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 = 0;
    if(pos > 28){
        return -1;
    }
    for(int i = pos ; i < pos + len ; i++){
        mask |= ( 1 << i);
    }
    reg &= mask;
    reg = (reg >> 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;
}