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;
  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                 break;
  20         case S_IFLNK:
  21                 changed |= !S_ISLNK(st->st_mode) ? TYPE_CHANGED : 0;
  22                 break;
  23         default:
  24                 die("internal error: ce_mode is %o", ntohl(ce->ce_mode));
  25         }
  26         if (ce->ce_mtime.sec != htonl(st->st_mtime))
  27                 changed |= MTIME_CHANGED;
  28         if (ce->ce_ctime.sec != htonl(st->st_ctime))
  29                 changed |= CTIME_CHANGED;
  30
  31 #ifdef NSEC
  32         /*
  33          * nsec seems unreliable - not all filesystems support it, so
  34          * as long as it is in the inode cache you get right nsec
  35          * but after it gets flushed, you get zero nsec.
  36          */
  37         if (ce->ce_mtime.nsec != htonl(st->st_mtim.tv_nsec))
  38                 changed |= MTIME_CHANGED;
  39         if (ce->ce_ctime.nsec != htonl(st->st_ctim.tv_nsec))
  40                 changed |= CTIME_CHANGED;
  41 #endif
  42
  43         if (ce->ce_uid != htonl(st->st_uid) ||
  44             ce->ce_gid != htonl(st->st_gid))
  45                 changed |= OWNER_CHANGED;
  46         /* We consider only the owner x bit to be relevant for "mode changes" */
  47         if (0100 & (ntohl(ce->ce_mode) ^ st->st_mode))
  48                 changed |= MODE_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_nr--;
 103         if (pos >= active_nr)
 104                 return 0;
 105         memmove(active_cache + pos, active_cache + pos + 1, (active_nr - pos) * sizeof(struct cache_entry *));
 106         return 1;
 107 }
 108
 109 int remove_file_from_cache(char *path)
 110 {
 111         int pos = cache_name_pos(path, strlen(path));
 112         if (pos < 0)
 113                 pos = -pos-1;
 114         while (pos < active_nr && !strcmp(active_cache[pos]->name, path))
 115                 remove_entry_at(pos);
 116         return 0;
 117 }
 118
 119 int same_name(struct cache_entry *a, struct cache_entry *b)
 120 {
 121         int len = ce_namelen(a);
 122         return ce_namelen(b) == len && !memcmp(a->name, b->name, len);
 123 }
 124
 125 int add_cache_entry(struct cache_entry *ce, int ok_to_add)
 126 {
 127         int pos;
 128
 129         pos = cache_name_pos(ce->name, htons(ce->ce_flags));
 130
 131         /* existing match? Just replace it */
 132         if (pos >= 0) {
 133                 active_cache[pos] = ce;
 134                 return 0;
 135         }
 136         pos = -pos-1;
 137
 138         /*
 139          * Inserting a merged entry ("stage 0") into the index
 140          * will always replace all non-merged entries..
 141          */
 142         if (pos < active_nr && ce_stage(ce) == 0) {
 143                 while (same_name(active_cache[pos], ce)) {
 144                         ok_to_add = 1;
 145                         if (!remove_entry_at(pos))
 146                                 break;
 147                 }
 148         }
 149
 150         if (!ok_to_add)
 151                 return -1;
 152
 153         /* Make sure the array is big enough .. */
 154         if (active_nr == active_alloc) {
 155                 active_alloc = alloc_nr(active_alloc);
 156                 active_cache = xrealloc(active_cache, active_alloc * sizeof(struct cache_entry *));
 157         }
 158
 159         /* Add it in.. */
 160         active_nr++;
 161         if (active_nr > pos)
 162                 memmove(active_cache + pos + 1, active_cache + pos, (active_nr - pos - 1) * sizeof(ce));
 163         active_cache[pos] = ce;
 164         return 0;
 165 }
 166
 167 static int verify_hdr(struct cache_header *hdr, unsigned long size)
 168 {
 169         SHA_CTX c;
 170         unsigned char sha1[20];
 171
 172         if (hdr->hdr_signature != htonl(CACHE_SIGNATURE))
 173                 return error("bad signature");
 174         if (hdr->hdr_version != htonl(2))
 175                 return error("bad index version");
 176         SHA1_Init(&c);
 177         SHA1_Update(&c, hdr, size - 20);
 178         SHA1_Final(sha1, &c);
 179         if (memcmp(sha1, (void *)hdr + size - 20, 20))
 180                 return error("bad index file sha1 signature");
 181         return 0;
 182 }
 183
 184 int read_cache(void)
 185 {
 186         int fd, i;
 187         struct stat st;
 188         unsigned long size, offset;
 189         void *map;
 190         struct cache_header *hdr;
 191
 192         errno = EBUSY;
 193         if (active_cache)
 194                 return error("more than one cachefile");
 195         errno = ENOENT;
 196         sha1_file_directory = getenv(DB_ENVIRONMENT);
 197         if (!sha1_file_directory)
 198                 sha1_file_directory = DEFAULT_DB_ENVIRONMENT;
 199         if (access(sha1_file_directory, X_OK) < 0)
 200                 return error("no access to SHA1 file directory");
 201         fd = open(get_index_file(), O_RDONLY);
 202         if (fd < 0)
 203                 return (errno == ENOENT) ? 0 : error("open failed");
 204
 205         size = 0; // avoid gcc warning
 206         map = (void *)-1;
 207         if (!fstat(fd, &st)) {
 208                 size = st.st_size;
 209                 errno = EINVAL;
 210                 if (size >= sizeof(struct cache_header) + 20)
 211                         map = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
 212         }
 213         close(fd);
 214         if (-1 == (int)(long)map)
 215                 return error("mmap failed");
 216
 217         hdr = map;
 218         if (verify_hdr(hdr, size) < 0)
 219                 goto unmap;
 220
 221         active_nr = ntohl(hdr->hdr_entries);
 222         active_alloc = alloc_nr(active_nr);
 223         active_cache = calloc(active_alloc, sizeof(struct cache_entry *));
 224
 225         offset = sizeof(*hdr);
 226         for (i = 0; i < active_nr; i++) {
 227                 struct cache_entry *ce = map + offset;
 228                 offset = offset + ce_size(ce);
 229                 active_cache[i] = ce;
 230         }
 231         return active_nr;
 232
 233 unmap:
 234         munmap(map, size);
 235         errno = EINVAL;
 236         return error("verify header failed");
 237 }
 238
 239 #define WRITE_BUFFER_SIZE 8192
 240 static char write_buffer[WRITE_BUFFER_SIZE];
 241 static unsigned long write_buffer_len;
 242
 243 static int ce_write(SHA_CTX *context, int fd, void *data, unsigned int len)
 244 {
 245         while (len) {
 246                 unsigned int buffered = write_buffer_len;
 247                 unsigned int partial = WRITE_BUFFER_SIZE - buffered;
 248                 if (partial > len)
 249                         partial = len;
 250                 memcpy(write_buffer + buffered, data, partial);
 251                 buffered += partial;
 252                 if (buffered == WRITE_BUFFER_SIZE) {
 253                         SHA1_Update(context, write_buffer, WRITE_BUFFER_SIZE);
 254                         if (write(fd, write_buffer, WRITE_BUFFER_SIZE) != WRITE_BUFFER_SIZE)
 255                                 return -1;
 256                         buffered = 0;
 257                 }
 258                 write_buffer_len = buffered;
 259                 len -= partial;
 260                 data += partial;
 261         }
 262         return 0;
 263 }
 264
 265 static int ce_flush(SHA_CTX *context, int fd)
 266 {
 267         unsigned int left = write_buffer_len;
 268
 269         if (left) {
 270                 write_buffer_len = 0;
 271                 SHA1_Update(context, write_buffer, left);
 272         }
 273
 274         /* Append the SHA1 signature at the end */
 275         SHA1_Final(write_buffer + left, context);
 276         left += 20;
 277         if (write(fd, write_buffer, left) != left)
 278                 return -1;
 279         return 0;
 280 }
 281
 282 int write_cache(int newfd, struct cache_entry **cache, int entries)
 283 {
 284         SHA_CTX c;
 285         struct cache_header hdr;
 286         int i;
 287
 288         hdr.hdr_signature = htonl(CACHE_SIGNATURE);
 289         hdr.hdr_version = htonl(2);
 290         hdr.hdr_entries = htonl(entries);
 291
 292         SHA1_Init(&c);
 293         if (ce_write(&c, newfd, &hdr, sizeof(hdr)) < 0)
 294                 return -1;
 295
 296         for (i = 0; i < entries; i++) {
 297                 struct cache_entry *ce = cache[i];
 298                 if (ce_write(&c, newfd, ce, ce_size(ce)) < 0)
 299                         return -1;
 300         }
 301         return ce_flush(&c, newfd);
 302 }