Re: Memory Access

[Adam Beneschan <adam@irvine.com>]

On Nov 7, 2:21 pm, Adam Beneschan <a...@irvine.com> wrote:
>
> If you known the address of the array data, then something like this
> will work even if you don't know the address until runtime:
>
>     Data_Address : System.Address;
>     ...
> begin
>     -- do some stuff that sets Data_Address to the address.  Or you
>     -- could make
>     -- Data_Address be a parameter to a subroutine, or something
>     -- Then:
>
>     declare
>        Dev_Table : Dev_Table_Type (1 .. Num_Devs_Cnst);
>        for Dev_Table'Address use Data_Address;
>     begin
>        -- and you can use Dev_Table in here
>     end;
>
> This will work whether Num_Devs_Cnst is known at compile time or not.
> (The _Cnst makes it look like it's a constant that's known at compile
> time.  But it doesn't need to be.)

An alternative, if you don't want to use an Address clause:

with System.Address_To_Access_Conversions;

...
   Data_Address : System.Address;
begin
   -- set Data_Address to something as above
   declare
      subtype Constrained_Dev_Table is Dev_Table_Type (1 ..
Num_Devs_Cnst);
      package Dev_Table_Pointer is new
         System.Address_To_Access_Conversions (Constrained_Dev_Table);
      Dev_Table : Dev_Table_Pointer.Object_Pointer :=
         Dev_Table_Pointer.To_Pointer (Data_Address);
   begin
      ...
   end;

Dev_Table is now declared as an access (pointer) to a constrained
array subtype, rather than an array, but you should still be able to
use it in the same way.  This method still won't let you create a
Dev_Table_Ptr_Type that points to the array, though.

                       -- Adam