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 int add_cache_entry(struct cache_entry *ce, int ok_to_add)
 127 {
 128         int pos;
 129
 130         pos = cache_name_pos(ce->name, htons(ce->ce_flags));
 131
 132         /* existing match? Just replace it */
 133         if (pos >= 0) {
 134                 active_cache_changed = 1;
 135                 active_cache[pos] = ce;
 136                 return 0;
 137         }
 138         pos = -pos-1;
 139
 140         /*
 141          * Inserting a merged entry ("stage 0") into the index
 142          * will always replace all non-merged entries..
 143          */
 144         if (pos < active_nr && ce_stage(ce) == 0) {
 145                 while (same_name(active_cache[pos], ce)) {
 146                         ok_to_add = 1;
 147                         if (!remove_entry_at(pos))
 148                                 break;
 149                 }
 150         }
 151
 152         if (!ok_to_add)
 153                 return -1;
 154
 155         /* Make sure the array is big enough .. */
 156         if (active_nr == active_alloc) {
 157                 active_alloc = alloc_nr(active_alloc);
 158                 active_cache = xrealloc(active_cache, active_alloc * sizeof(struct cache_entry *));
 159         }
 160
 161         /* Add it in.. */
 162         active_nr++;
 163         if (active_nr > pos)
 164                 memmove(active_cache + pos + 1, active_cache + pos, (active_nr - pos - 1) * sizeof(ce));
 165         active_cache[pos] = ce;
 166         active_cache_changed = 1;
 167         return 0;
 168 }
 169
 170 static int verify_hdr(struct cache_header *hdr, unsigned long size)
 171 {
 172         SHA_CTX c;
 173         unsigned char sha1[20];
 174
 175         if (hdr->hdr_signature != htonl(CACHE_SIGNATURE))
 176                 return error("bad signature");
 177         if (hdr->hdr_version != htonl(2))
 178                 return error("bad index version");
 179         SHA1_Init(&c);
 180         SHA1_Update(&c, hdr, size - 20);
 181         SHA1_Final(sha1, &c);
 182         if (memcmp(sha1, (void *)hdr + size - 20, 20))
 183                 return error("bad index file sha1 signature");
 184         return 0;
 185 }
 186
 187 int read_cache(void)
 188 {
 189         int fd, i;
 190         struct stat st;
 191         unsigned long size, offset;
 192         void *map;
 193         struct cache_header *hdr;
 194
 195         errno = EBUSY;
 196         if (active_cache)
 197                 return error("more than one cachefile");
 198         errno = ENOENT;
 199         fd = open(get_index_file(), O_RDONLY);
 200         if (fd < 0)
 201                 return (errno == ENOENT) ? 0 : error("open failed");
 202
 203         size = 0; // avoid gcc warning
 204         map = (void *)-1;
 205         if (!fstat(fd, &st)) {
 206                 size = st.st_size;
 207                 errno = EINVAL;
 208                 if (size >= sizeof(struct cache_header) + 20)
 209                         map = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
 210         }
 211         close(fd);
 212         if (-1 == (int)(long)map)
 213                 return error("mmap failed");
 214
 215         hdr = map;
 216         if (verify_hdr(hdr, size) < 0)
 217                 goto unmap;
 218
 219         active_nr = ntohl(hdr->hdr_entries);
 220         active_alloc = alloc_nr(active_nr);
 221         active_cache = calloc(active_alloc, sizeof(struct cache_entry *));
 222
 223         offset = sizeof(*hdr);
 224         for (i = 0; i < active_nr; i++) {
 225                 struct cache_entry *ce = map + offset;
 226                 offset = offset + ce_size(ce);
 227                 active_cache[i] = ce;
 228         }
 229         return active_nr;
 230
 231 unmap:
 232         munmap(map, size);
 233         errno = EINVAL;
 234         return error("verify header failed");
 235 }
 236
 237 #define WRITE_BUFFER_SIZE 8192
 238 static char write_buffer[WRITE_BUFFER_SIZE];
 239 static unsigned long write_buffer_len;
 240
 241 static int ce_write(SHA_CTX *context, int fd, void *data, unsigned int len)
 242 {
 243         while (len) {
 244                 unsigned int buffered = write_buffer_len;
 245                 unsigned int partial = WRITE_BUFFER_SIZE - buffered;
 246                 if (partial > len)
 247                         partial = len;
 248                 memcpy(write_buffer + buffered, data, partial);
 249                 buffered += partial;
 250                 if (buffered == WRITE_BUFFER_SIZE) {
 251                         SHA1_Update(context, write_buffer, WRITE_BUFFER_SIZE);
 252                         if (write(fd, write_buffer, WRITE_BUFFER_SIZE) != WRITE_BUFFER_SIZE)
 253                                 return -1;
 254                         buffered = 0;
 255                 }
 256                 write_buffer_len = buffered;
 257                 len -= partial;
 258                 data += partial;
 259         }
 260         return 0;
 261 }
 262
 263 static int ce_flush(SHA_CTX *context, int fd)
 264 {
 265         unsigned int left = write_buffer_len;
 266
 267         if (left) {
 268                 write_buffer_len = 0;
 269                 SHA1_Update(context, write_buffer, left);
 270         }
 271
 272         /* Append the SHA1 signature at the end */
 273         SHA1_Final(write_buffer + left, context);
 274         left += 20;
 275         if (write(fd, write_buffer, left) != left)
 276                 return -1;
 277         return 0;
 278 }
 279
 280 int write_cache(int newfd, struct cache_entry **cache, int entries)
 281 {
 282         SHA_CTX c;
 283         struct cache_header hdr;
 284         int i;
 285
 286         hdr.hdr_signature = htonl(CACHE_SIGNATURE);
 287         hdr.hdr_version = htonl(2);
 288         hdr.hdr_entries = htonl(entries);
 289
 290         SHA1_Init(&c);
 291         if (ce_write(&c, newfd, &hdr, sizeof(hdr)) < 0)
 292                 return -1;
 293
 294         for (i = 0; i < entries; i++) {
 295                 struct cache_entry *ce = cache[i];
 296                 if (ce_write(&c, newfd, ce, ce_size(ce)) < 0)
 297                         return -1;
 298         }
 299         return ce_flush(&c, newfd);
 300 }