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 USE_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 USE_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_ino != htonl(st->st_ino))
  69                 changed |= INODE_CHANGED;
  70
  71 #ifdef USE_STDEV
  72         /*
  73          * st_dev breaks on network filesystems where different
  74          * clients will have different views of what "device"
  75          * the filesystem is on
  76          */
  77         if (ce->ce_dev != htonl(st->st_dev))
  78                 changed |= INODE_CHANGED;
  79 #endif
  80
  81         if (ce->ce_size != htonl(st->st_size))
  82                 changed |= DATA_CHANGED;
  83         return changed;
  84 }
  85
  86 int base_name_compare(const char *name1, int len1, int mode1,
  87                       const char *name2, int len2, int mode2)
  88 {
  89         unsigned char c1, c2;
  90         int len = len1 < len2 ? len1 : len2;
  91         int cmp;
  92
  93         cmp = memcmp(name1, name2, len);
  94         if (cmp)
  95                 return cmp;
  96         c1 = name1[len];
  97         c2 = name2[len];
  98         if (!c1 && S_ISDIR(mode1))
  99                 c1 = '/';
 100         if (!c2 && S_ISDIR(mode2))
 101                 c2 = '/';
 102         return (c1 < c2) ? -1 : (c1 > c2) ? 1 : 0;
 103 }
 104
 105 int cache_name_compare(const char *name1, int flags1, const char *name2, int flags2)
 106 {
 107         int len1 = flags1 & CE_NAMEMASK;
 108         int len2 = flags2 & CE_NAMEMASK;
 109         int len = len1 < len2 ? len1 : len2;
 110         int cmp;
 111
 112         cmp = memcmp(name1, name2, len);
 113         if (cmp)
 114                 return cmp;
 115         if (len1 < len2)
 116                 return -1;
 117         if (len1 > len2)
 118                 return 1;
 119         if (flags1 < flags2)
 120                 return -1;
 121         if (flags1 > flags2)
 122                 return 1;
 123         return 0;
 124 }
 125
 126 int cache_name_pos(const char *name, int namelen)
 127 {
 128         int first, last;
 129
 130         first = 0;
 131         last = active_nr;
 132         while (last > first) {
 133                 int next = (last + first) >> 1;
 134                 struct cache_entry *ce = active_cache[next];
 135                 int cmp = cache_name_compare(name, namelen, ce->name, htons(ce->ce_flags));
 136                 if (!cmp)
 137                         return next;
 138                 if (cmp < 0) {
 139                         last = next;
 140                         continue;
 141                 }
 142                 first = next+1;
 143         }
 144         return -first-1;
 145 }
 146
 147 /* Remove entry, return true if there are more entries to go.. */
 148 int remove_cache_entry_at(int pos)
 149 {
 150         active_cache_changed = 1;
 151         active_nr--;
 152         if (pos >= active_nr)
 153                 return 0;
 154         memmove(active_cache + pos, active_cache + pos + 1, (active_nr - pos) * sizeof(struct cache_entry *));
 155         return 1;
 156 }
 157
 158 int remove_file_from_cache(char *path)
 159 {
 160         int pos = cache_name_pos(path, strlen(path));
 161         if (pos < 0)
 162                 pos = -pos-1;
 163         while (pos < active_nr && !strcmp(active_cache[pos]->name, path))
 164                 remove_cache_entry_at(pos);
 165         return 0;
 166 }
 167
 168 int ce_same_name(struct cache_entry *a, struct cache_entry *b)
 169 {
 170         int len = ce_namelen(a);
 171         return ce_namelen(b) == len && !memcmp(a->name, b->name, len);
 172 }
 173
 174 /* We may be in a situation where we already have path/file and path
 175  * is being added, or we already have path and path/file is being
 176  * added.  Either one would result in a nonsense tree that has path
 177  * twice when git-write-tree tries to write it out.  Prevent it.
 178  *
 179  * If ok-to-replace is specified, we remove the conflicting entries
 180  * from the cache so the caller should recompute the insert position.
 181  * When this happens, we return non-zero.
 182  */
 183 static int check_file_directory_conflict(const struct cache_entry *ce,
 184                                          int ok_to_replace)
 185 {
 186         int pos, replaced = 0;
 187         const char *path = ce->name;
 188         int namelen = strlen(path);
 189         int stage = ce_stage(ce);
 190         char *pathbuf = xmalloc(namelen + 1);
 191         char *cp;
 192
 193         memcpy(pathbuf, path, namelen + 1);
 194
 195         /*
 196          * We are inserting path/file.  Do they have path registered at
 197          * the same stage?  We need to do this for all the levels of our
 198          * subpath.
 199          */
 200         cp = pathbuf;
 201         while (1) {
 202                 char *ep = strchr(cp, '/');
 203                 int len;
 204                 if (!ep)
 205                         break;
 206                 *ep = 0;    /* first cut it at slash */
 207                 len = ep - pathbuf;
 208                 pos = cache_name_pos(pathbuf,
 209                                      htons(create_ce_flags(len, stage)));
 210                 if (0 <= pos) {
 211                         /* Our leading path component is registered as a file,
 212                          * and we are trying to make it a directory.  This is
 213                          * bad.
 214                          */
 215                         if (!ok_to_replace) {
 216                                 free(pathbuf);
 217                                 return -1;
 218                         }
 219                         fprintf(stderr, "removing file '%s' to replace it with a directory to create '%s'.\n", pathbuf, path);
 220                         remove_cache_entry_at(pos);
 221                         replaced = 1;
 222                 }
 223                 *ep = '/';  /* then restore it and go downwards */
 224                 cp = ep + 1;
 225         }
 226         free(pathbuf);
 227
 228         /* Do we have an entry in the cache that makes our path a prefix
 229          * of it?  That is, are we creating a file where they already expect
 230          * a directory there?
 231          */
 232         pos = cache_name_pos(path,
 233                              htons(create_ce_flags(namelen, stage)));
 234
 235         /* (0 <= pos) cannot happen because add_cache_entry()
 236          * should have taken care of that case.
 237          */
 238         pos = -pos-1;
 239
 240         /* pos would point at an existing entry that would come immediately
 241          * after our path.  It could be the same as our path in higher stage,
 242          * or different path but in a lower stage.
 243          *
 244          * E.g. when we are inserting path at stage 2,
 245          *
 246          *        1 path
 247          * pos->  3 path
 248          *        2 path/file1
 249          *        3 path/file1
 250          *        2 path/file2
 251          *        2 patho
 252          *
 253          * We need to examine pos, ignore it because it is at different
 254          * stage, examine next to find the path/file at stage 2, and
 255          * complain.  We need to do this until we are not the leading
 256          * path of an existing entry anymore.
 257          */
 258
 259         while (pos < active_nr) {
 260                 struct cache_entry *other = active_cache[pos];
 261                 if (strncmp(other->name, path, namelen))
 262                         break; /* it is not our "subdirectory" anymore */
 263                 if ((ce_stage(other) == stage) &&
 264                     other->name[namelen] == '/') {
 265                         if (!ok_to_replace)
 266                                 return -1;
 267                         fprintf(stderr, "removing file '%s' under '%s' to be replaced with a file\n", other->name, path);
 268                         remove_cache_entry_at(pos);
 269                         replaced = 1;
 270                         continue; /* cycle without updating pos */
 271                 }
 272                 pos++;
 273         }
 274         return replaced;
 275 }
 276
 277 int add_cache_entry(struct cache_entry *ce, int option)
 278 {
 279         int pos;
 280         int ok_to_add = option & ADD_CACHE_OK_TO_ADD;
 281         int ok_to_replace = option & ADD_CACHE_OK_TO_REPLACE;
 282         pos = cache_name_pos(ce->name, htons(ce->ce_flags));
 283
 284         /* existing match? Just replace it */
 285         if (pos >= 0) {
 286                 active_cache_changed = 1;
 287                 active_cache[pos] = ce;
 288                 return 0;
 289         }
 290         pos = -pos-1;
 291
 292         /*
 293          * Inserting a merged entry ("stage 0") into the index
 294          * will always replace all non-merged entries..
 295          */
 296         if (pos < active_nr && ce_stage(ce) == 0) {
 297                 while (ce_same_name(active_cache[pos], ce)) {
 298                         ok_to_add = 1;
 299                         if (!remove_cache_entry_at(pos))
 300                                 break;
 301                 }
 302         }
 303
 304         if (!ok_to_add)
 305                 return -1;
 306
 307         if (check_file_directory_conflict(ce, ok_to_replace)) {
 308                 if (!ok_to_replace)
 309                         return -1;
 310                 pos = cache_name_pos(ce->name, htons(ce->ce_flags));
 311                 pos = -pos-1;
 312         }
 313
 314         /* Make sure the array is big enough .. */
 315         if (active_nr == active_alloc) {
 316                 active_alloc = alloc_nr(active_alloc);
 317                 active_cache = xrealloc(active_cache, active_alloc * sizeof(struct cache_entry *));
 318         }
 319
 320         /* Add it in.. */
 321         active_nr++;
 322         if (active_nr > pos)
 323                 memmove(active_cache + pos + 1, active_cache + pos, (active_nr - pos - 1) * sizeof(ce));
 324         active_cache[pos] = ce;
 325         active_cache_changed = 1;
 326         return 0;
 327 }
 328
 329 static int verify_hdr(struct cache_header *hdr, unsigned long size)
 330 {
 331         SHA_CTX c;
 332         unsigned char sha1[20];
 333
 334         if (hdr->hdr_signature != htonl(CACHE_SIGNATURE))
 335                 return error("bad signature");
 336         if (hdr->hdr_version != htonl(2))
 337                 return error("bad index version");
 338         SHA1_Init(&c);
 339         SHA1_Update(&c, hdr, size - 20);
 340         SHA1_Final(sha1, &c);
 341         if (memcmp(sha1, (void *)hdr + size - 20, 20))
 342                 return error("bad index file sha1 signature");
 343         return 0;
 344 }
 345
 346 int read_cache(void)
 347 {
 348         int fd, i;
 349         struct stat st;
 350         unsigned long size, offset;
 351         void *map;
 352         struct cache_header *hdr;
 353
 354         errno = EBUSY;
 355         if (active_cache)
 356                 return error("more than one cachefile");
 357         errno = ENOENT;
 358         fd = open(get_index_file(), O_RDONLY);
 359         if (fd < 0)
 360                 return (errno == ENOENT) ? 0 : error("open failed");
 361
 362         size = 0; // avoid gcc warning
 363         map = (void *)-1;
 364         if (!fstat(fd, &st)) {
 365                 size = st.st_size;
 366                 errno = EINVAL;
 367                 if (size >= sizeof(struct cache_header) + 20)
 368                         map = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
 369         }
 370         close(fd);
 371         if (-1 == (int)(long)map)
 372                 return error("mmap failed");
 373
 374         hdr = map;
 375         if (verify_hdr(hdr, size) < 0)
 376                 goto unmap;
 377
 378         active_nr = ntohl(hdr->hdr_entries);
 379         active_alloc = alloc_nr(active_nr);
 380         active_cache = calloc(active_alloc, sizeof(struct cache_entry *));
 381
 382         offset = sizeof(*hdr);
 383         for (i = 0; i < active_nr; i++) {
 384                 struct cache_entry *ce = map + offset;
 385                 offset = offset + ce_size(ce);
 386                 active_cache[i] = ce;
 387         }
 388         return active_nr;
 389
 390 unmap:
 391         munmap(map, size);
 392         errno = EINVAL;
 393         return error("verify header failed");
 394 }
 395
 396 #define WRITE_BUFFER_SIZE 8192
 397 static unsigned char write_buffer[WRITE_BUFFER_SIZE];
 398 static unsigned long write_buffer_len;
 399
 400 static int ce_write(SHA_CTX *context, int fd, void *data, unsigned int len)
 401 {
 402         while (len) {
 403                 unsigned int buffered = write_buffer_len;
 404                 unsigned int partial = WRITE_BUFFER_SIZE - buffered;
 405                 if (partial > len)
 406                         partial = len;
 407                 memcpy(write_buffer + buffered, data, partial);
 408                 buffered += partial;
 409                 if (buffered == WRITE_BUFFER_SIZE) {
 410                         SHA1_Update(context, write_buffer, WRITE_BUFFER_SIZE);
 411                         if (write(fd, write_buffer, WRITE_BUFFER_SIZE) != WRITE_BUFFER_SIZE)
 412                                 return -1;
 413                         buffered = 0;
 414                 }
 415                 write_buffer_len = buffered;
 416                 len -= partial;
 417                 data += partial;
 418         }
 419         return 0;
 420 }
 421
 422 static int ce_flush(SHA_CTX *context, int fd)
 423 {
 424         unsigned int left = write_buffer_len;
 425
 426         if (left) {
 427                 write_buffer_len = 0;
 428                 SHA1_Update(context, write_buffer, left);
 429         }
 430
 431         /* Append the SHA1 signature at the end */
 432         SHA1_Final(write_buffer + left, context);
 433         left += 20;
 434         if (write(fd, write_buffer, left) != left)
 435                 return -1;
 436         return 0;
 437 }
 438
 439 int write_cache(int newfd, struct cache_entry **cache, int entries)
 440 {
 441         SHA_CTX c;
 442         struct cache_header hdr;
 443         int i;
 444
 445         hdr.hdr_signature = htonl(CACHE_SIGNATURE);
 446         hdr.hdr_version = htonl(2);
 447         hdr.hdr_entries = htonl(entries);
 448
 449         SHA1_Init(&c);
 450         if (ce_write(&c, newfd, &hdr, sizeof(hdr)) < 0)
 451                 return -1;
 452
 453         for (i = 0; i < entries; i++) {
 454                 struct cache_entry *ce = cache[i];
 455                 if (ce_write(&c, newfd, ce, ce_size(ce)) < 0)
 456                         return -1;
 457         }
 458         return ce_flush(&c, newfd);
 459 }