poly_collection/detail/any_model.hpp

0001 /* Copyright 2016-2020 Joaquin M Lopez Munoz.
0002  * Distributed under the Boost Software License, Version 1.0.
0003  * (See accompanying file LICENSE_1_0.txt or copy at
0004  * http://www.boost.org/LICENSE_1_0.txt)
0005  *
0006  * See http://www.boost.org/libs/poly_collection for library home page.
0007  */
0008
0009 #ifndef BOOST_POLY_COLLECTION_DETAIL_ANY_MODEL_HPP
0010 #define BOOST_POLY_COLLECTION_DETAIL_ANY_MODEL_HPP
0011
0012 #if defined(_MSC_VER)
0013 #pragma once
0014 #endif
0015
0016 #include <boost/core/addressof.hpp>
0017 #include <boost/mpl/map/map10.hpp>
0018 #include <boost/mpl/pair.hpp>
0019 #include <boost/mpl/vector/vector10.hpp>
0020 #include <boost/poly_collection/detail/any_iterator.hpp>
0021 #include <boost/poly_collection/detail/is_acceptable.hpp>
0022 #include <boost/poly_collection/detail/segment_backend.hpp>
0023 #include <boost/poly_collection/detail/split_segment.hpp>
0024 #include <boost/type_erasure/any.hpp>
0025 #include <boost/type_erasure/any_cast.hpp>
0026 #include <boost/type_erasure/binding.hpp>
0027 #include <boost/type_erasure/builtin.hpp>
0028 #include <boost/type_erasure/concept_of.hpp>
0029 #include <boost/type_erasure/is_subconcept.hpp>
0030 #include <boost/type_erasure/relaxed.hpp>
0031 #include <boost/type_erasure/static_binding.hpp>
0032 #include <boost/type_erasure/typeid_of.hpp>
0033 #include <memory>
0034 #include <type_traits>
0035 #include <typeinfo>
0036 #include <utility>
0037
0038 namespace boost{
0039
0040 namespace poly_collection{
0041
0042 namespace detail{
0043
0044 /* model for any_collection */
0045
0046 template<typename Concept>
0047 struct any_model;
0048
0049 /* Refine is_acceptable to cover type_erasure::any classes whose assignment
0050  * operator won't compile.
0051  */
0052
0053 template<typename Concept,typename Concept2,typename T>
0054 struct is_acceptable<
0055   type_erasure::any<Concept2,T>,any_model<Concept>,
0056   typename std::enable_if<
0057     !type_erasure::is_relaxed<Concept2>::value&&
0058     !type_erasure::is_subconcept<type_erasure::assignable<>,Concept2>::value&&
0059     !type_erasure::is_subconcept<
0060       type_erasure::assignable<type_erasure::_self,type_erasure::_self&&>,
0061       Concept2>::value
0062   >::type
0063 >:std::false_type{};
0064
0065 /* is_terminal defined out-class to allow for partial specialization */
0066
0067 template<typename Concept,typename T>
0068 using any_model_enable_if_has_typeid_=typename std::enable_if<
0069   type_erasure::is_subconcept<
0070     type_erasure::typeid_<typename std::decay<T>::type>,
0071     Concept
0072   >::value
0073 >::type*;
0074
0075 template<typename T,typename=void*>
0076 struct any_model_is_terminal:std::true_type{};
0077
0078 template<typename Concept,typename T>
0079 struct any_model_is_terminal<
0080   type_erasure::any<Concept,T>,any_model_enable_if_has_typeid_<Concept,T>
0081 >:std::false_type{};
0082
0083 /* used for make_value_type */
0084
0085 template<typename T,typename Q>
0086 struct any_model_make_reference
0087 {
0088   static T& apply(Q& x){return x;}
0089 };
0090
0091 template<typename Concept>
0092 struct any_model
0093 {
0094   using value_type=type_erasure::any<
0095     typename std::conditional<
0096       type_erasure::is_subconcept<type_erasure::typeid_<>,Concept>::value,
0097       Concept,
0098       mpl::vector2<Concept,type_erasure::typeid_<>>
0099     >::type,
0100     type_erasure::_self&
0101   >;
0102
0103   template<typename Concrete>
0104   using is_implementation=std::true_type; /* can't compile-time check concept
0105                                            * compliance */
0106   template<typename T>
0107   using is_terminal=any_model_is_terminal<T>;
0108
0109   template<typename T>
0110   static const std::type_info& subtypeid(const T&){return typeid(T);}
0111
0112   template<
0113     typename Concept2,typename T,
0114     any_model_enable_if_has_typeid_<Concept2,T> =nullptr
0115   >
0116   static const std::type_info& subtypeid(
0117     const type_erasure::any<Concept2,T>& a)
0118   {
0119     return type_erasure::typeid_of(a);
0120   }
0121
0122   template<typename T>
0123   static void* subaddress(T& x){return boost::addressof(x);}
0124
0125   template<typename T>
0126   static const void* subaddress(const T& x){return boost::addressof(x);}
0127
0128   template<
0129     typename Concept2,typename T,
0130     any_model_enable_if_has_typeid_<Concept2,T> =nullptr
0131   >
0132   static void* subaddress(type_erasure::any<Concept2,T>& a)
0133   {
0134     return type_erasure::any_cast<void*>(&a);
0135   }
0136
0137   template<
0138     typename Concept2,typename T,
0139     any_model_enable_if_has_typeid_<Concept2,T> =nullptr
0140   >
0141   static const void* subaddress(const type_erasure::any<Concept2,T>& a)
0142   {
0143     return type_erasure::any_cast<const void*>(&a);
0144   }
0145
0146   using base_iterator=any_iterator<value_type>;
0147   using const_base_iterator=any_iterator<const value_type>;
0148   using base_sentinel=value_type*;
0149   using const_base_sentinel=const value_type*;
0150   template<typename Concrete>
0151   using iterator=Concrete*;
0152   template<typename Concrete>
0153   using const_iterator=const Concrete*;
0154   template<typename Allocator>
0155   using segment_backend=detail::segment_backend<any_model,Allocator>;
0156   template<typename Concrete,typename Allocator>
0157   using segment_backend_implementation=
0158     split_segment<any_model,Concrete,Allocator>;
0159
0160   static base_iterator nonconst_iterator(const_base_iterator it)
0161   {
0162     return base_iterator{
0163       const_cast<value_type*>(static_cast<const value_type*>(it))};
0164   }
0165
0166   template<typename T>
0167   static iterator<T> nonconst_iterator(const_iterator<T> it)
0168   {
0169     return const_cast<iterator<T>>(it);
0170   }
0171
0172 private:
0173   template<typename,typename,typename>
0174   friend class split_segment;
0175
0176   template<typename Concrete>
0177   static value_type make_value_type(Concrete& x){return value_type{x};}
0178
0179   template<typename Concept2,typename T>
0180   static value_type make_value_type(type_erasure::any<Concept2,T>& x)
0181   {
0182     /* I don't pretend to understand what's going on here, see
0183      * https://lists.boost.org/boost-users/2017/05/87556.php
0184      */
0185
0186     using ref_type=type_erasure::any<Concept2,T>;
0187     using make_ref=any_model_make_reference<type_erasure::_self,ref_type>;
0188     using concept_=typename type_erasure::concept_of<value_type>::type;
0189
0190     auto b=type_erasure::make_binding<
0191       mpl::map1<mpl::pair<type_erasure::_self,ref_type>>>();
0192
0193     return {
0194       type_erasure::call(type_erasure::binding<make_ref>{b},make_ref{},x),
0195       type_erasure::binding<concept_>{b}
0196     };
0197   }
0198 };
0199
0200 } /* namespace poly_collection::detail */
0201
0202 } /* namespace poly_collection */
0203
0204 } /* namespace boost */
0205
0206 #endif