fdopendir: split into its own module

* lib/openat.c (fdopendir): Move...
* lib/fdopendir.c: ...into new file.
* modules/fdopendir: New module.
* m4/fdopendir.m4 (gl_FUNC_FDOPENDIR): New file.
* modules/openat (Depends-on): Add fdopendir.
* m4/openat.m4 (gl_FUNC_OPENAT): No longer need to check for
fdopendir here.
* modules/savedir (Depends-on): Only need fdopendir, not full
openat.
* lib/savedir.c (include): Use <dirent.h>, not "openat.h".
* lib/openat.h (fdopendir): Drop prototype.
* lib/dirent.in.h (fdopendir): Provide prototype.
* m4/dirent_h.m4 (gl_DIRENT_H_DEFAULTS): Add replacements.
* modules/dirent (Makefile.am): Substitute them.
* MODULES.html.sh (File system functions): Mention it.
* doc/posix-functions/fdopendir.texi (fdopendir): Likewise.
* modules/fdopendir-tests: New file.
* tests/test-fdopendir.c: Likewise.

Signed-off-by: Eric Blake <ebb9@byu.net>

1 files changed, 95 insertions, 0 deletions

diff --git a/lib/fdopendir.c b/lib/fdopendir.c
new file mode 100644
index 0000000000..70951562f4
--- /dev/null
+++ b/lib/fdopendir.c
@@ -0,0 +1,95 @@
+/* provide a replacement fdopendir function
+   Copyright (C) 2004-2009 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+/* written by Jim Meyering */
+
+#include <config.h>
+
+#include <dirent.h>
+
+#include <stdlib.h>
+#include <unistd.h>
+
+#include "openat.h"
+#include "openat-priv.h"
+#include "save-cwd.h"
+
+/* Replacement for Solaris' function by the same name.
+   <http://www.google.com/search?q=fdopendir+site:docs.sun.com>
+   First, try to simulate it via opendir ("/proc/self/fd/FD").  Failing
+   that, simulate it by doing save_cwd/fchdir/opendir(".")/restore_cwd.
+   If either the save_cwd or the restore_cwd fails (relatively unlikely),
+   then give a diagnostic and exit nonzero.
+   Otherwise, this function works just like Solaris' fdopendir.
+
+   W A R N I N G:
+   Unlike other fd-related functions, this one effectively consumes
+   its FD parameter.  The caller should not close or otherwise
+   manipulate FD if this function returns successfully.  Also, this
+   implementation does not guarantee that dirfd(fdopendir(n))==n;
+   the open directory stream may use a clone of FD, or have no
+   associated fd at all.  */
+DIR *
+fdopendir (int fd)
+{
+  struct saved_cwd saved_cwd;
+  int saved_errno;
+  DIR *dir;
+
+  char buf[OPENAT_BUFFER_SIZE];
+  char *proc_file = openat_proc_name (buf, fd, ".");
+  if (proc_file)
+    {
+      dir = opendir (proc_file);
+      saved_errno = errno;
+    }
+  else
+    {
+      dir = NULL;
+      saved_errno = EOPNOTSUPP;
+    }
+
+  /* If the syscall fails with an expected errno value, resort to
+     save_cwd/restore_cwd.  */
+  if (! dir && EXPECTED_ERRNO (saved_errno))
+    {
+      if (save_cwd (&saved_cwd) != 0)
+	openat_save_fail (errno);
+
+      if (fchdir (fd) != 0)
+	{
+	  dir = NULL;
+	  saved_errno = errno;
+	}
+      else
+	{
+	  dir = opendir (".");
+	  saved_errno = errno;
+
+	  if (restore_cwd (&saved_cwd) != 0)
+	    openat_restore_fail (errno);
+	}
+
+      free_cwd (&saved_cwd);
+    }
+
+  if (dir)
+    close (fd);
+  if (proc_file != buf)
+    free (proc_file);
+  errno = saved_errno;
+  return dir;
+}