19. Extract a Bit Field from a 32-bit Register

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

#define MASK(pos, len) (((1u<<len)-1)<<pos)   

uint32_t extract_field(uint32_t reg, uint8_t pos, uint8_t len) {
    uint32_t ret = 0;
    ret = (reg & MASK(pos, len))>>pos;

    return ret;
}

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;
}