Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ncar!gatech!emory!dtscp1!tridom!wht
From: wht@tridom.uucp (Warren Tucker)
Newsgroups: comp.lang.c
Subject: Re: "address" of a bitfield
Message-ID: <157@tridom.uucp>
Date: 17 Jul 89 15:31:22 GMT
References: <2840@blake.acs.washington.edu>
Organization: Tridom Corporation, Marietta GA
Lines: 14

In article <2840@blake.acs.washington.edu>, wiml@blake.acs.washington.edu (William Lewis) writes:
> 
>    BitFAddr(thing.field, start, offset, width);
>   which would assign to 'start' the (char *) pointing to the start of the
> bitfield, to 'offset' the number of bits into the char the bitfield starts,
> and to 'width' the width of the bitfield in bits. Using this info, I
> could read & write the bitfield using '<<' and the bitwise operators.
>
Completely non-portable, but that may be ok for you (the actual 
format of bit fields are are left to the compiler writer's whim).
Try passing the address of the structure to a function that knows which
field to manipulate.
The best way to be portable would be to scrap bitfields alllll tooogether
and use #defines for bit masks.