static List <UE_Property> Object_as_PropertyList(JsonReader reader)
            {
                var _R = new List <UE_Property>();

                reader.AssertReadToken(JsonToken.StartObject);
                while (true)
                {
                    var token = reader.AssertRead();
                    if (token == JsonToken.PropertyName)
                    {
                        string property_name         = reader.Value.ToString();
                        GvasFormat.UE_Value value    = UE_Value(reader);
                        UE_Property         property = new UE_Property()
                        {
                            Name  = property_name,
                            Value = value
                        };
                        _R.Add(property);
                    }
                    else if (token == JsonToken.EndObject)
                    {
                        break;
                    }
                    else
                    {
                        throw new FormatException();
                    }
                }
                return(_R);
            }
            static GvasFormat.SaveGameHeader SaveGameHeader(JsonReader reader)
            {
                var _R = new GvasFormat.SaveGameHeader();

                reader.AssertReadToken(JsonToken.StartObject);
                _R.FileTypeTag           = reader.AssertReadPropertyNameValue <int>(JsonNaming.SaveGameHeader.FileTypeTag);
                _R.SaveGameFileVersion   = reader.AssertReadPropertyNameValue <int>(JsonNaming.SaveGameHeader.SaveGameFileVersion);
                _R.PackageFileUE4Version = reader.AssertReadPropertyNameValue <int>(JsonNaming.SaveGameHeader.PackageFileUE4Version);
                reader.AssertReadPropertyName(JsonNaming.SaveGameHeader.SavedEngineVersion);
                {
                    _R.SavedEngineVersion = new EngineVersion();
                    reader.AssertReadToken(JsonToken.StartObject);
                    _R.SavedEngineVersion.Major      = reader.AssertReadPropertyNameValue <UInt16>(JsonNaming.SaveGameHeader.EngineVersion.Major);
                    _R.SavedEngineVersion.Minor      = reader.AssertReadPropertyNameValue <UInt16>(JsonNaming.SaveGameHeader.EngineVersion.Minor);
                    _R.SavedEngineVersion.Patch      = reader.AssertReadPropertyNameValue <UInt16>(JsonNaming.SaveGameHeader.EngineVersion.Patch);
                    _R.SavedEngineVersion.ChangeList = reader.AssertReadPropertyNameValue <UInt32>(JsonNaming.SaveGameHeader.EngineVersion.ChangeList);
                    _R.SavedEngineVersion.Branch     = reader.AssertReadPropertyNameValue <string>(JsonNaming.SaveGameHeader.EngineVersion.Branch);
                    reader.AssertReadToken(JsonToken.EndObject);
                }
                _R.CustomVersionFormat = reader.AssertReadPropertyNameValue <int>(JsonNaming.SaveGameHeader.CustomVersionFormat);
                reader.AssertReadPropertyName(JsonNaming.SaveGameHeader.CustomVersions);
                {
                    reader.AssertReadToken(JsonToken.StartObject);
                    reader.AssertReadPropertyNameValue <int>(JsonNaming.SaveGameHeader.CustomVersionContainer.Count);
                    reader.AssertReadPropertyName(JsonNaming.SaveGameHeader.CustomVersionContainer.Versions);
                    var version_list = new List <CustomVersion>();
                    reader.AssertReadToken(JsonToken.StartArray);
                    while (true)
                    {
                        var token = reader.AssertRead();
                        if (token == JsonToken.StartObject)
                        {
                            string key_string = reader.AssertReadPropertyNameValue <string>(JsonNaming.SaveGameHeader.CustomVersion.Key);
                            Guid   key        = Guid.Parse(key_string);
                            int    version    = reader.AssertReadPropertyNameValue <int>(JsonNaming.SaveGameHeader.CustomVersion.Version);
                            reader.AssertReadToken(JsonToken.EndObject);
                            var _ver = new CustomVersion();
                            _ver.Key     = key;
                            _ver.Version = version;
                            version_list.Add(_ver);
                        }
                        else if (token == JsonToken.EndArray)
                        {
                            break;
                        }
                        else
                        {
                            throw new FormatException();
                        }
                    }
                    reader.AssertReadToken(JsonToken.EndObject);
                    _R.CustomVersions          = new CustomVersionContainer();
                    _R.CustomVersions.Count    = version_list.Count;
                    _R.CustomVersions.Versions = version_list.ToArray();
                }
                _R.SaveGameClassName = reader.AssertReadPropertyNameValue <string>(JsonNaming.SaveGameHeader.SaveGameClassName);
                reader.AssertReadToken(JsonToken.EndObject);
                return(_R);
            }
            static List <GvasFormat.UE_Value> UE_Value_List(JsonReader reader)
            {
                var _R = new List <GvasFormat.UE_Value>();

                reader.AssertReadToken(JsonToken.StartArray);
                while (true)
                {
                    var token = reader.AssertRead();
                    if (token == JsonToken.StartObject)
                    {
                        _R.Add(Read.UE_Value(reader, true));
                    }
                    else if (token == JsonToken.EndArray)
                    {
                        break;
                    }
                    else
                    {
                        throw new FormatException();
                    }
                }
                return(_R);
            }
            static GvasFormat.UE_Value UE_Value(JsonReader reader, bool skip_start_token = false)
            {
                if (!skip_start_token)
                {
                    reader.AssertReadToken(JsonToken.StartObject);
                }
                string type_string = reader.AssertReadPropertyNameValue <string>(JsonNaming.UE_Value.TypeString);

                // code structure copied from GvasFormat.Serialization.Binary.UE_Property_Reader.Read_UE_Value
                GvasFormat.UE_Value result;
                switch (type_string)
                {
                //
                // non-container
                case UE_Value_TypeString.BoolProperty:
                    bool value_bool = reader.AssertReadPropertyNameValue <bool>(JsonNaming.UE_Value.Value);
                    result = new UE_ <bool>(type_string, value_bool);
                    break;

                case UE_Value_TypeString.ByteProperty:
                    byte value_byte = reader.AssertReadPropertyNameValue <byte>(JsonNaming.UE_Value.Value);
                    result = new UE_ <byte>(type_string, value_byte);
                    break;

                case UE_Value_TypeString.EnumProperty:
                    string enum_type  = reader.AssertReadPropertyNameValue <string>(JsonNaming.UE_Enum.EnumType);
                    string enum_value = reader.AssertReadPropertyNameValue <string>(JsonNaming.UE_Value.Value);
                    result = new UE_Enum(type_string, enum_type, enum_value);
                    break;

                case UE_Value_TypeString.FloatProperty:
                    float value_float = reader.AssertReadPropertyNameValue <float>(JsonNaming.UE_Value.Value);
                    result = new UE_ <float>(type_string, value_float);
                    break;

                case UE_Value_TypeString.IntProperty:
                    int value_int = reader.AssertReadPropertyNameValue <int>(JsonNaming.UE_Value.Value);
                    result = new UE_ <int>(type_string, value_int);
                    break;

                case UE_Value_TypeString.NameProperty:
                    //case UE_ValueTypeString.StrProperty:
                    string value_string = reader.AssertReadPropertyNameValue <string>(JsonNaming.UE_Value.Value);
                    result = new UE_ <string>(type_string, value_string);
                    break;

                //
                // container
                // redirect.
                // UE_Struct ... lots of them are not engine defined, but game author defined.
                case UE_Value_TypeString.StructProperty:
                    string struct_type = reader.AssertReadPropertyNameValue <string>(JsonNaming.UE_Struct.StructTypeString);
                    reader.AssertReadPropertyName(JsonNaming.UE_Value.Value);
                    switch (struct_type)
                    {
                    case UE_Value_TypeString.Struct.Vector:
                    case UE_Value_TypeString.Struct.Rotator:
                        reader.AssertReadToken(JsonToken.StartArray);
                        float x = reader.AssertReadValue <float>();
                        float y = reader.AssertReadValue <float>();
                        float z = reader.AssertReadValue <float>();
                        reader.AssertReadToken(JsonToken.EndArray);
                        result = new UE_Struct_Vector(struct_type, x, y, z);
                        break;

                    case UE_Value_TypeString.Struct.Quat:
                        reader.AssertReadToken(JsonToken.StartArray);
                        float a = reader.AssertReadValue <float>();
                        float b = reader.AssertReadValue <float>();
                        float c = reader.AssertReadValue <float>();
                        float d = reader.AssertReadValue <float>();
                        reader.AssertReadToken(JsonToken.EndArray);
                        result = new UE_Struct_Quat(struct_type, a, b, c, d);
                        break;

                    default:
                        List <UE_Property> property_list = Read.Object_as_PropertyList(reader);
                        result = new UE_Struct_Generic(struct_type, property_list);
                        break;
                    }
                    break;

                case UE_Value_TypeString.ArrayProperty:
                    string item_type = reader.AssertReadPropertyNameValue <string>(JsonNaming.UE_Array.ItemType);
                    reader.AssertReadPropertyNameValue <int>(JsonNaming.UE_Map.Count);
                    List <GvasFormat.UE_Value> item_list;
                    if (item_type == UE_Value_TypeString.StructProperty)
                    {
                        string sa_name               = reader.AssertReadPropertyNameValue <string>(JsonNaming.UE_StructArray.SA_Name);
                        string sa_item_type          = reader.AssertReadPropertyNameValue <string>(JsonNaming.UE_StructArray.SA_ItemType);
                        string sa_struct_type_string = reader.AssertReadPropertyNameValue <string>(JsonNaming.UE_StructArray.SA_StructTypeString);
                        reader.AssertReadPropertyName(JsonNaming.UE_Array.ItemList);
                        item_list = Read.UE_Value_List(reader);
                        result    = new UE_StructArray(type_string, item_type, item_list.Count, item_list.ToArray(), sa_name, sa_item_type, sa_struct_type_string);
                    }
                    else
                    {
                        reader.AssertReadPropertyName(JsonNaming.UE_Array.ItemList);
                        item_list = Read.UE_Value_List(reader);
                        result    = new UE_Array(type_string, item_type, item_list.Count, item_list.ToArray());
                    }
                    break;

                case UE_Value_TypeString.MapProperty:
                    string key_type   = reader.AssertReadPropertyNameValue <string>(JsonNaming.UE_Map.KeyType);
                    string value_type = reader.AssertReadPropertyNameValue <string>(JsonNaming.UE_Map.ValueType);
                    reader.AssertReadPropertyNameValue <int>(JsonNaming.UE_Map.Count);
                    reader.AssertReadPropertyName(JsonNaming.UE_Map.Map);
                    reader.AssertReadToken(JsonToken.StartArray);
                    var map = new List <UE_Map_KeyValuePair>();
                    while (true)
                    {
                        var token = reader.AssertRead();
                        if (token == JsonToken.StartObject)
                        {
                            reader.AssertReadPropertyName(JsonNaming.UE_Map_KeyValuePair.Key);
                            UE_Value key = Read.UE_Value(reader);
                            reader.AssertReadPropertyName(JsonNaming.UE_Map_KeyValuePair.Value);
                            UE_Value value = Read.UE_Value(reader);
                            reader.AssertReadToken(JsonToken.EndObject);
                            UE_Map_KeyValuePair kvp = new UE_Map_KeyValuePair(key, value);
                            map.Add(kvp);
                        }
                        else if (token == JsonToken.EndArray)
                        {
                            break;
                        }
                        else
                        {
                            throw new FormatException();
                        }
                    }
                    result = new UE_Map(type_string, key_type, value_type, map.Count, map);
                    break;

                default:
                    throw new FormatException($"Unknown value type `{type_string}`.");
                }
                reader.AssertReadToken(JsonToken.EndObject);
                return(result);
            }