Add Heartbeat request and response pair.

heartbeat_request.go

@@ -0,0 +1,43 @@
+package sarama
+
+type HeartbeatRequest struct {
+	GroupId      string
+	GenerationId string
+	MemberId     string
+}
+
+func (r *HeartbeatRequest) encode(pe packetEncoder) error {
+	if err := pe.putString(r.GroupId); err != nil {
+		return err
+	}
+	if err := pe.putString(r.GenerationId); err != nil {
+		return err
+	}
+	if err := pe.putString(r.MemberId); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (r *HeartbeatRequest) decode(pd packetDecoder) (err error) {
+	if r.GroupId, err = pd.getString(); err != nil {
+		return
+	}
+	if r.GenerationId, err = pd.getString(); err != nil {
+		return
+	}
+	if r.MemberId, err = pd.getString(); err != nil {
+		return
+	}
+
+	return nil
+}
+
+func (r *HeartbeatRequest) key() int16 {
+	return 12
+}
+
+func (r *HeartbeatRequest) version() int16 {
+	return 0
+}

heartbeat_response.go

@@ -0,0 +1,15 @@
+package sarama
+
+type HeartbeatResponse struct {
+	ErrorCode int16
+}
+
+func (r *HeartbeatResponse) encode(pe packetEncoder) error {
+	pe.putInt16(r.ErrorCode)
+	return nil
+}
+
+func (r *HeartbeatResponse) decode(pd packetDecoder) (err error) {
+	r.ErrorCode, err = pd.getInt16()
+	return
+}