object-introspection/types/std_variant.toml

[info]
type_name = "std::variant"
ctype = "STD_VARIANT_TYPE"
header = "variant"

# Old:
typeName = "std::variant"
ns = ["namespace std"]

[codegen]
decl = """
template<class... Types>
void getSizeType(const %1%<Types...> &container, size_t& returnArg);
"""

func = """
template<class... Types>
void getSizeType(const %1%<Types...> &container, size_t& returnArg)
{
  SAVE_SIZE(sizeof(%1%<Types...>));
  SAVE_DATA(container.index());

  // This check should be `container.valueless_by_exception()` but it doesn't
  // work with the variable sized integers used in `std::variant`. For fewer
  // than 256 options it uses a `uint8_t` index but checks against -1 of
  // `uintptr_t`. Manually check for any out of bounds indices as a workaround.
  if (container.index() >= sizeof...(Types)) {
    return;
  }

  std::visit([&returnArg](auto &&arg) {
    // Account for inline contents
    SAVE_SIZE(-sizeof(arg));
    getSizeType(arg, returnArg);
  }, container);
}
"""

handler = """
template <typename DB, typename... Types>
struct TypeHandler<DB, %1%<Types...>> {
    using type = types::st::Sum<DB, typename TypeHandler<DB, Types>::type..., types::st::Unit<DB>>;

    static types::st::Unit<DB> getSizeType(
        const %1%<Types...>& container,
        typename TypeHandler<DB, %1%<Types...>>::type returnArg) {
      return getSizeTypeRecursive(container, returnArg);
    }

  private:
    template <size_t I = 0>
    static types::st::Unit<DB> getSizeTypeRecursive(
        const %1%<Types...>& container,
        typename TypeHandler<DB, %1%<Types...>>::type returnArg) {
      if constexpr (I < sizeof...(Types)) {
        if (I == container.index()) {
          return returnArg.template delegate<I>([&container](auto ret) {
            return OIInternal::getSizeType<DB>(std::get<I>(container), ret);
          });
        } else {
          return getSizeTypeRecursive<I+1>(container, returnArg);
        }
      } else {
        return returnArg.template delegate<sizeof...(Types)>(std::identity());
      }
    }
};
"""