mess around with a sort node concept for communicating over packet RF things

node/node.go

@@ -0,0 +1,100 @@
+package node
+
+import (
+	"errors"
+)
+
+type Node struct {
+	id             NodeId
+	transport      Transport
+	sequenceNumber uint32
+}
+
+func New(id NodeId, transport Transport) *Node {
+	return &Node{
+		id:        id,
+		transport: transport,
+	}
+}
+
+type NodeId uint8
+
+func (id NodeId) IsBroadcast() bool {
+	return id == 0xFF
+}
+
+func (b *Node) Receive(timeout uint32) (NodeId, uint32, []byte, error) {
+	data, err := b.transport.Rx(timeout)
+	if err != nil {
+		return 0, 0, nil, err
+	}
+	if len(data) < 6 {
+		return 0, 0, nil, errors.New("invalid message length")
+	}
+	sourceId := NodeId(data[0])
+	targetId := NodeId(data[1])
+	if targetId != b.id && !targetId.IsBroadcast() {
+		return 0, 0, nil, nil
+	}
+	seq := uint32(data[2])<<24 | uint32(data[3])<<16 | uint32(data[4])<<8 | uint32(data[5])
+	payload := data[6:]
+	return sourceId, seq, payload, nil
+}
+
+func (b *Node) ReceiveWithAck(timeout uint32) (NodeId, uint32, []byte, error) {
+	data, err := b.transport.Rx(timeout)
+	if err != nil {
+		return 0, 0, nil, err
+	}
+	if len(data) < 6 {
+		return 0, 0, nil, errors.New("invalid message length")
+	}
+	sourceId := NodeId(data[0])
+	targetId := NodeId(data[1])
+	if targetId != b.id && !targetId.IsBroadcast() {
+		return 0, 0, nil, errors.New("message not intended for this node")
+	}
+	seq := uint32(data[2])<<24 | uint32(data[3])<<16 | uint32(data[4])<<8 | uint32(data[5])
+	payload := data[6:]
+	ackMsg := make([]byte, 6)
+	ackMsg[0] = byte(b.id)
+	ackMsg[1] = byte(sourceId)
+	ackMsg[2] = byte(seq >> 24)
+	ackMsg[3] = byte(seq >> 16)
+	ackMsg[4] = byte(seq >> 8)
+	ackMsg[5] = byte(seq)
+	err = b.transport.Tx(ackMsg, timeout)
+	if err != nil {
+		return 0, 0, nil, err
+	}
+	return sourceId, seq, payload, nil
+}
+
+func (b *Node) SendWithAck(target NodeId, payload []byte, timeout uint32) error {
+	if target.IsBroadcast() {
+		return errors.New("cannot send with ack to broadcast address")
+	}
+	msg := make([]byte, 6)
+	msg[0] = byte(b.id)
+	msg[1] = byte(target)
+	sentSeq := b.sequenceNumber
+	msg[2] = byte(sentSeq >> 24)
+	msg[3] = byte(sentSeq >> 16)
+	msg[4] = byte(sentSeq >> 8)
+	msg[5] = byte(sentSeq)
+	b.sequenceNumber++
+	msg = append(msg, payload...)
+	b.transport.Tx(msg, timeout)
+
+	sender, receivedSeq, _, err := b.Receive(timeout)
+	if err != nil {
+		return err
+	}
+	if sender != target {
+		return errors.New("received ACK from unexpected sender")
+	}
+	if receivedSeq != sentSeq {
+		return errors.New("received ACK with unexpected sequence number")
+	}
+	return nil
+}