21. Replace Bit Field in a 32-bit Register

#include <stdio.h>
#include <stdint.h>

uint32_t mask = 0xFFFFFFFF;

uint32_t replace_bit_field(uint32_t reg, uint32_t val, int pos, int len){
    for (int i = 0; i < len; i++){
        if((val >> i) & 1) reg |= (1 << (pos + i));
        else reg &= ~(1 << (pos + i));
    }
    return reg;
}

int main() {
    uint32_t reg, new_val;
    int pos, len;
    scanf("%u %u %d %d", &reg, &new_val, &pos, &len);
    printf("%u\n", replace_bit_field(reg, new_val, pos, len));
    return 0;
}