Re: Question about

[Ted Dennison<dennison@telepath.com>]

In article <dsGwyS7sA3+2@eisner.encompasserve.org>, Larry Kilgallen says...
>
>I have not worked with streams, but was wondering if anyone had tried
>using ASN.1 to achieve interoperability.  It solves endian problems
>and the DER representation is rather firm about "only one way to express
>something".

Is it? For instance, data can be encoded with lengths, or with an
"End-of-Contents" octet. 
The copy I have here is about 16 years old, and I don't have a "DER", just a
BER. My memory from when I did it was that there were indeed multiple ways to
encode most anything, but again that was many moons ago.

I'd think the big problems with ASN.1 streams would be:

o  ASN.1 is too damn complicated. 
o  The encoding data structures are too flexible to map directly into Ada.
o  Some ASN.1 types have no direct Ada analog.
o  Some Ada types have multipe possible ASN.1 analogs.
o  Since its type-based, you couldn't just do the job with a custom stream.
You'd also have to recode every type to output ASN.1 from its stream attributes.

The last is a bit of a problem for *any* custom stream in Ada. If you care about
the internal data types or things like record boundries, then you end up having
to rewrite all the type stream attributes. This is a lot of work. It also
prevents people from using just any type with your stream, and it prevents
anyone from using those types with any other streams that you may have lying
around.

---
T.E.D.    homepage   - http://www.telepath.com/dennison/Ted/TED.html
          home email - mailto:dennison@telepath.com