read-cache.c

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