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From: "Frank J. Lhota" <FrankLho.NOSPAM@rcn.com>
Newsgroups: comp.lang.ada
Subject: Re: The "black magic" of ioctl
Date: Sun, 24 Oct 2010 08:41:14 -0400
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Date: 2010-10-24T08:41:14-04:00
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On 10/23/2010 4:26 PM, Florian Weimer wrote:
> ioctl is a varargs function.  You cannot call C varargs functions
> directly from Ada.  You need to write a small wrapper with a fixed
> number of arguments.
>
> In addition, the ioctl constants are often difficult to extract from
> the header files.  The best way to get them seems to be a small C
> program which just prints them.
>
> So writing some C code is unavoidable here.

Actually, you can call a varargs function such as ioctl from Ada. 
Declare each ioctl profile that you need, e.g.

     -- ioctl for commands with no additional arguments
     function Ioctl (Fd  : in Interfaces.C.Int;
                     Cmd : in Interfaces.C.Int)
                     return Interfaces.C.Int;
     pragma Import (C, Ioctl, "ioctl");

     -- ioctl for commands with an additional argument
     -- for returning the device status
     function Ioctl (Fd     : in Interfaces.C.Int;
                     Cmd    : in Interfaces.C.Int;
                     Status : access Interfaces.C.Int)
                     return Interfaces.C.Int;
     pragma Import (C, Ioctl, "ioctl");

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