codec: add codec to support both vtproto and google.golang.org/protobuf and probably gogoproto

Signed-off-by: Adphi <philippe.adrien.nousse@gmail.com>

codec/codec.go

@@ -0,0 +1,52 @@
+package codec
+
+import (
+	"fmt"
+
+	"google.golang.org/protobuf/proto"
+)
+
+// Name is the name registered for the proto compressor.
+const Name = "proto"
+
+type Codec struct{}
+
+type vtprotoMessage interface {
+	MarshalVT() ([]byte, error)
+	UnmarshalVT([]byte) error
+}
+
+type protoMessage interface {
+	Marshal() ([]byte, error)
+	Unmarshal([]byte) error
+}
+
+func (Codec) Marshal(v interface{}) ([]byte, error) {
+	switch m := v.(type) {
+	case vtprotoMessage:
+		return m.MarshalVT()
+	case protoMessage:
+		return m.Marshal()
+	case proto.Message:
+		return proto.Marshal(m)
+	default:
+		return nil, fmt.Errorf("failed to marshal, message is %T, want proto.Message", v)
+	}
+}
+
+func (Codec) Unmarshal(data []byte, v interface{}) error {
+	switch m := v.(type) {
+	case vtprotoMessage:
+		return m.UnmarshalVT(data)
+	case protoMessage:
+		return m.Unmarshal(data)
+	case proto.Message:
+		return proto.Unmarshal(data, m)
+	default:
+		return fmt.Errorf("failed to unmarshal, message is %T, want proto.Message", v)
+	}
+}
+
+func (Codec) Name() string {
+	return Name
+}