/* Copyright 2016-2017 Joaquin M Lopez Munoz.
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* Distributed under the Boost Software License, Version 1.0.
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* (See accompanying file LICENSE_1_0.txt or copy at
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* http://www.boost.org/LICENSE_1_0.txt)
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*
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* See http://www.boost.org/libs/poly_collection for library home page.
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*/
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#ifndef BOOST_POLY_COLLECTION_DETAIL_CALLABLE_WRAPPER_HPP
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#define BOOST_POLY_COLLECTION_DETAIL_CALLABLE_WRAPPER_HPP
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#if defined(_MSC_VER)
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#pragma once
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#endif
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#include <boost/poly_collection/detail/is_invocable.hpp>
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#include <functional>
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#include <type_traits>
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#include <typeinfo>
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namespace boost{
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namespace poly_collection{
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namespace detail{
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/* lightweight std::function look-alike over non-owned callable entities */
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template<typename Signature>
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class callable_wrapper;
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template<typename R,typename... Args>
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class callable_wrapper<R(Args...)>
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{
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public:
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// TODO: we should prevent assignment by user code
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template<
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typename Callable,
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typename std::enable_if<
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!std::is_same<Callable,callable_wrapper>::value&&
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is_invocable_r<R,Callable,Args...>::value
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>::type* =nullptr
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>
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explicit callable_wrapper(Callable& x)noexcept:pt{info(x)},px{&x}{}
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callable_wrapper(const callable_wrapper&)=default;
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callable_wrapper& operator=(const callable_wrapper&)=default;
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explicit operator bool()const noexcept{return true;}
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R operator()(Args... args)const
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{return pt->call(px,std::forward<Args>(args)...);}
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const std::type_info& target_type()const noexcept{return pt->info;}
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template<typename T>
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T* target()noexcept
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{return typeid(T)==pt->info?static_cast<T*>(px):nullptr;}
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template<typename T>
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const T* target()const noexcept
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{return typeid(T)==pt->info?static_cast<const T*>(px):nullptr;}
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/* not in std::function interface */
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operator std::function<R(Args...)>()const noexcept{return pt->convert(px);}
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void* data()noexcept{return px;}
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const void* data()const noexcept{return px;}
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private:
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struct table
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{
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R(*call)(void*,Args...);
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const std::type_info& info;
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std::function<R(Args...)> (*convert)(void*);
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};
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template<typename Callable>
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static table* info(Callable&)noexcept
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{
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static table t={
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[](void* p,Args... args){
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auto r=std::ref(*static_cast<Callable*>(p));
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return static_cast<R>(r(std::forward<Args>(args)...));
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},
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typeid(Callable),
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[](void* p){
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auto r=std::ref(*static_cast<Callable*>(p));
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return std::function<R(Args...)>{r};
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}
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};
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return &t;
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}
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table* pt;
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void* px;
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};
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} /* namespace poly_collection::detail */
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} /* namespace poly_collection */
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} /* namespace boost */
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#endif
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