rename framing to framer

internal/framer/framer.go

@@ -0,0 +1,26 @@
+package framer
+
+import (
+	"fmt"
+)
+
+type Framer interface {
+	Decode([]byte) [][]byte
+	Encode([]byte) []byte
+	Clear()
+}
+
+func GetFramer(framingType string) (Framer, error) {
+	switch framingType {
+	case "CR":
+		return NewByteSeparatorFramer([]byte{'\r'}), nil
+	case "LF":
+		return NewByteSeparatorFramer([]byte{'\n'}), nil
+	case "CRLF":
+		return NewByteSeparatorFramer([]byte{'\r', '\n'}), nil
+	case "SLIP":
+		return NewSlipFramer(), nil
+	default:
+		return nil, fmt.Errorf("unknown framing method: %s", framingType)
+	}
+}

internal/framer/separator.go

@@ -0,0 +1,37 @@
+package framer
+
+import (
+	"bytes"
+)
+
+type ByteSeparatorFramer struct {
+	buffer    []byte
+	separator []byte
+}
+
+func NewByteSeparatorFramer(separator []byte) *ByteSeparatorFramer {
+	return &ByteSeparatorFramer{separator: separator, buffer: []byte{}}
+}
+
+func (bsf *ByteSeparatorFramer) Decode(data []byte) [][]byte {
+	messages := [][]byte{}
+
+	bsf.buffer = append(bsf.buffer, data...)
+
+	parts := bytes.Split(bsf.buffer, bsf.separator)
+
+	if len(parts) > 0 {
+		bsf.buffer = parts[len(parts)-1]
+		messages = parts[:len(parts)-1]
+	}
+
+	return messages
+}
+
+func (bsf *ByteSeparatorFramer) Encode(data []byte) []byte {
+	return append(data, bsf.separator...)
+}
+
+func (bsf *ByteSeparatorFramer) Clear() {
+	bsf.buffer = []byte{}
+}

internal/framer/slip.go

@@ -0,0 +1,76 @@
+package framer
+
+type SlipFramer struct {
+	buffer []byte
+}
+
+func NewSlipFramer() *SlipFramer {
+	return &SlipFramer{buffer: []byte{}}
+}
+
+func (sf *SlipFramer) Decode(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) Encode(data []byte) []byte {
+	END := byte(0xc0)
+	ESC := byte(0xdb)
+	ESC_END := byte(0xdc)
+	ESC_ESC := byte(0xdd)
+
+	var encodedBytes = []byte{END}
+
+	for _, byteToEncode := range data {
+		switch byteToEncode {
+		case END:
+			encodedBytes = append(encodedBytes, ESC_END)
+		case ESC:
+			encodedBytes = append(encodedBytes, ESC_ESC)
+		default:
+			encodedBytes = append(encodedBytes, byteToEncode)
+		}
+	}
+
+	encodedBytes = append(encodedBytes, END)
+	return encodedBytes
+}
+
+func (sf *SlipFramer) Clear() {
+	sf.buffer = []byte{}
+}