size = st.st_size;
 354                 errno = EINVAL;
 355                 if (size >= sizeof(struct cache_header) + 20)
 356                         map = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
 357         }
 358         close(fd);
 359         if (-1 == (int)(long)map)
 360                 return error("mmap failed");
 361
 362         hdr = map;
 363         if (verify_hdr(hdr, size) < 0)
 364                 goto unmap;
 365
 366         active_nr = ntohl(hdr->hdr_entries);
 367         active_alloc = alloc_nr(active_nr);
 368         active_cache = calloc(active_alloc, sizeof(struct cache_entry *));
 369
 370         offset = sizeof(*hdr);
 371         for (i = 0; i < active_nr; i++) {
 372                 struct cache_entry *ce = map + offset;
 373                 offset = offset + ce_size(ce);
 374                 active_cache[i] = ce;
 375         }
 376         return active_nr;
 377
 378 unmap:
 379         munmap(map, size);
 380         errno = EINVAL;
 381         return error("verify header failed");
 382 }
 383
 384 #define WRITE_BUFFER_SIZE 8192
 385 static unsigned char write_buffer[WRITE_BUFFER_SIZE];
 386 static unsigned long write_buffer_len;
 387
 388 static int ce_write(SHA_CTX *context, int fd, void *data, unsigned int len)
 389 {
 390         while (len) {
 391                 unsigned int buffered = write_buffer_len;
 392                 unsigned int partial = WRITE_BUFFER_SIZE - buffered;
 393                 if (partial > len)
 394                         partial = len;
 395                 memcpy(write_buffer + buffered, data, partial);
 396                 buffered += partial;
 397                 if (buffered == WRITE_BUFFER_SIZE) {
 398                         SHA1_Update(context, write_buffer, WRITE_BUFFER_SIZE);
 399                         if (write(fd, write_buffer, WRITE_BUFFER_SIZE) != WRITE_BUFFER_SIZE)
 400                                 return -1;
 401                         buffered = 0;
 402                 }
 403                 write_buffer_len = buffered;
 404                 len -= partial;
 405                 data += partial;
 406         }
 407         return 0;
 408 }
 409
 410 static int ce_flush(SHA_CTX *context, int fd)
 411 {
 412         unsigned int left = write_buffer_len;
 413
 414         if (left) {
 415                 write_buffer_len = 0;
 416                 SHA1_Update(context, write_buffer, left);
 417         }
 418
 419         /* Append the SHA1 signature at the end */
 420         SHA1_Final(write_buffer + left, context);
 421         left += 20;
 422         if (write(fd, write_buffer, left) != left)
 423                 return -1;
 424         return 0;
 425 }
 426
 427 int write_cache(int newfd, struct cache_entry **cache, int entries)
 428 {
 429         SHA_CTX c;
 430         struct cache_header hdr;
 431         int i;
 432
 433         hdr.hdr_signature = htonl(CACHE_SIGNATURE);
 434         hdr.hdr_version = htonl(2);
 435         hdr.hdr_entries = htonl(entries);
 436
 437         SHA1_Init(&c);
 438         if (ce_write(&c, newfd, &hdr, sizeof(hdr)) < 0)
 439                 return -1;
 440
 441         for (i = 0; i < entries; i++) {
 442                 struct cache_entry *ce = cache[i];
 443                 if (ce_write(&c, newfd, ce, ce_size(ce)) < 0)
 444                         return -1;
 445         }
 446         return ce_flush(&c, newfd);
 447 }