std::basic_string_view<CharT,Traits>::max_size
From cppreference.com
                    
                                        
                    < cpp | string | basic string view
                    
                                                            
                    |   constexpr size_type max_size() const noexcept;  | 
(since C++17) | |
The largest possible number of char-like objects that can be referred to by a basic_string_view.
Parameters
(none)
Return value
Maximum number of characters.
Complexity
Constant.
See also
|    returns the number of characters   (public member function)  | |
|    checks whether the view is empty    (public member function)  |