Concatenate hex numbers in C

Question

I've been trying to concatenate 4 hex numbers and can't seem to do it.

Example:

int a = 0x01;
int b = 0x00;
int c = 0x20;
int d = 0xF1;
//Result should be 0x010020F1

The results that I am getting using sprintf and bitwise operations always cut off zeros, giving me answers like 1020F1, which is much different than what I want. Anybody have a better method?

Answer 1

Supposing unsigned int a,b,c,d;

unsigned int result = (a<<24) | (b<<16)| (c<<8) | d;

But this is essentially implementation dependent since C++ standard only specifies minimal sizes of integers.

So for uint32_t a, b, c, d:

uint32_t result = (a<<24) | (b<<16)| (c<<8) | d;