Support multiple data sections.

* `Message.Data` changed to `[][]byte`.
* Added `NewMessage(data []byte)` and `Message.Data() []byte` helpers
  for setting/retrieving single data section messages.

example_test.go

@@ -40,9 +40,7 @@ func Example() {
 		ctx, cancel := context.WithTimeout(ctx, 5*time.Second)
 
 		// Send message
-		err = sender.Send(ctx, &amqp.Message{
-			Data: []byte("Hello!"),
-		})
+		err = sender.Send(ctx, amqp.NewMessage([]byte("Hello!")))
 		if err != nil {
 			log.Fatal("Sending message:", err)
 		}
@@ -75,7 +73,7 @@ func Example() {
 			// Accept message
 			msg.Accept()
 
-			fmt.Printf("Message received: %s\n", msg.Data)
+			fmt.Printf("Message received: %s\n", msg.GetData())
 		}
 	}
 }

fuzz.go

@@ -61,9 +61,7 @@ func FuzzConn(data []byte) int {
 		return 0
 	}
 
-	err = sender.Send(context.Background(), &Message{
-		Data: []byte(data),
-	})
+	err = sender.Send(context.Background(), NewMessage(data))
 	if err != nil {
 		return 0
 	}

integration_test.go

@@ -122,9 +122,7 @@ func TestIntegrationRoundTrip(t *testing.T) {
 
 					for i, data := range tt.data {
 						ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
-						err = sender.Send(ctx, &amqp.Message{
-							Data: []byte(data),
-						})
+						err = sender.Send(ctx, amqp.NewMessage([]byte(data)))
 						cancel()
 						if err != nil {
 							sendErr = fmt.Errorf("Error after %d sends: %+v", i, err)
@@ -161,8 +159,8 @@ func TestIntegrationRoundTrip(t *testing.T) {
 						// Accept message
 						msg.Accept()
 
-						if !bytes.Equal([]byte(data), msg.Data) {
-							receiveErr = fmt.Errorf("Expected received message %d to be %v, but it was %v", i+1, string(data), string(msg.Data))
+						if !bytes.Equal([]byte(data), msg.GetData()) {
+							receiveErr = fmt.Errorf("Expected received message %d to be %v, but it was %v", i+1, string(data), string(msg.GetData()))
 						}
 					}
 				}()
@@ -240,9 +238,7 @@ func TestIntegrationSend(t *testing.T) {
 
 			for i, data := range tt.data {
 				ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
-				err = sender.Send(ctx, &amqp.Message{
-					Data: []byte(data),
-				})
+				err = sender.Send(ctx, amqp.NewMessage([]byte(data)))
 				cancel()
 				if err != nil {
 					t.Fatalf("Error after %d sends: %+v", i, err)

marshal_test.go

@@ -471,7 +471,10 @@ var (
 			ApplicationProperties: map[string]interface{}{
 				"baz": "foo",
 			},
-			Data:  []byte("A nice little data payload."),
+			Data: [][]byte{
+				[]byte("A nice little data payload."),
+				[]byte("More payload."),
+			},
 			Value: uint8(42),
 			Footer: Annotations{
 				"hash": []uint8{0, 1, 2, 34, 5, 6, 7, 8, 9, 0},

types.go

@@ -1700,10 +1700,10 @@ type Message struct {
 	// the possibility of a null key) and the values are restricted to be of
 	// simple types only, that is, excluding map, list, and array types.
 
-	// Message payload.
-	Data []byte
+	// Data payloads.
+	Data [][]byte
 	// A data section contains opaque binary data.
-	// TODO: this could be data(s), amqp-sequence(s), amqp-value rather than singe data:
+	// TODO: this could be data(s), amqp-sequence(s), amqp-value rather than single data:
 	// "The body consists of one of the following three choices: one or more data
 	//  sections, one or more amqp-sequence sections, or a single amqp-value section."
 
@@ -1722,35 +1722,24 @@ type Message struct {
 	settled  bool       // whether transfer was settled by sender
 }
 
-// Annotations keys must be of type string, int, or int64.
+// NewMessage returns a *Message with data as the payload.
 //
-// String keys are encoded as AMQP Symbols.
-type Annotations map[interface{}]interface{}
-
-func (a Annotations) marshal(wr *buffer) error {
-	return writeMap(wr, a)
-}
-
-func (a *Annotations) unmarshal(r *buffer) error {
-	_, count, err := readMapHeader(r)
-	if err != nil {
-		return err
+// This constructor is intended as a helper for basic Messages with a
+// single data payload. It is valid to construct a Message directly for
+// more complex usages.
+func NewMessage(data []byte) *Message {
+	return &Message{
+		Data: [][]byte{data},
 	}
+}
 
-	m := make(Annotations, count/2)
-	for i := uint32(0); i < count; i += 2 {
-		key, err := readAny(r)
-		if err != nil {
-			return err
-		}
-		value, err := readAny(r)
-		if err != nil {
-			return err
-		}
-		m[key] = value
+// GetData returns the first []byte from the Data field
+// or nil if Data is empty.
+func (m *Message) GetData() []byte {
+	if len(m.Data) < 1 {
+		return nil
 	}
-	*a = m
-	return nil
+	return m.Data[0]
 }
 
 // Accept notifies the server that the message has been
@@ -1821,9 +1810,9 @@ func (m *Message) marshal(wr *buffer) error {
 		}
 	}
 
-	if m.Data != nil {
+	for _, data := range m.Data {
 		writeDescriptor(wr, typeCodeApplicationData)
-		err := writeBinary(wr, m.Data)
+		err := writeBinary(wr, data)
 		if err != nil {
 			return err
 		}
@@ -1883,7 +1872,16 @@ func (m *Message) unmarshal(r *buffer) error {
 			section = &m.ApplicationProperties
 
 		case typeCodeApplicationData:
-			section = &m.Data
+			r.skip(3)
+
+			var data []byte
+			err = unmarshal(r, &data)
+			if err != nil {
+				return err
+			}
+
+			m.Data = append(m.Data, data)
+			continue
 
 		case typeCodeFooter:
 			section = &m.Footer
@@ -1951,6 +1949,37 @@ func tryReadNull(r *buffer) bool {
 	return false
 }
 
+// Annotations keys must be of type string, int, or int64.
+//
+// String keys are encoded as AMQP Symbols.
+type Annotations map[interface{}]interface{}
+
+func (a Annotations) marshal(wr *buffer) error {
+	return writeMap(wr, a)
+}
+
+func (a *Annotations) unmarshal(r *buffer) error {
+	_, count, err := readMapHeader(r)
+	if err != nil {
+		return err
+	}
+
+	m := make(Annotations, count/2)
+	for i := uint32(0); i < count; i += 2 {
+		key, err := readAny(r)
+		if err != nil {
+			return err
+		}
+		value, err := readAny(r)
+		if err != nil {
+			return err
+		}
+		m[key] = value
+	}
+	*a = m
+	return nil
+}
+
 /*
 <type name="header" class="composite" source="list" provides="section">
     <descriptor name="amqp:header:list" code="0x00000000:0x00000070"/>