1/* provide a replacement fdopendir function
2   Copyright (C) 2004-2010 Free Software Foundation, Inc.
3
4   This program is free software: you can redistribute it and/or modify
5   it under the terms of the GNU General Public License as published by
6   the Free Software Foundation; either version 3 of the License, or
7   (at your option) any later version.
8
9   This program is distributed in the hope that it will be useful,
10   but WITHOUT ANY WARRANTY; without even the implied warranty of
11   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12   GNU General Public License for more details.
13
14   You should have received a copy of the GNU General Public License
15   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
16
17/* written by Jim Meyering */
18
19#include <config.h>
20
21#include <dirent.h>
22
23#include <stdlib.h>
24#include <unistd.h>
25
26#if !HAVE_FDOPENDIR
27
28# include "openat.h"
29# include "openat-priv.h"
30# include "save-cwd.h"
31
32# if GNULIB_DIRENT_SAFER
33#  include "dirent--.h"
34# endif
35
36/* Replacement for Solaris' function by the same name.
37   <http://www.google.com/search?q=fdopendir+site:docs.sun.com>
38   First, try to simulate it via opendir ("/proc/self/fd/FD").  Failing
39   that, simulate it by using fchdir metadata, or by doing
40   save_cwd/fchdir/opendir(".")/restore_cwd.
41   If either the save_cwd or the restore_cwd fails (relatively unlikely),
42   then give a diagnostic and exit nonzero.
43   Otherwise, this function works just like Solaris' fdopendir.
44
45   W A R N I N G:
46   Unlike other fd-related functions, this one effectively consumes
47   its FD parameter.  The caller should not close or otherwise
48   manipulate FD if this function returns successfully.  Also, this
49   implementation does not guarantee that dirfd(fdopendir(n))==n;
50   the open directory stream may use a clone of FD, or have no
51   associated fd at all.  */
52DIR *
53fdopendir (int fd)
54{
55  int saved_errno;
56  DIR *dir;
57
58  char buf[OPENAT_BUFFER_SIZE];
59  char *proc_file = openat_proc_name (buf, fd, ".");
60  if (proc_file)
61    {
62      dir = opendir (proc_file);
63      saved_errno = errno;
64    }
65  else
66    {
67      dir = NULL;
68      saved_errno = EOPNOTSUPP;
69    }
70
71  /* If the syscall fails with an expected errno value, resort to
72     save_cwd/restore_cwd.  */
73  if (! dir && EXPECTED_ERRNO (saved_errno))
74    {
75# if REPLACE_FCHDIR
76      const char *name = _gl_directory_name (fd);
77      if (name)
78        dir = opendir (name);
79      saved_errno = errno;
80# else /* !REPLACE_FCHDIR */
81      struct saved_cwd saved_cwd;
82      if (save_cwd (&saved_cwd) != 0)
83        openat_save_fail (errno);
84
85      if (fchdir (fd) != 0)
86        {
87          dir = NULL;
88          saved_errno = errno;
89        }
90      else
91        {
92          dir = opendir (".");
93          saved_errno = errno;
94
95          if (restore_cwd (&saved_cwd) != 0)
96            openat_restore_fail (errno);
97        }
98
99      free_cwd (&saved_cwd);
100# endif /* !REPLACE_FCHDIR */
101    }
102
103  if (dir)
104    close (fd);
105  if (proc_file != buf)
106    free (proc_file);
107  errno = saved_errno;
108  return dir;
109}
110
111#else /* HAVE_FDOPENDIR */
112
113# include <errno.h>
114# include <sys/stat.h>
115
116# undef fdopendir
117
118/* Like fdopendir, but work around GNU/Hurd bug by validating FD.  */
119
120DIR *
121rpl_fdopendir (int fd)
122{
123  struct stat st;
124  if (fstat (fd, &st))
125    return NULL;
126  if (!S_ISDIR (st.st_mode))
127    {
128      errno = ENOTDIR;
129      return NULL;
130    }
131  return fdopendir (fd);
132}
133
134#endif /* HAVE_FDOPENDIR */
135