使用快速json库编写json可以消除所有缩进

我正在使用快速json https://rapidjson.org/读取一个json文件，并将其写入到另一个使用cpp on windows应用程序的Windows应用程序，使用的是VisualStudio2017.

文件读取码

FILE* fp = fopen(inputJson, "rb"); // non-Windows use "r" 
char readBuffer[65536];
FileReadStream is(fp, readBuffer, sizeof(readBuffer));
Document d;
d.ParseStream(is);
fclose(fp);

std::string json_str(readBuffer);

文件写入代码

FILE* fp2 = fopen(outputJson, "wb"); // non-Windows use "w" 
char writeBuffer[65536];
FileWriteStream os(fp2, writeBuffer, sizeof(writeBuffer));
Writer<FileWriteStream> writer(os);
d.Accept(writer);
fclose(fp2);

但在目标文件中，缩进都丢失了.

源文件

{
    "name" : "test_rapid",
    "rect_obj": 
    [
        {   "name": "high school mathematics",
            "price": 12,
            "fg_color": 
            {
                "input_type": "val_map_c",
                "input": 
                {   
                    "measname": "MetaData_eOrigin_c",
                    "values":  [0],
                    "mapping": ["white"],
                    "out_of_range" : "white"
                }
            }
        },

目标文件中的缩进丢失

{"name":"test_rapid","rect_obj":[{"name":"high school mathematics","price":12,"fg_color":{"input_type":"val_map_c","input":{

如何保持凹痕？