Re: C array to Ada pointer to unconstrained array without copyingmemory

[Duncan Sands <duncan.sands@math.u-psud.fr>]

On Wednesday 08 October 2003 00:52, Chad R. Meiners wrote:
> "Chad R. Meiners" <crmeiners@hotmail.com> wrote in message
> news:blvfo6$q6s$1@msunews.cl.msu.edu...
>
> > declare
> >     C_Data_Ptr       :  Systems.Address := To_Address(My_C_Ptr);
> >     C_Data_Length :  Natural   := ...;
> >
> >     type My_Ada_Type_Element is ...;
> >     type My_Ada_Array is array(Natural range <>) of My_Ada_Type_Element;
> >
> >     subtype My_C_Data_As_An_Ada_Array_Type is
> > My_Ada_Array(1..C_Data_Length);
> >     package My_Converter is new
> > Address_To_Access_Conversions(My_C_Data_As_An_Ada_Array_Type);
> >     C_Data_In_Ada : My_Ada_Array renames
> > My_Converter.To_Pointer(C_Data_Ptr).all;
> >     -- No copying of the array done, but the array dope that you want is
> > built from the subtype information.
> > begin
> > ...
> > end;
>
> I should probably add that you can just get the pointer with
>
> My_Ada_Array_Ptr : My_Converter.Object_Pointer :=
> My_Converter.To_Pointer(C_Data_Ptr);
>
> I believe that this satisfies your needs?

Not in the slightest.  Once you leave this local block, the pointer is
unusable because the array dope, stored as a local variable of the
block, will disappear.  The data continues to hang around of course.

Thanks anyway,

Duncan.