cleanly separate version handling

packer/packer.go

@@ -46,63 +46,68 @@ func splitHeader(header []byte, names []string) (map[string]string, error) {
 	return result, nil
 }
 
-//ReadMessage -
+// ReadMessage checks the protocol and switches accordingly
 func ReadMessage(b []byte) (*Packer, error) {
 	// Detect protocol in use
 	if b[0] == packerV1 {
-		// Separate the header and body using the header length in the second byte.
-		p := NewPacker(nil)
-		header := b[2 : b[1]+2]
-		data := b[b[1]+2:]
-
-		// Handle the different parts of the header.
-		parts, err := splitHeader(header, []string{"address family", "address", "port", "data length", "service"})
-		if err != nil {
-			return nil, err
-		}
-
-		if familyText := parts["address family"]; familyText == addressFamilyText[FamilyIPv4] {
-			p.Header.family = FamilyIPv4
-		} else if familyText == addressFamilyText[FamilyIPv6] {
-			p.Header.family = FamilyIPv6
-		} else {
-			return nil, fmt.Errorf("Address family %q not supported", familyText)
-		}
-
-		p.Header.address = net.ParseIP(parts["address"])
-		if p.Header.address == nil {
-			return nil, fmt.Errorf("Invalid network address %q", parts["address"])
-		} else if p.Header.family == FamilyIPv4 && p.Header.address.To4() == nil {
-			return nil, fmt.Errorf("Address %q is not in address family %s", parts["address"], p.Header.Family())
-		}
-
-		//handle port
-		if port, err := strconv.Atoi(parts["port"]); err != nil {
-			return nil, fmt.Errorf("Error converting port %q: %v", parts["port"], err)
-		} else if port <= 0 || port > 65535 {
-			return nil, fmt.Errorf("Port %d out of range", port)
-		} else {
-			p.Header.port = port
-		}
-
-		//handle data length
-		if dataLen, err := strconv.Atoi(parts["data length"]); err != nil {
-			return nil, fmt.Errorf("Error converting data length %q: %v", parts["data length"], err)
-		} else if dataLen != len(data) {
-			return nil, fmt.Errorf("Data length %d doesn't match received length %d", dataLen, len(data))
-		}
-
-		//handle Service
-		p.Header.service = parts["service"]
-
-		//handle payload
-		p.Data.AppendBytes(data)
-		return p, nil
+		return ReadV1Message(b)
 	}
 
 	return nil, fmt.Errorf("Version %d not supported", 255-b[0])
 }
 
+// ReadV1Message parses a v1-formatted message
+func ReadV1Message(b []byte) (*Packer, error) {
+	// Separate the header and body using the header length in the second byte.
+	p := NewPacker(nil)
+	header := b[2 : b[1]+2]
+	data := b[b[1]+2:]
+
+	// Handle the different parts of the header.
+	parts, err := splitHeader(header, []string{"address family", "address", "port", "data length", "service"})
+	if err != nil {
+		return nil, err
+	}
+
+	if familyText := parts["address family"]; familyText == addressFamilyText[FamilyIPv4] {
+		p.Header.family = FamilyIPv4
+	} else if familyText == addressFamilyText[FamilyIPv6] {
+		p.Header.family = FamilyIPv6
+	} else {
+		return nil, fmt.Errorf("Address family %q not supported", familyText)
+	}
+
+	p.Header.address = net.ParseIP(parts["address"])
+	if p.Header.address == nil {
+		return nil, fmt.Errorf("Invalid network address %q", parts["address"])
+	} else if p.Header.family == FamilyIPv4 && p.Header.address.To4() == nil {
+		return nil, fmt.Errorf("Address %q is not in address family %s", parts["address"], p.Header.Family())
+	}
+
+	//handle port
+	if port, err := strconv.Atoi(parts["port"]); err != nil {
+		return nil, fmt.Errorf("Error converting port %q: %v", parts["port"], err)
+	} else if port <= 0 || port > 65535 {
+		return nil, fmt.Errorf("Port %d out of range", port)
+	} else {
+		p.Header.port = port
+	}
+
+	//handle data length
+	if dataLen, err := strconv.Atoi(parts["data length"]); err != nil {
+		return nil, fmt.Errorf("Error converting data length %q: %v", parts["data length"], err)
+	} else if dataLen != len(data) {
+		return nil, fmt.Errorf("Data length %d doesn't match received length %d", dataLen, len(data))
+	}
+
+	//handle Service
+	p.Header.service = parts["service"]
+
+	//handle payload
+	p.Data.AppendBytes(data)
+	return p, nil
+}
+
 //PackV1 -- Outputs version 1 of packer
 func (p *Packer) PackV1() bytes.Buffer {
 	header := strings.Join([]string{