anchor.diff:                                     (sys.int::ub64ref/le superblock 104))
                        :volume-name (map 'string #'code-char (subseq superblock 120 136))
                        :last-mounted (map 'string #'code-char (subseq superblock 136 200))
  -                     :algo-bitmap (sys.int::ub32ref/le superblock 200)
  +                     :algorithm-bitmap (sys.int::ub32ref/le superblock 200)
                        :prealloc-blocks (aref superblock 204)
                        :prealloc-dir-blocks (aref superblock 205)
  +                     :reserved-gdt-blocks (sys.int::ub16ref/le superblock 206)
                        :journal-uuid (logior (ash (sys.int::ub64ref/le superblock 216) 64)
                                              (sys.int::ub64ref/le superblock 208))
                        :journal-inum (sys.int::ub32ref/le superblock 224)
  
positive.code: 
  (defstruct superblock
    (inodes-count nil :type (unsigned-byte 32))
    (blocks-count nil :type (unsigned-byte 32))
    (r-blocks-count nil :type (unsigned-byte 32))
    (free-blocks-count nil :type (unsigned-byte 32))
    (free-inodes-count nil :type (unsigned-byte 32))
    (first-data-block nil :type (unsigned-byte 32))
    (log-block-size nil :type (unsigned-byte 32))
    (log-frag-size nil :type (unsigned-byte 32))
    (blocks-per-group nil :type (unsigned-byte 32))
    (frags-per-group nil :type (unsigned-byte 32))
    (inodes-per-group nil :type (unsigned-byte 32))
    (mtime nil :type (unsigned-byte 32))
    (wtime nil :type (unsigned-byte 32))
  
negative.code:   (uuid nil :type (unsigned-byte 128))
    (volume-name nil :type string)
    (last-mounted nil :type string)
    (algorithm-bitmap nil :type (unsigned-byte 32))
    (prealloc-blocks nil :type (unsigned-byte 8))
    (prealloc-dir-blocks nil :type (unsigned-byte 8))
    (reserved-gdt-blocks nil :type (unsigned-byte 16))
    (journal-uuid nil :type (unsigned-byte 128))
    (journal-inum nil :type (unsigned-byte 32))
    (journal-dev nil :type (unsigned-byte 32))
    (last-orphan nil :type (unsigned-byte 32))
    (hash-seed nil)
    (def-hash-version nil :type (unsigned-byte 8))
    (jnl-backup-type nil :type (unsigned-byte 8))
    (desc-size nil :type (unsigned-byte 16))
    (default-mount-options nil :type (unsigned-byte 32))
    (first-meta-bg nil :type (unsigned-byte 32))
    (mkfs-time nil :type (unsigned-byte 32))
    (jnl-blocks nil)
    (min-extra-isize nil :type (unsigned-byte 16))
    (want-extra-isize nil :type (unsigned-byte 16))
    (flags nil :type (unsigned-byte 32))
    (raid-stride nil :type (unsigned-byte 16))
    (mmp-interval nil :type (unsigned-byte 16))
    (mmp-block nil :type (unsigned-byte 64))
    (raid-stripe-width nil :type (unsigned-byte 32))
    (log-groups-per-flex nil :type (unsigned-byte 8))
    (checksum-type nil :type (unsigned-byte 8))
    (reserved-pad nil :type (unsigned-byte 16))
    (kbytes-written nil :type (unsigned-byte 64))
    (snapshot-inum nil :type (unsigned-byte 32))
    (snapshot-id nil :type (unsigned-byte 32))
    (snapshot-r-blocks-count nil :type (unsigned-byte 64))
    (snapshot-list nil :type (unsigned-byte 32))
    (error-count nil :type (unsigned-byte 32))
    (first-error-time nil :type (unsigned-byte 32))
    (first-error-ino nil :type (unsigned-byte 32))
    (first-error-block nil :type (unsigned-byte 64))
    (first-error-func nil)
    (first-error-line nil :type (unsigned-byte 32))
    (last-error-time nil :type (unsigned-byte 32))
    (last-error-ino nil :type (unsigned-byte 32))
    (last-error-line nil :type (unsigned-byte 32))
    (last-error-block nil :type (unsigned-byte 64))
    (last-error-func nil)
    (mount-opts nil)
    (usr-quota-inum nil :type (unsigned-byte 32))
    (grp-quota-inum nil :type (unsigned-byte 32))
    (overhead-blocks nil :type (unsigned-byte 32))
    (backup-bgs nil)
    (encrypt-algos nil)
    (encrypt-pw-salt nil)
    (lpf-ino nil :type (unsigned-byte 32))
    (prj-quota-inum nil :type (unsigned-byte 32))
    (checksum-seed nil :type (unsigned-byte 32))
    (reserved nil)
    (checksum nil :type (unsigned-byte 32)))
  
  (defun check-magic (magic)
    (unless (= magic #xEF53)
  