fix #121

nbt/encode.go

@@ -40,8 +40,8 @@ func NewEncoder(w io.Writer) *Encoder {
 // You haven't ability to encode them as TagList as root element at this time,
 // issue or pull-request is welcome.
 func (e *Encoder) Encode(v interface{}, tagName string) error {
-	val := reflect.ValueOf(v)
-	return e.marshal(val, getTagType(val), tagName)
+	t, val := getTagType(reflect.ValueOf(v))
+	return e.marshal(val, t, tagName)
 }
 
 func (e *Encoder) marshal(val reflect.Value, tagType byte, tagName string) error {
@@ -101,7 +101,7 @@ func (e *Encoder) writeValue(val reflect.Value, tagType byte) error {
 	case TagList:
 		var eleType byte
 		if val.Len() > 0 {
-			eleType = getTagType(val.Index(0))
+			eleType, _ = getTagType(val.Index(0))
 		} else {
 			eleType = getTagTypeByType(val.Type().Elem())
 		}
@@ -110,8 +110,8 @@ func (e *Encoder) writeValue(val reflect.Value, tagType byte) error {
 		}
 
 		for i := 0; i < val.Len(); i++ {
-			arrVal := val.Index(i)
-			err := e.writeValue(arrVal, getTagType(arrVal))
+			arrType, arrVal := getTagType(val.Index(i))
+			err := e.writeValue(arrVal, arrType)
 			if err != nil {
 				return err
 			}
@@ -154,8 +154,7 @@ func (e *Encoder) writeValue(val reflect.Value, tagType byte) error {
 				} else {
 					tagName = r.Key().String()
 				}
-				tagValue := r.Value()
-				tagType := getTagType(tagValue)
+				tagType, tagValue := getTagType(r.Value())
 				if tagType == TagNone {
 					return errors.New("unsupported value " + tagValue.String())
 				}
@@ -172,32 +171,64 @@ func (e *Encoder) writeValue(val reflect.Value, tagType byte) error {
 	return nil
 }
 
-func getTagType(v reflect.Value) byte {
+func getTagType(v reflect.Value) (byte, reflect.Value) {
+	for {
+		// Load value from interface
+		if v.Kind() == reflect.Interface && !v.IsNil() {
+			v = v.Elem()
+			continue
+		}
+
+		if v.Kind() != reflect.Ptr {
+			break
+		}
+
+		// Prevent infinite loop if v is an interface pointing to its own address:
+		//     var v interface{}
+		//     v = &v
+		if v.Elem().Kind() == reflect.Interface && v.Elem().Elem() == v {
+			v = v.Elem()
+			break
+		}
+		if v.IsNil() {
+			v.Set(reflect.New(v.Type().Elem()))
+		}
+		if v.Type().NumMethod() > 0 && v.CanInterface() {
+			if u, ok := v.Interface().(NBTEncoder); ok {
+				return u.TagType(), v
+			}
+		}
+
+		v = v.Elem()
+	}
+
 	if v.CanInterface() {
 		if encoder, ok := v.Interface().(NBTEncoder); ok {
-			return encoder.TagType()
+			return encoder.TagType(), v
 		}
 	}
+
 	switch v.Kind() {
 	case reflect.Array, reflect.Slice:
 		var elemType byte
 		if v.Len() > 0 {
-			elemType = getTagType(v.Index(0))
+			elemType, _ = getTagType(v.Index(0))
 		} else {
 			elemType = getTagTypeByType(v.Type().Elem())
 		}
 		switch elemType {
 		case TagByte: // Special types for these values
-			return TagByteArray
+			return TagByteArray, v
 		case TagInt:
-			return TagIntArray
+			return TagIntArray, v
 		case TagLong:
-			return TagLongArray
+			return TagLongArray, v
 		default:
-			return TagList
+			return TagList, v
 		}
+
 	default:
-		return getTagTypeByType(v.Type())
+		return getTagTypeByType(v.Type()), v
 	}
 }
 
@@ -217,7 +248,7 @@ func getTagTypeByType(vk reflect.Type) byte {
 		return TagDouble
 	case reflect.String:
 		return TagString
-	case reflect.Struct, reflect.Interface, reflect.Map:
+	case reflect.Struct, reflect.Map:
 		return TagCompound
 	default:
 		return TagNone
@@ -237,7 +268,7 @@ func parseTag(f reflect.StructField, v reflect.Value, tagName string) (result ta
 	}
 
 	nbtType := f.Tag.Get("nbt_type")
-	result.Type = getTagType(v)
+	result.Type, v = getTagType(v)
 	if strings.Contains(nbtType, "list") {
 		if IsArrayTag(result.Type) {
 			result.Type = TagList // for expanding the array to a standard list

nbt/encode_test.go

@@ -230,3 +230,26 @@ func TestRawMessage_Encode(t *testing.T) {
 		t.Fatalf("Encode error: want %v, get: %v", data, buf.Bytes())
 	}
 }
+
+func TestEncoder_Encode_interface(t *testing.T) {
+	data := map[string]interface{}{
+		"Key":   int32(12),
+		"Value": "Tnze",
+	}
+	var buf bytes.Buffer
+	if err := NewEncoder(&buf).Encode(data, "ab"); err != nil {
+		t.Fatalf("Encode error: %v", err)
+	}
+
+	var container struct {
+		Key   int32
+		Value string
+	}
+	if _, err := NewDecoder(&buf).Decode(&container); err != nil {
+		t.Fatalf("Decode error: %v", err)
+	}
+
+	if container.Key != 12 || container.Value != "Tnze" {
+		t.Fatalf("want: (%v, %v), but got (%v, %v)", 12, "Tnze", container.Key, container.Value)
+	}
+}