CSAPP 习题2.52 replace_byte

// 替换unsigned int中的某一指定byte


#include<iostream>

using namespace std;

unsigned replace_byte(unsigned x, int i, unsigned char b)
{
cout << hex << (unsigned)b << endl;
unsigned ub = (unsigned)b;
unsigned ubp = ub << i*8;
unsigned mask = ~(0xff << i*8);

return (unsigned)((x&mask) | ubp);
}

int main()
{
cout << "0x" << hex << replace_byte(0x12345678, 2, 0xAB);
return 0;
}