Re: xen vbd: better.

[Avery Pennarun <apenwarr@nit.ca>]

On Fri, Oct 22, 2004 at 08:08:18PM +0100, Keir Fraser wrote:

> > Plan 9 works just fine without packed structs, as do the many operating 
> > systems written by people using compilers that didn't do packed structs 
> > either, or even compilers that always packed structs (V6  C). All these 
> > systems twiddled bits just fine. 
> 
> I'm interested to know how. How do you define a network header layout,
> for example, and how do you access subfields? e.g., is there an
> explicit IDL with integration into the compiler?

Typically fixed-format data structures are done by simply accessing the data
as a char[] array instead of a struct.  This may not be as pretty, but it
compiles down into the same machine code and it's 100% portable.  (And you
can do it pretty decently with some preprocessor macros.)

Have fun,

Avery


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