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

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

uint32_t extract_field(uint32_t reg, uint8_t pos, uint8_t len) {
    // Your code here
    uint8_t mask = 0;
    len--;
    while (len) {
        mask |= (1 << len);
        len--;

        if (len == 0)
            mask |= (1 << len);
    }
    return (reg >> pos) & mask;
}

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;
}