WhyCan Forum(哇酷开发者社区)

union它不香吗
用匿名union可以用多种方式访问同一地址，形式也很简洁。像USB Request就很适合用这种表达方式。

typedef __packed struct _REQUEST_TYPE {
    U8 Recipient : 5;                     /* D4..0: Recipient */
    U8 Type      : 2;                     /* D6..5: Type */
    U8 Dir       : 1;                     /* D7:    Data Phase Txsfer Direction */
} REQUEST_TYPE;
typedef __packed struct _USB_SETUP_PACKET {
    REQUEST_TYPE bmRequestType;           /* bmRequestType */
    U8  bRequest;                         /* bRequest */
    __packed union {
        U16        wValue;                  /* wValue */
        __packed struct {
            U8         wValueL;
            U8         wValueH;
        };
    };
    __packed union {
        U16        wIndex;                  /* wIndex */
        __packed struct {
            U8         wIndexL;
            U8         wIndexH;
        };
    };
    U16          wLength;                 /* wLength */
} USB_SETUP_PACKET;

#define mian main
#define MAIN main
#define MIAN main