From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <edwin+ml-ocaml@etorok.net>
X-Original-To: caml-list@sympa.inria.fr
Delivered-To: caml-list@sympa.inria.fr
Received: from mail1-relais-roc.national.inria.fr (mail1-relais-roc.national.inria.fr [192.134.164.82])
	by sympa.inria.fr (Postfix) with ESMTPS id 64EFF7ED26
	for <caml-list@sympa.inria.fr>; Wed,  6 Jun 2012 15:17:04 +0200 (CEST)
X-IronPort-Anti-Spam-Filtered: true
X-IronPort-Anti-Spam-Result: Av8EAEBXz0+wCYo3/2dsb2JhbABFtDWBB4IYAQEEAUABATYBAQ8LGAkWDwkDAgECAUUTAQUCAogCCaNYhC4BBY8cBosUJIJfgxaIPYxihVGDUIZXgmM
X-IronPort-AV: E=Sophos;i="4.75,724,1330902000"; 
   d="scan'208";a="161593753"
Received: from mail.etorok.net ([176.9.138.55])
  by mail1-smtp-roc.national.inria.fr with ESMTP; 06 Jun 2012 15:17:04 +0200
Received: from [192.168.1.101] (unknown [86.125.229.82])
	by mail.etorok.net (Postfix) with ESMTPSA id 4808346B0;
	Wed,  6 Jun 2012 15:17:03 +0200 (CEST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=etorok.net;
	s=MAILOUT; t=1338988623;
	bh=d2byofRRbftTw16+wdE0r3gxtb91GgM6zrySGtQTeVU=;
	h=Message-ID:Date:From:MIME-Version:To:CC:Subject:References:
	 In-Reply-To:Content-Type:Content-Transfer-Encoding;
	b=NgXBc6zArEbK2VMV2bkvqmb8tVS7fcDXXxhL7NCimHHpZTTj1T+SZrbYO90d1WxjG
	 jV6JiCEpbDT0meAs42cxTqQ7wLE8UOUwovZqZF+KbXlrDrdNF6hsDoc/gaBFGCOTn3
	 qrj2XxD+vf5NAihZ2ZqeqAVmdb+RLUN1jwI/b2X0=
Message-ID: <4FCF584E.2000309@etorok.net>
Date: Wed, 06 Jun 2012 16:17:02 +0300
From: =?ISO-8859-1?Q?T=F6r=F6k_Edwin?= <edwin+ml-ocaml@etorok.net>
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.4) Gecko/20120510 Icedove/10.0.4
MIME-Version: 1.0
To: rixed@happyleptic.org
CC: caml-list@inria.fr
References: <20120606130646.GA23115@securactive.lan>
In-Reply-To: <20120606130646.GA23115@securactive.lan>
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
X-Virus-Scanned: clamav-milter 0.97.3 at mail
X-Virus-Status: Clean
Subject: Re: [Caml-list] Unix.single_write, doc and atomicity

On 06/06/2012 04:06 PM, rixed@happyleptic.org wrote:
> I was reading the code for unix_single_write recently, and noticed two strange
> things that I prefer to discuss here before filling the bug tracker with
> dubious tickets.
> 
> First, the doc of Unix.single_write claims that this function "attemps to write
> only once", although the underlying unix_single_write C function clearly loops
> around a write if the buffer being written is larger than the internal buffer
> (16K).

Are we looking at the same file / function?
The one that loops is unix_write, I don't see any loops in unix_single_write:

CAMLprim value unix_single_write(value fd, value buf, value vofs, value vlen)
{
  long ofs, len;
  int numbytes, ret;
  char iobuf[UNIX_BUFFER_SIZE];

  Begin_root (buf);
    ofs = Long_val(vofs);
    len = Long_val(vlen);
    ret = 0;
    if (len > 0) {
      numbytes = len > UNIX_BUFFER_SIZE ? UNIX_BUFFER_SIZE : len;
      memmove (iobuf, &Byte(buf, ofs), numbytes);
      enter_blocking_section();
      ret = write(Int_val(fd), iobuf, numbytes);
      leave_blocking_section();
      if (ret == -1) uerror("single_write", Nothing);
    }
  End_roots();
  return Val_int(ret);


> 
> So this boils down to : unix_single_write really should perform a single write!

AFAICT it does only a single write.

Best regards,
--Edwin