std::basic_string_view::size, std::basic_string_view::length

From cppreference.com
constexpr size_type size() const noexcept;
(since C++17)
constexpr size_type length() const noexcept;
(since C++17)

Returns the number of CharT elements in the view, i.e. std::distance(begin(), end()).

Parameters

(none)

Return value

The number of CharT elements in the view.

Complexity

Constant.

See also

checks whether the view is empty
(public member function)
returns the maximum number of characters
(public member function)