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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: What is the best method for transmitting objects/tagged records?
Date: Thu, 9 Jun 2011 15:55:11 -0500
Organization: Jacob Sparre Andersen Research & Innovation
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Date: 2011-06-09T15:55:11-05:00
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"Simon Wright" <simon@pushface.org> wrote in message 
news:m2sjrj4mpe.fsf@pushface.org...
> "Randy Brukardt" <randy@rrsoftware.com> writes:
>
>> Right, but you don't need to use Ada.Tags (or anything tags) in order
>> to stream tagged types. Just use the provided T'Class'Input and
>> T'Class'Output attributes. For those to have portable results, you
>> need to specify your external tag values for your tagged types (we
>> previously discussed that).
>
> Not sure what you mean by 'portable' here, Randy; are compilers required
> to conform to standard representations on the wire? Because GNAT
> certainly doesn't out of the box (for example, it uses native byte
> order).

Good point; the byte order could change. As a matter of course, I would only 
put things (records) on the wire that already had representation clauses 
fully specifying their layout (and that includes external tag). In that 
case, your results will continue to work until/unless you have to change 
processors (the native byte order surely doesn't change).

Ada doesn't out of the box support any sort of hetrogeneous partitioning 
(the assumption is that all of the processors are similar) and if your 
implementation provides some it is doing so outside of Ada. (That is, if you 
have partitions with different native byte orders communicating, you are 
trying to do something Ada was not designed for.)

                                           Randy.