# File ruby/bstream.rb, line 617
        def exec(out)
          @out = out
          begin
                write_int1(M_RETURN)
                write(@sid)
                write_int1(@code)
                case @code
                when R_OK
                  write(@value)
                when R_APP_ERROR,R_PROTOCOL_ERROR,R_FATAL_ERROR
                  write(@err_klass)
                  write(@err_message)
                  write(@err_detail)
                else
                  raise IOError.new("Unknown return code: #{@code}")
                end
          ensure
                @out.flush
                @out = nil
          end
        end