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Date: 25 May 93 14:12:35 GMT
From: dog.ee.lbl.gov!overload.lbl.gov!agate!howland.reston.ans.net!zaphod.mps.o
hio-state.edu!cs.utexas.edu!csc.ti.com!tilde.csc.ti.com!mksol!mkserv!ddessert@u
cbvax.Berkeley.EDU  (Dave Dessert)
Subject: Packed BIT fields -- any help??
Message-ID: <1993May25.141235.14712@mksol.dseg.ti.com>
List-Id: <comp.lang.ada>

I've run up against an "age-old" problem and hope that maybe someone can
shed some light on a "simple" solution.

We are trying to pass data memory-to-memory between two machines - a Sun SPARC
using SunAda (Verdix) and a TI TMX320C30 using Tartan Ada.  Much of the data is
packed into bit fields.  The problem is that the two comilers have chosen
opposite orders for bit numbering -- Tartan uses LSB = 0, Verdix uses MSB = 0.
We would like to use the same source code for defining types on both machines
be have been unable to invent a method for specifying the bits (using constants
, etc)
that will compile to the same pattern on both machines.  Using "pragma PACK" do
esn't
help either -- the compilers re-arrange and pack differently, too.

We can't be the first folks to run up against this -- has anybody already got
an elegant (or, at least, workable) way to avoid maintaining two sets of source
code, or two sets of type names??