Convert Hexadecimal String to Integer Without strtol or sscanf functions

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

uint16_t hex_to_uint(const char *str) {
    int val = 0;
    int digit = 0;
    for(int i = 0; str[i]; i++){
        char c = str[i];
        if (c >= 'a'){
            digit = c - 'a' + 10;
        }else if(c >= 'A'){
            digit = c - 'A' + 10;
        }else{
            digit = c - '0';
        }
        val = (val<<4) | digit;
    }
    // Your logic here
    return val;
}

int main() {
    char hex[10];
    scanf("%s", hex);

    printf("%u", hex_to_uint(hex));
    return 0;
}