refs.c

   1 #include "refs.h"
   2 #include "cache.h"
   3
   4 #include <errno.h>
   5 #include <ctype.h>
   6
   7 /* We allow "recursive" symbolic refs. Only within reason, though */
   8 #define MAXDEPTH 5
   9
  10 const char *resolve_ref(const char *path, unsigned char *sha1, int reading)
  11 {
  12         int depth = MAXDEPTH, len;
  13         char buffer[256];
  14
  15         for (;;) {
  16                 struct stat st;
  17                 char *buf;
  18                 int fd;
  19
  20                 if (--depth < 0)
  21                         return NULL;
  22
  23                 /* Special case: non-existing file.
  24                  * Not having the refs/heads/new-branch is OK
  25                  * if we are writing into it, so is .git/HEAD
  26                  * that points at refs/heads/master still to be
  27                  * born.  It is NOT OK if we are resolving for
  28                  * reading.
  29                  */
  30                 if (lstat(path, &st) < 0) {
  31                         if (reading || errno != ENOENT)
  32                                 return NULL;
  33                         memset(sha1, 0, 20);
  34                         return path;
  35                 }
  36
  37                 /* Follow "normalized" - ie "refs/.." symlinks by hand */
  38                 if (S_ISLNK(st.st_mode)) {
  39                         len = readlink(path, buffer, sizeof(buffer)-1);
  40                         if (len >= 5 && !memcmp("refs/", buffer, 5)) {
  41                                 path = git_path("%.*s", len, buffer);
  42                                 continue;
  43                         }
  44                 }
  45
  46                 /*
  47                  * Anything else, just open it and try to use it as
  48                  * a ref
  49                  */
  50                 fd = open(path, O_RDONLY);
  51                 if (fd < 0)
  52                         return NULL;
  53                 len = read(fd, buffer, sizeof(buffer)-1);
  54                 close(fd);
  55
  56                 /*
  57                  * Is it a symbolic ref?
  58                  */
  59                 if (len < 4 || memcmp("ref:", buffer, 4))
  60                         break;
  61                 buf = buffer + 4;
  62                 len -= 4;
  63                 while (len && isspace(*buf))
  64                         buf++, len--;
  65                 while (len && isspace(buf[len-1]))
  66                         buf[--len] = 0;
  67                 path = git_path("%.*s", len, buf);
  68         }
  69         if (len < 40 || get_sha1_hex(buffer, sha1))
  70                 return NULL;
  71         return path;
  72 }
  73
  74 int read_ref(const char *filename, unsigned char *sha1)
  75 {
  76         if (resolve_ref(filename, sha1, 1))
  77                 return 0;
  78         return -1;
  79 }
  80
  81 static int do_for_each_ref(const char *base, int (*fn)(const char *path, const unsigned char *sha1))
  82 {
  83         int retval = 0;
  84         DIR *dir = opendir(git_path("%s", base));
  85
  86         if (dir) {
  87                 struct dirent *de;
  88                 int baselen = strlen(base);
  89                 char *path = xmalloc(baselen + 257);
  90
  91                 if (!strncmp(base, "./", 2)) {
  92                         base += 2;
  93                         baselen -= 2;
  94                 }
  95                 memcpy(path, base, baselen);
  96                 if (baselen && base[baselen-1] != '/')
  97                         path[baselen++] = '/';
  98
  99                 while ((de = readdir(dir)) != NULL) {
 100                         unsigned char sha1[20];
 101                         struct stat st;
 102                         int namelen;
 103
 104                         if (de->d_name[0] == '.')
 105                                 continue;
 106                         namelen = strlen(de->d_name);
 107                         if (namelen > 255)
 108                                 continue;
 109                         memcpy(path + baselen, de->d_name, namelen+1);
 110                         if (stat(git_path("%s", path), &st) < 0)
 111                                 continue;
 112                         if (S_ISDIR(st.st_mode)) {
 113                                 retval = do_for_each_ref(path, fn);
 114                                 if (retval)
 115                                         break;
 116                                 continue;
 117                         }
 118                         if (read_ref(git_path("%s", path), sha1) < 0)
 119                                 continue;
 120                         if (!has_sha1_file(sha1))
 121                                 continue;
 122                         retval = fn(path, sha1);
 123                         if (retval)
 124                                 break;
 125                 }
 126                 free(path);
 127                 closedir(dir);
 128         }
 129         return retval;
 130 }
 131
 132 int head_ref(int (*fn)(const char *path, const unsigned char *sha1))
 133 {
 134         unsigned char sha1[20];
 135         if (!read_ref(git_path("HEAD"), sha1))
 136                 return fn("HEAD", sha1);
 137         return 0;
 138 }
 139
 140 int for_each_ref(int (*fn)(const char *path, const unsigned char *sha1))
 141 {
 142         return do_for_each_ref("refs", fn);
 143 }
 144
 145 static char *ref_file_name(const char *ref)
 146 {
 147         char *base = get_refs_directory();
 148         int baselen = strlen(base);
 149         int reflen = strlen(ref);
 150         char *ret = xmalloc(baselen + 2 + reflen);
 151         sprintf(ret, "%s/%s", base, ref);
 152         return ret;
 153 }
 154
 155 static char *ref_lock_file_name(const char *ref)
 156 {
 157         char *base = get_refs_directory();
 158         int baselen = strlen(base);
 159         int reflen = strlen(ref);
 160         char *ret = xmalloc(baselen + 7 + reflen);
 161         sprintf(ret, "%s/%s.lock", base, ref);
 162         return ret;
 163 }
 164
 165 int get_ref_sha1(const char *ref, unsigned char *sha1)
 166 {
 167         const char *filename;
 168
 169         if (check_ref_format(ref))
 170                 return -1;
 171         filename = git_path("refs/%s", ref);
 172         return read_ref(filename, sha1);
 173 }
 174
 175 static int lock_ref_file(const char *filename, const char *lock_filename,
 176                          const unsigned char *old_sha1)
 177 {
 178         int fd = open(lock_filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 179         unsigned char current_sha1[20];
 180         int retval;
 181         if (fd < 0) {
 182                 return error("Couldn't open lock file for %s: %s",
 183                              filename, strerror(errno));
 184         }
 185         retval = read_ref(filename, current_sha1);
 186         if (old_sha1) {
 187                 if (retval) {
 188                         close(fd);
 189                         unlink(lock_filename);
 190                         return error("Could not read the current value of %s",
 191                                      filename);
 192                 }
 193                 if (memcmp(current_sha1, old_sha1, 20)) {
 194                         close(fd);
 195                         unlink(lock_filename);
 196                         error("The current value of %s is %s",
 197                               filename, sha1_to_hex(current_sha1));
 198                         return error("Expected %s",
 199                                      sha1_to_hex(old_sha1));
 200                 }
 201         } else {
 202                 if (!retval) {
 203                         close(fd);
 204                         unlink(lock_filename);
 205                         return error("Unexpectedly found a value of %s for %s",
 206                                      sha1_to_hex(current_sha1), filename);
 207                 }
 208         }
 209         return fd;
 210 }
 211
 212 int lock_ref_sha1(const char *ref, const unsigned char *old_sha1)
 213 {
 214         char *filename;
 215         char *lock_filename;
 216         int retval;
 217         if (check_ref_format(ref))
 218                 return -1;
 219         filename = ref_file_name(ref);
 220         lock_filename = ref_lock_file_name(ref);
 221         retval = lock_ref_file(filename, lock_filename, old_sha1);
 222         free(filename);
 223         free(lock_filename);
 224         return retval;
 225 }
 226
 227 static int write_ref_file(const char *filename,
 228                           const char *lock_filename, int fd,
 229                           const unsigned char *sha1)
 230 {
 231         char *hex = sha1_to_hex(sha1);
 232         char term = '\n';
 233         if (write(fd, hex, 40) < 40 ||
 234             write(fd, &term, 1) < 1) {
 235                 error("Couldn't write %s\n", filename);
 236                 close(fd);
 237                 return -1;
 238         }
 239         close(fd);
 240         rename(lock_filename, filename);
 241         return 0;
 242 }
 243
 244 int write_ref_sha1(const char *ref, int fd, const unsigned char *sha1)
 245 {
 246         char *filename;
 247         char *lock_filename;
 248         int retval;
 249         if (fd < 0)
 250                 return -1;
 251         if (check_ref_format(ref))
 252                 return -1;
 253         filename = ref_file_name(ref);
 254         lock_filename = ref_lock_file_name(ref);
 255         retval = write_ref_file(filename, lock_filename, fd, sha1);
 256         free(filename);
 257         free(lock_filename);
 258         return retval;
 259 }
 260
 261 int check_ref_format(const char *ref)
 262 {
 263         char *middle;
 264         if (ref[0] == '.' || ref[0] == '/')
 265                 return -1;
 266         middle = strchr(ref, '/');
 267         if (!middle || !middle[1])
 268                 return -1;
 269         if (strchr(middle + 1, '/'))
 270                 return -1;
 271         return 0;
 272 }
 273
 274 int write_ref_sha1_unlocked(const char *ref, const unsigned char *sha1)
 275 {
 276         char *filename;
 277         char *lock_filename;
 278         int fd;
 279         int retval;
 280         if (check_ref_format(ref))
 281                 return -1;
 282         filename = ref_file_name(ref);
 283         lock_filename = ref_lock_file_name(ref);
 284         fd = open(lock_filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 285         if (fd < 0) {
 286                 error("Writing %s", lock_filename);
 287                 perror("Open");
 288         }
 289         retval = write_ref_file(filename, lock_filename, fd, sha1);
 290         free(filename);
 291         free(lock_filename);
 292         return retval;
 293 }