Cygwin: change virtual_ftype_t to not rely on negative values

So far negative values were denoting files, positive values
denoting directories.  We should prefer a less error prone
method.  Redefine virtual_ftype_t to contain only positive
values and replace checks for negativ or positive values with
inline functions virt_ftype_isfile() and virt_ftype_isdir().

Drop outdcated comments referring to numerical virtual_ftype_t
values.

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

winsup/cygwin/fhandler.h

@@ -126,20 +126,33 @@ enum del_lock_called_from {
 };
 
 enum virtual_ftype_t {
-  virt_fdsymlink = -8,	/* Fd symlink (e.g. /proc/<PID>/fd/0) */
-  virt_blk = -7,	/* Block special */
-  virt_chr = -6,	/* Character special */
-  virt_fsfile = -5,	/* FS-based file via /proc/sys */
-  virt_socket = -4,	/* Socket */
-  virt_pipe = -3,	/* Pipe */
-  virt_symlink = -2,	/* Symlink */
-  virt_file = -1,	/* Regular file */
-  virt_none = 0,	/* Invalid, Error */
-  virt_directory = 1,	/* Directory */
-  virt_rootdir = 2,	/* Root directory of virtual FS */
-  virt_fsdir = 3,	/* FS-based directory via /proc/sys */
+  virt_none	 = 0x0000,	/* Invalid, Error */
+  virt_file	 = 0x0001,	/* Regular file */
+  virt_symlink	 = 0x0002,	/* Symlink */
+  virt_pipe	 = 0x0003,	/* Pipe */
+  virt_socket	 = 0x0004,	/* Socket */
+  virt_chr	 = 0x0005,	/* Character special */
+  virt_blk	 = 0x0006,	/* Block special */
+  virt_fdsymlink = 0x0007,	/* Fd symlink (e.g. /proc/<PID>/fd/0) */
+  virt_fsfile	 = 0x0008,	/* FS-based file via /proc/sys */
+  virt_dir_type	 = 0x1000,
+  virt_directory = 0x1001,	/* Directory */
+  virt_rootdir	 = 0x1002,	/* Root directory of virtual FS */
+  virt_fsdir	 = 0x1003,	/* FS-based directory via /proc/sys */
 };
 
+static inline bool
+virt_ftype_isfile (virtual_ftype_t _f)
+{
+  return _f != virt_none && !(_f & virt_dir_type);
+}
+
+static inline bool
+virt_ftype_isdir (virtual_ftype_t _f)
+{
+  return _f & virt_dir_type;
+}
+
 class fhandler_base
 {
   friend class dtable;

winsup/cygwin/fhandler_netdrive.cc

@@ -145,8 +145,6 @@ create_thread_and_wait (int what, PVOID in, PVOID out, DWORD outsize,
   return ndi.ret;
 }
 
-/* Returns 0 if path doesn't exist, >0 if path is a directory,
-   -1 if path is a file, -2 if it's a symlink.  */
 virtual_ftype_t
 fhandler_netdrive::exists ()
 {

winsup/cygwin/fhandler_proc.cc

@@ -168,8 +168,6 @@ fhandler_proc::get_proc_fhandler (const char *path)
     return FH_PROC;
 }
 
-/* Returns 0 if path doesn't exist, >0 if path is a directory,
-   -1 if path is a file, -2 if it's a symlink.  */
 virtual_ftype_t
 fhandler_proc::exists ()
 {

winsup/cygwin/fhandler_process.cc

@@ -169,7 +169,7 @@ fhandler_process::fstat (struct stat *buf)
       buf->st_uid = p->uid;
       buf->st_gid = p->gid;
       buf->st_mode |= S_IFDIR | S_IXUSR | S_IXGRP | S_IXOTH;
-      if (file_type == 1)
+      if (file_type == virt_directory)
 	buf->st_nlink = 2;
       else
 	buf->st_nlink = 3;

winsup/cygwin/fhandler_procnet.cc

@@ -41,10 +41,6 @@ static const virt_tab_t procnet_tab[] =
 static const int PROCNET_LINK_COUNT =
   (sizeof (procnet_tab) / sizeof (virt_tab_t)) - 1;
 
-/* Returns 0 if path doesn't exist, >0 if path is a directory,
- * -1 if path is a file, -2 if path is a symlink, -3 if path is a pipe,
- * -4 if path is a socket.
- */
 virtual_ftype_t
 fhandler_procnet::exists ()
 {

winsup/cygwin/fhandler_procsys.cc

@@ -39,8 +39,6 @@ const size_t procsys_len = sizeof (procsys) - 1;
 	  RtlInitUnicodeString ((p), namebuf); \
 	}
 
-/* Returns 0 if path doesn't exist, >0 if path is a directory,
-   -1 if path is a file, -2 if it's a symlink.  */
 virtual_ftype_t
 fhandler_procsys::exists (struct stat *buf)
 {

winsup/cygwin/fhandler_procsysvipc.cc

@@ -52,9 +52,6 @@ static const virt_tab_t procsysvipc_tab[] =
 static const int PROCSYSVIPC_LINK_COUNT =
   (sizeof (procsysvipc_tab) / sizeof (virt_tab_t)) - 1;
 
-/* Returns 0 if path doesn't exist, >0 if path is a directory,
- * -1 if path is a file.
- */
 virtual_ftype_t
 fhandler_procsysvipc::exists ()
 {

winsup/cygwin/fhandler_registry.cc

@@ -306,13 +306,8 @@ multi_wcstombs (char *dst, size_t len, const wchar_t *src, size_t nwc)
   return sum;
 }
 
-/* Returns 0 if path doesn't exist, >0 if path is a directory,
- * <0 if path is a file.
- *
- * We open the last key but one and then enum it's sub-keys and values to see if the
- * final component is there. This gets round the problem of not having security access
- * to the final key in the path.
- */
+/* Returns 0 if path doesn't exist, otherwise a virtual_ftype_t value
+   specifying the exact file type. */
 virtual_ftype_t
 fhandler_registry::exists ()
 {
@@ -502,7 +497,7 @@ fhandler_registry::fstat (struct stat *buf)
       const char *path = get_name () + proc_len + prefix_len + 2;
       hKey =
 	open_key (path, STANDARD_RIGHTS_READ | KEY_QUERY_VALUE, wow64,
-		  (file_type < virt_none) ? true : false);
+		  virt_ftype_isfile (file_type) ? true : false);
 
       if (hKey == HKEY_PERFORMANCE_DATA)
 	/* RegQueryInfoKey () always returns write time 0,
@@ -519,7 +514,7 @@ fhandler_registry::fstat (struct stat *buf)
 	      to_timestruc_t ((PLARGE_INTEGER) &ftLastWriteTime, &buf->st_mtim);
 	      buf->st_ctim = buf->st_birthtim = buf->st_mtim;
 	      time_as_timestruc_t (&buf->st_atim);
-	      if (file_type > virt_none)
+	      if (virt_ftype_isdir (file_type))
 		buf->st_nlink = subkey_count + 2;
 	      else
 		{

winsup/cygwin/fhandler_virtual.cc

@@ -45,7 +45,7 @@ fhandler_virtual::opendir (int fd)
   DIR *res = NULL;
   size_t len;
 
-  if (exists () <= 0)
+  if (!virt_ftype_isdir (exists ()))
     set_errno (ENOTDIR);
   else if ((len = strlen (get_name ())) > PATH_MAX - 3)
     set_errno (ENAMETOOLONG);