question: private void writeRootBlock ( final boolean isRootBlock0 , final IRootBlockView rootBlock ) throws IOException { if ( rootBlock == null ) throw new IllegalArgumentException ( ) ; final long position = isRootBlock0 ? OFFSET_ROOT_BLOCK0 : OFFSET_ROOT_BLOCK1 ; FileChannelUtility . writeAll ( reopener , rootBlock . asReadOnlyBuffer ( ) , position ) ; if ( haLog . isDebugEnabled ( ) ) haLog . debug ( "wrote root block: " + rootBlock ) ; }
target:  Writes the root block at the given offset.