How to hide instantiation of Direct_IO?

[Dale Stanbrough <dale@goanna.cs.rmit.EDU.AU>]

I'ld like to develop a package on top of the rather low level Direct_IO,
but prevent access to the instantiation of Direct_IO itself. 

I could do this by instantiating direct_io in a private part of a 
package, and then declare higher level routines in child packages which 
for the most part, simply forward the work onto the equivalent direct_io
routines.

However there seems no way to declare a type Count for my higher level
package such that it has the same range as that defined in Direct_IO
(type Count is 0..implementation-defined) - I can't reference the 
private instantiation - 'cos it's private!

Is there _any_ way around this problem? The _only_ solution I can think
of is not to declare a type, and just have a rather yucky function...

	function Max_File_Size return Integer; -- truly non portable!
	
	function Size(File : My_File_Type) return Integer;



Dale