/* vi: set sw=4 ts=4: */
/*
 * devno.c - find a particular device by its device number (major/minor)
 *
 * Copyright (C) 2000, 2001, 2003 Theodore Ts'o
 * Copyright (C) 2001 Andreas Dilger
 *
 * %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>
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#include <stdlib.h>
#include <string.h>
#ifdef HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
#include <sys/stat.h>
#include <dirent.h>
#ifdef HAVE_ERRNO_H
#include <errno.h>
#endif
#ifdef HAVE_SYS_MKDEV_H
#include <sys/mkdev.h>
#endif

#include "blkidP.h"

struct dir_list {
        char    *name;
        struct dir_list *next;
};

char *blkid_strndup(const char *s, int length)
{
        char *ret;

        if (!s)
                return NULL;

        if (!length)
                length = strlen(s);

        ret = xmalloc(length + 1);
        strncpy(ret, s, length);
        ret[length] = '\0';
        return ret;
}

char *blkid_strdup(const char *s)
{
        return blkid_strndup(s, 0);
}

/*
 * This function adds an entry to the directory list
 */
static void add_to_dirlist(const char *name, struct dir_list **list)
{
        struct dir_list *dp;

        dp = xmalloc(sizeof(struct dir_list));
        dp->name = blkid_strdup(name);
        dp->next = *list;
        *list = dp;
}

/*
 * This function frees a directory list
 */
static void free_dirlist(struct dir_list **list)
{
        struct dir_list *dp, *next;

        for (dp = *list; dp; dp = next) {
                next = dp->next;
                free(dp->name);
                free(dp);
        }
        *list = NULL;
}

static void scan_dir(char *dir_name, dev_t devno, struct dir_list **list,
                            char **devname)
{
        DIR     *dir;
        struct dirent *dp;
        char    path[1024];
        int     dirlen;
        struct stat st;

        if ((dir = opendir(dir_name)) == NULL)
                return;
        dirlen = strlen(dir_name) + 2;
        while ((dp = readdir(dir)) != 0) {
                if (dirlen + strlen(dp->d_name) >= sizeof(path))
                        continue;

                if (dp->d_name[0] == '.' &&
                    ((dp->d_name[1] == 0) ||
                     ((dp->d_name[1] == '.') && (dp->d_name[2] == 0))))
                        continue;

                sprintf(path, "%s/%s", dir_name, dp->d_name);
                if (stat(path, &st) < 0)
                        continue;

                if (S_ISDIR(st.st_mode))
                        add_to_dirlist(path, list);
                else if (S_ISBLK(st.st_mode) && st.st_rdev == devno) {
                        *devname = blkid_strdup(path);
                        DBG(DEBUG_DEVNO,
                            printf("found 0x%llx at %s (%p)\n", devno,
                                   path, *devname));
                        break;
                }
        }
        closedir(dir);
}

/* Directories where we will try to search for device numbers */
const char *blkid_devdirs[] = { "/devices", "/devfs", "/dev", NULL };

/*
 * This function finds the pathname to a block device with a given
 * device number.  It returns a pointer to allocated memory to the
 * pathname on success, and NULL on failure.
 */
char *blkid_devno_to_devname(dev_t devno)
{
        struct dir_list *list = NULL, *new_list = NULL;
        char *devname = NULL;
        const char **dir;

        /*
         * Add the starting directories to search in reverse order of
         * importance, since we are using a stack...
         */
        for (dir = blkid_devdirs; *dir; dir++)
                add_to_dirlist(*dir, &list);

        while (list) {
                struct dir_list *current = list;

                list = list->next;
                DBG(DEBUG_DEVNO, printf("directory %s\n", current->name));
                scan_dir(current->name, devno, &new_list, &devname);
                free(current->name);
                free(current);
                if (devname)
                        break;
                /*
                 * If we're done checking at this level, descend to
                 * the next level of subdirectories. (breadth-first)
                 */
                if (list == NULL) {
                        list = new_list;
                        new_list = NULL;
                }
        }
        free_dirlist(&list);
        free_dirlist(&new_list);

        if (!devname) {
                DBG(DEBUG_DEVNO,
                    printf("blkid: cannot find devno 0x%04lx\n",
                           (unsigned long) devno));
        } else {
                DBG(DEBUG_DEVNO,
                    printf("found devno 0x%04llx as %s\n", devno, devname));
        }


        return devname;
}

#ifdef TEST_PROGRAM
int main(int argc, char** argv)
{
        char    *devname, *tmp;
        int     major, minor;
        dev_t   devno;
        const char *errmsg = "Cannot parse %s: %s\n";

        blkid_debug_mask = DEBUG_ALL;
        if ((argc != 2) && (argc != 3)) {
                fprintf(stderr, "Usage:\t%s device_number\n\t%s major minor\n"
                        "Resolve a device number to a device name\n",
                        argv[0], argv[0]);
                exit(1);
        }
        if (argc == 2) {
                devno = strtoul(argv[1], &tmp, 0);
                if (*tmp) {
                        fprintf(stderr, errmsg, "device number", argv[1]);
                        exit(1);
                }
        } else {
                major = strtoul(argv[1], &tmp, 0);
                if (*tmp) {
                        fprintf(stderr, errmsg, "major number", argv[1]);
                        exit(1);
                }
                minor = strtoul(argv[2], &tmp, 0);
                if (*tmp) {
                        fprintf(stderr, errmsg, "minor number", argv[2]);
                        exit(1);
                }
                devno = makedev(major, minor);
        }
        printf("Looking for device 0x%04Lx\n", devno);
        devname = blkid_devno_to_devname(devno);
        free(devname);
        return 0;
}
#endif