forked from enlightenment/efl
348 lines
8.5 KiB
C++
348 lines
8.5 KiB
C++
#ifndef EINA_VARIANT_HH_
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#define EINA_VARIANT_HH_
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#include <cstddef>
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#include <algorithm>
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#include <utility>
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#include <type_traits>
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#include <tuple>
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#include <eina_aligned_union.hh>
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namespace efl { namespace eina {
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namespace _impl {
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template <typename T, typename U, typename...Others>
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struct is_one_of : std::conditional<std::is_same<T, U>::value
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, std::is_same<T, U>
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, is_one_of<T, Others...> >::type::type
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{};
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template <typename T, typename U>
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struct is_one_of<T, U> : std::is_same<T, U>
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{};
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template <std::size_t size, typename T, typename U, typename...Args>
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struct find_impl : find_impl<size+1, T, Args...>
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{};
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template <std::size_t size, typename T, typename...Args>
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struct find_impl<size, T, T, Args...> : std::integral_constant<std::size_t, size> {};
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template <typename T, typename U, typename...Args>
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struct find : find_impl<0u, T, U, Args...>
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{};
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}
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template <std::size_t N, std::size_t L, typename Tuple>
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struct call_visitor
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{
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template <typename F>
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static typename F::result_type call(int type, void const* buffer, F f)
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{
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if(type == N)
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{
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using std::tuple_element;
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typedef typename tuple_element<N, Tuple>::type type;
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type const* o = static_cast<type const*>(buffer);
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return f(*o);
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}
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else
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return call_visitor<N+1, L, Tuple>::call(type, buffer, f);
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}
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template <typename F>
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static typename F::result_type call(int type, void* buffer, F f)
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{
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if(type == N)
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{
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using std::tuple_element;
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typedef typename tuple_element<N, Tuple>::type type;
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type* o = static_cast<type*>(buffer);
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return f(*o);
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}
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else
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return call_visitor<N+1, L, Tuple>::call(type, buffer, f);
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}
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};
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template <std::size_t L, typename Tuple>
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struct call_visitor<L, L, Tuple>
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{
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template <typename F>
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static typename F::result_type call(int, void const*, F)
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{
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std::abort();
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}
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};
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struct compare_equal_visitor
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{
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void const* buffer;
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typedef bool result_type;
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template <typename T>
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bool operator()(T const& other) const
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{
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return *static_cast<T const*>(buffer) == other;
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}
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};
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struct copy_visitor
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{
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typedef void result_type;
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void* buffer;
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template <typename T>
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void operator()(T const& other) const
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{
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new (buffer) T(other);
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}
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};
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struct move_visitor
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{
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typedef void result_type;
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void* buffer;
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template <typename T>
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void operator()(T& other) const
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{
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typedef typename std::remove_cv<typename std::remove_reference<T>::type>::type type;
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new (buffer) type(std::move(other));
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}
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};
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struct assign_visitor
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{
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typedef void result_type;
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void* buffer;
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template <typename T>
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void operator()(T const& other) const
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{
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typedef typename std::remove_cv<typename std::remove_reference<T>::type>::type type;
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type* assigned = static_cast<type*>(buffer);
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*assigned = other;
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}
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};
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struct move_assign_visitor
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{
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typedef void result_type;
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void* buffer;
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template <typename T>
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void operator()(T& other) const
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{
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typedef typename std::remove_cv<typename std::remove_reference<T>::type>::type type;
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type* assigned = static_cast<type*>(buffer);
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*assigned = std::move(other);
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}
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};
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struct destroy_visitor
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{
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typedef void result_type;
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template <typename T>
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void operator()(T&& other) const noexcept
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{
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typedef typename std::remove_cv<typename std::remove_reference<T>::type>::type type;
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other.~type();
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}
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};
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template <typename T>
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struct get_visitor
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{
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typedef T* result_type;
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T* operator()(T& object) const
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{
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return &object;
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}
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template <typename U>
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T* operator()(U&) const { return nullptr; }
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};
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template <typename... Args>
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struct variant
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{
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typedef variant<Args...> _self_type; /**< Type for the optional class itself. */
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constexpr variant()
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: type(-1)
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{}
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template <typename T>
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variant(T object,
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typename std::enable_if<_impl::is_one_of
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<typename std::remove_cv<typename std::remove_reference<T>::type>::type, Args...>::value>::type* = 0)
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: type(_impl::find<typename std::remove_cv<typename std::remove_reference<T>::type>::type, Args...>::value)
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{
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construct(object);
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}
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variant(variant const& other)
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: type(other.type)
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{
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if(other.type != -1)
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other.visit(copy_visitor{static_cast<void*>(&buffer)});
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}
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variant& operator=(variant const& other)
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{
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if(type == other.type && type != -1)
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{
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other.visit(assign_visitor{static_cast<void*>(&buffer)});
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}
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else if(type != other.type)
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{
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if(type != -1)
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destroy_unsafe();
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type = other.type;
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other.visit(copy_visitor{static_cast<void*>(&buffer)});
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}
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return *this;
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}
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variant(variant&& other)
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: type(other.type)
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{
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if(other.type != -1)
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other.visit(move_visitor{static_cast<void*>(&buffer)});
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}
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variant& operator=(variant&& other)
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{
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if(type == other.type && type != -1)
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{
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other.visit(move_assign_visitor{static_cast<void*>(&buffer)});
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}
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else if(type != other.type)
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{
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if(type != -1)
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destroy_unsafe();
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type = other.type;
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other.visit(move_visitor{static_cast<void*>(&buffer)});
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}
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return *this;
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}
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~variant()
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{
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if(type != -1)
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destroy_unsafe();
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}
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void destroy()
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{
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if(type != -1)
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{
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destroy_unsafe();
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type = -1;
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}
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}
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void destroy_unsafe()
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{
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visit_unsafe(destroy_visitor());
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}
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bool empty() const
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{
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return type == -1;
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}
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template <typename F>
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typename F::result_type visit(F f) const
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{
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if(type == -1)
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{
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throw std::runtime_error("variant is empty");
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}
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else
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return call_visitor<0u, sizeof...(Args), std::tuple<Args...>>::call(type, static_cast<const void*>(&buffer), f);
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}
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template <typename F>
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typename F::result_type visit(F f)
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{
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if(type == -1)
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{
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throw std::runtime_error("variant is empty");
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}
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else
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return call_visitor<0u, sizeof...(Args), std::tuple<Args...>>::call(type, static_cast<void*>(&buffer), f);
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}
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template <typename F>
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typename F::result_type visit_unsafe(F f) const
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{
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return call_visitor<0u, sizeof...(Args), std::tuple<Args...>>::call(type, static_cast<const void*>(&buffer), f);
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}
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template <typename F>
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typename F::result_type visit_unsafe(F f)
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{
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return call_visitor<0u, sizeof...(Args), std::tuple<Args...>>::call(type, static_cast<void*>(&buffer), f);
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}
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private:
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template <typename T>
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void construct(T object)
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{
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new (&buffer) T(std::move(object));
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}
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typedef typename eina::aligned_union<1, Args...>::type buffer_type;
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friend bool operator==(variant<Args...> const& lhs, variant<Args...> const& rhs)
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{
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return rhs.type == lhs.type
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&& (rhs.type == -1
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|| rhs.visit(compare_equal_visitor{&lhs.buffer}));
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}
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int type;
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/**
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* Member variable for holding the contained value.
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*/
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buffer_type buffer;
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};
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template <typename...Args>
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inline bool operator!=(variant<Args...>const& lhs, variant<Args...> const& rhs)
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{
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return !(lhs == rhs);
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}
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template <typename T, typename...Args>
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T* get(variant<Args...>* variant, typename std::enable_if<_impl::is_one_of
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<typename std::remove_cv<typename std::remove_reference<T>::type>::type, Args...>::value>::type* = 0)
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{
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return variant->visit(get_visitor<T>{});
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}
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template <typename T, typename...Args>
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T const* get(variant<Args...>const* variant, typename std::enable_if<_impl::is_one_of
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<typename std::remove_cv<typename std::remove_reference<T>::type>::type, Args...>::value>::type* = 0)
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{
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return variant->visit(get_visitor<T const>{});
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}
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template <typename T, typename...Args>
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T& get(variant<Args...>& variant, typename std::enable_if<_impl::is_one_of
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<typename std::remove_cv<typename std::remove_reference<T>::type>::type, Args...>::value>::type* = 0)
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{
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T* p = variant.visit(get_visitor<T>{});
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if(p)
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return *p;
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else
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throw std::logic_error("");
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}
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template <typename T, typename...Args>
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T const& get(variant<Args...>const& variant, typename std::enable_if<_impl::is_one_of
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<typename std::remove_cv<typename std::remove_reference<T>::type>::type, Args...>::value>::type* = 0)
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{
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T const* p = variant.visit(get_visitor<T const>{});
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if(p)
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return *p;
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else
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throw std::logic_error("");
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}
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} }
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#endif
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