Do percent encoding matching grpc-java for the statusDesc.

Signed-off-by: Peter Edge <peter.edge@gmail.com>

transport/handler_server.go

@@ -192,7 +192,7 @@ func (ht *serverHandlerTransport) WriteStatus(s *Stream, statusCode codes.Code,
 		h := ht.rw.Header()
 		h.Set("Grpc-Status", fmt.Sprintf("%d", statusCode))
 		if statusDesc != "" {
-			h.Set("Grpc-Message", statusDesc)
+			h.Set("Grpc-Message", grpcMessageEncode(statusDesc))
 		}
 		if md := s.Trailer(); len(md) > 0 {
 			for k, vv := range md {

transport/handler_server_test.go

@@ -333,7 +333,7 @@ func handleStreamCloseBodyTest(t *testing.T, statusCode codes.Code, msg string)
 		"Content-Type": {"application/grpc"},
 		"Trailer":      {"Grpc-Status", "Grpc-Message"},
 		"Grpc-Status":  {fmt.Sprint(uint32(statusCode))},
-		"Grpc-Message": {msg},
+		"Grpc-Message": {grpcMessageEncode(msg)},
 	}
 	if !reflect.DeepEqual(st.rw.HeaderMap, wantHeader) {
 		t.Errorf("Header+Trailer mismatch.\n got: %#v\nwant: %#v", st.rw.HeaderMap, wantHeader)
@@ -381,7 +381,7 @@ func TestHandlerTransport_HandleStreams_Timeout(t *testing.T) {
 		"Content-Type": {"application/grpc"},
 		"Trailer":      {"Grpc-Status", "Grpc-Message"},
 		"Grpc-Status":  {"4"},
-		"Grpc-Message": {"too slow"},
+		"Grpc-Message": {grpcMessageEncode("too slow")},
 	}
 	if !reflect.DeepEqual(rw.HeaderMap, wantHeader) {
 		t.Errorf("Header+Trailer Map mismatch.\n got: %#v\nwant: %#v", rw.HeaderMap, wantHeader)

transport/http2_server.go

@@ -485,7 +485,7 @@ func (t *http2Server) WriteStatus(s *Stream, statusCode codes.Code, statusDesc s
 			Name:  "grpc-status",
 			Value: strconv.Itoa(int(statusCode)),
 		})
-	t.hEnc.WriteField(hpack.HeaderField{Name: "grpc-message", Value: statusDesc})
+	t.hEnc.WriteField(hpack.HeaderField{Name: "grpc-message", Value: grpcMessageEncode(statusDesc)})
 	// Attach the trailer metadata.
 	for k, v := range s.trailer {
 		for _, entry := range v {

transport/http_util.go

@@ -149,7 +149,7 @@ func (d *decodeState) processHeaderField(f hpack.HeaderField) {
 		}
 		d.statusCode = codes.Code(code)
 	case "grpc-message":
-		d.statusDesc = f.Value
+		d.statusDesc = grpcMessageDecode(f.Value)
 	case "grpc-timeout":
 		d.timeoutSet = true
 		var err error

transport/transport.go

@@ -43,6 +43,7 @@ import (
 	"fmt"
 	"io"
 	"net"
+	"strconv"
 	"sync"
 	"time"
 
@@ -506,3 +507,50 @@ func wait(ctx context.Context, closing <-chan struct{}, proceed <-chan int) (int
 		return i, nil
 	}
 }
+
+const (
+	spaceByte   = byte(int(' '))
+	tildaByte   = byte(int('~'))
+	percentByte = byte(int('%'))
+)
+
+// matching https://github.com/grpc/grpc-java/pull/1517/files
+func grpcMessageEncode(grpcMessage string) string {
+	if grpcMessage == "" {
+		return ""
+	}
+	var buffer bytes.Buffer
+	for _, c := range []byte(grpcMessage) {
+		if c >= spaceByte && c < tildaByte && c != percentByte {
+			_ = buffer.WriteByte(c)
+		} else {
+			_, _ = buffer.WriteString(fmt.Sprintf("%%%02X", c))
+		}
+	}
+	return buffer.String()
+}
+
+// matching https://github.com/grpc/grpc-java/pull/1517/files
+func grpcMessageDecode(encodedGrpcMessage string) string {
+	if encodedGrpcMessage == "" {
+		return ""
+	}
+	var buffer bytes.Buffer
+	data := []byte(encodedGrpcMessage)
+	lenData := len(data)
+	for i := 0; i < lenData; i++ {
+		c := data[i]
+		if c == percentByte && i+2 < lenData {
+			parsed, err := strconv.ParseInt(string(data[i+1:i+3]), 16, 8)
+			if err != nil {
+				_ = buffer.WriteByte(c)
+			} else {
+				_ = buffer.WriteByte(byte(parsed))
+				i += 2
+			}
+		} else {
+			_ = buffer.WriteByte(c)
+		}
+	}
+	return buffer.String()
+}

transport/transport_test.go

@@ -720,3 +720,29 @@ func TestIsReservedHeader(t *testing.T) {
 		}
 	}
 }
+
+func TestGrpcMessageEncode(t *testing.T) {
+	testGrpcMessageEncode(t, "my favorite character is \u0000", "my favorite character is %00")
+	testGrpcMessageEncode(t, "my favorite character is %", "my favorite character is %25")
+}
+
+func TestGrpcMessageDecode(t *testing.T) {
+	testGrpcMessageDecode(t, "Hello", "Hello")
+	testGrpcMessageDecode(t, "H%61o", "Hao")
+	testGrpcMessageDecode(t, "H%6", "H%6")
+	testGrpcMessageDecode(t, "%G0", "%G0")
+}
+
+func testGrpcMessageEncode(t *testing.T, input string, expected string) {
+	actual := grpcMessageEncode(input)
+	if expected != actual {
+		t.Errorf("Expected %s from grpcMessageEncode, got %s", expected, actual)
+	}
+}
+
+func testGrpcMessageDecode(t *testing.T, input string, expected string) {
+	actual := grpcMessageDecode(input)
+	if expected != actual {
+		t.Errorf("Expected %s from grpcMessageDecode, got %s", expected, actual)
+	}
+}