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                 if (!ep)
 204                         break;
 205                 *ep = 0;    /* first cut it at slash */
 206                 pos = cache_name_pos(pathbuf,
 207                                      htons(create_ce_flags(ep-cp, stage)));
 208                 if (0 <= pos) {
 209                         /* Our leading path component is registered as a file,
 210                          * and we are trying to make it a directory.  This is
 211                          * bad.
 212                          */
 213                         if (!ok_to_replace) {
 214                                 free(pathbuf);
 215                                 return -1;
 216                         }
 217                         fprintf(stderr, "removing file '%s' to replace it with a directory to create '%s'.\n", pathbuf, path);
 218                         remove_cache_entry_at(pos);
 219                         replaced = 1;
 220                 }
 221                 *ep = '/';  /* then restore it and go downwards */
 222                 cp = ep + 1;
 223         }
 224         free(pathbuf);
 225
 226         /* Do we have an entry in the cache that makes our path a prefix
 227          * of it?  That is, are we creating a file where they already expect
 228          * a directory there?
 229          */
 230         pos = cache_name_pos(path,
 231                              htons(create_ce_flags(namelen, stage)));
 232
 233         /* (0 <= pos) cannot happen because add_cache_entry()
 234          * should have taken care of that case.
 235          */
 236         pos = -pos-1;
 237
 238         /* pos would point at an existing entry that would come immediately
 239          * after our path.  It could be the same as our path in higher stage,
 240          * or different path but in a lower stage.
 241          *
 242          * E.g. when we are inserting path at stage 2,
 243          *
 244          *        1 path
 245          * pos->  3 path
 246          *        2 path/file1
 247          *        3 path/file1
 248          *        2 path/file2
 249          *        2 patho
 250          *
 251          * We need to examine pos, ignore it because it is at different
 252          * stage, examine next to find the path/file at stage 2, and
 253          * complain.  We need to do this until we are not the leading
 254          * path of an existing entry anymore.
 255          */
 256
 257         while (pos < active_nr) {
 258                 struct cache_entry *other = active_cache[pos];
 259                 if (strncmp(other->name, path, namelen))
 260                         break; /* it is not our "subdirectory" anymore */
 261                 if ((ce_stage(other) == stage) &&
 262                     other->name[namelen] == '/') {
 263                         if (!ok_to_replace)
 264                                 return -1;
 265                         fprintf(stderr, "removing file '%s' under '%s' to be replaced with a file\n", other->name, path);
 266                         remove_cache_entry_at(pos);
 267                         replaced = 1;
 268                         continue; /* cycle without updating pos */
 269                 }
 270                 pos++;
 271         }
 272         return replaced;
 273 }
 274
 275 int add_cache_entry(struct cache_entry *ce, int option)
 276 {
 277         int pos;
 278         int ok_to_add = option & ADD_CACHE_OK_TO_ADD;
 279         int ok_to_replace = option & ADD_CACHE_OK_TO_REPLACE;
 280         pos = cache_name_pos(ce->name, htons(ce->ce_flags));
 281
 282         /* existing match? Just replace it */
 283         if (pos >= 0) {
 284                 active_cache_changed = 1;
 285                 active_cache[pos] = ce;
 286                 return 0;
 287         }
 288         pos = -pos-1;
 289
 290         /*
 291          * Inserting a merged entry ("stage 0") into the index
 292          * will always replace all non-merged entries..
 293          */
 294         if (pos < active_nr && ce_stage(ce) == 0) {
 295                 while (ce_same_name(active_cache[pos], ce)) {
 296                         ok_to_add = 1;
 297                         if (!remove_cache_entry_at(pos))
 298                                 break;
 299                 }
 300         }
 301
 302         if (!ok_to_add)
 303                 return -1;
 304
 305         if (check_file_directory_conflict(ce, ok_to_replace)) {
 306                 if (!ok_to_replace)
 307                         return -1;
 308                 pos = cache_name_pos(ce->name, htons(ce->ce_flags));
 309                 pos = -pos-1;
 310         }
 311
 312         /* Make sure the array is big enough .. */
 313         if (active_nr == active_alloc) {
 314                 active_alloc = alloc_nr(active_alloc);
 315                 active_cache = xrealloc(active_cache, active_alloc * sizeof(struct cache_entry *));
 316         }
 317
 318         /* Add it in.. */
 319         active_nr++;
 320         if (active_nr > pos)
 321                 memmove(active_cache + pos + 1, active_cache + pos, (active_nr - pos - 1) * sizeof(ce));
 322         active_cache[pos] = ce;
 323         active_cache_changed = 1;
 324         return 0;
 325 }
 326
 327 static int verify_hdr(struct cache_header *hdr, unsigned long size)
 328 {
 329         SHA_CTX c;
 330         unsigned char sha1[20];
 331
 332         if (hdr->hdr_signature != htonl(CACHE_SIGNATURE))
 333                 return error("bad signature");
 334         if (hdr->hdr_version != htonl(2))
 335                 return error("bad index version");
 336         SHA1_Init(&c);
 337         SHA1_Update(&c, hdr, size - 20);
 338         SHA1_Final(sha1, &c);
 339         if (memcmp(sha1, (void *)hdr + size - 20, 20))
 340                 return error("bad index file sha1 signature");
 341         return 0;
 342 }
 343
 344 int read_cache(void)
 345 {
 346         int fd, i;
 347         struct stat st;
 348         unsigned long size, offset;
 349         void *map;
 350         struct cache_header *hdr;
 351
 352         errno = EBUSY;
 353         if (active_cache)
 354                 return error("more than one cachefile");
 355         errno = ENOENT;
 356         fd = open(get_index_file(), O_RDONLY);
 357         if (fd < 0)
 358                 return (errno == ENOENT) ? 0 : error("open failed");
 359
 360         size = 0; // avoid gcc warning
 361         map = (void *)-1;
 362         if (!fstat(fd, &st)) {
 363                 size = st.st_size;
 364                 errno = EINVAL;
 365                 if (size >= sizeof(struct cache_header) + 20)
 366                         map = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
 367         }
 368         close(fd);
 369         if (-1 == (int)(long)map)
 370                 return error("mmap failed");
 371
 372         hdr = map;
 373         if (verify_hdr(hdr, size) < 0)
 374                 goto unmap;
 375
 376         active_nr = ntohl(hdr->hdr_entries);
 377         active_alloc = alloc_nr(active_nr);
 378         active_cache = calloc(active_alloc, sizeof(struct cache_entry *));
 379
 380         offset = sizeof(*hdr);
 381         for (i = 0; i < active_nr; i++) {
 382                 struct cache_entry *ce = map + offset;
 383                 offset = offset + ce_size(ce);
 384                 active_cache[i] = ce;
 385         }
 386         return active_nr;
 387
 388 unmap:
 389         munmap(map, size);
 390         errno = EINVAL;
 391         return error("verify header failed");
 392 }
 393
 394 #define WRITE_BUFFER_SIZE 8192
 395 static unsigned char write_buffer[WRITE_BUFFER_SIZE];
 396 static unsigned long write_buffer_len;
 397
 398 static int ce_write(SHA_CTX *context, int fd, void *data, unsigned int len)
 399 {
 400         while (len) {
 401                 unsigned int buffered = write_buffer_len;
 402                 unsigned int partial = WRITE_BUFFER_SIZE - buffered;
 403                 if (partial > len)
 404                         partial = len;
 405                 memcpy(write_buffer + buffered, data, partial);
 406                 buffered += partial;
 407                 if (buffered == WRITE_BUFFER_SIZE) {
 408                         SHA1_Update(context, write_buffer, WRITE_BUFFER_SIZE);
 409                         if (write(fd, write_buffer, WRITE_BUFFER_SIZE) != WRITE_BUFFER_SIZE)
 410                                 return -1;
 411                         buffered = 0;
 412                 }
 413                 write_buffer_len = buffered;
 414                 len -= partial;
 415                 data += partial;
 416         }
 417         return 0;
 418 }
 419
 420 static int ce_flush(SHA_CTX *context, int fd)
 421 {
 422         unsigned int left = write_buffer_len;
 423
 424         if (left) {
 425                 write_buffer_len = 0;
 426                 SHA1_Update(context, write_buffer, left);
 427         }
 428
 429         /* Append the SHA1 signature at the end */
 430         SHA1_Final(write_buffer + left, context);
 431         left += 20;
 432         if (write(fd, write_buffer, left) != left)
 433                 return -1;
 434         return 0;
 435 }
 436
 437 int write_cache(int newfd, struct cache_entry **cache, int entries)
 438 {
 439         SHA_CTX c;
 440         struct cache_header hdr;
 441         int i;
 442
 443         hdr.hdr_signature = htonl(CACHE_SIGNATURE);
 444         hdr.hdr_version = htonl(2);
 445         hdr.hdr_entries = htonl(entries);
 446
 447         SHA1_Init(&c);
 448         if (ce_write(&c, newfd, &hdr, sizeof(hdr)) < 0)
 449                 return -1;
 450
 451         for (i = 0; i < entries; i++) {
 452                 struct cache_entry *ce = cache[i];
 453                 if (ce_write(&c, newfd, ce, ce_size(ce)) < 0)
 454                         return -1;
 455         }
 456         return ce_flush(&c, newfd);
 457 }