[AFS3-std] AFS-3 XDR discriminated union primitive type I-D

[Tom Keiser]

On Mon, Mar 7, 2011 at 6:47 PM, Simon Wilkinson <simon@sxw.org.uk> wrote:
>
> On 7 Mar 2011, at 20:46, Tom Keiser wrote:
>
>> Hi all,
>>
>> I've published a new I-D, based upon the on-list consensus from the othe=
r week, defining a new discriminated union primitive type. =A0Feedback and =
comments are hereby invited...
>
> I'm puzzled as to why length isn't just the length of the arm. If you mod=
ify the encoding so that length is just the length of the encoded arm, then=
 you can actually decode these "new" unions using an existing rpcgen, by en=
coding them as
>

Hi Simon,

It was an arbitrary decision.  Actually, now that I think about it,
this brings up an interesting question: will we ever want to use XDR
to encode large streams of data (e.g., a next-generation dump format)?
 If so, we would likely want the length field to be a hyper.  On the
other hand, that would result in a significant increase in common-case
overhead.  Should we defer that until we need it, perhaps with an
afs-union64?


> struct {
> =A0 int type;
> =A0 opaque arm;
> }
>
> ... which I suspect might come in useful somewhere down the line.
>

Indeed it would.  I'll change the language for -01.

Cheers,

-Tom