任何一种计算机语言都会通过编译器转换成机器语言来执行，在编程中，位操作是常见且高效的数据处理手段之一，为了便于日常开发中学习和使用，下面IT培训网用实例讲解一下C语言的位操作，希望能帮到大家。

常见的C语言的位操作案例

实例一：编写函数 getbits(x,p,n) 从数值x的第p位开始返回n位数值

#include

int getbits(unsigned x, int p, int n);

int main() {

unsigned x = 0xF994;

int p = 4;

int n = 3;

int z = getbits(x, p, n);

printf("getbits(%u (%x), %d, %d) = %u (%X)\n", x, x, p, n, z, z);

}

// ff94 11111111100.101.00 # original number

// >> p+1-n [2] 0011111111100.101. # shift desired bits to right

// & ~(~0 << n) [7] 0000000000000.101. # clear all the other (left) bits

int getbits(unsigned x, int p, int n) { return x >> (p - n + 1) & ~(~0 << n); }

实例二：编写一个函数setbits(x,p,n,y),该函数返回对x执行下列的操作的结果的值：将x中从左第p位开始的n个(二进制)位设置为y中最右边n位的值，x的其余各位保持不变

#include

unsigned setbits(unsigned x, unsigned p, unsigned n, unsigned y);

int intLen(unsigned x);

int main() {

unsigned x = 171; // 1010 1011 --- > 101[0 1]011

unsigned p = 3;

unsigned n = 2;

unsigned y = 38; // 0010 0110

printf("result : %u \n", setbits(x, p, n, y));

return 1;

}

int intLen(unsigned x) {

int len = 0;

for (; x; x >>= 1) {

len++;

}

return len;

}

unsigned setbits(unsigned x, unsigned p, unsigned n, unsigned y) {

int length_y = intLen(y);

int length_x = intLen(x);

if (length_x - p - n < 0) {

printf("move over size by x");

return 0;

}

if (length_y < n) {

printf("move over size by y");

return 0;

}

// int pos = p -n + 1;

// unsigned cpy = y & ~ (~0 << n);

// unsigned xx = (x >> pos) & (~0 << n);

// return xx |= cpy;

unsigned tail = length_x - (p + n);

// x需要分离的子数据

unsigned sub = x & ~(~0 << tail);

// y 中需要替换的n位数据

unsigned cpy = y & ~(~0 << n);

// x向右移位，保留左边

x >>= length_x - p;

// x再向左移，这样最右边的n为可以为0

x <<= n;

//这样可以把y的拷贝值拷贝过去

x |= cpy;

// x再向左推进， 把刚刚的分离的n为先补0先

x <<= tail;

// x的分离再补充回数值

x |= sub;

return x;

}

实例三：编写一个函数invert(x,p,n), 该函数返回对x执行下列操作后的结果的值：将x中左起第p位开始的n个(二进制)位求反(即，1变成0，0变成1)，x的其余各位保持不变

#include

unsigned invert(unsigned x, unsigned p, unsigned n);

int intLen(unsigned x);

int main() {

unsigned x = 171; // 1010 1011 --- > 101[0 1]011

printf("result: %u\n", invert(x, 3, 2));

return 1;

}

int intLen(unsigned x) {

int len = 0;

for (; x; x >>= 1) {

len++;

}

return len;

}

unsigned invert(unsigned x, unsigned p, unsigned n) {

int length_x = intLen(x);

if (length_x - p - n < 0) {

printf("move over size by x");

return 0;

}

unsigned tail = length_x - (p + n);

// x需要分离的子数据

unsigned sub = x & ~(~0 << tail);

// 0001 01[0 1]

x >>= tail;

// x ^= 0011

// 0001 0110

x ^= ~(~0 << n);

// 101[10]000

x <<= tail;

// 101[10]011

x |= sub;

return x;

}

实例四：编写一个函数rightrot(x,n)：该函数返回将x循环右移(即从最右端移出的为将从最左端移入)n (二进制) 位后所得到的值

#include

int intLen(unsigned x);

unsigned rightrot(unsigned x, int n);

int main() {

unsigned x = 171; // 1010 1011

int n = 5;

// assert x = 01011 101 = 93

printf("result = %u\n", rightrot(x, n));

return 1;

}

int intLen(unsigned x) {

int len = 0;

for (; x; x >>= 1) {

len++;

}

return len;

}

unsigned rightrot(unsigned x, int n) {

int length_x = intLen(x);

if (length_x) {

n %= length_x;

if (n) {

// x需要分离的子数据

unsigned sub = x & ~(~0 << n);

// x 向右移动n位

x >>= n;

//计算左边位置需要填报多少位

int mov = length_x - n;

//通过上面分离的子串构造新的等长新串

unsigned subx = sub << mov;

subx ^= x;

return subx;

} else {

return x;

}

}

return 0;

}

实例五：在求对二的补码时，表达式 x&(x-1) 可以删除x中最右边值为1的一个二进制位。用这一方法重写bitcount函数，以加快其执行速度

#include

int bitcount(unsigned x);

int main() {

printf("%d's bit count: %d\n", 1023, bitcount(1023));

printf("%d's bit count: %d\n", 1024, bitcount(1024));

}

int bitcount(unsigned x) {

int len = 0;

for (; x; x &= x - 1) {

len++;

}

return len;

}

总之，有关C语言位操作案例就简单分享如下，为了便于后期的学习和运用，请大家在下面多多实践练习，把C语言位操作熟悉掌握。