gistfile1.txt

(defmethod tess-begin-polygon ((tess tessellator) &optional (polygon-data nil))
  (let* ((polygon-data-id 
          (or (loop for value being the hash-values of (polygon-data tess)
                 using (hash-key key)
                 when (eq value polygon-data)
                 return key)
              (hash-table-count (polygon-data tess))))
         (foreign-key (foreign-alloc :uint64 :initial-contents (list (id tess) polygon-data-id))))
    
    (setf (gethash polygon-data-id (polygon-data tess)) polygon-data)

    (save-data-to-free foreign-key tess)
    (glu-tess-begin-polygon (glu-tessellator tess) foreign-key)))