anchor.diff:      (setf (nibbles:ub64ref/le data 40) (getf header :entry-fref))
       (setf (nibbles:ub64ref/le data 48) (getf header :initial-thread))
       (setf (nibbles:ub64ref/le data 56) (getf header :nil-value))
  -    (setf (nibbles:ub32ref/le data 64) (encode-architecture (getf header :architecture)))
  +    (setf (aref data 64) (encode-architecture (getf header :architecture)))
  +    (setf (nibbles:ub64ref/le data 72) (getf header :initial-stack-pointer))
       (setf (nibbles:ub64ref/le data 96) (getf header :bml4))
       (setf (nibbles:ub64ref/le data 104) (getf header :freelist))
       data))
  
positive.code:                             (1 :x86-64)
                              (2 :arm64)
                              (t `(:unknown ,architecture)))
              :bml4 bml4
              :freelist freelist))))
  
  
negative.code:   (let ((major (nibbles:ub16ref/le header 32))
          (minor (nibbles:ub16ref/le header 34)))
      (when (not (and (eql major 0)
                      (eql minor 26)))
        (error "Image has unsupported protocol version ~D.~D.~%" major minor))
      (let* ((uuid (subseq header 16 32))
             (entry-fref (nibbles:ub64ref/le header 40))
             (initial-thread (nibbles:ub64ref/le header 48))
             (nil-value (nibbles:ub64ref/le header 56))
             (architecture (aref header 64))
             (initial-stack-pointer (nibbles:ub64ref/le header 72))
             (bml4 (nibbles:ub64ref/le header 96))
             (freelist (nibbles:ub64ref/le header 104)))
        (list :uuid uuid
  