anchor.diff:    (error "Feature not implemented: ~a" 'sys.gray:stream-file-position))
   
   (defmethod sys.gray:stream-file-length ((stream fat32-file-stream))
  -  (error "Feature not implemented: ~a" 'sys.gray:stream-file-length))
  +  (read-buffer-size stream))
   
   ;;;; testing
   #|
  
positive.code: 
    (with-fat32-host-locked (host)
      (let ((buffer nil)
            (read-buffer-size 0))
  
        (when (member direction '(:output :io))
  
negative.code:                            (make-instance 'fat32-file-character-stream
                                            :direction direction
                                            :read-buffer buffer
                                            :read-buffer-position read-buffer-position
                                            :read-buffer-size read-buffer-size))
                            ((and (subtypep element-type '(unsigned-byte 8))
                                  (subtypep '(unsigned-byte 8) element-type))
  