[cxml-devel] CXML vs usocket

[Magnus Henoch]

I'm trying to use CXML, specifically the Klacks parser, to read
streaming XML from a network socket (I'm writing a Jabber library),
but I'm having problems with buffering.  I'm using this code for
testing:

(defun cxml-test (host port &key (buffering nil))
  (let ((socket
	 (usocket:socket-connect host port :element-type '(unsigned-byte 8))))
    (cxml:make-source (usocket:socket-stream socket)
		      :buffering buffering
		      :pathname "foo")))

And then I run (klacks:consume src) repeatedly.

On the sending end, I use "nc -l -w 5 -p 42000", either typing in XML
by hand or by redirecting a real XML file to netcat.

With buffering enabled, this basically works.  However, I need to
process "stanzas" (Jabber term for complete elements that are children
of the root element) as soon as they come in, not when the buffer is
full or when the stream or the root element is closed.  But when I
disable buffering, I get (using CLISP from recent CVS):

AREF: index 1 for #(60) is out of range
   [Condition of type SIMPLE-TYPE-ERROR]

Restarts:
 0: [ABORT] Return to SLIME's top level.
 1: [CLOSE-CONNECTION] Close SLIME connection

Backtrace:
[ SLIME parts skipped ]
  5: INVOKE-DEBUGGER
  6: AREF
  7: REPLACE
  8: #<COMPILED-FUNCTION
       #:|257 305 (DEFMETHOD XSTREAM-UNDERFLOW (#) ...)-25-1-1|>
  9: CXML:MAKE-SOURCE
 10: CXML:MAKE-SOURCE
 11: (CXML:MAKE-SOURCE (USOCKET:SOCKET-STREAM SOCKET) :BUFFERING BUFFERING
      :PATHNAME "foo")
 12: LET
 13: (CXML-TEST '"localhost" '42000 ':BUFFERING 'NIL)

SBCL 1.0.8.46 gets a similar error:

The bounding indices 0 and 2 are bad for a sequence of length 1.
   [Condition of type SB-KERNEL:BOUNDING-INDICES-BAD-ERROR]See also:
  Common Lisp Hyperspec, bounding index designator [glossary]
  Common Lisp Hyperspec, SUBSEQ-OUT-OF-BOUNDS:IS-AN-ERROR [issue]

Restarts:
 0: [ABORT] Return to SLIME's top level.
 1: [ABORT] Exit debugger, returning to top level.

Backtrace:
  0: (SB-IMPL::SIGNAL-BOUNDING-INDICES-BAD-ERROR #(60) 0 2)
  1: (SB-IMPL::SIGNAL-BOUNDING-INDICES-BAD-ERROR #(60) 0 2)
  2: ((SB-PCL::FAST-METHOD RUNES::XSTREAM-UNDERFLOW (RUNES:XSTREAM))
      #<unavailable argument>
      #<unavailable argument>
      #<RUNES:XSTREAM [main document :MAIN file://+/home/foo]>)
  3: (CXML:MAKE-SOURCE
      #<RUNES:XSTREAM [main document :MAIN file://+/home/foo]>)
  4: (NIL)
  5: (SB-INT:SIMPLE-EVAL-IN-LEXENV
      (SETF SRC (CXML-TEST "localhost" 42000 :BUFFERING NIL))
      #<NULL-LEXENV>)

It would be nice if this worked, and if additionally KLACKS:PEEK would
do a non-blocking read.

Magnus