# File lib/spreadsheet/excel/writer/workbook.rb, line 72
  def complete_sst_update? workbook
    stored = workbook.sst.collect do |entry| entry.content end
    current = worksheets(workbook).inject [] do |memo, worksheet|
      memo.concat worksheet.strings
    end
    total = current.size
    current.uniq!
    current.delete ''
    if (stored - current).empty? && !stored.empty?
      ## if all previously stored strings are still needed, we don't have to
      #  rewrite all cells because the sst-index of such string does not change.
      additions = current - stored
      [:partial_update, total, stored + additions]
    else
      [:complete_update, total, current]
    end
  end