This is the current specification for the BadBlockBlock. The end of data
occurs when bbb_Next is NULL ($FFFFFFFF), and the summed data is exhausted.


   bbb_ID                  == 'BADB'

   bbb_SummedLongs         size of this checksummed structure
                           Note that this is not 64 like most of the other
                           structures.  This is the number of valid longs
                           in this image, and can be from 6 to
                           rdb_blockbytes/4.  the latter is the best size
                           for all blocks other than the last one.

   bbb_ChkSum              block checksum (longword sum to zero)

   bbb_HostID              SCSI Target ID of host
                           This describes the initiator ID for the creator
                           of these blocks.  (see rdb_hostid discussion)

   bbb_Next                block number of the next BadBlockBlock
   bbb_Reserved            set to zeros

   bbb_BlockPairs[61]      pairs of block remapping information
                           The data starts here and continues as long as
                           indicated by bbb_SummedLongs-6: e.g. if
                           bbb_SummedLongs is 128 (512 bytes), 61 pairs
                           are described here.