C语言位域、struct和union的联合使用

示例代码：

#include "stdio.h"
#include "stdlib.h"
#include "stdint.h"

typedef union {
    struct {
        uint8_t b0 : 1;     //lsb
        uint8_t b1 : 1;
        uint8_t b2 : 1;
        uint8_t b3 : 1;
        uint8_t b4 : 1;
        uint8_t b5 : 1;
        uint8_t b6 : 1;
        uint8_t b7 : 1;     //msb
    }bit;
    uint8_t value;
}switch_t;

int print_m(switch_t var);

int main(void)
{
    switch_t sw1;
    switch_t sw2;
    //1 1 0 1 0 1 1 0
    sw1.bit.b0 = 0;
    sw1.bit.b1 = 1;
    sw1.bit.b2 = 1;
    sw1.bit.b3 = 0;
    sw1.bit.b4 = 1;
    sw1.bit.b5 = 0;
    sw1.bit.b6 = 1;
    sw1.bit.b7 = 1;
    print_m(sw1);
    
    sw2.value = 0xA3;    //1 0 1 0 0 0 1 1
    print_m(sw2);
    
    return 0;
}

int print_m(switch_t var)
{
    printf("------------\n");
    printf("var=0x%02x\n", var.value);
    printf("var.bit.b0=%d\n", var.bit.b0);
    printf("var.bit.b1=%d\n", var.bit.b1);
    printf("var.bit.b2=%d\n", var.bit.b2);
    printf("var.bit.b3=%d\n", var.bit.b3);
    printf("var.bit.b4=%d\n", var.bit.b4);
    printf("var.bit.b5=%d\n", var.bit.b5);
    printf("var.bit.b6=%d\n", var.bit.b6);
    printf("var.bit.b7=%d\n", var.bit.b7);

    return 0;
}

输出结果：

$ ./a.exe
------------
var=0xd6
var.bit.b0=0
var.bit.b1=1
var.bit.b2=1
var.bit.b3=0
var.bit.b4=1
var.bit.b5=0
var.bit.b6=1
var.bit.b7=1
------------
var=0xa3
var.bit.b0=1
var.bit.b1=1
var.bit.b2=0
var.bit.b3=0
var.bit.b4=0
var.bit.b5=1
var.bit.b6=0
var.bit.b7=1