Initial commit

raknet/datagram.go

@@ -0,0 +1,122 @@
+package raknet
+
+type Datagram struct {
+	SeqNum uint32
+	Frames []*Frame
+}
+
+func (d *Datagram) Encode() []byte {
+	s := NewStream()
+	s.WriteByte(0x84)
+	s.WriteUint24LE(d.SeqNum)
+	for _, f := range d.Frames {
+		f.Encode(s)
+	}
+	return s.Bytes()
+}
+
+func DecodeDatagram(data []byte) (*Datagram, error) {
+	s := NewStreamBytes(data)
+	_, err := s.ReadByte()
+	if err != nil {
+		return nil, err
+	}
+	seq, err := s.ReadUint24LE()
+	if err != nil {
+		return nil, err
+	}
+	d := &Datagram{SeqNum: seq}
+	for s.Len() >= 3 {
+		f, err := DecodeFrame(s)
+		if err != nil {
+			break
+		}
+		d.Frames = append(d.Frames, f)
+	}
+	return d, nil
+}
+
+func (d *Datagram) Size() int {
+	size := 4
+	for _, f := range d.Frames {
+		size += f.Size()
+	}
+	return size
+}
+
+func EncodeACK(seqNums []uint32) []byte {
+	return encodeAckNack(0xc0, seqNums)
+}
+
+func EncodeNACK(seqNums []uint32) []byte {
+	return encodeAckNack(0xa0, seqNums)
+}
+
+func encodeAckNack(id byte, seqNums []uint32) []byte {
+	if len(seqNums) == 0 {
+		s := NewStream()
+		s.WriteByte(id)
+		s.WriteUint16BE(0)
+		return s.Bytes()
+	}
+
+	type run struct{ start, end uint32 }
+	var runs []run
+	cur := run{seqNums[0], seqNums[0]}
+	for _, n := range seqNums[1:] {
+		if n == cur.end+1 {
+			cur.end = n
+		} else {
+			runs = append(runs, cur)
+			cur = run{n, n}
+		}
+	}
+	runs = append(runs, cur)
+
+	s := NewStream()
+	s.WriteByte(id)
+	s.WriteUint16BE(uint16(len(runs)))
+	for _, r := range runs {
+		if r.start == r.end {
+			s.WriteBool(true)
+			s.WriteUint24LE(r.start)
+		} else {
+			s.WriteBool(false)
+			s.WriteUint24LE(r.start)
+			s.WriteUint24LE(r.end)
+		}
+	}
+	return s.Bytes()
+}
+
+func DecodeACKNACK(data []byte) ([]uint32, error) {
+	s := NewStreamBytes(data)
+	s.Skip(1)
+	count, err := s.ReadUint16BE()
+	if err != nil {
+		return nil, err
+	}
+	var nums []uint32
+	for i := 0; i < int(count); i++ {
+		single, err := s.ReadBool()
+		if err != nil {
+			return nil, err
+		}
+		start, err := s.ReadUint24LE()
+		if err != nil {
+			return nil, err
+		}
+		if single {
+			nums = append(nums, start)
+		} else {
+			end, err := s.ReadUint24LE()
+			if err != nil {
+				return nil, err
+			}
+			for n := start; n <= end; n++ {
+				nums = append(nums, n)
+			}
+		}
+	}
+	return nums, nil
+}