lib/blkid/save.c

   1 /*
   2  * save.c - write the cache struct to disk
   3  *
   4  * Copyright (C) 2001 by Andreas Dilger
   5  *
   6  * %Begin-Header%
   7  * This file may be redistributed under the terms of the
   8  * GNU Lesser General Public License.
   9  * %End-Header%
  10  */
  11
  12 #include <stdio.h>
  13 #include <string.h>
  14 #include <stdlib.h>
  15 #include <unistd.h>
  16 #include <sys/types.h>
  17 #ifdef HAVE_SYS_STAT_H
  18 #include <sys/stat.h>
  19 #endif
  20 #ifdef HAVE_SYS_MKDEV_H
  21 #include <sys/mkdev.h>
  22 #endif
  23 #ifdef HAVE_ERRNO_H
  24 #include <errno.h>
  25 #endif
  26 #include "blkid/blkid.h"
  27
  28 #ifdef DEBUG_SAVE
  29 #define DEB_SAVE(fmt, arg...) printf("save: " fmt, ## arg)
  30 #else
  31 #define DEB_SAVE(fmt, arg...) do {} while (0)
  32 #endif
  33
  34 static int save_dev(blkid_dev *dev, FILE *file)
  35 {
  36         struct list_head *p;
  37
  38         if (!dev)
  39                 return 0;
  40
  41         DEB_SAVE("device %s, type %s\n", dev->bid_name, dev->bid_type);
  42
  43         fprintf(file,
  44                 "<device TYPE=\"%s\" DEVNO=\"0x%04Lx\" ID=\"%d\" TIME=\"%Ld\"",
  45                 dev->bid_type, dev->bid_devno,
  46                 dev->bid_id, (long long)dev->bid_time);
  47         list_for_each(p, &dev->bid_tags) {
  48                 blkid_tag *tag = list_entry(p, blkid_tag, bit_tags);
  49                 if (strcmp(tag->bit_name, "TYPE"))
  50                         fprintf(file, " %s=\"%s\"", tag->bit_name,tag->bit_val);
  51         }
  52         fprintf(file, ">%s</device>\n", dev->bid_name);
  53
  54         return 0;
  55 }
  56
  57 int blkid_save_cache_file(blkid_cache *cache, FILE *file)
  58 {
  59         struct list_head *p;
  60         int ret = 0;
  61
  62         if (!cache || !file)
  63                 return -BLKID_ERR_PARAM;
  64
  65         if (list_empty(&cache->bic_devs) ||
  66             !cache->bic_flags & BLKID_BIC_FL_CHANGED)
  67                 return 0;
  68
  69         list_for_each(p, &cache->bic_devs) {
  70                 blkid_dev *dev = list_entry(p, blkid_dev, bid_devs);
  71                 if ((ret = save_dev(dev, file)) < 0)
  72                         break;
  73         }
  74
  75         if (ret >= 0) {
  76                 cache->bic_flags &= ~BLKID_BIC_FL_CHANGED;
  77                 ret = 1;
  78         }
  79
  80         return ret;
  81 }
  82
  83 /*
  84  * Write out the cache struct to the cache file on disk.
  85  */
  86 int blkid_save_cache(blkid_cache *cache, char *filename)
  87 {
  88         char tmp[4096] = { '\0', };
  89         char *opened = NULL;
  90         FILE *file = NULL;
  91         int ret;
  92
  93         if (!cache)
  94                 return -BLKID_ERR_PARAM;
  95
  96         if (list_empty(&cache->bic_devs) ||
  97             !(cache->bic_flags & BLKID_BIC_FL_CHANGED)) {
  98                 DEB_SAVE("empty cache, not saving\n");
  99                 return 0;
 100         }
 101
 102         if (!filename || !strlen(filename))
 103                 filename = BLKID_CACHE_FILE;
 104
 105         if (!strcmp(filename, "-") || !strcmp(filename, "stdout"))
 106                 file = stdout;
 107         else {
 108                 struct stat st;
 109
 110                 /* If we can't write to the cache file, then don't even try */
 111                 if (((ret = stat(filename, &st)) < 0 && errno != ENOENT) ||
 112                     (ret == 0 && access(filename, W_OK) < 0)) {
 113                         DEB_SAVE("can't write to cache file %s\n", filename);
 114                         return 0;
 115                 }
 116
 117                 /*
 118                  * Try and create a temporary file in the same directory so
 119                  * that in case of error we don't overwrite the cache file.
 120                  * If the cache file doesn't yet exist, it isn't a regular
 121                  * file (e.g. /dev/null or a socket), or we couldn't create
 122                  * a temporary file then we open it directly.
 123                  */
 124                 if (ret == 0 && S_ISREG(st.st_mode)) {
 125                         snprintf(tmp, sizeof(tmp) - 1, "%s-XXXXXX", filename);
 126                         if (mktemp(tmp) == tmp && *tmp != '\0') {
 127                                 file = fopen(tmp, "w");
 128                                 opened = tmp;
 129                         }
 130                 }
 131
 132                 if (!file) {
 133                         file = fopen(filename, "w");
 134                         opened = filename;
 135                 }
 136
 137                 DEB_SAVE("cache file %s (really %s)\n", filename, opened);
 138
 139                 if (!file) {
 140                         perror(opened);
 141                         return errno;
 142                 }
 143         }
 144
 145         ret = blkid_save_cache_file(cache, file);
 146
 147         if (file != stdout) {
 148                 fclose(file);
 149                 if (opened != filename) {
 150                         if (ret < 0) {
 151                                 unlink(opened);
 152                                 DEB_SAVE("unlinked temp cache %s\n", opened);
 153                         } else {
 154                                 char backup[4096];
 155
 156                                 snprintf(backup, sizeof(backup) - 1, "%s.old",
 157                                          filename);
 158                                 unlink(backup);
 159                                 link(filename, backup);
 160                                 rename(opened, filename);
 161                                 DEB_SAVE("moved temp cache %s\n", opened);
 162                         }
 163                 }
 164         }
 165
 166         return ret;
 167 }
 168
 169 #ifdef TEST_PROGRAM
 170 int main(int argc, char **argv)
 171 {
 172         blkid_cache *cache = NULL;
 173         int ret;
 174
 175         if (argc > 2) {
 176                 fprintf(stderr, "Usage: %s [filename]\n"
 177                         "Test loading/saving a cache (filename)\n", argv[0]);
 178                 exit(1);
 179         }
 180         if ((ret = blkid_probe_all(&cache) < 0))
 181                 fprintf(stderr, "error probing devices\n");
 182         else if ((ret = blkid_save_cache(cache, argv[1])) < 0)
 183                 fprintf(stderr, "error %d saving cache to %s\n", ret,
 184                         argv[1] ? argv[1] : BLKID_CACHE_FILE);
 185
 186         blkid_free_cache(cache);
 187
 188         return ret;
 189 }
 190 #endif