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From: "Martin Dowie" <martin.dowie@btopenworld.com>
Newsgroups: comp.lang.ada
Subject: Re: Interoperability: differing storage units and/or endianess
Date: Fri, 20 Feb 2004 13:52:34 +0000 (UTC)
Organization: BT Openworld
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"Jeffrey Carter" <spam@spam.com> wrote in message
news:li6Zb.293$aT1.271@newsread1.news.pas.earthlink.net...
> Bibb Latting wrote:
>
> > Hi, I am working on a distributed application where the processors
> > have differing storage unit sizes and/or endianess.  My problem is how
> > to handle the specification of memory contents and the delivery of
> > data to applications with minimal variation between implementations.
> > I'd like to know what solutions have worked well for others.
>
> If you can use Annex E (for example, GNAT/GLADE), then this is handled
> for you. If you have to roll your own, you could probably use the
> marshalling/unmarshalling code from GLADE to achieve this.
>
> The basic idea is to pick a representation for transmission, and ensure
> that every box converts to this representation before transmission, and
> converts from this representation after reception.

Another thing to consider is the relative processing power and system
demands of the nodes on the network. I worked on one system which
used an Alpha and a PowerPC. The PowerPC had little spare processing
time and the Alpha was _much_ quicker_, so we did all conversions on the
Alpha.

You could set up lookup tables and index them based on 'source' and
'destination' and thus keep all the transforms in one set of source code.

Cheers

-- Martin