Function enum_flags_name

include/magic_enum/magic_enum_flags.hpp:67–93

// If enum-flags value does not have name or value out of range, returns empty string.
template <typename E>
[[nodiscard]] auto enum_flags_name(E value, char_type sep = static_cast<char_type>('|')) -> detail::enable_if_t<E, string> {
  using D = std::decay_t<E>;
  using U = underlying_type_t<D>;
  constexpr auto S = detail::enum_subtype::flags;
  static_assert(detail::is_reflected_v<D, S>, "magic_enum requires enum implementation and valid max and min.");

  string name;
  auto check_value = U{0};
  for (std::size_t i = 0; i < detail::count_v<D, S>; ++i) {
    if (const auto v = static_cast<U>(enum_value<D, S>(i)); (static_cast<U>(value) & v) != 0) {
      if (const auto n = detail::names_v<D, S>[i]; !n.empty()) {
        check_value |= v;
        if (!name.empty()) {
          name.append(1, sep);
        }
        name.append(n.data(), n.size());
      } else {
        return {}; // Value out of range.
      }
    }
  }

  if (check_value != 0 && check_value == static_cast<U>(value)) {
    return name;
  }
  return {}; // Invalid value or out of range.
}

// Returns enum-flags value from integer value.
// Returns optional with enum-flags value.