add SLIP framing

internals/framing/slip.go

@@ -0,0 +1,52 @@
+package framing
+
+type SlipFramer struct {
+	buffer []byte
+}
+
+func NewSlipFramer() *SlipFramer {
+	return &SlipFramer{buffer: []byte{}}
+}
+
+func (sf *SlipFramer) Frame(data []byte) [][]byte {
+	messages := [][]byte{}
+	END := byte(0xc0)
+	ESC := byte(0xdb)
+	ESC_END := byte(0xdc)
+	ESC_ESC := byte(0xdd)
+
+	escapeNext := false
+	for _, packetByte := range data {
+
+		if packetByte == ESC {
+			escapeNext = true
+			continue
+		}
+
+		if escapeNext {
+			if packetByte == ESC_END {
+				sf.buffer = append(sf.buffer, END)
+			} else if packetByte == ESC_ESC {
+				sf.buffer = append(sf.buffer, ESC)
+			}
+			escapeNext = false
+		} else if packetByte == END {
+			if len(sf.buffer) == 0 {
+				// opening END byte, can discard
+				continue
+			} else {
+				message := sf.buffer
+				messages = append(messages, message)
+			}
+			sf.buffer = []byte{}
+		} else {
+			sf.buffer = append(sf.buffer, packetByte)
+		}
+	}
+
+	return messages
+}
+
+func (sf *SlipFramer) Clear() {
+	sf.buffer = []byte{}
+}