anchor.diff:                             (make-instance 'fat32-file-character-stream
                                             :direction direction
                                             :read-buffer buffer
  -                                          :read-buffer-position -1
  +                                          :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))
  
positive.code:   (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))
  
  ;;;; testing
  #|
  
negative.code: 
    (with-fat32-host-locked (host)
      (let ((buffer nil)
            (read-buffer-position 0)
            (read-buffer-size 0))
  
        (when (member direction '(:output :io))
  