message: check if char is included in range;
diff: @@ -82,12 +82,18 @@ pub fn encode_iter(input: &(impl AsRef<[u8]> + ?Sized)) -> impl Iterator<Item =
  /// Returns true if all chars in a string are uppercase or lowercase.
  /// Returns false if the string is mixed case or if there are no alphabetic chars.
  fn string_is_same_case<T: AsRef<[u8]> + ?Sized>(s: &T) -> bool {
  - let mut chars = s.as_ref().iter().filter(|c| c.is_ascii_alphabetic());
  + let lower_range = 97..=102u8; // a..=f
  + let upper_range = 65..=70u8; // A..=F
  +
  + let mut chars = s
  + .as_ref()
  + .iter()
  + .filter(|c| lower_range.contains(c) || upper_range.contains(c));
  match chars.next() {
  Some(first) => {
  - let is_upper = first.is_ascii_uppercase();
  - chars.all(|c| c.is_ascii_uppercase() == is_upper)
  + let is_upper = upper_range.contains(first);
  + chars.all(|c| upper_range.contains(c) == is_upper)
  }
  None => {
  // String has no actual characters.
  