Returns the next code-block in the current tile for the specified component. The order in which code-blocks are returned is not specified. However each code-block is returned only once and all code-blocks will be returned if the method is called 'N' times, where 'N' is the number of code-blocks in the tile. After all the code-blocks have been returned for the current tile calls to this method will return 'null'.

       <p>When changing the current tile (through 'setTile()' or 'nextTile()')
       this method will always return the first code-block, as if this method
       was never called before for the new current tile.</p><p>The data returned by this method is the data in the internal buffer
       of this object, and thus can not be modified by the caller. The
       'offset' and 'scanw' of the returned data have, in general, some
       non-zero value. The 'magbits' of the returned data is not set by this
       method and should be ignored. See the 'CBlkWTData' class.</p><p>The 'ulx' and 'uly' members of the returned 'CBlkWTData' object
       contain the coordinates of the top-left corner of the block, with
       respect to the tile, not the subband.</p>