From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <laurent.thevenoux@inria.fr>
Received: from mail2-relais-roc.national.inria.fr (mail2-relais-roc.national.inria.fr [192.134.164.83])
	by sympa.inria.fr (Postfix) with ESMTPS id 37FF68027D
	for <caml-list@sympa.inria.fr>; Fri, 13 Oct 2017 12:57:34 +0200 (CEST)
X-IronPort-AV: E=Sophos;i="5.43,370,1503352800"; 
   d="scan'208";a="296061163"
Received: from dhcp-13-128.lip.ens-lyon.fr ([140.77.13.128])
  by mail2-relais-roc.national.inria.fr with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 13 Oct 2017 12:57:34 +0200
From: =?utf-8?Q?Laurent_Th=C3=A9venoux?= <laurent.thevenoux@inria.fr>
Content-Type: text/plain;
	charset=utf-8
Content-Transfer-Encoding: quoted-printable
Mime-Version: 1.0 (Mac OS X Mail 11.0 \(3445.1.7\))
Message-Id: <3380AF33-0E0F-46E9-BF03-E61B65E6B838@inria.fr>
Date: Fri, 13 Oct 2017 12:57:33 +0200
To: caml-list@inria.fr
X-Mailer: Apple Mail (2.3445.1.7)
Subject: [Caml-list] Interfacing C with OCaml and file descriptors

Hi,

I have a naive question about file descriptors and C interface (when interf=
acing C with OCaml).

For instance, a file.ml file which looks like:


external my_c_interface : out_channel -> int =3D c_function


where c_function writes something to a file and return the number of writte=
n char.
The c_function takes a FILE* file descriptor, as for example:


CAMLprim value c_function (value channel)
{
	CAMLparam1 (channel);
	FILE* fd =3D ???;
	CAMLreturn (Val_int (call_to_c_func (fd)));
}


So, if possible, how to convert the =E2=80=98value channel=E2=80=99 to a =
=E2=80=98FILE*=E2=80=99?

Thanks for your help,
Laurent=