static char string_hex2int(int c) {
  if (isdigit(c)) {
    return c - '0';
  }
  if (c >= 'A' && c <= 'F') {
    return c - 'A' + 10;
  }
  if (c >= 'a' && c <= 'f') {
    return c - 'a' + 10;
  }
  return -1;
}
Unknown