Replace Bit Field in a 32-bit Register

Code

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

uint32_t replace_field(uint32_t reg, uint32_t val, uint8_t pos, uint8_t len) {
    // I think the easiest way to do this is just to clear before setting
    uint32_t clear_mask = (1 << len) - 1;
    clear_mask <<= pos;
    reg &= ~(clear_mask);

    // You can just or val (as long as the val is in the correct spot and 
    // the rest of the bits are 0)
    val = (val << pos);
    return reg | val;
}

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;
}

Solving Approach