compat/fdopendir.c

   1 /*****************************************************************************
   2  * fdopendir.c: POSIX fdopendir replacement
   3  *****************************************************************************
   4  * Copyright © 2011 Rémi Denis-Courmont
   5  *
   6  * This program is free software; you can redistribute it and/or modify it
   7  * under the terms of the GNU Lesser General Public License as published by
   8  * the Free Software Foundation; either version 2.1 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  14  * GNU Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public License
  17  * along with this program; if not, write to the Free Software Foundation,
  18  * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
  19  *****************************************************************************/
  20
  21 #ifdef HAVE_CONFIG_H
  22 # include <config.h>
  23 #endif
  24
  25 #include <stdio.h>
  26 #include <errno.h>
  27 #include <sys/types.h>
  28 #include <sys/stat.h>
  29 #include <fcntl.h>
  30 #include <unistd.h>
  31 #include <dirent.h>
  32
  33 DIR *fdopendir (int fd)
  34 {
  35 #ifdef F_GETFL
  36     /* Check read permission on file descriptor */
  37     int mode = fcntl (fd, F_GETFL);
  38     if (mode == -1 || (mode & O_ACCMODE) == O_WRONLY)
  39     {
  40         errno = EBADF;
  41         return NULL;
  42     }
  43 #endif
  44     /* Check directory file type */
  45     struct stat st;
  46     if (fstat (fd, &st))
  47         return NULL;
  48
  49     if (!S_ISDIR (st.st_mode))
  50     {
  51         errno = ENOTDIR;
  52         return NULL;
  53     }
  54
  55     /* Try to open the directory through /proc where available.
  56      * Not all operating systems support this. Fix your libc! */
  57     char path[sizeof ("/proc/self/fd/") + 3 * sizeof (int)];
  58     sprintf (path, "/proc/self/fd/%u", fd);
  59
  60     DIR *dir = opendir (path);
  61     if (dir != NULL)
  62     {
  63         close (fd);
  64         return dir;
  65     }
  66
  67     /* Hide impossible errors for fdopendir() */
  68     switch (errno)
  69     {
  70         case EACCES:
  71 #ifdef ELOOP
  72         case ELOOP:
  73 #endif
  74         case ENAMETOOLONG:
  75         case ENOENT:
  76         case EMFILE:
  77         case ENFILE:
  78             errno = EIO;
  79     }
  80     return NULL;
  81 }