Question

我的结构如下：

struct myCoolStuff{
    uint32_t stuff1 :  4;
    uint32_t stuff2 :  4;
    uint32_t stuff3 : 24;
    uint32_t differentField;
}

如何将这些字段组合为十六进制格式以打印到屏幕或写出文件？谢谢。

struct myCoolStuff data = {.stuff1=0xFF, .stuff2=0x66, .stuff3=0x112233, .differentField=99};

printf("my combined stuff is: %x\n", <combined stuff>);
printf("My full field is: %x\n", data.differentField);

Expected Output: 
my combined stuff is: 0xFF66112233 
My different field is: 99

Answer 1

首先，将0xFF放入4位变量后，您将无法获得0xFF。 0xFF占8位。与0x66相同。

关于将位域重新解释为单个整数，您可以，以非常不便携的方式（存在大尾数/小尾数问题以及填充位的可能性）使用union。

（此：

#include <stdio.h>
#include <stdint.h>
#include <inttypes.h>

struct myCoolStuff{
    union{
        struct {
        uint32_t stuff1 :  4;
        uint32_t stuff2 :  4;
        uint32_t stuff3 : 24;
        };
        uint32_t fullField;
    };
};
struct myCoolStuff data = {.stuff1=0xFF, .stuff2=0x66, .stuff3=0x112233};

int main()
{
    printf("My full field is: %" PRIX32 "\n", data.fullField);
}

在我的x86_64上打印1122336F。）

要方便地进行操作，您只需将位字段手动将它们放在一起：

此：

#include <stdio.h>
#include <stdint.h>
#include <inttypes.h>

struct myCoolStuff{
        uint32_t stuff1 :  4;
        uint32_t stuff2 :  4;
        uint32_t stuff3 : 24;
};
struct myCoolStuff data = {.stuff1=0xFF, .stuff2=0x66, .stuff3=0x112233};

int main()
{
    uint32_t fullfield = data.stuff1 << 28 | data.stuff2 << 24 | data.stuff3;
    printf("My full field is: %" PRIX32 "\n", fullfield);
}

应该在编译的任何地方打印F6112233（不保证存在uint32_t（尽管在POSIX平台上会存在）； uint_least32_t会更易于移植。）

请注意确保data.stuff1有足够的位数可移动28。您这样做是因为输入的是uint32_t，但是这样做会更安全，例如，使用(data.stuff1 + 0UL)<<28或(data.stuff1 + UINT32_C(0))<<28且第二个班次相同。

Answer 2

在此结构内添加一个联合，可用于重新解释字段。

struct myCoolStuff{
    union {
        struct {
            uint32_t stuff1 :  4;
            uint32_t stuff2 :  4;
            uint32_t stuff3 : 24;
        };
        uint32_t stuff;
    }
    uint32_t fullField;
};

...

printf("my combined stuff is: %x\n", data.stuff);

Answer 3

相乘（至少使用uint32_t个数学运算），然后使用匹配的说明符进行打印。

#include <inttypes.h>

struct myCoolStuff{
    uint32_t stuff1 :  4;
    uint32_t stuff2 :  4;
    uint32_t stuff3 : 24;
    uint32_t differentField;
}

uint32_t combined stuff = ((uint32_t) data.stuff1 << (4 + 24)) | 
    ((uint32_t) data.stuff2 <<  24) |  data.stuff3;

printf("my combined stuff is: 0x%" PRIX32 "\n", combined stuff);
printf("My full field is: %x\n", data.differentField);

Answer 4

也许这样会有所帮助：

unsigned char *ptr = (unsigned char *)&data; // store start address
int size = sizeof(myCoolStuff); // get size of struct in bytes
while(size--) // for each byte
{
    unsigned char c = *ptr++; // get byte value
    printf(" %x ", (unsigned)c); // print byte value
}

从结构位域以十六进制打印完整的uint32_t

4 个答案: