/* 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 = xfdopen_for_write(fd);
                        opened = tmp;
                }
                fchmod(fd, 0644);
        }

        if (!file) {
                file = fopen_for_write(filename);
                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