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

/*
 * 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>
#if HAVE_UNISTD_H
#include <unistd.h>
#endif
#include <stdlib.h>
#include <string.h>
#if HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
#if HAVE_SYS_STAT_H
#include <sys/stat.h>
#endif
#include <dirent.h>
#if HAVE_ERRNO_H
#include <errno.h>
#endif
#if 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);
    return;
}

/* 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: couldn't 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 = "Couldn't 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