C/C++语言技巧：记录32bit数据的一些常用位操作

最近协议里面用到了这个东西，每次都要重新写，还怕出错，特记录之：

#include <stdio.h>
#include <string.h>

#define GET_INT_LOW_BYTE0(x) ((x >> 0) & 0x000000FF)            /* GET BYTE 0 */
#define GET_INT_LOW_BYTE1(x) ((x >> 8) & 0x000000FF)            /* GET BYTE 1 */
#define GET_INT_LOW_BYTE2(x) ((x >> 16) & 0x000000FF)           /* GET BYTE 2 */
#define GET_INT_LOW_BYTE3(x) ((x >> 24) & 0x000000FF)           /* GET BYTE 3 */

#define GET_BIT(x, bit) ((x & (1 << bit)) >> bit)               /* GET BIT N */

#define CLEAR_INT_LOW_BYTE0(x) (x &= 0xFFFFFF00)                /* CLEAR BYTE 0 */
#define CLEAR_INT_LOW_BYTE1(x) (x &= 0xFFFF00FF)                /* CLEAR BYTE 1 */
#define CLEAR_INT_LOW_BYTE2(x) (x &= 0xFF00FFFF)                /* CLEAR BYTE 2 */
#define CLEAR_INT_LOW_BYTE3(x) (x &= 0x00FFFFFF)                /* CLEAR BYTE 3 */

#define CLEAR_BIT(x, bit) (x &= (~(1 << bit)))                  /* CLEAR BIT N */

#define SET_INT_LOW_BYTE0(x) (x |= 0x000000FF)                  /* SET BYTE 0 TO 1 */
#define SET_INT_LOW_BYTE1(x) (x |= 0x0000FF00)                  /* SET BYTE 1 TO 1 */
#define SET_INT_LOW_BYTE2(x) (x |= 0x00FF0000)                  /* SET BYTE 2 TO 1 */
#define SET_INT_LOW_BYTE3(x) (x |= 0xFF000000)                  /* SET BYTE 3 TO 1 */

#define SET_BIT(x, bit) (x |= (1 << bit))                       /* SET BIT N TO 1 */

#define GET_INT_BIT_M_TO_N(x, m, n) ((unsigned int)(x << (31 - (n))) >> ((31 - (n)) + (m))) /* GET BIT M~N */

int main()
{

    // 获取单字节
    printf("------------------- Get single byte --------------------\n");
    unsigned int a = 0x12345678;

    printf("0x%x byte0: 0x%x\n", a, GET_INT_LOW_BYTE0(a));
    printf("0x%x byte1: 0x%x\n", a, GET_INT_LOW_BYTE1(a));
    printf("0x%x byte2: 0x%x\n", a, GET_INT_LOW_BYTE2(a));
    printf("0x%x byte3: 0x%x\n", a, GET_INT_LOW_BYTE3(a));

    // 获取某一bit位
    printf("-------------------- Get a bit -------------------\n");
    unsigned int b = 0x68; /* 二进制：01101000b */

    printf("0x%x bit0: %d\n", b, GET_BIT(b, 0));
    printf("0x%x bit1: %d\n", b, GET_BIT(b, 1));
    printf("0x%x bit2: %d\n", b, GET_BIT(b, 2));
    printf("0x%x bit3: %d\n", b, GET_BIT(b, 3));
    printf("0x%x bit4: %d\n", b, GET_BIT(b, 4));
    printf("0x%x bit5: %d\n", b, GET_BIT(b, 5));
    printf("0x%x bit6: %d\n", b, GET_BIT(b, 6));
    printf("0x%x bit7: %d\n", b, GET_BIT(b, 7));

    // 清零某个字节
    printf("-------------------- clear single byte -------------------\n");
    unsigned int c1 = 0x12345678;
    unsigned int c2 = 0x12345678;
    unsigned int c3 = 0x12345678;
    unsigned int c4 = 0x12345678;

    printf("0x12345678 clear byte0: 0x%08x\n", CLEAR_INT_LOW_BYTE0(c1));
    printf("0x12345678 clear byte1: 0x%08x\n", CLEAR_INT_LOW_BYTE1(c2));
    printf("0x12345678 clear byte2: 0x%08x\n", CLEAR_INT_LOW_BYTE2(c3));
    printf("0x12345678 clear byte3: 0x%08x\n", CLEAR_INT_LOW_BYTE3(c4));

    // 清零某一bit位
    printf("-------------------- clear single byte -------------------\n");
    unsigned int d = 0x68; /* 二进制：01101000b */

    printf("0x68 clear bit3: 0x%x\n", CLEAR_BIT(d, 3));

    // 置某个字节为1
    printf("---------------------- set one byte to 1-----------------\n");
    unsigned int e1 = 0x12345678;
    unsigned int e2 = 0x12345678;
    unsigned int e3 = 0x12345678;
    unsigned int e4 = 0x12345678;

    printf("0x12345678 set byte0 to 1: 0x%08x\n", SET_INT_LOW_BYTE0(e1));
    printf("0x12345678 set byte1 to 1: 0x%08x\n", SET_INT_LOW_BYTE1(e2));
    printf("0x12345678 set byte2 to 1: 0x%08x\n", SET_INT_LOW_BYTE2(e3));
    printf("0x12345678 set byte3 to 1: 0x%08x\n", SET_INT_LOW_BYTE3(e4));

    // 将某个bit位置为1
    printf("----------------------- set bit to 1 ----------------\n");
    unsigned int f = 0x68; /* 二进制：01101000b */

    printf("0x68 set bit2 to 1: 0x%x\n", SET_BIT(f, 2));

    // 判断某一位的值是否为1
    printf("------------------------ check whether the value of a bit is 1 ---------------\n");
    unsigned int g = 0x68; /* 二进制：01101000b */

    if (g & (1 << 3))
    {
        printf("0x68's bit3 is 1\n");
    }
    else
    {
        printf("0x68's bit3 is 0\n");
    }

    // 获取某几位连续的值
    printf("------------------------ get bit range value ---------------\n");
    unsigned int h = 0x68; /* 二进制：01101000b */
    printf("0x68's [2:3] bit range value: 0x%08x\n", GET_INT_BIT_M_TO_N(h, 2, 3));

    return 0;
}

运行：

------------------- Get single byte --------------------
0x12345678 byte0: 0x78
0x12345678 byte1: 0x56
0x12345678 byte2: 0x34
0x12345678 byte3: 0x12
-------------------- Get a bit -------------------
0x68 bit0: 0
0x68 bit1: 0
0x68 bit2: 0
0x68 bit3: 1
0x68 bit4: 0
0x68 bit5: 1
0x68 bit6: 1
0x68 bit7: 0
-------------------- clear single byte -------------------
0x12345678 clear byte0: 0x12345600
0x12345678 clear byte1: 0x12340078
0x12345678 clear byte2: 0x12005678
0x12345678 clear byte3: 0x00345678
-------------------- clear single byte -------------------
0x68 clear bit3: 0x60
---------------------- set one byte to 1-----------------
0x12345678 set byte0 to 1: 0x123456ff
0x12345678 set byte1 to 1: 0x1234ff78
0x12345678 set byte2 to 1: 0x12ff5678
0x12345678 set byte3 to 1: 0xff345678
----------------------- set bit to 1 ----------------
0x68 set bit2 to 1: 0x6c
------------------------ check whether the value of a bit is 1 ---------------
0x68's bit3 is 1
------------------------ get bit range value ---------------
0x68's [2:3] bit range value: 0x00000002