make Codec configurable when creating grpc.ClientConn and grpc.Server

server.go

@@ -85,12 +85,19 @@ type Server struct {
 }
 
 type options struct {
+	codec Codec
 	maxConcurrentStreams uint32
 }
 
 // A ServerOption sets options.
 type ServerOption func(*options)
 
+func CustomCodec(codec Codec) ServerOption {
+	return func(o *options) {
+		o.codec = codec
+	}
+}
+
 // MaxConcurrentStreams returns an Option that will apply a limit on the number
 // of concurrent streams to each ServerTransport.
 func MaxConcurrentStreams(n uint32) ServerOption {
@@ -106,6 +113,10 @@ func NewServer(opt ...ServerOption) *Server {
 	for _, o := range opt {
 		o(&opts)
 	}
+	if opts.codec == nil {
+		// Set the default codec.
+		opts.codec = &protoCodec{}
+	}
 	return &Server{
 		lis:   make(map[net.Listener]bool),
 		opts:  opts,
@@ -203,7 +214,7 @@ func (s *Server) Serve(lis net.Listener) error {
 }
 
 func (s *Server) sendResponse(t transport.ServerTransport, stream *transport.Stream, msg interface{}, pf payloadFormat, opts *transport.Options) error {
-	p, err := encode(protoCodec{}, msg, pf)
+	p, err := encode(s.opts.codec, msg, pf)
 	if err != nil {
 		// This typically indicates a fatal issue (e.g., memory
 		// corruption or hardware faults) the application program
@@ -286,6 +297,7 @@ func (s *Server) processStreamingRPC(t transport.ServerTransport, stream *transp
 		t: t,
 		s: stream,
 		p: &parser{s: stream},
+		codec: s.opts.codec,
 	}
 	if appErr := sd.Handler(srv.server, ss); appErr != nil {
 		if err, ok := appErr.(rpcError); ok {