Remove Order member from Message

Because messages bodies are automatically decoded, the byte order is
only interesting when encoding messages. Now the byte order is passed
to the EncodeTo function.

Author: guelfey

call.go

@@ -1,7 +1,6 @@
 package dbus
 
 import (
-	"encoding/binary"
 	"errors"
 	"strings"
 )
@@ -68,7 +67,6 @@ func (o *Object) Go(method string, flags Flags, ch chan *Call, args ...interface
 	}
 	method = method[i+1:]
 	msg := new(Message)
-	msg.Order = binary.LittleEndian
 	msg.Type = TypeMethodCall
 	msg.serial = <-o.conn.serial
 	msg.Flags = flags & (FlagNoAutoStart | FlagNoReplyExpected)

conn.go

@@ -2,7 +2,6 @@ package dbus
 
 import (
 	"bytes"
-	"encoding/binary"
 	"errors"
 	"io"
 	"os"
@@ -420,7 +419,6 @@ func (conn *Conn) Send(msg *Message, ch chan *Call) *Call {
 // it to conn.out.
 func (conn *Conn) sendError(e Error, dest string, serial uint32) {
 	msg := new(Message)
-	msg.Order = binary.LittleEndian
 	msg.Type = TypeError
 	msg.serial = <-conn.serial
 	msg.Headers = make(map[HeaderField]Variant)
@@ -442,7 +440,6 @@ func (conn *Conn) sendError(e Error, dest string, serial uint32) {
 // sends it to conn.out.
 func (conn *Conn) sendReply(dest string, serial uint32, values ...interface{}) {
 	msg := new(Message)
-	msg.Order = binary.LittleEndian
 	msg.Type = TypeMethodReply
 	msg.serial = <-conn.serial
 	msg.Headers = make(map[HeaderField]Variant)

export.go

@@ -1,7 +1,6 @@
 package dbus
 
 import (
-	"encoding/binary"
 	"errors"
 	"reflect"
 	"strings"
@@ -116,7 +115,6 @@ func (conn *Conn) handleCall(msg *Message) {
 	}
 	if msg.Flags&FlagNoReplyExpected == 0 {
 		reply := new(Message)
-		reply.Order = binary.LittleEndian
 		reply.Type = TypeMethodReply
 		reply.serial = <-conn.serial
 		reply.Headers = make(map[HeaderField]Variant)
@@ -156,7 +154,6 @@ func (conn *Conn) Emit(path ObjectPath, name string, values ...interface{}) erro
 		return errors.New("invalid interface name")
 	}
 	msg := new(Message)
-	msg.Order = binary.LittleEndian
 	msg.Type = TypeSignal
 	msg.serial = <-conn.serial
 	msg.Headers = make(map[HeaderField]Variant)

message.go

@@ -3,6 +3,7 @@ package dbus
 import (
 	"bytes"
 	"encoding/binary"
+	"errors"
 	"fmt"
 	"io"
 	"reflect"
@@ -84,9 +85,6 @@ var requiredFields = [typeMax][]HeaderField{
 
 // Message represents a single DBus message.
 type Message struct {
-	// must be binary.BigEndian or binary.LittleEndian
-	Order binary.ByteOrder
-
 	Type
 	Flags
 	Headers map[HeaderField]Variant
@@ -103,10 +101,10 @@ type header struct {
 	Variant
 }
 
-// DecodeMessage tries to decode a single message from the given reader.
-// The byte order is figured out from the first byte. The possibly returned
-// error can be an error of the underlying reader, an InvalidMessageError or a
-// FormatError.
+// DecodeMessage tries to decode a single message in the D-Bus wire format
+// from the given reader. The byte order is figured out from the first byte.
+// The possibly returned error can be an error of the underlying reader, an
+// InvalidMessageError or a FormatError.
 func DecodeMessage(rd io.Reader) (msg *Message, err error) {
 	var order binary.ByteOrder
 	var hlength, length uint32
@@ -131,7 +129,6 @@ func DecodeMessage(rd io.Reader) (msg *Message, err error) {
 	dec.pos = 1
 
 	msg = new(Message)
-	msg.Order = order
 	err = dec.Decode(&msg.Type, &msg.Flags, &proto, &length, &msg.serial)
 	if err != nil {
 		return nil, err
@@ -185,21 +182,24 @@ func DecodeMessage(rd io.Reader) (msg *Message, err error) {
 	return
 }
 
-// EncodeTo encodes and sends a message to the given writer. If the message is
-// not valid or an error occurs when writing, an error is returned.
-func (msg *Message) EncodeTo(out io.Writer) error {
+// EncodeTo encodes and sends a message to the given writer. The byte order must
+// be either binary.LittleEndian or binary.BigEndian. If the message is not
+// valid or an error occurs when writing, an error is returned.
+func (msg *Message) EncodeTo(out io.Writer, order binary.ByteOrder) error {
 	if err := msg.IsValid(); err != nil {
 		return err
 	}
 	var vs [7]interface{}
-	switch msg.Order {
+	switch order {
 	case binary.LittleEndian:
 		vs[0] = byte('l')
 	case binary.BigEndian:
 		vs[0] = byte('B')
+	default:
+		return errors.New("dbus: invalid byte order")
 	}
 	body := new(bytes.Buffer)
-	enc := NewEncoder(body, msg.Order)
+	enc := NewEncoder(body, order)
 	if len(msg.Body) != 0 {
 		enc.Encode(msg.Body...)
 	}
@@ -214,7 +214,7 @@ func (msg *Message) EncodeTo(out io.Writer) error {
 	}
 	vs[6] = headers
 	var buf bytes.Buffer
-	enc = NewEncoder(&buf, msg.Order)
+	enc = NewEncoder(&buf, order)
 	enc.Encode(vs[:]...)
 	enc.align(8)
 	body.WriteTo(&buf)
@@ -230,11 +230,6 @@ func (msg *Message) EncodeTo(out io.Writer) error {
 // IsValid checks whether msg is a valid message and returns an
 // InvalidMessageError if it is not.
 func (msg *Message) IsValid() error {
-	switch msg.Order {
-	case binary.LittleEndian, binary.BigEndian:
-	default:
-		return InvalidMessageError("invalid byte order")
-	}
 	if msg.Flags & ^(FlagNoAutoStart|FlagNoReplyExpected) != 0 {
 		return InvalidMessageError("invalid flags")
 	}

proto_test.go

@@ -208,15 +208,14 @@ func TestProtoStoreNestedStruct(t *testing.T) {
 func TestMessage(t *testing.T) {
 	buf := new(bytes.Buffer)
 	message := new(Message)
-	message.Order = binary.LittleEndian
 	message.Type = TypeMethodCall
 	message.serial = 32
 	message.Headers = map[HeaderField]Variant{
 		FieldPath:   MakeVariant(ObjectPath("/org/foo/bar")),
 		FieldMember: MakeVariant("baz"),
 	}
 	message.Body = make([]interface{}, 0)
-	err := message.EncodeTo(buf)
+	err := message.EncodeTo(buf, binary.LittleEndian)
 	if err != nil {
 		t.Error(err)
 	}
@@ -228,7 +227,6 @@ func TestMessage(t *testing.T) {
 
 // ordinary org.freedesktop.DBus.Hello call
 var smallMessage = &Message{
-	Order:  binary.LittleEndian,
 	Type:   TypeMethodCall,
 	serial: 1,
 	Headers: map[HeaderField]Variant{
@@ -241,7 +239,6 @@ var smallMessage = &Message{
 
 // org.freedesktop.Notifications.Notify
 var bigMessage = &Message{
-	Order:  binary.LittleEndian,
 	Type:   TypeMethodCall,
 	serial: 2,
 	Headers: map[HeaderField]Variant{
@@ -271,7 +268,7 @@ func BenchmarkDecodeMessageSmall(b *testing.B) {
 
 	b.StopTimer()
 	buf := new(bytes.Buffer)
-	err = smallMessage.EncodeTo(buf)
+	err = smallMessage.EncodeTo(buf, binary.LittleEndian)
 	if err != nil {
 		b.Fatal(err)
 	}
@@ -292,7 +289,7 @@ func BenchmarkDecodeMessageBig(b *testing.B) {
 
 	b.StopTimer()
 	buf := new(bytes.Buffer)
-	err = bigMessage.EncodeTo(buf)
+	err = bigMessage.EncodeTo(buf, binary.LittleEndian)
 	if err != nil {
 		b.Fatal(err)
 	}
@@ -310,7 +307,7 @@ func BenchmarkDecodeMessageBig(b *testing.B) {
 func BenchmarkEncodeMessageSmall(b *testing.B) {
 	var err error
 	for i := 0; i < b.N; i++ {
-		err = smallMessage.EncodeTo(ioutil.Discard)
+		err = smallMessage.EncodeTo(ioutil.Discard, binary.LittleEndian)
 		if err != nil {
 			b.Fatal(err)
 		}
@@ -320,7 +317,7 @@ func BenchmarkEncodeMessageSmall(b *testing.B) {
 func BenchmarkEncodeMessageBig(b *testing.B) {
 	var err error
 	for i := 0; i < b.N; i++ {
-		err = bigMessage.EncodeTo(ioutil.Discard)
+		err = bigMessage.EncodeTo(ioutil.Discard, binary.LittleEndian)
 		if err != nil {
 			b.Fatal(err)
 		}

transport_generic.go

@@ -1,6 +1,7 @@
 package dbus
 
 import (
+	"encoding/binary"
 	"errors"
 	"io"
 )
@@ -30,5 +31,5 @@ func (t genericTransport) SendMessage(msg *Message) error {
 			return errors.New("unix fd passing not enabled")
 		}
 	}
-	return msg.EncodeTo(t)
+	return msg.EncodeTo(t, binary.LittleEndian)
 }

transport_unix.go

@@ -169,7 +169,7 @@ func (t *unixTransport) SendMessage(msg *Message) error {
 		msg.Headers[FieldUnixFDs] = MakeVariant(uint32(len(fds)))
 		oob := syscall.UnixRights(fds...)
 		buf := new(bytes.Buffer)
-		msg.EncodeTo(buf)
+		msg.EncodeTo(buf, binary.LittleEndian)
 		n, oobn, err := t.UnixConn.WriteMsgUnix(buf.Bytes(), oob, nil)
 		if err != nil {
 			return err
@@ -178,7 +178,7 @@ func (t *unixTransport) SendMessage(msg *Message) error {
 			return io.ErrShortWrite
 		}
 	} else {
-		if err := msg.EncodeTo(t); err != nil {
+		if err := msg.EncodeTo(t, binary.LittleEndian); err != nil {
 			return nil
 		}
 	}