How to proper working with Union and Sctruct nested

[ozguracar]

I´m trying to create some types that will be used with node-ffi, but I have some doubts about how to use Union and Struct type nested.
Should I define first the nested fields as new types, or can I does directly like this:

union _error {
  BYTE byte;
  struct
  {
    BYTE memoryFull : 1;
    BYTE extEpromError : 1;
    BYTE intEpromError : 1;
    BYTE rtcError : 1;
    BYTE romError : 1;
    BYTE batteryEmpty : 1;
    BYTE : 1;
    BYTE : 1;
  };
};

union _otomatStatus {
  BYTE byte;
  struct
  {
    BYTE sended : 1;
    BYTE received : 1;
    BYTE tickedReduced : 1;
    BYTE tickedFinished : 1;
    BYTE : 1;
    BYTE : 1;
    BYTE : 1;
    BYTE : 1;
  };
};

struct _H_status
{
  union {
    BYTE block[32];
    struct
    {
      BYTE day;
      BYTE month;
      BYTE year;
      BYTE hour;
      BYTE minute;
      BYTE second;
      _error error;
      BYTE state;
      int recordCount;
      union {
        DWORD status;
        struct
        {
          BYTE relay0 : 1;
          BYTE relay1 : 1;
          BYTE relay2 : 1;
          BYTE relay3 : 1;
          BYTE cardOperationCont : 1;
          BYTE newCard : 1;
          BYTE taskEnable : 1;
          BYTE relaxMode : 1;
          BYTE redLed : 1;
          BYTE greenLed : 1;
          BYTE blueLed : 1;
          BYTE accessValue : 1;
          BYTE accessReady : 1;
          BYTE : 1;
          BYTE : 1;
          BYTE : 1;
          BYTE input0 : 1;
          BYTE input1 : 1;
          BYTE : 1;
          BYTE : 1;
          BYTE : 1;
          BYTE : 1;
          BYTE cardWriteOperation : 1;
          BYTE cardWriteResult : 1;
          BYTE battery : 4;
          BYTE registerMode : 1;
          BYTE menuMode : 1;
          BYTE deviceNotWorkingTime : 1;
          BYTE lastPowerType : 1;
        };
      };
      int cardCode;
      WORD accessCode;
      BYTE appIndex;
      BYTE cardMsgNo;
      BYTE inOut;
      int totalCredit;
      _otomatStatus otomatStatus[3];
    };
  };
};

#####################################3

var ffi = require('ffi')
var ref = require('ref')
var StructType = require('ref-struct')
var UnionType = require('ref-union')




var deviceSerial = 0xC8CC3FB
var devicePass = 0xA25E8AD0
var deviceIP = 0x2801A8C0
var devicePORT = 0x1592
var BYTE = ref.types.uint8
var WORD = ref.types.uint16
var DWORD = ref.types.uint32
var INT = ref.types.int
var BOOL = ref.types.bool
var UIDPtr = ref.refType('uint32');


var union = UnionType({
    "byte": BYTE,
    "s": StructType({
        "memoryFull": BYTE,
        "extEpromError": BYTE,
        "intEpromError": BYTE,
        "rtcError": BYTE,
        "romError": BYTE,
        "batteryEmpty": BYTE,
        "c": BYTE,
        "d": BYTE,
    })
})
var otomat = UnionType({
    "byte": BYTE,
    "s": StructType({
        "sended": BYTE,
        "received": BYTE,
        "tickedReduced": BYTE,
        "tickedFinished": BYTE,
        "a": BYTE,
        "b": BYTE,
        "c": BYTE,
        "d": BYTE,
    })
})
var HStruct = StructType({
    "un": UnionType({
        "block": BYTE,
        "h": StructType({
            "day": BYTE,
            "month": BYTE,
            "year": BYTE,
            "hour": BYTE,
            "minute": BYTE,
            "second": BYTE,
            "_error": union,
            "state": BYTE,
            "recordCount": INT,
            "status": UnionType({
                "status": DWORD,
                "s": StructType({
                    "relay0": BYTE,
                    "relay1": BYTE,
                    "relay2": BYTE,
                    "relay3": BYTE,
                    "cardOperationCont": BYTE,
                    "newCard": BYTE,
                    "taskEnable": BYTE,
                    "relaxMode": BYTE,
                    "redLed": BYTE,
                    "greenLed": BYTE,
                    "blueLed": BYTE,
                    "accessValue": BYTE,
                    "accessReady": BYTE,
                    "a": BYTE,
                    "b": BYTE,
                    "c": BYTE,
                    "input0": BYTE,
                    "input1": BYTE,
                    "d": BYTE,
                    "e": BYTE,
                    "f": BYTE,
                    "g": BYTE,
                    "cardWriteOperation": BYTE,
                    "cardWriteResult": BYTE,
                    "battery": BYTE,
                    "registerMode": BYTE,
                    "menuMode": BYTE,
                    "deviceNotWorkingTime": BYTE,
                    "lastPowerType": BYTE
                })
            }),
            "cardCode": INT,
            "accessCode": WORD,
            "appIndex": BYTE,
            "cardMsgNo": BYTE,
            "inOut": BYTE,
            "totalCredit": INT,
            "_otomatStatus": otomat

        })
    })

})
var status = new HStruct

var sdk = ffi.Library('./_RC_UTIL.dll', {
    '__Get_Status': [INT, [DWORD, DWORD, DWORD, WORD, BOOL, "pointer"]],
    '__Get_Card_UID_Readed': [INT, [DWORD, DWORD, DWORD, WORD, UIDPtr]],
    '__Device_Resume': [INT, [DWORD, DWORD, DWORD, WORD]],
    '__Device_Finish': [INT, [DWORD, DWORD, DWORD, WORD, "pointer"]],
    '__Set_Led_Color': [INT, [DWORD, DWORD, DWORD, WORD, BYTE, BOOL, "pointer"]],
    '__Clear_Memory': [INT, [DWORD, DWORD, DWORD, WORD]],
})
sdk.__Set_Led_Color(deviceSerial, devicePass, deviceIP, devicePORT, 8, true, status.ref())

sdk.__Get_Status(deviceSerial, devicePass, deviceIP, devicePORT, true, status.ref())
console.log(status)
var outUID = ref.alloc('uint32');

sdk.__Get_Card_UID_Readed(deviceSerial, devicePass, deviceIP, devicePORT, outUID);
sdk.__Device_Resume(deviceSerial, devicePass, deviceIP, devicePORT);
sdk.__Device_Finish(deviceSerial, devicePass, deviceIP, devicePORT, status.ref());
var actualNumber = outUID.deref();
console.log(actualNumber)
console.log(outUID)