Method: Spreadsheet::Excel::Writer::Workbook#write_changes

Defined in:

lib/spreadsheet/excel/writer/workbook.rb

#write_changes(workbook, io) ⇒ Object

Copy unchanged data verbatim, adjust offsets and write new records for changed data.

# File 'lib/spreadsheet/excel/writer/workbook.rb', line 160

def write_changes workbook, io
  sanitize_worksheets workbook.worksheets
  collect_formats workbook, :existing_document => true
  reader = workbook.ole
  sheet_data = {}
  sst_status, sst_total, sst_strings = complete_sst_update? workbook
  sst = {}
  sst_strings.each_with_index do |str, idx| sst.store str, idx end
  sheets = worksheets(workbook)
  positions = []
  newsheets = []
  sheets.each do |sheet|
    @sst[sheet] = sst
    pos, len = workbook.offsets[sheet.worksheet]
    if pos
      positions.push pos
      sheet.write_changes reader, pos + len, sst_status
    else
      newsheets.push sheet
      sheet.write_from_scratch
    end
    sheet_data[sheet.worksheet] = sheet.data
  end
  Ole::Storage.open io do |ole|
    ole.file.open 'Workbook', 'w' do |writer|
      reader.seek lastpos = 0
      workbook.offsets.select do |key, pair|
        workbook.changes.include? key
      end.sort_by do |key, (pos, len)|
        pos
      end.each do |key, (pos, len)|
        data = reader.read(pos - lastpos)
        writer.write data
        case key
        when Spreadsheet::Worksheet
          writer.write sheet_data[key]
        when :boundsheets
          ## boundsheets are hard to calculate. The offset below is only
          #  correct if there are no more changes in the workbook globals
          #  string after this.
          oldoffset = positions.min - len
          lastpos = pos + len
          bytechange = 0
          buffer = StringIO.new ''
          if tuple = workbook.offsets[:sst]
            write_sst_changes workbook, buffer, writer.pos,
                              sst_total, sst_strings
            pos, len = tuple
            if offset = workbook.offsets[:extsst]
              len += offset[1].to_i
            end
            bytechange = buffer.size - len
            write_boundsheets workbook, writer, oldoffset + bytechange
            reader.seek lastpos
            writer.write reader.read(pos - lastpos)
            buffer.rewind
            writer.write buffer.read
          elsif sst.empty? || workbook.biff_version < 8
            write_boundsheets workbook, writer, oldoffset + bytechange
          else
            write_sst workbook, buffer, writer.pos
            write_boundsheets workbook, writer, oldoffset + buffer.size
            pos = lastpos
            len = positions.min - lastpos
            if len > OPCODE_SIZE
              reader.seek pos
              writer.write reader.read(len - OPCODE_SIZE)
            end
            buffer.rewind
            writer.write buffer.read
            write_eof workbook, writer
          end
        else
          send "write_#{key}", workbook, writer
        end
        lastpos = [pos + len, reader.size - 1].min
        reader.seek lastpos
      end
      writer.write reader.read
      newsheets.each do |sheet|
        writer.write sheet.data
      end
    end
  end
end