385 lines
9.3 KiB
C++
385 lines
9.3 KiB
C++
#ifndef UTIL_VARIANT_HPP
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#define UTIL_VARIANT_HPP
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#include <utility>
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#include <typeinfo>
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#include <type_traits>
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#include <algorithm> // std::move/swap
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#include <stdexcept> // runtime_error
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#include <new> // operator new
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#include <cstddef> // size_t
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#include <iosfwd>
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#ifdef NDEBUG
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#define VARIANT_INLINE inline __attribute__((always_inline))
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#else
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#define VARIANT_INLINE __attribute__((noinline))
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#endif
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namespace llmr {
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namespace util {
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namespace detail {
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static constexpr std::size_t invalid_value = std::size_t(-1);
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template <typename T, typename...Types>
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struct type_traits;
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template <typename T, typename First, typename...Types>
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struct type_traits<T, First, Types...>
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{
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static constexpr std::size_t id = std::is_same<T, First>::value ? sizeof...(Types) : type_traits<T, Types...>::id;
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};
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template <typename T>
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struct type_traits<T>
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{
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static constexpr std::size_t id = invalid_value;
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};
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template <typename T, typename...Types>
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struct is_valid_type;
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template <typename T, typename First, typename... Types>
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struct is_valid_type<T,First,Types...>
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{
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static constexpr bool value = std::is_same<T,First>::value
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|| is_valid_type<T,Types...>::value;
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};
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template <typename T>
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struct is_valid_type<T> : std::false_type {};
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}
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template <std::size_t arg1, std::size_t ... others>
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struct static_max;
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template <std::size_t arg>
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struct static_max<arg>
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{
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static const std::size_t value = arg;
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};
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template <std::size_t arg1, std::size_t arg2, std::size_t ... others>
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struct static_max<arg1, arg2, others...>
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{
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static const std::size_t value = arg1 >= arg2 ? static_max<arg1, others...>::value :
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static_max<arg2, others...>::value;
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};
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template<typename... Types>
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struct variant_helper;
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template<typename T, typename... Types>
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struct variant_helper<T, Types...>
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{
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VARIANT_INLINE static void destroy(std::size_t id, void * data)
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{
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if (id == sizeof...(Types))
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{
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reinterpret_cast<T*>(data)->~T();
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}
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else
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{
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variant_helper<Types...>::destroy(id, data);
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}
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}
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VARIANT_INLINE static void move(const std::size_t old_t, void * old_v, void * new_v)
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{
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if (old_t == sizeof...(Types))
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{
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new (new_v) T(std::move(*reinterpret_cast<T*>(old_v)));
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//std::memcpy(new_v, old_v, sizeof(T));
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// ^^ DANGER: this should only be considered for relocatable types e.g built-in types
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// Also, I don't see any measurable performance benefit just yet
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}
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else
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{
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variant_helper<Types...>::move(old_t, old_v, new_v);
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}
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}
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VARIANT_INLINE static void copy(const std::size_t old_t, const void * old_v, void * new_v)
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{
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if (old_t == sizeof...(Types))
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{
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new (new_v) T(*reinterpret_cast<const T*>(old_v));
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}
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else
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{
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variant_helper<Types...>::copy(old_t, old_v, new_v);
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}
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}
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};
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template<> struct variant_helper<>
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{
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VARIANT_INLINE static void destroy(const std::size_t, void *) {}
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VARIANT_INLINE static void move(const std::size_t, void *, void *) {}
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VARIANT_INLINE static void copy(const std::size_t, const void *, void *) {}
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};
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namespace detail {
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template <typename F, typename V, typename...Types>
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struct dispatcher;
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template <typename F, typename V, typename T, typename...Types>
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struct dispatcher<F,V,T,Types...>
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{
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typedef typename std::result_of<F(V const&)>::type result_type;
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VARIANT_INLINE static result_type apply(V const& v, F f)
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{
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if (v.get_type_id() == sizeof...(Types))
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{
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return f(v. template get<T>());
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}
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else
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{
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return dispatcher<F,V,Types...>::apply(v, f);
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}
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}
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};
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template<typename F,typename V>
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struct dispatcher<F,V>
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{
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typedef typename std::result_of<F(V const&)>::type result_type;
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VARIANT_INLINE static result_type apply(V const&, F)
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{
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throw std::runtime_error("dispatch: FAIL");
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}
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};
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// comparator functors
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struct equal_comp
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{
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template <typename T>
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bool operator()(T const& lhs, T const& rhs) const
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{
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return lhs == rhs;
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}
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};
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struct less_comp
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{
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template <typename T>
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bool operator()(const T& lhs, const T& rhs) const
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{
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return lhs < rhs;
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}
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};
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template <typename Variant, typename Comp>
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struct comparer
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{
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public:
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explicit comparer(Variant const& lhs) noexcept
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: lhs_(lhs) {}
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comparer& operator=(const comparer&) = delete;
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// visitor
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template<typename T>
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bool operator()(T const& rhs_content) const
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{
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T const& lhs_content = lhs_.template get<T>();
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return Comp()(lhs_content, rhs_content);
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}
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private:
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Variant const& lhs_;
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};
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// operator<< helper
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template <typename Out>
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struct printer
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{
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public:
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explicit printer(Out & out)
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: out_(out) {}
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printer& operator=(const printer&) = delete;
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// visitor
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template <typename T>
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void operator()(const T& operand) const
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{
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out_ << operand;
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}
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private:
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Out & out_;
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};
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} // detail
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template<typename... Types>
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struct variant
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{
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private:
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static const std::size_t data_size = static_max<sizeof(Types)...>::value;
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static const std::size_t data_align = static_max<alignof(Types)...>::value;
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using data_t = typename std::aligned_storage<data_size, data_align>::type;
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using helper_t = variant_helper<Types...>;
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std::size_t type_id;
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data_t data;
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public:
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VARIANT_INLINE variant()
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: type_id(detail::invalid_value) {}
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template <typename T>
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VARIANT_INLINE explicit variant(T const& val) noexcept
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: type_id(detail::type_traits<T, Types...>::id)
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{
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static_assert(detail::is_valid_type<T,Types...>::value, "Not a valid type for this variant");
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new (&data) T(val);
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}
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template <typename T>
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VARIANT_INLINE variant(T && val) noexcept
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: type_id(detail::type_traits<T,Types...>::id)
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{
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static_assert(detail::is_valid_type<T,Types...>::value, "Not a valid type for this variant");
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new (&data) T(std::forward<T>(val)); // nothrow
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}
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VARIANT_INLINE variant(variant<Types...> const& old)
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: type_id(old.type_id)
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{
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helper_t::copy(old.type_id, &old.data, &data);
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}
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VARIANT_INLINE variant(variant<Types...>&& old) noexcept
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: type_id(old.type_id)
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{
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helper_t::move(old.type_id, &old.data, &data);
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}
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friend void swap(variant<Types...> & first, variant<Types...> & second)
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{
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using std::swap; //enable ADL
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swap(first.type_id, second.type_id);
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swap(first.data, second.data);
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}
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VARIANT_INLINE variant<Types...>& operator= (variant<Types...> other)
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{
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swap(*this, other);
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return *this;
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}
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template<typename T>
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VARIANT_INLINE bool is() const
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{
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return (type_id == detail::type_traits<T, Types...>::id);
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}
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VARIANT_INLINE bool valid() const
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{
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return (type_id != detail::invalid_value);
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}
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template<typename T, typename... Args>
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VARIANT_INLINE void set(Args&&... args)
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{
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helper_t::destroy(type_id, &data);
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new (&data) T(std::forward<Args>(args)...);
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type_id = detail::type_traits<T,Types...>::id;
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}
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template<typename T>
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VARIANT_INLINE T& get()
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{
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if (type_id == detail::type_traits<T,Types...>::id)
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{
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return *reinterpret_cast<T*>(&data);
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}
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else
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{
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throw std::runtime_error("in get()");
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}
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}
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template<typename T>
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VARIANT_INLINE T const& get() const
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{
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if (type_id == detail::type_traits<T,Types...>::id)
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{
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return *reinterpret_cast<T const*>(&data);
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}
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else
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{
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throw std::runtime_error("in get()");
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}
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}
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VARIANT_INLINE std::size_t get_type_id() const
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{
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return type_id;
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}
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// visitor
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template <typename F, typename V>
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typename std::result_of<F(V const&)>::type
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VARIANT_INLINE static visit(V const& v, F f)
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{
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return detail::dispatcher<F, V, Types...>::apply(v, f);
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}
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~variant() noexcept
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{
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helper_t::destroy(type_id, &data);
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}
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// comparison operators
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// equality
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VARIANT_INLINE bool operator==(variant const& rhs) const
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{
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if (this->get_type_id() != rhs.get_type_id())
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return false;
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detail::comparer<variant, detail::equal_comp> visitor(*this);
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return visit(rhs, visitor);
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}
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// less than
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VARIANT_INLINE bool operator<(variant const& rhs) const
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{
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if (this->get_type_id() != rhs.get_type_id())
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{
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return this->get_type_id() < rhs.get_type_id();
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// ^^ borrowed from boost::variant
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}
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detail::comparer<variant, detail::less_comp> visitor(*this);
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return visit(rhs, visitor);
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}
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};
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// unary visitor interface
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template <typename V, typename F>
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typename std::result_of<F(V const&)>::type
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VARIANT_INLINE static apply_visitor(V const& v, F f)
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{
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return V::visit(v,f);
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}
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// operator<<
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template <typename charT, typename traits, typename Variant>
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VARIANT_INLINE std::basic_ostream<charT,traits>&
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operator<< (std::basic_ostream<charT,traits>& out, Variant const& rhs)
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{
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detail::printer<std::basic_ostream<charT,traits> > visitor(out);
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apply_visitor(rhs, visitor);
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return out;
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}
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}
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}
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#endif // UTIL_VARIANT_HPP
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