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 #ifdef HAVE_UNISTD_H
  31 # include <unistd.h>
  32 #endif
  33 #include <dirent.h>
  34
  35 DIR *fdopendir (int fd)
  36 {
  37 #ifdef F_GETFL
  38     /* Check read permission on file descriptor */
  39     int mode = fcntl (fd, F_GETFL);
  40     if (mode == -1 || (mode & O_ACCMODE) == O_WRONLY)
  41     {
  42         errno = EBADF;
  43         return NULL;
  44     }
  45 #endif
  46     /* Check directory file type */
  47     struct stat st;
  48     if (fstat (fd, &st))
  49         return NULL;
  50
  51     if (!S_ISDIR (st.st_mode))
  52     {
  53         errno = ENOTDIR;
  54         return NULL;
  55     }
  56
  57     /* Try to open the directory through /proc where available.
  58      * Not all operating systems support this. Fix your libc! */
  59     char path[sizeof ("/proc/self/fd/") + 3 * sizeof (int)];
  60     sprintf (path, "/proc/self/fd/%u", fd);
  61
  62     DIR *dir = opendir (path);
  63     if (dir != NULL)
  64     {
  65         close (fd);
  66         return dir;
  67     }
  68
  69     /* Hide impossible errors for fdopendir() */
  70     switch (errno)
  71     {
  72         case EACCES:
  73 #ifdef ELOOP
  74         case ELOOP:
  75 #endif
  76         case ENAMETOOLONG:
  77         case ENOENT:
  78         case EMFILE:
  79         case ENFILE:
  80             errno = EIO;
  81     }
  82     return NULL;
  83 }