source: MondoRescue/branches/stable/mindi-busybox/e2fsprogs/blkid/save.c@ 821

/*
 * 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