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