Initial commit

raknet/frame.go

@@ -0,0 +1,109 @@
+package raknet
+
+import "fmt"
+
+type Frame struct {
+	Reliability  Reliability
+	Split        bool
+	MessageIndex uint32
+	OrderIndex   uint32
+	OrderChannel byte
+	SplitCount   uint32
+	SplitID      uint16
+	SplitIndex   uint32
+	Payload      []byte
+}
+
+func (f *Frame) Encode(s *Stream) {
+	flags := byte(f.Reliability) << 5
+	if f.Split {
+		flags |= 0x10
+	}
+	s.WriteByte(flags)
+	s.WriteUint16BE(uint16(len(f.Payload) * 8))
+
+	if f.Reliability.IsReliable() {
+		s.WriteUint24LE(f.MessageIndex)
+	}
+	if f.Reliability.IsOrdered() || f.Reliability.IsSequenced() {
+		s.WriteUint24LE(f.OrderIndex)
+		s.WriteByte(f.OrderChannel)
+	}
+	if f.Split {
+		s.WriteUint32BE(f.SplitCount)
+		s.WriteUint16BE(f.SplitID)
+		s.WriteUint32BE(f.SplitIndex)
+	}
+	s.WriteBytes(f.Payload)
+}
+
+func DecodeFrame(s *Stream) (*Frame, error) {
+	flags, err := s.ReadByte()
+	if err != nil {
+		return nil, err
+	}
+	f := &Frame{}
+	f.Reliability = Reliability((flags >> 5) & 0x07)
+	f.Split = (flags & 0x10) != 0
+
+	bitLen, err := s.ReadUint16BE()
+	if err != nil {
+		return nil, err
+	}
+	length := int(bitLen / 8)
+
+	if f.Reliability.IsReliable() {
+		f.MessageIndex, err = s.ReadUint24LE()
+		if err != nil {
+			return nil, err
+		}
+	}
+	if f.Reliability.IsOrdered() || f.Reliability.IsSequenced() {
+		f.OrderIndex, err = s.ReadUint24LE()
+		if err != nil {
+			return nil, err
+		}
+		f.OrderChannel, err = s.ReadByte()
+		if err != nil {
+			return nil, err
+		}
+	}
+	if f.Split {
+		sc, err := s.ReadUint32BE()
+		if err != nil {
+			return nil, err
+		}
+		f.SplitCount = sc
+		si, err := s.ReadUint16BE()
+		if err != nil {
+			return nil, err
+		}
+		f.SplitID = si
+		idx, err := s.ReadUint32BE()
+		if err != nil {
+			return nil, err
+		}
+		f.SplitIndex = idx
+	}
+
+	f.Payload, err = s.ReadBytes(length)
+	if err != nil {
+		return nil, fmt.Errorf("frame payload: need %d, %w", length, err)
+	}
+	return f, nil
+}
+
+func (f *Frame) Size() int {
+	size := 3
+	if f.Reliability.IsReliable() {
+		size += 3
+	}
+	if f.Reliability.IsOrdered() || f.Reliability.IsSequenced() {
+		size += 4
+	}
+	if f.Split {
+		size += 10
+	}
+	size += len(f.Payload)
+	return size
+}