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From: lutz@iks-jena.de (Lutz Donnerhacke)
Newsgroups: comp.lang.ada
Subject: Re: Ada Address = C pointer ?
Date: Tue, 30 Oct 2001 12:02:16 +0000 (UTC)
Organization: IKS GmbH Jena
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Date: 2001-10-30T12:02:16+00:00
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* M. A. Alves wrote:
>I am in fact using Address and Access_To_Address_Conversions(*) because I
>simply did not find out how to do the trick otherwise.  For example, the C
>function is returning an array of unsigned long.  I want to access that
>array without copying it.  How can you do that with Interfaces.C.Strings
>or even Interfaces.C.Pointers?

How about:

with Interfaces.C.Pointers;

procedure t is
   type long_array is array (Integer range <>) of aliased Interfaces.C.long;
   
   package long_pointers is new Interfaces.C.Pointers (
     Index              => Integer,
     Element            => Interfaces.C.long,
     Element_Array      => long_array,
     Default_Terminator => 0
   );
   
   function get (a : long_pointers.Pointer; i : Interfaces.C.ptrdiff_t)
     return Interfaces.C.long is
     
      use type long_pointers.Pointer;
      
      v : long_array (1 .. 1) :=
        long_pointers.Value (a + i, Interfaces.C.ptrdiff_t (1));
   begin
      return v (1);
   end get;
   pragma Inline (get);
   
   --  real work starts here
   
   function get_long_array return long_pointers.Pointer;
   pragma Import (C, get_long_array);
   
   my_array : constant long_pointers.Pointer := get_long_array;
begin
   ... := get (my_array, 4);
end t;