anchor.diff:  (defmethod sys.gray:stream-element-type ((stream fat32-file-character-stream))
     'character)
   
  +;; WIP
  +;; TODO resize to files bigger than 1 cluster
   (defmethod sys.gray:stream-write-byte ((stream fat32-file-stream) byte)
  -  (error "Feature not implemented: ~a" 'sys.gray:stream-write-byte))
  +  (assert (member (direction stream) '(:output :io)))
  +  (when (> (buffer-offset stream)
  +           (read-buffer-size stream))
  +    (setf (read-buffer-size stream)
  +          (buffer-offset stream)))
  +  (setf (aref (read-buffer stream)
  +              (buffer-offset stream))
  +        byte)
  +  (incf (buffer-offset stream)))
   
   (defmethod sys.gray:stream-read-byte ((stream fat32-file-stream))
     (assert (member (direction stream) '(:input :io)))
     (let ((char (aref (read-buffer stream)
  -                    (incf (read-buffer-offset stream)))))
  -    (if (<= (read-buffer-size stream)
  -            (read-buffer-offset stream))
  +                    (buffer-offset stream))))
  +    (incf (buffer-offset stream))
  +    (if (or (< 4095 ;; tmp
  +               (buffer-offset stream))
  +             (<= (read-buffer-size stream)
  +                 (buffer-offset stream)))
           :eof
           char)))
   
  
positive.code: ;;;; Copyright (c) 2017-2018 Bruno Cichon <ebrasca@librepanther.com>
  ;;;; This code is licensed under the MIT license.
  ;;;; For now only support reading fat32 FS.
  
  (defpackage :mezzano.fat32-file-system
    (:use :cl :mezzano.file-system)
    (:export #:read-fat32-structure
             #:read-fat32-info-structure
             #:read-sector
             #:read-cluster
             #:read-file
             #:file-p
             #:read-dir-from-file
             #:read-dir-from-cluster
             #:decode-time
             #:decode-date))
  
  (in-package :mezzano.fat32-file-system)
  
  
negative.code: 
  (defun check-media-type (media-type)
    (loop :for n :in '(#xF0 #xF8 #xF9 #xFA #xFB #xFC #xFD #xFE #xFF)
          :do (when (= n media-type)
                (return media-type))
          :finally (error "Bad media-type : ~a .
  Valid media-type ara #xF0 #xF8 #xF9 #xFA #xFB #xFC #xFD #xFE #xFF" media-type)))
  
  (defun check-fat-type-label32 (fat-type-label)
  