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From: vladimir@speedy.intrepid.com (Vladimir Vukicevic)
Newsgroups: comp.lang.ada
Subject: Re: Importing C Structures
Date: 23 Mar 1995 07:55:27 GMT
Organization: Intrepid Technology, Inc.
Message-ID: <VLADIMIR.95Mar22235527@speedy.intrepid.com>
References: <3kr4q3$jd9@newsflash.concordia.ca>
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In-reply-to: ct_oreg@vega.concordia.ca's message of 23 Mar 1995 06:34:43 GMT
Date: 1995-03-23T07:55:27+00:00
List-Id: <comp.lang.ada>

In article <3kr4q3$jd9@newsflash.concordia.ca> ct_oreg@vega.concordia.ca (Chris O'Regan) writes:

> 
>    For my Real-Time Systems project, my partner and I are writing a program
> to control a train set.  We will be working on an Indy using GNAT 2.03, and
> as little C code as possible.
> 
>    We need to interface the Indy's serial port.  We have some documention
> which explains how to do this in standard C, but we would prefer to do this
> in Ada.  We figure that we will need to import the functions and types from
> the standard C library.
> 
>    Importing a function isn't a problem, but what about data types?
> Rationale and the Reference Manual claim that it is possible, but without an
> sample code snippet, we don't know where to begin.
> 
>    Could someone shed some light on the subject?  Or should we give in and
> write our serial port routines in C?

No. Write them in Ada. :-)

First, decide which functions you'll need. I'm assuming open (),
read(), write(), ioctl() and the like. open () returns an int, so that's
no problem. read/write would use Interfaces.C.Strings. ioctl () would
use System.Address and others. If you need to pass around pointers,
and don't care what they point to, treat them as System.Addresses.

If there is some some struct that you need to map to Ada, it should be
farily straightforward. i.e.

typedef struct {
	int foo;
	char bar[10];
	long *q;
} A_Struct;

becomes

with Interfaces.C;
package IC renames Interfaces.C;
type A_Struct is
	record
		foo : IC.int;
		bar : IC.char_array (1 .. 10);
		q : access IC.long;
	end record;

	- Vladimir