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devno.c

/*
 * 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 = malloc(length + 1);
      if (ret) {
            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 = malloc(sizeof(struct dir_list));
      if (!dp)
            return;
      dp->name = blkid_strdup(name);
      if (!dp->name) {
            free(dp);
            return;
      }
      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 *dirname, 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(dirname)) == NULL)
            return;
      dirlen = strlen(dirname) + 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", dirname, 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%Lx 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%04Lx 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);
      if (devname)
            free(devname);
      return 0;
}
#endif

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