# File lib/spreadsheet/excel/writer/workbook.rb, line 76
  def complete_sst_update? workbook
    stored = workbook.sst.collect do |entry| entry.content end
    num_total = 0
    current = worksheets(workbook).inject(Hash.new(0)) do |memo, worksheet|
      worksheet.strings.each do |k,v|
        memo[k] += v
        num_total += v
      end
      memo
    end
    current.delete ''
    if !stored.empty? && stored.all?{|x| current.include?(x) }
      ## 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.keys - stored
      [:partial_update, num_total, stored + additions]
    else
      [:complete_update, num_total, current.keys]
    end
  end