Convert Hexadecimal String to Integer Without strtol or sscanf functions

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

uint16_t hex_to_uint(const char *str) {
    uint16_t res;
    for(int i=0; str[i]; i++)
    {
        if(str[i] >='0' && str[i]<='9')
            res = (res<<4) | (str[i] - '0');
        else if(str[i] >='A' && str[i]<= 'F')
           res = (res<<4) | (str[i] - 'A' + 10);
        else 
            res = (res<<4) | (str[i] - 'a' + 10); 
    }
    return res;
}

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

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