anchor.diff:        ((cffi:pointerp data)
   
          (%gl:Buffer-Data target
  -			(* (get-size this) (cffi:foreign-type-size type))
  +			(size-in-bytes this)
   			data
   			usage)
          (setf loaded? t))
  
positive.code:      (unwind-protect
  	  (progn ,@body)
         (clinch::unmap-buffer ,buffer))))
    
    
negative.code: (defmethod size-in-bytes ((this buffer))
    "Calculates how many bytes this buffer consists of."
    (* 
     (get-size this)
     (cffi:foreign-type-size (slot-value this 'type))))
  
  
  