Cygwin: opendir(3): move ENOTDIR check into main function

So far the check for a directory is in the fhandler::opendir
methods. Given that path_conv::check sets FILE_ATTRIBUTE_DIRECTORY
on virtual files either, we can move the check up into the
opendir(3) function. This avoids calling exists() twice when
calling opendir(3).

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

winsup/cygwin/dir.cc

@@ -61,13 +61,18 @@ opendir (const char *name)
       set_errno (fh->error ());
       res = NULL;
     }
-  else if (fh->exists ())
-    res = fh->opendir (-1);
-  else
+  else if (!fh->exists ())
     {
       set_errno (ENOENT);
       res = NULL;
     }
+  else if (!fh->pc.isdir ())
+    {
+      set_errno (ENOTDIR);
+      res = NULL;
+    }
+  else
+    res = fh->opendir (-1);
 
   if (!res && fh)
     delete fh;

winsup/cygwin/fhandler/disk_file.cc

@@ -2156,9 +2156,7 @@ fhandler_disk_file::opendir (int fd)
   DIR *dir;
   DIR *res = NULL;
 
-  if (!pc.isdir ())
-    set_errno (ENOTDIR);
-  else if ((dir = (DIR *) malloc (sizeof (DIR))) == NULL)
+  if ((dir = (DIR *) malloc (sizeof (DIR))) == NULL)
     set_errno (ENOMEM);
   else if ((dir->__d_dirname = (char *) malloc ( sizeof (struct __DIR_cache)))
 	   == NULL)

winsup/cygwin/fhandler/virtual.cc

@@ -45,9 +45,7 @@ fhandler_virtual::opendir (int fd)
   DIR *res = NULL;
   size_t len;
 
-  if (!virt_ftype_isdir (exists ()))
-    set_errno (ENOTDIR);
-  else if ((len = strlen (get_name ())) > PATH_MAX - 3)
+  if ((len = strlen (get_name ())) > PATH_MAX - 3)
     set_errno (ENAMETOOLONG);
   else if ((dir = (DIR *) malloc (sizeof (DIR))) == NULL)
     set_errno (ENOMEM);