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         if (ce->ce_mtime.sec != htonl(st->st_mtime))
  17                 changed |= MTIME_CHANGED;
  18         if (ce->ce_ctime.sec != htonl(st->st_ctime))
  19                 changed |= CTIME_CHANGED;
  20
  21 #ifdef NSEC
  22         /*
  23          * nsec seems unreliable - not all filesystems support it, so
  24          * as long as it is in the inode cache you get right nsec
  25          * but after it gets flushed, you get zero nsec.
  26          */
  27         if (ce->ce_mtime.nsec != htonl(st->st_mtim.tv_nsec))
  28                 changed |= MTIME_CHANGED;
  29         if (ce->ce_ctime.nsec != htonl(st->st_ctim.tv_nsec))
  30                 changed |= CTIME_CHANGED;
  31 #endif
  32
  33         if (ce->ce_uid != htonl(st->st_uid) ||
  34             ce->ce_gid != htonl(st->st_gid))
  35                 changed |= OWNER_CHANGED;
  36         /* We consider only the owner x bit to be relevant for "mode changes" */
  37         if (0100 & (ntohl(ce->ce_mode) ^ st->st_mode))
  38                 changed |= MODE_CHANGED;
  39         if (ce->ce_dev != htonl(st->st_dev) ||
  40             ce->ce_ino != htonl(st->st_ino))
  41                 changed |= INODE_CHANGED;
  42         if (ce->ce_size != htonl(st->st_size))
  43                 changed |= DATA_CHANGED;
  44         return changed;
  45 }
  46
  47 int cache_name_compare(const char *name1, int flags1, const char *name2, int flags2)
  48 {
  49         int len1 = flags1 & CE_NAMEMASK;
  50         int len2 = flags2 & CE_NAMEMASK;
  51         int len = len1 < len2 ? len1 : len2;
  52         int cmp;
  53
  54         cmp = memcmp(name1, name2, len);
  55         if (cmp)
  56                 return cmp;
  57         if (len1 < len2)
  58                 return -1;
  59         if (len1 > len2)
  60                 return 1;
  61         if (flags1 < flags2)
  62                 return -1;
  63         if (flags1 > flags2)
  64                 return 1;
  65         return 0;
  66 }
  67
  68 int cache_name_pos(const char *name, int namelen)
  69 {
  70         int first, last;
  71
  72         first = 0;
  73         last = active_nr;
  74         while (last > first) {
  75                 int next = (last + first) >> 1;
  76                 struct cache_entry *ce = active_cache[next];
  77                 int cmp = cache_name_compare(name, namelen, ce->name, htons(ce->ce_flags));
  78                 if (!cmp)
  79                         return next;
  80                 if (cmp < 0) {
  81                         last = next;
  82                         continue;
  83                 }
  84                 first = next+1;
  85         }
  86         return -first-1;
  87 }
  88
  89 /* Remove entry, return true if there are more entries to go.. */
  90 int remove_entry_at(int pos)
  91 {
  92         active_nr--;
  93         if (pos >= active_nr)
  94                 return 0;
  95         memmove(active_cache + pos, active_cache + pos + 1, (active_nr - pos) * sizeof(struct cache_entry *));
  96         return 1;
  97 }
  98
  99 int remove_file_from_cache(char *path)
 100 {
 101         int pos = cache_name_pos(path, strlen(path));
 102         if (pos < 0)
 103                 pos = -pos-1;
 104         while (pos < active_nr && !strcmp(active_cache[pos]->name, path))
 105                 remove_entry_at(pos);
 106         return 0;
 107 }
 108
 109 int same_name(struct cache_entry *a, struct cache_entry *b)
 110 {
 111         int len = ce_namelen(a);
 112         return ce_namelen(b) == len && !memcmp(a->name, b->name, len);
 113 }
 114
 115 int add_cache_entry(struct cache_entry *ce, int ok_to_add)
 116 {
 117         int pos;
 118
 119         pos = cache_name_pos(ce->name, htons(ce->ce_flags));
 120
 121         /* existing match? Just replace it */
 122         if (pos >= 0) {
 123                 active_cache[pos] = ce;
 124                 return 0;
 125         }
 126         pos = -pos-1;
 127
 128         /*
 129          * Inserting a merged entry ("stage 0") into the index
 130          * will always replace all non-merged entries..
 131          */
 132         if (pos < active_nr && ce_stage(ce) == 0) {
 133                 while (same_name(active_cache[pos], ce)) {
 134                         ok_to_add = 1;
 135                         if (!remove_entry_at(pos))
 136                                 break;
 137                 }
 138         }
 139
 140         if (!ok_to_add)
 141                 return -1;
 142
 143         /* Make sure the array is big enough .. */
 144         if (active_nr == active_alloc) {
 145                 active_alloc = alloc_nr(active_alloc);
 146                 active_cache = xrealloc(active_cache, active_alloc * sizeof(struct cache_entry *));
 147         }
 148
 149         /* Add it in.. */
 150         active_nr++;
 151         if (active_nr > pos)
 152                 memmove(active_cache + pos + 1, active_cache + pos, (active_nr - pos - 1) * sizeof(ce));
 153         active_cache[pos] = ce;
 154         return 0;
 155 }
 156
 157 static int verify_hdr(struct cache_header *hdr, unsigned long size)
 158 {
 159         SHA_CTX c;
 160         unsigned char sha1[20];
 161
 162         if (hdr->hdr_signature != htonl(CACHE_SIGNATURE))
 163                 return error("bad signature");
 164         if (hdr->hdr_version != htonl(2))
 165                 return error("bad index version");
 166         SHA1_Init(&c);
 167         SHA1_Update(&c, hdr, size - 20);
 168         SHA1_Final(sha1, &c);
 169         if (memcmp(sha1, (void *)hdr + size - 20, 20))
 170                 return error("bad index file sha1 signature");
 171         return 0;
 172 }
 173
 174 int read_cache(void)
 175 {
 176         int fd, i;
 177         struct stat st;
 178         unsigned long size, offset;
 179         void *map;
 180         struct cache_header *hdr;
 181
 182         errno = EBUSY;
 183         if (active_cache)
 184                 return error("more than one cachefile");
 185         errno = ENOENT;
 186         sha1_file_directory = getenv(DB_ENVIRONMENT);
 187         if (!sha1_file_directory)
 188                 sha1_file_directory = DEFAULT_DB_ENVIRONMENT;
 189         if (access(sha1_file_directory, X_OK) < 0)
 190                 return error("no access to SHA1 file directory");
 191         fd = open(get_index_file(), O_RDONLY);
 192         if (fd < 0)
 193                 return (errno == ENOENT) ? 0 : error("open failed");
 194
 195         size = 0; // avoid gcc warning
 196         map = (void *)-1;
 197         if (!fstat(fd, &st)) {
 198                 size = st.st_size;
 199                 errno = EINVAL;
 200                 if (size >= sizeof(struct cache_header) + 20)
 201                         map = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
 202         }
 203         close(fd);
 204         if (-1 == (int)(long)map)
 205                 return error("mmap failed");
 206
 207         hdr = map;
 208         if (verify_hdr(hdr, size) < 0)
 209                 goto unmap;
 210
 211         active_nr = ntohl(hdr->hdr_entries);
 212         active_alloc = alloc_nr(active_nr);
 213         active_cache = calloc(active_alloc, sizeof(struct cache_entry *));
 214
 215         offset = sizeof(*hdr);
 216         for (i = 0; i < active_nr; i++) {
 217                 struct cache_entry *ce = map + offset;
 218                 offset = offset + ce_size(ce);
 219                 active_cache[i] = ce;
 220         }
 221         return active_nr;
 222
 223 unmap:
 224         munmap(map, size);
 225         errno = EINVAL;
 226         return error("verify header failed");
 227 }
 228
 229 #define WRITE_BUFFER_SIZE 8192
 230 static char write_buffer[WRITE_BUFFER_SIZE];
 231 static unsigned long write_buffer_len;
 232
 233 static int ce_write(SHA_CTX *context, int fd, void *data, unsigned int len)
 234 {
 235         while (len) {
 236                 unsigned int buffered = write_buffer_len;
 237                 unsigned int partial = WRITE_BUFFER_SIZE - buffered;
 238                 if (partial > len)
 239                         partial = len;
 240                 memcpy(write_buffer + buffered, data, partial);
 241                 buffered += partial;
 242                 if (buffered == WRITE_BUFFER_SIZE) {
 243                         SHA1_Update(context, write_buffer, WRITE_BUFFER_SIZE);
 244                         if (write(fd, write_buffer, WRITE_BUFFER_SIZE) != WRITE_BUFFER_SIZE)
 245                                 return -1;
 246                         buffered = 0;
 247                 }
 248                 write_buffer_len = buffered;
 249                 len -= partial;
 250                 data += partial;
 251         }
 252         return 0;
 253 }
 254
 255 static int ce_flush(SHA_CTX *context, int fd)
 256 {
 257         unsigned int left = write_buffer_len;
 258
 259         if (left) {
 260                 write_buffer_len = 0;
 261                 SHA1_Update(context, write_buffer, left);
 262         }
 263
 264         /* Append the SHA1 signature at the end */
 265         SHA1_Final(write_buffer + left, context);
 266         left += 20;
 267         if (write(fd, write_buffer, left) != left)
 268                 return -1;
 269         return 0;
 270 }
 271
 272 int write_cache(int newfd, struct cache_entry **cache, int entries)
 273 {
 274         SHA_CTX c;
 275         struct cache_header hdr;
 276         int i;
 277
 278         hdr.hdr_signature = htonl(CACHE_SIGNATURE);
 279         hdr.hdr_version = htonl(2);
 280         hdr.hdr_entries = htonl(entries);
 281
 282         SHA1_Init(&c);
 283         if (ce_write(&c, newfd, &hdr, sizeof(hdr)) < 0)
 284                 return -1;
 285
 286         for (i = 0; i < entries; i++) {
 287                 struct cache_entry *ce = cache[i];
 288                 if (ce_write(&c, newfd, ce, ce_size(ce)) < 0)
 289                         return -1;
 290         }
 291         return ce_flush(&c, newfd);
 292 }