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update variant (add support for 'unwrapping' std::reference_wrapper<T> and accessing std::reference_wrapper<T>::type through get<T>())

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This commit is contained in:
artemp 2015-03-25 10:52:33 +01:00
parent f2673c6432
commit 22de30bb37
1 changed files with 40 additions and 0 deletions
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40
include/mapnik/util/variant.hpp
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@ -276,6 +276,15 @@ struct unwrapper<recursive_wrapper<T>>
}
};
template <typename T>
struct unwrapper<std::reference_wrapper<T>>
{
auto operator() (std::reference_wrapper<T> const& obj) const
-> typename recursive_wrapper<T>::type const&
{
return obj.get();
}
};
template <typename F, typename V, typename R, typename...Types>
struct dispatcher;
@ -693,6 +702,37 @@ public:
}
}
// get<T>() - T stored as std::reference_wrapper<T>
template <typename T, typename std::enable_if<
(detail::direct_type<std::reference_wrapper<T>, Types...>::index != detail::invalid_value)
>::type* = nullptr>
VARIANT_INLINE T& get()
{
if (type_index == detail::direct_type<std::reference_wrapper<T>, Types...>::index)
{
return (*reinterpret_cast<std::reference_wrapper<T>*>(&data)).get();
}
else
{
throw std::runtime_error("in get<T>()");
}
}
template <typename T,typename std::enable_if<
(detail::direct_type<std::reference_wrapper<T const>, Types...>::index != detail::invalid_value)
>::type* = nullptr>
VARIANT_INLINE T const& get() const
{
if (type_index == detail::direct_type<std::reference_wrapper<T const>, Types...>::index)
{
return (*reinterpret_cast<std::reference_wrapper<T const> const*>(&data)).get();
}
else
{
throw std::runtime_error("in get<T>()");
}
}
VARIANT_INLINE std::size_t get_type_index() const
{
return type_index;