def data(rec)
      @io.seek(rec.data_offset, IO::SEEK_SET)
      @io.read(rec.data_length)
    end
def data(rec)
      @io.seek(rec.data_offset, IO::SEEK_SET)
      @io.read(rec.data_length)
    end
Reads the data for a given record.

 @param rec [ResourceRecord] the record to read the data for.