Extract a Bit Field from a 32-bit Register

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

#define GENMASK(pos, len) ((~(~0x0 << len)) << pos)

uint32_t extract_field(uint32_t reg, uint8_t pos, uint8_t len) {
    // Your code here
    reg = ((reg & GENMASK(pos, len)) >> pos);
    return reg;
}

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