anchor.diff:      (let ((log (make-instance 'log-stream
   			      :stream mapping-stream
   			      :header header
  +			      :tag (let ((octets (flexi-streams:string-to-octets (or tag "DEBG"))))
  +				     (assert (= (length octets) 4))
  +				     octets)
   			      :count count
   			      :size size)))
         ;; write the header back to the file
  
positive.code:   id
    lvl
    time
    msg)
  
  (defun read-log-message (stream)
  
negative.code: ;; ------------
  
      
  (defun make-log-stream (mapping-stream &key (size 512) tag)
    (file-position mapping-stream 0)
    (let* ((map (mapping-stream-mapping mapping-stream))
  	 (header (read-log-header mapping-stream))
  