types: add note about ReadMessage having no cap

types/application.go

@@ -75,8 +75,6 @@ func (BaseApplication) EndBlock(req RequestEndBlock) ResponseEndBlock {
 
 //-------------------------------------------------------
 
-var _ Application = (*GRPCApplication)(nil)
-
 // GRPCApplication is a GRPC wrapper for Application
 type GRPCApplication struct {
 	app Application

types/messages.go

@@ -7,6 +7,31 @@ import (
 	wire "github.com/tendermint/go-wire"
 )
 
+// WriteMessage writes a length-delimited protobuf message.
+func WriteMessage(msg proto.Message, w io.Writer) error {
+	bz, err := proto.Marshal(msg)
+	if err != nil {
+		return err
+	}
+	var n int
+	wire.WriteByteSlice(bz, w, &n, &err)
+	return err
+}
+
+// ReadMessage reads a length delimited protobuf message.
+func ReadMessage(r io.Reader, msg proto.Message) error {
+	var n int
+	var err error
+	bz := wire.ReadByteSlice(r, 0, &n, &err) //XXX: no max
+	if err != nil {
+		return err
+	}
+	err = proto.Unmarshal(bz, msg)
+	return err
+}
+
+//----------------------------------------
+
 func ToRequestEcho(message string) *Request {
 	return &Request{
 		Value: &Request_Echo{&RequestEcho{message}},
@@ -146,28 +171,3 @@ func ToResponseEndBlock(res ResponseEndBlock) *Response {
 		Value: &Response_EndBlock{&res},
 	}
 }
-
-//----------------------------------------
-
-// Write proto message, length delimited
-func WriteMessage(msg proto.Message, w io.Writer) error {
-	bz, err := proto.Marshal(msg)
-	if err != nil {
-		return err
-	}
-	var n int
-	wire.WriteByteSlice(bz, w, &n, &err)
-	return err
-}
-
-// Read proto message, length delimited
-func ReadMessage(r io.Reader, msg proto.Message) error {
-	var n int
-	var err error
-	bz := wire.ReadByteSlice(r, 0, &n, &err)
-	if err != nil {
-		return err
-	}
-	err = proto.Unmarshal(bz, msg)
-	return err
-}

types/messages_test.go

@@ -0,0 +1,28 @@
+package types
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/gogo/protobuf/proto"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestWriteReadMessage(t *testing.T) {
+	cases := []proto.Message{
+		&RequestEcho{"hello"},
+		// TODO: add the rest
+	}
+
+	for _, c := range cases {
+		buf := new(bytes.Buffer)
+		err := WriteMessage(c, buf)
+		assert.Nil(t, err)
+
+		msg := new(RequestEcho)
+		err = ReadMessage(buf, msg)
+		assert.Nil(t, err)
+
+		assert.Equal(t, c, msg)
+	}
+}