def store_autofilterinfo   #:nodoc:
    # Only write the record if the worksheet contains an autofilter.
    return '' if @filter_area.count == 0

    record      = 0x009D      # Record identifier
    length      = 0x0002      # Number of bytes to follow
    num_filters = @filter_area.count

    header = [record, length].pack('vv')
    data   = [num_filters].pack('v')

    prepend(header, data)
  end
def store_autofilterinfo   #:nodoc:
    # Only write the record if the worksheet contains an autofilter.
    return '' if @filter_area.count == 0

    record      = 0x009D      # Record identifier
    length      = 0x0002      # Number of bytes to follow
    num_filters = @filter_area.count

    header = [record, length].pack('vv')
    data   = [num_filters].pack('v')

    prepend(header, data)
  end
Write BIFF record AUTOFILTERINFO.