Replace Bit Field in a 32-bit Register

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

uint32_t replace_field(uint32_t reg, uint32_t val, uint8_t pos, uint8_t len) {
    uint32_t one = 1;
    uint32_t zero = 0;
    val <<= pos;
    for(int i=pos; i<=pos+len-1;i++)
    {
        if((reg >> i) & one == one)
        {
            if(((val>>i) & one) == zero)
            {
                reg &= ~(1<<i);
            }
        }
        else if((reg >> i) & one == zero)
        {
            if(((val>>i) & zero) == one)
            {
                reg |= (1<<i);
            }
        }
    }
    return reg;
}

int main() {
    uint32_t reg, val;
    uint8_t pos, len;
    scanf("%u %u %hhu %hhu", &reg, &val, &pos, &len);
    printf("%u", replace_field(reg, val, pos, len));
    return 0;
}