Convert Binary String to Integer Without strtol function or Libraries

Code

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

uint16_t binary_to_uint(const char *str) {
    uint8_t len = 0;
    uint16_t num = 0;
    uint16_t p2 = 1;

    while(*(str + len) != '\0')
    {
        len ++;
    }

    for (int i = len - 1; i >= 0; i--)
    {
        num = num + (*(str + i) - '0') * p2;
        p2 <<= 1;
    }

    return num;
}

int main() {
    char bin[20];
    scanf("%s", bin);

    printf("%u", binary_to_uint(bin));
    return 0;
}

Solving Approach