text: /* vi: set sw=4 ts=4: */
  /*
   * save.c - write the cache struct to disk
   *
   * Copyright (C) 2001 by Andreas Dilger
   * Copyright (C) 2003 Theodore Ts'o
   *
   * %Begin-Header%
   * This file may be redistributed under the terms of the
   * GNU Lesser General Public License.
   * %End-Header%
   */
  
  #include <stdio.h>
  #include <string.h>
  #include <stdlib.h>
  #include <unistd.h>
  #include <sys/types.h>
  #ifdef HAVE_SYS_STAT_H
  #include <sys/stat.h>
  #endif
  #ifdef HAVE_SYS_MKDEV_H
  #include <sys/mkdev.h>
  #endif
  #ifdef HAVE_ERRNO_H
  #include <errno.h>
  #endif
  #include "blkidP.h"
  
  static int save_dev(blkid_dev dev, FILE *file)
  {
  	struct list_head *p;
  
  	if (!dev || dev->bid_name[0] != '/')
  		return 0;
  
  	DBG(DEBUG_SAVE,
  	    printf("device %s, type %s\n", dev->bid_name, dev->bid_type));
  
  	fprintf(file,
  		"<device DEVNO=\"0x%04lx\" TIME=\"%lu\"",
  		(unsigned long) dev->bid_devno, dev->bid_time);
  	if (dev->bid_pri)
  		fprintf(file, " PRI=\"%d\"", dev->bid_pri);
  	list_for_each(p, &dev->bid_tags) {
  		blkid_tag tag = list_entry(p, struct blkid_struct_tag, bit_tags);
  		fprintf(file, " %s=\"%s\"", tag->bit_name,tag->bit_val);
  	}
  	fprintf(file, ">%s</device>\n", dev->bid_name);
  
  	return 0;
  }
  
  /*
   * Write out the cache struct to the cache file on disk.
   */
  int blkid_flush_cache(blkid_cache cache)
  {
  	struct list_head *p;
  	char *tmp = NULL;
  	const char *opened = NULL;
  	const char *filename;
  	FILE *file = NULL;
  	int fd, ret = 0;
  	struct stat st;
  
  	if (!cache)
  		return -BLKID_ERR_PARAM;
  
  	if (list_empty(&cache->bic_devs) ||
  	    !(cache->bic_flags & BLKID_BIC_FL_CHANGED)) {
  		DBG(DEBUG_SAVE, printf("skipping cache file write\n"));
  		return 0;
  	}
  
  	filename = cache->bic_filename ? cache->bic_filename: BLKID_CACHE_FILE;
  
  	/* If we can't write to the cache file, then don't even try */
  	if (((ret = stat(filename, &st)) < 0 && errno != ENOENT) ||
  	    (ret == 0 && access(filename, W_OK) < 0)) {
  		DBG(DEBUG_SAVE,
  		    printf("can't write to cache file %s\n", filename));
  		return 0;
  	}
  
  	/*
  	 * Try and create a temporary file in the same directory so
  	 * that in case of error we don't overwrite the cache file.
  	 * If the cache file doesn't yet exist, it isn't a regular
  	 * file (e.g. /dev/null or a socket), or we couldn't create
  	 * a temporary file then we open it directly.
  	 */
  	if (ret == 0 && S_ISREG(st.st_mode)) {
  		tmp = xmalloc(strlen(filename) + 8);
  		sprintf(tmp, "%s-XXXXXX", filename);
  		fd = mkstemp(tmp);
  		if (fd >= 0) {
  			file = fdopen(fd, "w");
  			opened = tmp;
  		}
  		fchmod(fd, 0644);
  	}
  
  	if (!file) {
  		file = fopen(filename, "w");
  		opened = filename;
  	}
  
  	DBG(DEBUG_SAVE,
  	    printf("writing cache file %s (really %s)\n",
  		   filename, opened));
  
  	if (!file) {
  		ret = errno;
  		goto errout;
  	}
  
  	list_for_each(p, &cache->bic_devs) {
  		blkid_dev dev = list_entry(p, struct blkid_struct_dev, bid_devs);
  		if (!dev->bid_type)
  			continue;
  		if ((ret = save_dev(dev, file)) < 0)
  			break;
  	}
  
  	if (ret >= 0) {
  		cache->bic_flags &= ~BLKID_BIC_FL_CHANGED;
  		ret = 1;
  	}
  
  	fclose(file);
  	if (opened != filename) {
  		if (ret < 0) {
  			unlink(opened);
  			DBG(DEBUG_SAVE,
  			    printf("unlinked temp cache %s\n", opened));
  		} else {
  			char *backup;
  
  			backup = xmalloc(strlen(filename) + 5);
  			sprintf(backup, "%s.old", filename);
  			unlink(backup);
  			link(filename, backup);
  			free(backup);
  			rename(opened, filename);
  			DBG(DEBUG_SAVE,
  			    printf("moved temp cache %s\n", opened));
  		}
  	}
  
  errout:
  	free(tmp);
  	return ret;
  }
  
  #ifdef TEST_PROGRAM
  int main(int argc, char **argv)
  {
  	blkid_cache cache = NULL;
  	int ret;
  
  	blkid_debug_mask = DEBUG_ALL;
  	if (argc > 2) {
  		fprintf(stderr, "Usage: %s [filename]\n"
  			"Test loading/saving a cache (filename)\n", argv[0]);
  		exit(1);
  	}
  
  	if ((ret = blkid_get_cache(&cache, bb_dev_null)) != 0) {
  		fprintf(stderr, "%s: error creating cache (%d)\n",
  			argv[0], ret);
  		exit(1);
  	}
  	if ((ret = blkid_probe_all(cache)) < 0) {
  		fprintf(stderr, "error (%d) probing devices\n", ret);
  		exit(1);
  	}
  	cache->bic_filename = blkid_strdup(argv[1]);
  
  	if ((ret = blkid_flush_cache(cache)) < 0) {
  		fprintf(stderr, "error (%d) saving cache\n", ret);
  		exit(1);
  	}
  
  	blkid_put_cache(cache);
  
  	return ret;
  }
  #endif
  