refs.c

   1 #include "refs.h"
   2 #include "cache.h"
   3
   4 #include <errno.h>
   5
   6 static char *ref_file_name(const char *ref)
   7 {
   8         char *base = get_refs_directory();
   9         int baselen = strlen(base);
  10         int reflen = strlen(ref);
  11         char *ret = xmalloc(baselen + 2 + reflen);
  12         sprintf(ret, "%s/%s", base, ref);
  13         return ret;
  14 }
  15
  16 static char *ref_lock_file_name(const char *ref)
  17 {
  18         char *base = get_refs_directory();
  19         int baselen = strlen(base);
  20         int reflen = strlen(ref);
  21         char *ret = xmalloc(baselen + 7 + reflen);
  22         sprintf(ret, "%s/%s.lock", base, ref);
  23         return ret;
  24 }
  25
  26 static int read_ref_file(const char *filename, unsigned char *sha1) {
  27         int fd = open(filename, O_RDONLY);
  28         char hex[41];
  29         if (fd < 0) {
  30                 return error("Couldn't open %s\n", filename);
  31         }
  32         if ((read(fd, hex, 41) < 41) ||
  33             (hex[40] != '\n') ||
  34             get_sha1_hex(hex, sha1)) {
  35                 error("Couldn't read a hash from %s\n", filename);
  36                 close(fd);
  37                 return -1;
  38         }
  39         close(fd);
  40         return 0;
  41 }
  42
  43 int get_ref_sha1(const char *ref, unsigned char *sha1)
  44 {
  45         char *filename;
  46         int retval;
  47         if (check_ref_format(ref))
  48                 return -1;
  49         filename = ref_file_name(ref);
  50         retval = read_ref_file(filename, sha1);
  51         free(filename);
  52         return retval;
  53 }
  54
  55 static int lock_ref_file(const char *filename, const char *lock_filename,
  56                          const unsigned char *old_sha1)
  57 {
  58         int fd = open(lock_filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
  59         unsigned char current_sha1[20];
  60         int retval;
  61         if (fd < 0) {
  62                 return error("Couldn't open lock file for %s: %s",
  63                              filename, strerror(errno));
  64         }
  65         retval = read_ref_file(filename, current_sha1);
  66         if (old_sha1) {
  67                 if (retval) {
  68                         close(fd);
  69                         unlink(lock_filename);
  70                         return error("Could not read the current value of %s",
  71                                      filename);
  72                 }
  73                 if (memcmp(current_sha1, old_sha1, 20)) {
  74                         close(fd);
  75                         unlink(lock_filename);
  76                         error("The current value of %s is %s",
  77                               filename, sha1_to_hex(current_sha1));
  78                         return error("Expected %s",
  79                                      sha1_to_hex(old_sha1));
  80                 }
  81         } else {
  82                 if (!retval) {
  83                         close(fd);
  84                         unlink(lock_filename);
  85                         return error("Unexpectedly found a value of %s for %s",
  86                                      sha1_to_hex(current_sha1), filename);
  87                 }
  88         }
  89         return fd;
  90 }
  91
  92 int lock_ref_sha1(const char *ref, const unsigned char *old_sha1)
  93 {
  94         char *filename;
  95         char *lock_filename;
  96         int retval;
  97         if (check_ref_format(ref))
  98                 return -1;
  99         filename = ref_file_name(ref);
 100         lock_filename = ref_lock_file_name(ref);
 101         retval = lock_ref_file(filename, lock_filename, old_sha1);
 102         free(filename);
 103         free(lock_filename);
 104         return retval;
 105 }
 106
 107 static int write_ref_file(const char *filename,
 108                           const char *lock_filename, int fd,
 109                           const unsigned char *sha1)
 110 {
 111         char *hex = sha1_to_hex(sha1);
 112         char term = '\n';
 113         if (write(fd, hex, 40) < 40 ||
 114             write(fd, &term, 1) < 1) {
 115                 error("Couldn't write %s\n", filename);
 116                 close(fd);
 117                 return -1;
 118         }
 119         close(fd);
 120         rename(lock_filename, filename);
 121         return 0;
 122 }
 123
 124 int write_ref_sha1(const char *ref, int fd, const unsigned char *sha1)
 125 {
 126         char *filename;
 127         char *lock_filename;
 128         int retval;
 129         if (fd < 0)
 130                 return -1;
 131         if (check_ref_format(ref))
 132                 return -1;
 133         filename = ref_file_name(ref);
 134         lock_filename = ref_lock_file_name(ref);
 135         retval = write_ref_file(filename, lock_filename, fd, sha1);
 136         free(filename);
 137         free(lock_filename);
 138         return retval;
 139 }
 140
 141 int check_ref_format(const char *ref)
 142 {
 143         char *middle;
 144         if (ref[0] == '.' || ref[0] == '/')
 145                 return -1;
 146         middle = strchr(ref, '/');
 147         if (!middle || !middle[1])
 148                 return -1;
 149         if (strchr(middle + 1, '/'))
 150                 return -1;
 151         return 0;
 152 }
 153
 154 int write_ref_sha1_unlocked(const char *ref, const unsigned char *sha1)
 155 {
 156         char *filename;
 157         char *lock_filename;
 158         int fd;
 159         int retval;
 160         if (check_ref_format(ref))
 161                 return -1;
 162         filename = ref_file_name(ref);
 163         lock_filename = ref_lock_file_name(ref);
 164         fd = open(lock_filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 165         if (fd < 0) {
 166                 error("Writing %s", lock_filename);
 167                 perror("Open");
 168         }
 169         retval = write_ref_file(filename, lock_filename, fd, sha1);
 170         free(filename);
 171         free(lock_filename);
 172         return retval;
 173 }