python types, ino_t and off_t

Hi ports@,
I'm tying to port a python package that uses the dirent struct
defining the fields like this:

_fields_ = (
('d_ino', ctypes.c_uint32), # must be uint32, not ulong
('d_off', ctypes.c_long),
('d_reclen', ctypes.c_ushort),
('d_type', ctypes.c_ubyte),
('d_namlen', ctypes.c_ubyte),
('d_name', ctypes.c_char * 256),
)

Now, aren't ino_t and off_t architecture dependent ? If not, how do I
find the length of each types ?
The others are defined in the dirent description.
If dependent of the architecture, I should find a way of using the
real definitions in python...

Cheers.
Elias.