c - 如何在c中编写替换函数

Question

编写一个函数，该函数将返回一个值，其中i-th 字节x已被 替换b：

unsigned replace_f (unsigned x, int i, unsigned char b){

}

前任：replace_f(0x12345678, 2, 0xBC) --> 0x12BC5678

Answer 1

没试过，但这可以工作：

unsigned replace_f (unsigned x, int i, unsigned char b){
    char *c;

    c = (char *)&x;
    c[i] = b;
    return x;
}

Answer 2

unsigned replace_f (unsigned x, int i, unsigned char b){
    unsigned char *place = (unsigned char*)&x;
    place[sizeof(int)-i] = b;
    return x;
}

假设小端