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) {
        uint32_t mask = ((1 << len) - 1) << pos;
        reg &= ~(mask);
        reg |= (val << pos) & mask;
        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;
    }

Solving Approach