optimize deafult UnknownFieldsProxy realisations with []byte in place of interface{}

unknown_fields.go

@@ -1,8 +1,6 @@
 package easyjson
 
 import (
-	json "encoding/json"
-
 	jlexer "github.com/mailru/easyjson/jlexer"
 	"github.com/mailru/easyjson/jwriter"
 )
@@ -10,14 +8,14 @@ import (
 // UnknownFieldsProxy implemets UnknownsUnmarshaler and UnknownsMarshaler
 // use it as embedded field in your structure to parse and then serialize unknown struct fields
 type UnknownFieldsProxy struct {
-	unknownFields map[string]interface{}
+	unknownFields map[string][]byte
 }
 
 func (s *UnknownFieldsProxy) UnmarshalUnknown(in *jlexer.Lexer, key string) {
 	if s.unknownFields == nil {
-		s.unknownFields = make(map[string]interface{}, 1)
+		s.unknownFields = make(map[string][]byte, 1)
 	}
-	s.unknownFields[key] = in.Interface()
+	s.unknownFields[key] = in.Raw()
 }
 
 func (s UnknownFieldsProxy) MarshalUnknowns(out *jwriter.Writer, first bool) {
@@ -29,6 +27,6 @@ func (s UnknownFieldsProxy) MarshalUnknowns(out *jwriter.Writer, first bool) {
 		}
 		out.String(string(key))
 		out.RawByte(':')
-		out.Raw(json.Marshal(val))
+		out.Raw(val, nil)
 	}
 }