anchor.diff:                         :direction :output
                          :if-exists :overwrite
                          :element-type '(unsigned-byte 8))
  -      (when (= (file-position f offset) offset)
  +      (when (file-position f offset)
           (write-sequence zeroes-buffer f)))))
   
   (defun write-token (path token &optional (offset 0))
  
positive.code:                      :direction :output
                       :if-exists :overwrite
                       :element-type '(unsigned-byte 8))
      (when (= (file-position f offset) offset)
        (write-sequence token f))))
  
negative.code:   (with-open-file (f path
                       :direction :input
                       :element-type '(unsigned-byte 8))
      (when (file-position f offset)
        (let ((bytes (make-array *fingerprint-length* :element-type '(unsigned-byte 8))))
          (read-sequence bytes f)
          (every #'= bytes *fingerprint*)))))
  