From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.3 required=5.0 tests=BAYES_00,INVALID_MSGID
	autolearn=no autolearn_force=no version=3.4.4
X-Google-Language: ENGLISH,ASCII-7-bit
X-Google-Thread: 103376,d2c23a44c4c8fd6b
X-Google-Attributes: gid103376,public
From: Laurent Pautet <pautet@inf.enst.fr>
Subject: Re: fixed point types over an interface
Date: 1997/02/12
Message-ID: <rcawwsedshp.fsf@quasimodo.enst.fr>#1/1
X-Deja-AN: 218256168
Sender: pautet@quasimodo.enst.fr
References: <32FBB550.41C67EA6@efogm.msd.ray.com> <dewar.855364096@merv>
Content-Type: text/plain; charset=iso-8859-1
Organization: ENST, France
Mime-Version: 1.0
Newsgroups: comp.lang.ada
Date: 1997-02-12T00:00:00+00:00
List-Id: <comp.lang.ada>



    >> Another possibility is to use a target independent
    >> implementation of Stream_IO, such as is provided with GLADE
    >> (the GNAT implementation of the distributed annex PCS). GLADE
    >> uses XDR for stream representation, which avoids any endian (or
    >> other target dependent) problems.

    nassera> good choice. I just wanted to also add that Sun NFS and
    nassera> Sun RPC also uses XDR.

    nassera> man xdr: (on solaris 2.5)

    nassera> DESCRIPTION XDR routines allow C programmers to describe
    nassera> arbitrary data structures in a machine-independent
    nassera> fashion.  Data for remote procedure calls (RPC) are
    nassera> transmitted using these routines.

    nassera> by the way, I wonder why the man output above mentions
    nassera> only "C programmers".

Because it doesn't apply to Ada :-) For instance:

XDR says :

The representation of all items requires a multiple of four bytes (or
32 bits) of data.

LRM says :

For composite types, the Write or Read attribute for each component is
called in a canonical order ... Read and Write should use the smallest
number of stream elements needed to represent all values in the base
range of the scalar type.

So a string of 7 characters is stored on 8 bytes with XDR and 7 with Ada.

GLADE is only 95% XDR in order to follow LRM requirements. The 5%
comes from the XDR 4 bytes rule (basically strings).