func (self *Packet) PrintTo(p printer.Interface) {
	p.Printf("#%d %s", self.Id, flagString(self.Flag))
	p.Printf("ques %v", self.Question)
	self.Answer.PrintNameTo(p, "answ")
	self.Authority.PrintNameTo(p, "auth")
	self.Addition.PrintNameTo(p, "addi")
}

func (self *Exchange) printTimeTaken(p printer.Interface) {
	d := self.Recv.Timestamp.Sub(self.Send.Timestamp)
	n := d.Nanoseconds()
	var s string
	if n < 1e3 {
		s = fmt.Sprintf("%dns", n)
	} else if n < 1e6 {
		s = fmt.Sprintf("%.1fus", float64(n)/1e3)
	} else if n < 1e9 {
		s = fmt.Sprintf("%.2fms", float64(n)/1e6)
	} else {
		s = fmt.Sprintf("%.3fs", float64(n)/1e9)
	}

	p.Printf("(in %v)", s)
}

func (self *Exchange) printSend(p printer.Interface) {
	p.Printf("%s {", self.Query.String())
	p.ShiftIn()

	switch self.PrintFlag {
	case PrintAll:
		p.Print("send {")
		p.ShiftIn()
		self.Send.PrintTo(p)
		p.ShiftOut("}")
	case PrintReply:
		// do nothing
	default:
		panic("unknown print flag")
	}
}

func (self Section) PrintNameTo(p printer.Interface, name string) {
	if self == nil {
		return
	}
	if len(self) == 0 {
		return
	}

	if len(self) == 1 {
		p.Printf("%s %v", name, self[0])
	} else {
		p.Printf("%s {", name)
		p.ShiftIn()
		self.PrintTo(p)
		p.ShiftOut("}")
	}
}

func (self *Info) PrintTo(p printer.Interface) {
	if len(self.Cnames) > 0 {
		p.Print("cnames {")
		p.ShiftIn()
		for _, r := range self.Cnames {
			p.Printf("%v -> %v", r.Domain, rdata.ToDomain(r.Rdata))
		}
		p.ShiftOut("}")
	}

	if len(self.Results) == 0 {
		p.Print("(unresolvable)")
	} else {
		p.Print("ips {")
		p.ShiftIn()

		for _, r := range self.Results {
			d := r.Domain
			ip := rdata.ToIPv4(r.Rdata)
			if d.Equal(self.Domain) {
				p.Printf("%v", ip)
			} else {
				p.Printf("%v(%v)", ip, d)
			}
		}

		p.ShiftOut("}")
	}

	if len(self.NameServers) > 0 {
		p.Print("servers {")
		p.ShiftIn()

		for _, ns := range self.NameServers {
			p.Printf("%v", ns)
		}

		p.ShiftOut("}")
	}

	if len(self.Records) > 0 {
		p.Print("records {")
		p.ShiftIn()

		for _, rr := range self.Records {
			p.Printf("%v", rr.Digest())
		}

		p.ShiftOut("}")
	}
}

func (self *Exchange) printRecv(p printer.Interface) {
	switch self.PrintFlag {
	case PrintAll:
		if self.Recv != nil {
			p.Print("recv {")
			p.ShiftIn()
			self.Recv.PrintTo(p)
			p.ShiftOut("}")
		}

		if self.Error != nil {
			p.Printf("error %v", self.Error)
		}
	case PrintReply:
		if self.Recv != nil {
			self.Recv.Packet.PrintTo(p)
			self.printTimeTaken(p)
		}
		if self.Error != nil {
			p.Printf("error %v", self.Error)
		}
	default:
		panic("unknown print flag")
	}

	p.ShiftOut("}")
}

func (self *Message) PrintTo(p printer.Interface) {
	p.Printf("@%s", addrString(self.RemoteAddr))
	self.Packet.PrintTo(p)
}

func (self Section) PrintTo(p printer.Interface) {
	for _, rr := range self {
		p.Print(rr)
	}
}