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type_safe_union : visit() and apply_to_contents() performance improvements (#2615)
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pfeatherstone
GitHub
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commit
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@ -9,7 +9,7 @@
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#include <type_traits>
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#include <functional>
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#include "../serialize.h"
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#include "../invoke.h"
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#include "../utility.h"
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namespace dlib
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{
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@ -139,41 +139,38 @@ namespace dlib
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typename std::aligned_union<0, Types...>::type mem;
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int type_identity = 0;
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template<
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typename F,
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typename TSU,
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std::size_t I
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>
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static void apply_to_contents_as_type(
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F&& f,
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TSU&& me
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)
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template<typename F, typename TSU>
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struct dispatcher
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{
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std::forward<F>(f)(me.template unchecked_get<get_type_t<I>>());
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constexpr static const std::size_t N = sizeof...(Types);
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using R = decltype(std::declval<F>()(std::declval<TSU>().template unchecked_get<get_type_t<0>>()));
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constexpr static const bool is_noexcept =
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And<std::is_default_constructible<R>::value &&
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noexcept(std::declval<F>()(std::declval<TSU>().template unchecked_get<Types>()))...>::value;
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template<size_t I, typename std::enable_if<I == N, bool>::type = true>
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inline R operator()(F&&, TSU&&, size_<I>)
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noexcept(is_noexcept) { return R(); }
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template<size_t I, typename std::enable_if<I < N, bool>::type = true>
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inline R operator()(F&& f, TSU&& me, size_<I>)
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noexcept(is_noexcept)
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{
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if (me.is_empty())
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return R();
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else if (me.get_current_type_id() == (I+1))
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return std::forward<F>(f)(me.template unchecked_get<get_type_t<I>>());
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else
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return (*this)(std::forward<F>(f), std::forward<TSU>(me), size_<I+1>{});
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}
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template<
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typename F,
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typename TSU,
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std::size_t... I
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>
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static void apply_to_contents_impl(
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F&& f,
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TSU&& me,
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dlib::index_sequence<I...>
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)
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{
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using func_t = void(*)(F&&, TSU&&);
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const func_t vtable[] = {
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/*! Empty (type_identity == 0) case !*/
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[](F&&, TSU&&) {
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},
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/*! Non-empty cases !*/
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&apply_to_contents_as_type<F&&,TSU&&,I>...
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};
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return vtable[me.get_current_type_id()](std::forward<F>(f), std::forward<TSU>(me));
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template<typename F, typename TSU>
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static inline auto dispatch(F&& f, TSU&& me)
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noexcept(noexcept(dispatcher<F&&,TSU&&>{}(std::forward<F>(f), std::forward<TSU>(me), size_<0>{})))
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-> decltype(dispatcher<F&&,TSU&&>{}(std::forward<F>(f), std::forward<TSU>(me), size_<0>{})) {
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return dispatcher<F&&,TSU&&>{}(std::forward<F>(f), std::forward<TSU>(me), size_<0>{});
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}
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template <typename T>
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@ -402,19 +399,19 @@ namespace dlib
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}
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template <typename F>
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void apply_to_contents(
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auto apply_to_contents(
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F&& f
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)
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{
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apply_to_contents_impl(std::forward<F>(f), *this, dlib::make_index_sequence<sizeof...(Types)>{});
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) noexcept(noexcept(dispatch(std::forward<F>(f), std::declval<type_safe_union&>())))
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-> decltype(dispatch(std::forward<F>(f), *this)) {
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return dispatch(std::forward<F>(f), *this);
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}
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template <typename F>
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void apply_to_contents(
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auto apply_to_contents(
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F&& f
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) const
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{
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apply_to_contents_impl(std::forward<F>(f), *this, dlib::make_index_sequence<sizeof...(Types)>{});
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) const noexcept(noexcept(dispatch(std::forward<F>(f), std::declval<const type_safe_union&>())))
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-> decltype(dispatch(std::forward<F>(f), *this)) {
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return dispatch(std::forward<F>(f), *this);
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}
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template <typename T>
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@ -492,7 +489,7 @@ namespace dlib
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{
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if (type_identity == item.type_identity)
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{
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item.apply_to_contents(swap_to{*this});
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apply_to_contents(swap_to{item});
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}
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else if (is_empty())
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{
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@ -540,48 +537,6 @@ namespace dlib
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)...
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};
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}
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template<
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typename R,
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typename F,
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typename TSU,
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std::size_t I
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>
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R visit_impl_as_type(
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F&& f,
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TSU&& tsu
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)
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{
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using Tsu = typename std::decay<TSU>::type;
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using T = type_safe_union_alternative_t<I, Tsu>;
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return dlib::invoke(std::forward<F>(f), tsu.template cast_to<T>());
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}
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template<
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typename R,
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typename F,
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typename TSU,
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std::size_t... I
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>
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R visit_impl(
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F&& f,
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TSU&& tsu,
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dlib::index_sequence<I...>
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)
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{
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using func_t = R(*)(F&&, TSU&&);
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const func_t vtable[] = {
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/*! Empty (type_identity == 0) case !*/
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[](F&&, TSU&&) {
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return R();
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},
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/*! Non-empty cases !*/
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&visit_impl_as_type<R,F&&,TSU&&,I>...
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};
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return vtable[tsu.get_current_type_id()](std::forward<F>(f), std::forward<TSU>(tsu));
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}
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}
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template<
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@ -598,20 +553,13 @@ namespace dlib
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detail::for_each_type_impl(std::forward<F>(f), std::forward<TSU>(tsu), dlib::make_index_sequence<Size>{});
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}
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template<
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typename F,
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typename TSU,
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typename Tsu = typename std::decay<TSU>::type,
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typename T0 = type_safe_union_alternative_t<0, Tsu>
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>
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template<typename F, typename TSU>
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auto visit(
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F&& f,
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TSU&& tsu
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) -> dlib::invoke_result_t<F, decltype(tsu.template cast_to<T0>())>
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{
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using ReturnType = dlib::invoke_result_t<F, decltype(tsu.template cast_to<T0>())>;
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static constexpr std::size_t Size = type_safe_union_size<Tsu>::value;
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return detail::visit_impl<ReturnType>(std::forward<F>(f), std::forward<TSU>(tsu), dlib::make_index_sequence<Size>{});
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) noexcept(noexcept(tsu.apply_to_contents(std::forward<F>(f))))
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-> decltype(tsu.apply_to_contents(std::forward<F>(f))) {
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return tsu.apply_to_contents(std::forward<F>(f));
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}
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namespace detail
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@ -124,6 +124,19 @@ namespace dlib
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struct are_nothrow_swappable<T> : is_nothrow_swappable<T> {};
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// ---------------------------------------------------------------------
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template<bool First, bool... Rest>
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struct And : std::integral_constant<bool, First && And<Rest...>::value> {};
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template<bool Value>
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struct And<Value> : std::integral_constant<bool, Value>{};
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// ---------------------------------------------------------------------
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template<std::size_t I>
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using size_ = std::integral_constant<std::size_t, I>;
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// ---------------------------------------------------------------------
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}
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#endif //DLIB_UTILITY_Hh_
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