函数怎么什么意思

只看该作者 · 2020-3-23 23:06

请教一下这个函数怎么理解，先一个宏定义，然后定义一个结构体，之后在函数中做判断，这个if.......else if 语句怎么理解，具体代码如下，谢谢各位。
#define LPC_UART       LPC_UART0
typedef struct
{
  union {
  __I  uint8_t  RBR;
  __O  uint8_t  THR;
  __IO uint8_t  DLL;
   uint32_t RESERVED0;
  };
  union {
  __IO uint8_t  DLM;
  __IO uint32_t IER;
  };
  union {
  __I  uint32_t IIR;
  __O  uint8_t  FCR;
  };
  __IO uint8_t  LCR;
   uint8_t  RESERVED1[3];
  __IO uint8_t  MCR;
   uint8_t  RESERVED2[3];
  __I  uint8_t  LSR;
   uint8_t  RESERVED3[3];
  __I  uint8_t  MSR;
   uint8_t  RESERVED4[3];
  __IO uint8_t  SCR;
   uint8_t  RESERVED5[3];
  __IO uint32_t ACR;
   uint32_t RESERVED6;
  __IO uint32_t FDR;
   uint32_t RESERVED7;
  __IO uint8_t  TER;
   uint8_t  RESERVED8[27];
  __IO uint8_t  RS485CTRL;
   uint8_t  RESERVED9[3];
  __IO uint8_t  ADRMATCH;
   uint8_t  RESERVED10[3];
  __IO uint8_t  RS485DLY;
   uint8_t  RESERVED11[3];
  __I  uint8_t  FIFOLVL;
} LPC_UART1_TypeDef;

if (LPC_UART == LPC_UART0)
{}
else if ((LPC_UART1_TypeDef *)LPC_UART == LPC_UART1)
{}