From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <p.donadeo@gmail.com>
X-Original-To: caml-list@yquem.inria.fr
Delivered-To: caml-list@yquem.inria.fr
Received: from mail3-relais-sop.national.inria.fr (mail3-relais-sop.national.inria.fr [192.134.164.104])
	by yquem.inria.fr (Postfix) with ESMTP id EAFABBC57
	for <caml-list@yquem.inria.fr>; Tue,  8 Jun 2010 18:24:10 +0200 (CEST)
X-IronPort-Anti-Spam-Filtered: true
X-IronPort-Anti-Spam-Result: AjUCAAsLDkzRVdS0imdsb2JhbACDHZsbCBUBAQEKCQwHDwUfrkg5ggKFSC6ITwEBAwWBIYMCbgQ
X-IronPort-AV: E=Sophos;i="4.53,385,1272837600"; 
   d="scan'208";a="51988474"
Received: from mail-px0-f180.google.com ([209.85.212.180])
  by mail3-smtp-sop.national.inria.fr with ESMTP; 08 Jun 2010 18:24:10 +0200
Received: by pxi17 with SMTP id 17so1591524pxi.39
        for <caml-list@yquem.inria.fr>; Tue, 08 Jun 2010 09:24:08 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
        d=gmail.com; s=gamma;
        h=domainkey-signature:received:mime-version:received:in-reply-to
         :references:from:date:message-id:subject:to:content-type;
        bh=MFH4IIduJjjIHFtc+dvtLuWHD5jyq4NPaMYM8DHZu58=;
        b=j/EYWQpnUs2wbh7hRfJcy/h3p8uiO8UtKph/xpw7e9OhaZyKeujiRNQHmdpEvOZYTf
         vBC9TxjFmf1g7mstwErkUgzNttHkAMnUNA6MWf0tJTcD7rt8alosNe8UZTHALuHOa7cJ
         SIUgcVjAgCZI8o0aXwdjqAzMm/Ibk09lxbivs=
DomainKey-Signature: a=rsa-sha1; c=nofws;
        d=gmail.com; s=gamma;
        h=mime-version:in-reply-to:references:from:date:message-id:subject:to
         :content-type;
        b=BREaY7NWhG8qeugHH5/fifBLmHZHxDu2Xpl7R99BDqjaOAju3xY9poYGzqjtMmeDDS
         FEAs5F5io/DaAJVML6Y4pmVrgsRW6+SLh+Ni5JgOVX7GshwO6lYcHzv8ixCUjUmTFayV
         zezFVMi2TyPU8rrCXYD8AsxFWySOsqCGbrbQg=
Received: by 10.229.184.203 with SMTP id cl11mr6118215qcb.178.1276014247510; 
	Tue, 08 Jun 2010 09:24:07 -0700 (PDT)
MIME-Version: 1.0
Received: by 10.220.77.156 with HTTP; Tue, 8 Jun 2010 09:23:47 -0700 (PDT)
In-Reply-To: <4C0E6561.20207@inescporto.pt>
References: <4C0E6561.20207@inescporto.pt>
From: Paolo Donadeo <p.donadeo@gmail.com>
Date: Tue, 8 Jun 2010 18:23:47 +0200
Message-ID: <AANLkTikXhoT3Ifmgr6Njd2UCQ4ssCOeoCLKAMq7YwLHN@mail.gmail.com>
Subject: Re: [Caml-list] Escaped string in sexplib
To: caml-list caml-list <caml-list@yquem.inria.fr>
Content-Type: text/plain; charset=UTF-8
X-Spam: no; 0.00; sig:01 val:01 val:01 struct:01 sexp:01 sexp:01 blog:98 blog:98 cryptokit:01 cryptokit:01 encode:01 encode:01 caml-list:01 functions:01 data:02 

I'm using Sexplib to store and retrieve the sessions of a web
application into a data base. A "session" has this signature:

module type SESSION_DATA =
  sig
    type t
    val default : t
    val string_of_t : t -> string (* Is this what you want? *)
    val t_of_string : string -> t (* Is this what you want? *)
  end

and the concrete session, which is a blog session, is:

module Blog_session =
  struct
    type user =
      {
        email : string;
        passwd : string;
        first_name : string option;
        last_name : string option;
        displ_name : string option;
        website : string option
      } with sexp

    type t =
      | Anonymous
      | Logged of user
        with sexp

    let default = Anonymous

    let string_of_t = sexp_of_t |- Sexplib.Sexp.to_string_hum |- hex_encode

    let t_of_string s =
      try s |> hex_decode |> Sexplib.Sexp.of_string |> t_of_sexp
      with Sexplib.Conv.Of_sexp_error (_, _) -> default
  end

Functions "hex_encode" and "hex_decode" are trivially implemented
using Cryptokit:

let hex_encode = Cryptokit.transform_string (Cryptokit.Hexa.encode ())
let hex_decode = Cryptokit.transform_string (Cryptokit.Hexa.decode ())

The operators (|-) and (|>) are defined as always:

http://thelema.github.com/batteries-included/hdoc/BatPervasives.html#6_Fundamentalfunctionsandoperators


Hope this helps,


-- 
Paolo