Remove magic numbers

protocol.go

@@ -8,9 +8,9 @@ import (
 )
 
 const (
-	RequestPayload = 1 << iota
-	ResponsePayload
-	ReplayedResponsePayload
+	RequestPayload = '1'
+	ResponsePayload = '2'
+	ReplayedResponsePayload = '3'
 )
 
 func uuid() []byte {
@@ -43,26 +43,18 @@ func payloadScanner(data []byte, atEOF bool) (advance int, token []byte, err err
 
 
 // Timing is request start or round-trip time, depending on payloadType
-func payloadHeader(payloadType int, uuid []byte, timing int64) (header []byte) {
+func payloadHeader(payloadType byte, uuid []byte, timing int64) (header []byte) {
 	sTime := strconv.FormatInt(timing, 10)
 
 	//Example:
 	//  3 f45590522cd1838b4a0d5c5aab80b77929dea3b3 1231\n
 	// `+ 1` indicates space characters or end of line
 	header = make([]byte, 1+1+len(uuid)+1+len(sTime)+1)
+	header[0] = payloadType
 	header[1] = ' '
 	header[2+len(uuid)] = ' '
 	header[len(header)-1] = '\n'
 
-	switch payloadType {
-	case RequestPayload:
-		header[0] = '1'
-	case ResponsePayload:
-		header[0] = '2'
-	case ReplayedResponsePayload:
-		header[0] = '3'
-	}
-
 	copy(header[2:], uuid)
 	copy(header[3+len(uuid):], sTime)
 
@@ -81,7 +73,7 @@ func payloadMeta(payload []byte) [][]byte {
 
 func isOriginPayload(payload []byte) bool {
 	switch payload[0] {
-	case '1', '2':
+	case RequestPayload, ResponsePayload:
 		return true
 	default:
 		return false
@@ -89,5 +81,5 @@ func isOriginPayload(payload []byte) bool {
 }
 
 func isRequestPayload(payload []byte) bool {
-	return payload[0] == '1'
+	return payload[0] == RequestPayload
 }