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) {
    uint32_t mask = (1U << len) - 1;   // create mask of length `len`
    mask = mask << pos;                 // shift mask to position
    mask = reg & mask;                  // apply mask
    mask = mask >> pos;                 // shift down to LSB
    return 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;
}