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) {
    // Your code here
    // extract  value 
    // build mask 
    uint32_t  value;
    uint8_t  mask;
    for(uint8_t i=0 ; i< len ;i++)
    {
         mask |= (1<<i);
    }
    value = ( reg >> pos)& mask;

    // extract
    return value;
}

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