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From: "Pat Rogers" <progers@NOclasswideSPAM.com>
Subject: endian-independent  rep clauses (was Re: GNAT Opinions)
Date: 1998/12/27
Message-ID: <7667t3$3kj$1@remarQ.com>#1/1
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References: <75rj7i$2cq$1@nnrp1.dejanews.com>
 <75rvnq$h75@dfw-ixnews10.ix.netcom.com> <75tr9e$3h8$1@remarQ.com>
 <760d41$p6r$1@nnrp1.dejanews.com>
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Organization: Software Arts & Sciences
Newsgroups: comp.lang.ada
Date: 1998-12-27T00:00:00+00:00
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dewarr@my-dejanews.com wrote in message
<760d41$p6r$1@nnrp1.dejanews.com>...
>In article <75tr9e$3h8$1@remarQ.com>,
>  "Pat Rogers" <progers@NOclasswideSPAM.com> wrote:
>
>> Since you mentioned it, endian-independent representation
>> clauses
>> can be written (although they are not easy to read, but
>> then, they
>> never require changes due to endianess).  Norm Cohen
>> wrote about how
>> to do it in Ada Letters.  I have a free package to
>> support it, with
>> a demo program, at my web site:
>
>This approach solves only a limited part of the problem
>that people would like to solve. There are many variations
>of this problem that occur in actual practice,
>
>Consider one of the most fundamental, which
>is that you have an external data stream that produces a
>big endian integer as four consecutive bytes in big-endian
>order. There is no magic rep clause to cause a compiler on
>a little-endian machine to acquire this data "correctly".
>Indeed the difficulty may vary from machine to machine, on
>some machines a quite long and tedious sequence of
>instructions may be required to reassemble the data.


I answer with more than a little trepidation, knowing that you are
capable of arguing one side to "victory" only to then switch and
argue the other side!  :-)

Seriously, I would consider the above to be a separate problem,
since indeed a record rep clause will not handle it.  It does what
Norm said it does, and nothing more.

---
Pat Rogers                          Training & Development in:
http://www.classwide.com    Deadline Schedulability Analysis
progers@acm.org                 Software Fault Tolerance
(281)648-3165                       Real-Time/OO Languages