Re: C array to ada record interface

[fjloma@andaluciajunta.es (Francisco Javier Loma Daza)]

Jeffrey Carter <spam@spam.com> wrote in message news:<W%kJc.3320$Qu5.3121@newsread2.news.pas.earthlink.net>...
> Francisco Javier Loma Daza wrote:
> 
> > struct
> > {
> >    int a,b,c:
> >    int len;
> >    struct b* arr;
> > } A;
> > 
> > And I would love to interface in Ada with a record with a discriminant
> > 
> > type B_array(len: Positive) is record
> >     arr: array of B(1..len);
> > end record;
> > 
> > type A(len: Positive) is
> >    a,b,c: Integer;
> >    arr:   A(len);
> > end record;
> 
> Assuming you meant
> 
>     Arr : B_Array (Len => Len);
> 
> this won't work. What you have from C is a pointer; the actual array may 
>   not even be contiguous with the struct. You'll have to do something like
> 
> type B_Ptr is access all B;
> pragma Convention (C, B_Ptr);
> 
> type A_Info is record
>     A, B, C : Interfaces.C.Int;
>     Len     : Interfaces.C.Int;
>     Arr     : B_Ptr;
> end record;
> pragma Convention (C, A_Info);
> 
> You only use these types when talking directly to C. For the rest of 
> your application, you use something like the record you presented, and 
> have your operations that talk to C convert between the 2.


Thanks, I think you understood well

I would want to use some more ada like array, you suggest to implement
that with accesors functions ... I was just wondering if it can be
done, the Len + Arr part, to be set up as an Ada array ...