(define (session:extract-key self key)
  (let ((params (sdat-get-params self)))
    (session:extract-key-from-param self params key)))

(define (session:extract-key-from-param self params key)
  (let ((r1     (regexp (string-append "^" key "=([^=]+)$"))))
    ;; (err:log "INFO: Looking for " key " in " params)
    (if (< (length params) 1) #f
	(let loop ((head   (car params))
		   (tail   (cdr params)))
	  (let ((match (string-match r1 head)))
	    (cond
	     (match
	      (let ((session-key (list-ref match 1)))
		;; (err:log "INFO: Found session key=" session-key)
		(sdat-set-session-key! self (list-ref match 1))
		session-key))
	     ((null? tail)
	      #f)
	     (else
	      (loop (car tail)
		    (cdr tail)))))))))