xmerl_scan for XMPP -- too much lookahead?

Tony Garnock-Jones tonyg@REDACTED
Wed Sep 23 15:46:45 CEST 2009

Hi all,

I'm trying to use xmerl_scan to handle XMPP stanzas, and I think I've
found a problem with it. I don't think it's intended for streaming XML
in XMPP-like interleaved-request-and-response-document situations.

The attached program feeds the string "<opentag>" to xmerl_scan. I would
have expected to receive the open-tag event before blocking for more
data, but instead it requires at least one more character of input data
before it will emit the open-tag event! If I instead pass "<opentag> ",
with a space after the close-bracket, it emits the open-tag event as
expected, plus the start of an xmlText, before blocking for more data.

My question, then, is:

  Is this a bug? Should xmerl_scan supply the open-tag event before
  blocking, when it is fed "<opentag>"?

(The specific context of this problem is dealing with the
<stream:stream> sent by the server at the handshake stage of XEP-114.)


P.S.: to run the attached program,
  $ erlc lookaheadbug.erl && erl -run lookaheadbug go
 [][][] Tony Garnock-Jones     | Mob: +44 (0)7905 974 211
   [][] LShift Ltd             | Tel: +44 (0)20 7729 7060
 []  [] http://www.lshift.net/ | Email: tonyg@REDACTED

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