Convert Hexadecimal String to Integer Without strtol or sscanf functions

Code

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

uint16_t hex_to_uint(const char *str) {
    int value=0;
    char a = 'A';

    while(*str){
    if(*str>'F') a = 'a';

    int d = (*str>='A')? (*str-a+10) : (*str-'0');
    str++;
    value=(value<<4)|d;
    }
    
    return value;
}

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

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

Solving Approach