[slime-devel] New wire format

Hugo Duncan hugo at hugoduncan.org
Mon Nov 7 13:56:09 UTC 2011

On Mon, 07 Nov 2011 03:11:50 -0500, Helmut Eller <heller at common-lisp.net>  

> * Hugo Duncan [2011-11-07 04:04] writes:
>> Is there a reason to start using a binary encoding of the message
>> length?
> No deep reason.  We actually used binary encoding before we used
> hex-strings.  That worked fine with latin-1 but not with utf-8.  I guess
> it's just instinct; now that we explicitly work on a byte stream it's
> even more natural.  Should probably have used network byte order.
>> This makes the messages less easy to inspect, and less easy
>> to write integration tests for.
> Only marginally.  Shifting 3 bytes together is not exactly rocket since.

It isn't rocket science, but does remove the possibility of visual  
verification, and of being able to send messages via scripting or a simple  
console. HTTP, SIP, SMTP, and STOMP are all good examples of protocols  
with text headers, and I think appropriate, if one looks at swank as a  
sort of control protocol.

What is the gain from changing to a binary header? As far as I can see it  
is just saving a few bytes.

>>> The playload is an s-exp encoded as UTF8 text.
>> Normalising on utf-8 and counting bytes sounds like it would solve the
>> original issue without changing to a binary encoding of the message
>> length.
> Right.  It would not be backward compatible, tho.

It seems to be worth solving encoding issues, so something has to give.

Given this is a breaking change, I also see the desire to introduce an  
extension mechanism at the same time. I would argue a text based  
header/value extension would be more appropriate.

At the end of the day, I realise the balance between the respective merits  
of binary and text headers is somewhat subjective.


Hugo Duncan

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