anchor.diff:    "Get the handle currently in use by cl-slp"
     (if *slp-handle*
         (mem-ref *slp-handle* 'slp-handle)
  -      (error 'slp-condition
  -			 :message "SLP not opened, call OPEN-SLP first")))
  +      (error 'slp-error
  +	     :code ""
  +	     :message "SLP not opened, call OPEN-SLP first")))
   
   ;; slp free
   
  
positive.code: 
  (defparameter *slp-handle* nil)
  
  (defcfun ("SLPOpen" %slp-open) slp-error
    (lang :string)
    (is-async slp-bool)
    (handle (:pointer slp-handle)))
  
  (defun slp-open (&optional is-async)
    "Initialise access to the OpenSLP library"
    (unless *slp-handle*
      (let ((handle (foreign-alloc 'slp-handle)))
        (with-foreign-string (lang "en")
  		(let ((ret-code (%slp-open lang is-async handle)))
  		  (setf *slp-handle* handle)
  		  (slp-error ret-code))))))
  
  ;; close
  
  
negative.code: 
  (define-register-callback default-deregister-callback
      (handle error-code cookie)
    t)
  
  (defun slp-deregister (url
  