# File lib/gettext/mofile.rb, line 207
    def save_to_stream(io)
      header_size = 4 * 7
      table_size  = 4 * 2 * size

      hash_table_size = next_prime((size * 4) / 3) 
      hash_table_size = 3 if hash_table_size <= 2
      header = Header.new(
                          MAGIC_LITTLE_ENDIAN,          # magic
                          0,                            # revision
                          size,                         # nstrings
                          header_size,                  # orig_table_offset
                          header_size + table_size,     # translated_table_offset
                          hash_table_size,              # hash_table_size
                          header_size + table_size * 2  # hash_table_offset
                          )
      io.write(header.to_a.pack('a4V*'))

      ary = to_a
      ary.sort!{|a, b| a[0] <=> b[0]} # sort by original string

      pos = header.hash_table_size * 4 + header.hash_table_offset

      orig_table_data = Array.new()
      ary.each{|item, _|
        orig_table_data.push(item.bytesize)
        orig_table_data.push(pos)
        pos += item.bytesize + 1 # +1 is <NUL>
      }
      io.write(orig_table_data.pack('V*'))

      trans_table_data = Array.new()
      ary.each{|_, item|
        trans_table_data.push(item.bytesize)
        trans_table_data.push(pos)
        pos += item.bytesize + 1 # +1 is <NUL>
      }
      io.write(trans_table_data.pack('V*'))

      hash_tab = Array.new(hash_table_size)
      j = 0
      ary[0...size].each {|key, _|
        hash_val = hash_string(key)
        idx = hash_val % hash_table_size
        if hash_tab[idx] != nil
          incr = 1 + (hash_val % (hash_table_size - 2))
          begin
            if (idx >= hash_table_size - incr)
              idx -= hash_table_size - incr
            else
              idx += incr
            end
          end until (hash_tab[idx] == nil)
        end
        hash_tab[idx] = j + 1
        j += 1
      }
      hash_tab.collect!{|i| i ? i : 0}

      io.write(hash_tab.pack('V*'))

      ary.each{|item, _| io.write(item); io.write("\0") }
      ary.each{|_, item| io.write(item); io.write("\0") }

      self
    end