Re: Endianness independance

[John Harbaugh <john.s.harbaugh2@boeing.com>]

If you are looking for an implementation that is platform and compiler
independent, take a look at the December 1999 Ada Letters.  Mike Mardis
wrote a very good article titled "Endian-Safe Record Representation
Clauses for Ada Programs."

Cheers,

	- John Harbaugh

"David C. Hoos, Sr." wrote:
> 
> ----- Original Message -----
> From: <Lionel.DRAGHI@fr.thalesgroup.com>
> To: <comp.lang.ada@ada.eu.org>
> Sent: March 04, 2003 5:34 AM
> Subject: RE: Endianness independance
> 
> >
> >
> > | -----Message d'origine-----
> > | De: David C. Hoos [mailto:david.c.hoos.sr@ada95.com]
> > ...
> > | Yes, Glade does it, but the only thing Glade has to worry
> > | about is that
> > | the stream representation is independent of hardware platform and OS.
> > |
> > | Glade does this by providing a replacement body for the
> > | System.Stream_Attributes package.
> > |
> > | However, I have done a lot of endianess-independent work where a
> > | specific network representation is required -- i.e., where an Ada
> > | program has to communicate with a program writen in a language
> > | not necessarily known to me.
> > |
> > OK, but i don't pretend to get this general case taken into account within
> > the language scope, altrough some
> > for My_Stream'representation use XDR;
> > could be great!
> >
> > My point is just about interoperability between the same Ada code compiled
> > on two platform. I want both exe to put the same thing in the stream.
> > It's not the case even with a representation clause, and i feel this is
> > abnormal.
> > I know it's far from easy to achieve, but i thought Norman's proposal was
> > helping a lot...
> >
> Representation clauses are neither the issue, nor the answer to the problem.
> 
> If all you want is platform-independence, then replace the file s-stratt.adb
> in your standard gnat distribution with the one from the same version of
> glade, and re-compile and rebuild the library files (.a), and you have
> what you want.  Now, as long as your types are declared the same on both
> platforms (with no representation clauses) you will have platform-
> independence.
> 
> I'm not sure why GNAT didn't do this from the beginning -- perhaps because
> they didn't provide an implementation of the Distributed Systems Annex at
> the beginning.  Also, there is a small performance penalty paid for
> shuffling bits around to achieve platform independence.
>