Extract a Bit Field from a 32-bit Register

Code

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

uint32_t extract_field(uint32_t reg, uint8_t pos, uint8_t len) {
    uint32_t mask = 0;
    uint32_t value;
    while (len!=0) {
        mask = mask + (1 << (len - 1));
        len --;
    }
    value = (reg >> pos) & mask;
    // Your code here
    return value;
    //return (reg >> pos) & ((1U << len) - 1);
}

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;
}

Solving Approach