From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00 autolearn=ham
	autolearn_force=no version=3.4.4
X-Google-Thread: 103376,c1bdceb867926fdb
X-Google-NewGroupId: yes
X-Google-Attributes: gida07f3367d7,domainid0,public,usenet
X-Google-Language: ENGLISH,ASCII-7-bit
Path: 
 g2news1.google.com!news3.google.com!proxad.net!feeder1-2.proxad.net!usenet-fr.net!gegeweb.org!aioe.org!not-for-mail
From: tmoran@acm.org
Newsgroups: comp.lang.ada
Subject: Re: Interfacing Ada with C
Date: Sun, 25 Jul 2010 00:22:11 +0000 (UTC)
Organization: Aioe.org NNTP Server
Message-ID: <i2g03i$fno$1@speranza.aioe.org>
References: 
 <e5c8cec4-0ecd-407e-9790-e4a842d36f3d@k19g2000yqc.googlegroups.com>
NNTP-Posting-Host: J4HSNf9Eqj44wTz1J3b8lQ.user.speranza.aioe.org
X-Complaints-To: abuse@aioe.org
X-Notice: Filtered by postfilter v. 0.8.2
X-Newsreader: Tom's custom newsreader
Xref: g2news1.google.com comp.lang.ada:12535
Date: 2010-07-25T00:22:11+00:00
List-Id: <comp.lang.ada>

> On Jul 24, 6:44=A0pm, "Dmitry A. Kazakov" <mail...@dmitry-kazakov.de>
> wrote:
>
> > Since C does not have arrays, especially 2D ones, you will have some cust=
> om
> > representation on the C side. It means that examples of bindings (there a=
> re
> > plenty of) won't help you unless you understand how you describe a
> > C-compatible object in Ada.
>
>
> Thanks for the "warnings". One way that I'm thinking is to write the
> elements of the matrix sequentially into a file in Ada, read them into
> C, put them into a matrix in C, do the appropriate computations in C
> (with the IMSL C library), write the output in C in a file, and
> finally importing them back into Ada again for further processing.

   Why do somersaults when you can just walk a few steps. As Dmitry
says, it really does depend on just what you are supposed to pass to
the C routine.  For instance, there's a very fast C routine to
calculate an FFT of a 256 element complex vector.  Using

  type Complex_Vectors is array(Integer range <>)
    of Ada.Numerics.Complex_Types.Complex;

  subtype Complex_256s is Complex_Vectors(1 .. 256);

  procedure fftc4_256(V : in out Complex_256s);
  pragma import(c, fftc4_256,"fftc4_256");

it can be called with

  X : Complex_256s;
  ...
  fftc4(X);

Hard to get any simpler.  If the C routine wants a pointer to an array of
pointers to rows, plus a couple of dimensions, that's a little harder.
But if the array is stored simply, and C expects the elements laid out the
same way as Ada, you can probably just pass in a pointer to the first
element in the array:

  type Matrix_Type is array(Integer Range <>, Integer range <>)
    of aliased Ada.Numerics.Complex_Types.Complex;

  type Pointer_To_Element is access all Ada.Numerics.Complex_Types.Complex;

  procedure C_Routine(M : in Pointer_To_Element;
                      Height, Width : in Interfaces.C.Unsigned);
  pragma import(C, C_Routine, "c_routine");

  M : Matrix_Type(1 .. 10, 0 .. 100);
  ...
  C_Routine(M(M'first(1), M'first(2))'access,
            Height => M'length(1),
            Width  => M'length(2));

For a whole lot of examples of Ada calling C, download the source for
CLAW (Class Library for Ada Windows) from www.rrsoftware.com