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From: "M. A. Alves" <maa@liacc.up.pt>
Newsgroups: comp.lang.ada
Subject: Re: Ada Address = C pointer ?
Date: Tue, 30 Oct 2001 12:53:01 +0000 (GMT)
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Date: 2001-10-30T12:53:01+00:00

On Tue, 30 Oct 2001, Lutz Donnerhacke wrote:
> 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;

Seems right.  The C.Pointers tutorial I was missing, thanks a lot.

However, I am still not sure of the equivalence between null (a value of
Pointer) and NULL (C), i.e. is it garanteed that if the C function returns
NULL get_long_array returns null?

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