From: Simon Wright <simon.j.wright@mac.com>
Subject: Re: Enumeration representation clause surprise.
Date: Fri, 13 Jun 2008 06:49:09 +0100
Date: 2008-06-13T06:49:09+01:00 [thread overview]
Message-ID: <m23anhriju.fsf@mac.com> (raw)
In-Reply-To: 0120c799-fd71-41dc-bad1-c5e4f71c87f4@34g2000hsh.googlegroups.com
Mike Silva <snarflemike@yahoo.com> writes:
> On Jun 12, 4:52�pm, Simon Wright <simon.j.wri...@mac.com> wrote:
>> The only reason I have ever written representation clauses is to
>> ensure that the contents of raw memory are what some external
>> hardware (or software, eg at the other end of a network connection)
>> requires them to be.
>
> OK, I understand that - so how would you pass this raw memory to the
> external hardware or software?
Obtain the address to which the hardware registers are mapped (talking
VME here) & convert to a pointer to a structure which describes how
the hardware expects to see memory, then write through that pointer.
Or, for example, function To_Stream_Element here:
http://coldframe.cvs.sourceforge.net/coldframe/adasntp/SNTP.impl/sntp_support.adb?revision=1.4&view=markup
where I'm packing an unrepresented Status into a single byte for
transmission.
Nowadays I might do this using shift-and-mask to avoid messing with
endianness (this code has to work with Ada 95, even if the new 05
features would help).
> And in this case, how did the use of
> biased representations ever get into compilers at all? Is there any
> possible use of biased representations that does not fail the
> requirement you have established?
If I don't care how the compiler wedges the data into the record so
long as it's as small as possible (pragma Pack) then a biased rep
would be quite reasonable.
next prev parent reply other threads:[~2008-06-13 5:49 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-06-11 11:38 Enumeration representation clause surprise Markus Schoepflin
2008-06-11 12:30 ` christoph.grein
2008-06-11 12:56 ` Markus Schoepflin
2008-06-11 13:08 ` christoph.grein
2008-06-11 13:28 ` Samuel Tardieu
2008-06-11 13:48 ` Markus Schoepflin
2008-06-11 13:56 ` Samuel Tardieu
2008-06-11 14:58 ` Adam Beneschan
2008-06-11 15:23 ` Markus Schoepflin
2008-06-12 2:37 ` Randy Brukardt
2008-06-12 2:37 ` Randy Brukardt
2008-06-11 15:56 ` Samuel Tardieu
2008-06-11 19:10 ` Adam Beneschan
2008-06-11 19:59 ` Niklas Holsti
2008-06-12 1:16 ` tmoran
2008-06-12 8:27 ` christoph.grein
2008-06-12 8:45 ` Markus Schoepflin
2008-06-12 16:43 ` Mike Silva
2008-06-12 18:41 ` Markus Schöpflin
2008-06-12 20:10 ` Mike Silva
2008-06-12 20:52 ` Simon Wright
2008-06-12 23:36 ` Mike Silva
2008-06-13 5:49 ` Simon Wright [this message]
2008-06-13 7:21 ` Keith Thompson
2008-06-13 13:31 ` Mike Silva
2008-06-13 14:45 ` Markus Schoepflin
2008-06-13 17:52 ` Keith Thompson
2008-06-13 9:14 ` Jean-Pierre Rosen
2008-06-12 19:05 ` richtmyer
2008-06-12 21:26 ` Samuel Tardieu
2008-06-12 22:42 ` Adam Beneschan
2008-06-13 7:11 ` Samuel Tardieu
2008-06-13 8:27 ` christoph.grein
2008-06-13 16:21 ` Adam Beneschan
2008-06-15 19:33 ` Robert A Duff
2008-06-16 14:50 ` Adam Beneschan
2008-06-16 19:18 ` Robert A Duff
2008-06-17 6:03 ` christoph.grein
2008-06-17 7:22 ` christoph.grein
2008-06-13 8:24 ` Peter Hermann
2008-06-13 14:47 ` Samuel Tardieu
2008-06-14 11:48 ` John B. Matthews
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