Re: How to pass two dimensional arrays to C

["Jerry" <lanceboyle@qwest.net>]

Dmitry A. Kazakov wrote:
> On 2 Aug 2006 01:20:34 -0700, Jerry wrote:
>
> > =============== my_common.ads
> > package My_Common is
> >     type Long_Float_Array_1D is array (Integer range <>) of aliased
> > Long_Float;
> >     type Long_Float_Array_2D is array (Integer range <>, integer range
> > <>) of aliased Long_Float;
>
> You cannot be sure that Integer is Interfaces.C.Int and Long_Float is
> Interfaces.C.Double.

My understanding is that with GNAT, these equivalences are guaranteed.
I know that what I've done is bad practice for portability, but I don't
think that it is the source of my problems. Please correct me if I am
wrong. However, I'll double-check this.

>
> > end My_Common;
> >
> > =============== plplotthin.ads
> > with
> >     Interfaces.C,
> >     Interfaces.C.Pointers,
> >     My_Common;
> > use
> >     Interfaces.C,
> >     Ada.Text_IO;
> >
> > package PLplotThin is
> >     subtype PLINT  is Integer;
> >     subtype PLFLT  is Long_Float;
>
> Same as above.
>
> >     subtype PL_Float_Array    is My_Common.Long_Float_Array_1D;
> >     subtype PL_Float_Array_2D is My_Common.Long_Float_Array_2D;
> >
> >     package PLFLT_Pointers is new Interfaces.C.Pointers
> >        (Index              => PLINT,
> >         Element            => PLFLT,
> >         Element_Array      => PL_Float_Array, -- was PLFLT_Array
> >         Default_Terminator => 0.0);
> >     subtype PLFLT_Ptr is PLFLT_Pointers.Pointer;
> >     type PLFLT_Ptr_Array is array (PLINT range <>) of aliased
> > PLFLT_Ptr;
> >
> >     procedure plmesh(
> > 		x   : PL_Float_Array;
> > 		y   : PL_Float_Array;
> > 		z   : PLFLT_Ptr_Array;
> > 		nx  : PLINT;
> > 		ny  : PLINT;
> > 		opt : PLINT);
> >     pragma Import(C, plmesh, "c_plmesh");
> > end PLplotThin;
> >
> > =============== plplot.adb
> > with
> >     PLplotThin,
> >     My_Common,
> >     Interfaces.C.Pointers,
> >     Interfaces.C;
> > use
> >     PLplotThin,
> >     My_Common,
> >     Interfaces.C;
> >
> > package body PLplot is
> >
> >     procedure Mesh_3D
> >        (x, y    : Long_Float_Array_1D;
> >         z       : in out Long_Float_Array_2D;
> >         Options : Integer) is
> >
> >         Index_Of_First_Column : Integer := z'First(2);
> >
> >        Pointer_Array : PLFLT_Ptr_Array(z'range(1));
> >
> >    begin
> >        for Index in z'range(1) loop
> >            Pointer_Array(Index) := z(Index, Index_Of_First_Column)'access;
>
> Use Unchecked_Access here.

I tried that before and got a segfault.

>
> >       end loop;
> >      plmesh(x, y, Pointer_Array, x'Length, y'Length, Options);
> >    end Mesh_3D;
> > end PLplot;
>
> --
> Regards,
> Dmitry A. Kazakov
> http://www.dmitry-kazakov.de

Best,
Jerry