/*      $OpenBSD: devname.c,v 1.15 2026/03/09 12:22:44 deraadt Exp $ */
/*
 * Copyright (c) 1989, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/stat.h>
#include <sys/types.h>

#include <db.h>
#include <dirent.h>
#include <fcntl.h>
#include <limits.h>
#include <paths.h>
#include <stdbool.h>
#include <string.h>
#include <stdlib.h>

static char *
devname_nodb(dev_t dev, mode_t type)
{
        static char buf[NAME_MAX + 1];
        char *name = NULL;
        struct dirent *dp;
        struct stat sb;
        DIR *dirp;

        if ((dirp = opendir(_PATH_DEV)) == NULL)
                return (NULL);
        while ((dp = readdir(dirp)) != NULL) {
                if (dp->d_type != DT_UNKNOWN && DTTOIF(dp->d_type) != type)
                        continue;
                if (fstatat(dirfd(dirp), dp->d_name, &sb, AT_SYMLINK_NOFOLLOW)
                    || sb.st_rdev != dev || (sb.st_mode & S_IFMT) != type)
                        continue;
                strlcpy(buf, dp->d_name, sizeof(buf));
                name = buf;
                break;
        }
        closedir(dirp);
        return (name);
}

/*
 * Keys in dev.db are a mode_t followed by a dev_t.  The former is the
 * type of the file (mode & S_IFMT), the latter is the st_rdev field.
 * Note that the structure may contain padding.
 */
char *
devname(dev_t dev, mode_t type)
{
        static DB *db;
        static bool failure;
        struct {
                mode_t type;
                dev_t dev;
        } bkey;
        DBT data, key;
        char *name = NULL;

        if (!db && !failure) {
                if (!(db = __hash_open(_PATH_DEVDB, -1, O_RDONLY, 0, NULL, 0)))
                        failure = true;
        }
        if (!failure) {
                /* Be sure to clear any padding that may be found in bkey.  */
                memset(&bkey, 0, sizeof(bkey));
                bkey.dev = dev;
                bkey.type = type;
                key.data = &bkey;
                key.size = sizeof(bkey);
                if ((db->get)(db, &key, &data, 0) == 0)
                        name = data.data;
        } else {
                name = devname_nodb(dev, type);
        }
        return (name ? name : "??");
}
DEF_WEAK(devname);