Re: How to pass two dimensional arrays to C

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

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.

> 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.

>       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