301 lines
9.0 KiB
C++
301 lines
9.0 KiB
C++
/* Copyright 2018 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_ALLOCATOR_ADAPTOR_HPP
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#define BOOST_POLY_COLLECTION_DETAIL_ALLOCATOR_ADAPTOR_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/mp11/function.hpp>
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#include <boost/mp11/integer_sequence.hpp>
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#include <boost/poly_collection/detail/is_constructible.hpp>
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#include <new>
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#include <memory>
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#include <tuple>
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#include <type_traits>
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#include <utility>
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namespace boost{
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namespace poly_collection{
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namespace detail{
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/* [container.requirements.general]/3 state that containers must use the
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* allocator's construct/destroy member functions to construct/destroy
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* elements and *not at all* for any other type. Since poly_collection is
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* implemented as a multi-level structure of container and container-like
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* objects, we need to use an adaptor for the user-provided Allocator that
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* prevents intermediate entities from calling Allocator::[construct|destroy].
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* allocator_adaptor<Allocator> does this by taking advantage of the fact that
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* elements are ultimately held within a value_holder:
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* - construct(value_holder<T>*,...) uses placement new construction and
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* passes the wrapped Allocator object for value_holder<T> to use for
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* its inner construction of T.
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* - For the rest of types, construct uses placement new construction and
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* passes down the adaptor object itself as an argument following an
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* approach analogous to that of std::scoped_allocator_adaptor.
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* - destroy(value_holder<T>) resorts to Allocator::destroy to destroy the
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* contained T element.
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* - For the rest of types, destroy(T) calls ~T directly.
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*
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* Code has been ripped and adapted from libc++'s implementation of
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* std::scoped_allocator_adaptor.
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*/
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template<typename T>
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class value_holder_base;
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template<typename T>
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class value_holder;
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template<typename T,typename Allocator,typename... Args>
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struct uses_alloc_ctor_impl
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{
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using RawAllocator=typename std::remove_cv<
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typename std::remove_reference<Allocator>::type
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>::type;
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static const bool ua=std::uses_allocator<T,RawAllocator>::value;
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static const int ic=is_constructible<
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T,std::allocator_arg_t,Allocator,Args...>::value?1:0;
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static const int value=ua?2-ic:0;
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};
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template<typename T,typename Allocator,typename... Args>
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struct uses_alloc_ctor:
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std::integral_constant<int,uses_alloc_ctor_impl<T,Allocator,Args...>::value>
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{};
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template<typename Allocator,typename=void>
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struct allocator_is_always_equal:std::is_empty<Allocator>{};
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template<typename Allocator>
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struct allocator_is_always_equal<
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Allocator,
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mp11::mp_void<
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typename std::allocator_traits<Allocator>::is_always_equal
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>
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>:std::allocator_traits<Allocator>::is_always_equal{};
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template<typename Allocator>
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struct allocator_adaptor:Allocator
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{
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using traits=std::allocator_traits<Allocator>;
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using value_type=typename traits::value_type;
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using size_type=typename traits::size_type;
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using difference_type=typename traits::difference_type;
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using pointer=typename traits::pointer;
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using const_pointer=typename traits::const_pointer;
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using void_pointer=typename traits::void_pointer;
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using const_void_pointer=typename traits::const_void_pointer;
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using propagate_on_container_copy_assignment=
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typename traits::propagate_on_container_copy_assignment;
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using propagate_on_container_move_assignment=
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typename traits::propagate_on_container_move_assignment;
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using propagate_on_container_swap=
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typename traits::propagate_on_container_swap;
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using is_always_equal=typename allocator_is_always_equal<Allocator>::type;
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template<typename U>
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struct rebind
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{
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using other=allocator_adaptor<typename traits::template rebind_alloc<U>>;
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};
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allocator_adaptor()=default;
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allocator_adaptor(const allocator_adaptor&)=default;
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template<
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typename Allocator2,
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typename std::enable_if<
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is_constructible<Allocator,const Allocator2&>::value
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>::type* =nullptr
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>
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allocator_adaptor(const Allocator2& x)noexcept:Allocator{x}{}
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template<
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typename Allocator2,
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typename std::enable_if<
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is_constructible<Allocator,const Allocator2&>::value
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>::type* =nullptr
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>
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allocator_adaptor(const allocator_adaptor<Allocator2>& x)noexcept:
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Allocator{x.allocator()}{}
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allocator_adaptor& operator=(const allocator_adaptor&)=default;
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Allocator& allocator()noexcept{return *this;}
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const Allocator& allocator()const noexcept{return *this;}
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template<typename T,typename... Args>
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void construct(T* p,Args&&... args)
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{
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construct_(
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uses_alloc_ctor<T,allocator_adaptor&,Args...>{},
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p,std::forward<Args>(args)...);
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}
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template<typename T,typename... Args>
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void construct(value_holder<T>* p,Args&&... args)
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{
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::new ((void*)p) value_holder<T>(allocator(),std::forward<Args>(args)...);
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}
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template<typename T1,typename T2,typename... Args1,typename... Args2>
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void construct(
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std::pair<T1,T2>* p,std::piecewise_construct_t,
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std::tuple<Args1...> x,std::tuple<Args2...> y)
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{
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::new ((void*)p) std::pair<T1,T2>(
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std::piecewise_construct,
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transform_tuple(
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uses_alloc_ctor<T1,allocator_adaptor&,Args1...>{},
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std::move(x),
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mp11::make_index_sequence<sizeof...(Args1)>{}),
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transform_tuple(
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uses_alloc_ctor<T2,allocator_adaptor&,Args2...>{},
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std::move(y),
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mp11::make_index_sequence<sizeof...(Args2)>{})
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);
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}
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template<typename T1,typename T2>
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void construct(std::pair<T1,T2>* p)
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{
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construct(p,std::piecewise_construct,std::tuple<>{},std::tuple<>{});
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}
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template<typename T1,typename T2,typename U,typename V>
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void construct(std::pair<T1,T2>* p,U&& x,V&& y)
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{
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construct(
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p,std::piecewise_construct,
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std::forward_as_tuple(std::forward<U>(x)),
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std::forward_as_tuple(std::forward<V>(y)));
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}
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template<typename T1,typename T2,typename U,typename V>
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void construct(std::pair<T1,T2>* p,const std::pair<U,V>& x)
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{
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construct(
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p,std::piecewise_construct,
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std::forward_as_tuple(x.first),std::forward_as_tuple(x.second));
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}
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template<typename T1,typename T2,typename U,typename V>
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void construct(std::pair<T1,T2>* p,std::pair<U,V>&& x)
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{
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construct(
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p,std::piecewise_construct,
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std::forward_as_tuple(std::forward<U>(x.first)),
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std::forward_as_tuple(std::forward<V>(x.second)));
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}
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template<typename T>
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void destroy(T* p)
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{
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p->~T();
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}
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template<typename T>
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void destroy(value_holder<T>* p)
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{
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traits::destroy(
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allocator(),
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reinterpret_cast<T*>(static_cast<value_holder_base<T>*>(p)));
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}
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allocator_adaptor
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select_on_container_copy_construction()const noexcept
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{
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return traits::select_on_container_copy_construction(allocator());
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}
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private:
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template<typename T,typename... Args>
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void construct_(
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std::integral_constant<int,0>, /* doesn't use allocator */
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T* p,Args&&... args)
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{
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::new ((void*)p) T(std::forward<Args>(args)...);
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}
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template<typename T,typename... Args>
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void construct_(
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std::integral_constant<int,1>, /* with std::allocator_arg */
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T* p,Args&&... args)
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{
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::new ((void*)p) T(std::allocator_arg,*this,std::forward<Args>(args)...);
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}
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template<typename T,typename... Args>
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void construct_(
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std::integral_constant<int,2>, /* allocator at the end */
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T* p,Args&&... args)
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{
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::new ((void*)p) T(std::forward<Args>(args)...,*this);
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}
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template<typename... Args,std::size_t... I>
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std::tuple<Args&&...> transform_tuple(
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std::integral_constant<int,0>, /* doesn't use allocator */
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std::tuple<Args...>&& t,mp11::index_sequence<I...>)
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{
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return std::tuple<Args&&...>(std::get<I>(std::move(t))...);
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}
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template<typename... Args,std::size_t... I>
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std::tuple<std::allocator_arg_t,allocator_adaptor&,Args&&...>
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transform_tuple(
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std::integral_constant<int,1>, /* with std::allocator_arg */
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std::tuple<Args...>&& t,mp11::index_sequence<I...>)
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{
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return std::tuple<
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std::allocator_arg_t,allocator_adaptor&,Args&&...>(
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std::allocator_arg,*this,std::get<I>(std::move(t))...);
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}
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template<typename... Args,std::size_t... I>
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std::tuple<Args&&...,allocator_adaptor&>
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transform_tuple(
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std::integral_constant<int,2>, /* allocator at the end */
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std::tuple<Args...>&& t,mp11::index_sequence<I...>)
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{
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return std::tuple<Args&&...,allocator_adaptor&>(
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std::get<I>(std::move(t))...,*this);
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}
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};
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template<typename Allocator1,typename Allocator2>
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bool operator==(
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const allocator_adaptor<Allocator1>& x,
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const allocator_adaptor<Allocator2>& y)noexcept
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{
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return x.allocator()==y.allocator();
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}
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template<typename Allocator1,typename Allocator2>
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bool operator!=(
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const allocator_adaptor<Allocator1>& x,
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const allocator_adaptor<Allocator2>& y)noexcept
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{
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return !(x==y);
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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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