Convert Hexadecimal String to Integer Without strtol or sscanf functions

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

uint16_t hex_to_uint(const char *str) {
    // Your logic here
    char * digit = (char *)str;
    uint16_t result = 0;

    while(*digit != '\0'){
        result = result << 4;
        
        // [0, 9]
        if( *digit >= '0' && *digit <= '9'){
            result += *digit - '0';
        }else if(*digit >= 'A' && *digit <= 'F') {
            result += *digit - 'A'+ 10;
        }else if (*digit >= 'a' && *digit <= 'f'){
            result += *digit - 'a'+ 10;
        }

        digit++;


    }

    return result;
}

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

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