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) {
    char hex = 0;
    uint16_t value = 0; 
    
    while(*str != '\0'){
      
      if(*str >= '0' && *str <= '9'){
         hex = *str - '0';  
      }
      
      if((*str >= 'A' && *str <= 'F')){
         hex = (*str - 'A') + 10;
      }
      
      if((*str >= 'a' && *str <= 'f')){
         hex = (*str - 'a') + 10;
      }
      
      value = (value << 4) | hex;
        
        
        
      str++;
    }
    return value;
}

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

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

Solving Approach