285 lines
8.8 KiB
C++
285 lines
8.8 KiB
C++
// Pointer Traits -*- C++ -*-
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// Copyright (C) 2011-2022 Free Software Foundation, Inc.
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//
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// This file is part of the GNU ISO C++ Library. This library is free
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// software; you can redistribute it and/or modify it under the
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// terms of the GNU General Public License as published by the
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// Free Software Foundation; either version 3, or (at your option)
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// any later version.
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// Under Section 7 of GPL version 3, you are granted additional
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// permissions described in the GCC Runtime Library Exception, version
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// 3.1, as published by the Free Software Foundation.
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// You should have received a copy of the GNU General Public License and
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// a copy of the GCC Runtime Library Exception along with this program;
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// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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// <http://www.gnu.org/licenses/>.
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/** @file bits/ptr_traits.h
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* This is an internal header file, included by other library headers.
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* Do not attempt to use it directly. @headername{memory}
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*/
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#ifndef _PTR_TRAITS_H
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#define _PTR_TRAITS_H 1
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#if __cplusplus >= 201103L
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#include <bits/move.h>
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#if __cplusplus > 201703L
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#include <concepts>
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#define __cpp_lib_constexpr_memory 201811L
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namespace __gnu_debug { struct _Safe_iterator_base; }
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#endif
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namespace std _GLIBCXX_VISIBILITY(default)
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{
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_GLIBCXX_BEGIN_NAMESPACE_VERSION
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class __undefined;
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// For a specialization `SomeTemplate<T, Types...>` the member `type` is T,
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// otherwise `type` is `__undefined`.
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template<typename _Tp>
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struct __get_first_arg
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{ using type = __undefined; };
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template<template<typename, typename...> class _SomeTemplate, typename _Tp,
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typename... _Types>
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struct __get_first_arg<_SomeTemplate<_Tp, _Types...>>
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{ using type = _Tp; };
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// For a specialization `SomeTemplate<T, Args...>` and a type `U` the member
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// `type` is `SomeTemplate<U, Args...>`, otherwise there is no member `type`.
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template<typename _Tp, typename _Up>
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struct __replace_first_arg
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{ };
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template<template<typename, typename...> class _SomeTemplate, typename _Up,
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typename _Tp, typename... _Types>
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struct __replace_first_arg<_SomeTemplate<_Tp, _Types...>, _Up>
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{ using type = _SomeTemplate<_Up, _Types...>; };
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#if __cpp_concepts
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// When concepts are supported detection of _Ptr::element_type is done
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// by a requires-clause, so __ptr_traits_elem_t only needs to do this:
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template<typename _Ptr>
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using __ptr_traits_elem_t = typename __get_first_arg<_Ptr>::type;
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#else
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// Detect the element type of a pointer-like type.
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template<typename _Ptr, typename = void>
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struct __ptr_traits_elem : __get_first_arg<_Ptr>
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{ };
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// Use _Ptr::element_type if is a valid type.
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template<typename _Ptr>
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struct __ptr_traits_elem<_Ptr, __void_t<typename _Ptr::element_type>>
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{ using type = typename _Ptr::element_type; };
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template<typename _Ptr>
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using __ptr_traits_elem_t = typename __ptr_traits_elem<_Ptr>::type;
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#endif
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// Define pointer_traits<P>::pointer_to.
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template<typename _Ptr, typename _Elt, bool = is_void<_Elt>::value>
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struct __ptr_traits_ptr_to
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{
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using pointer = _Ptr;
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using element_type = _Elt;
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/**
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* @brief Obtain a pointer to an object
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* @param __r A reference to an object of type `element_type`
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* @return `pointer::pointer_to(__e)`
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* @pre `pointer::pointer_to(__e)` is a valid expression.
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*/
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static pointer
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pointer_to(element_type& __e)
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#if __cpp_lib_concepts
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requires requires {
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{ pointer::pointer_to(__e) } -> convertible_to<pointer>;
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}
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#endif
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{ return pointer::pointer_to(__e); }
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};
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// Do not define pointer_traits<P>::pointer_to if element type is void.
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template<typename _Ptr, typename _Elt>
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struct __ptr_traits_ptr_to<_Ptr, _Elt, true>
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{ };
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// Partial specialization defining pointer_traits<T*>::pointer_to(T&).
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template<typename _Tp>
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struct __ptr_traits_ptr_to<_Tp*, _Tp, false>
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{
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using pointer = _Tp*;
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using element_type = _Tp;
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/**
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* @brief Obtain a pointer to an object
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* @param __r A reference to an object of type `element_type`
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* @return `addressof(__r)`
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*/
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static _GLIBCXX20_CONSTEXPR pointer
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pointer_to(element_type& __r) noexcept
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{ return std::addressof(__r); }
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};
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template<typename _Ptr, typename _Elt>
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struct __ptr_traits_impl : __ptr_traits_ptr_to<_Ptr, _Elt>
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{
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private:
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template<typename _Tp, typename = void>
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struct __difference { using type = ptrdiff_t; };
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template<typename _Tp>
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#if __cpp_concepts
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requires requires { typename _Tp::difference_type; }
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struct __difference<_Tp>
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#else
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struct __difference<_Tp, __void_t<typename _Tp::difference_type>>
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#endif
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{ using type = typename _Tp::difference_type; };
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template<typename _Tp, typename _Up, typename = void>
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struct __rebind : __replace_first_arg<_Tp, _Up> { };
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template<typename _Tp, typename _Up>
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#if __cpp_concepts
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requires requires { typename _Tp::template rebind<_Up>; }
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struct __rebind<_Tp, _Up>
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#else
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struct __rebind<_Tp, _Up, __void_t<typename _Tp::template rebind<_Up>>>
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#endif
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{ using type = typename _Tp::template rebind<_Up>; };
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public:
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/// The pointer type.
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using pointer = _Ptr;
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/// The type pointed to.
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using element_type = _Elt;
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/// The type used to represent the difference between two pointers.
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using difference_type = typename __difference<_Ptr>::type;
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/// A pointer to a different type.
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template<typename _Up>
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using rebind = typename __rebind<_Ptr, _Up>::type;
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};
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// _GLIBCXX_RESOLVE_LIB_DEFECTS
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// 3545. std::pointer_traits should be SFINAE-friendly
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template<typename _Ptr>
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struct __ptr_traits_impl<_Ptr, __undefined>
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{ };
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/**
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* @brief Uniform interface to all pointer-like types
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* @ingroup pointer_abstractions
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* @since C++11
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*/
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template<typename _Ptr>
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struct pointer_traits : __ptr_traits_impl<_Ptr, __ptr_traits_elem_t<_Ptr>>
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{ };
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#if __cpp_concepts
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template<typename _Ptr> requires requires { typename _Ptr::element_type; }
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struct pointer_traits<_Ptr>
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: __ptr_traits_impl<_Ptr, typename _Ptr::element_type>
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{ };
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#endif
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/**
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* @brief Partial specialization for built-in pointers.
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* @ingroup pointer_abstractions
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* @since C++11
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*/
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template<typename _Tp>
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struct pointer_traits<_Tp*> : __ptr_traits_ptr_to<_Tp*, _Tp>
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{
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/// The pointer type
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typedef _Tp* pointer;
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/// The type pointed to
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typedef _Tp element_type;
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/// Type used to represent the difference between two pointers
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typedef ptrdiff_t difference_type;
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/// A pointer to a different type.
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template<typename _Up> using rebind = _Up*;
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};
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/// Convenience alias for rebinding pointers.
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template<typename _Ptr, typename _Tp>
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using __ptr_rebind = typename pointer_traits<_Ptr>::template rebind<_Tp>;
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template<typename _Tp>
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constexpr _Tp*
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__to_address(_Tp* __ptr) noexcept
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{
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static_assert(!std::is_function<_Tp>::value, "not a function pointer");
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return __ptr;
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}
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#if __cplusplus <= 201703L
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template<typename _Ptr>
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constexpr typename std::pointer_traits<_Ptr>::element_type*
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__to_address(const _Ptr& __ptr)
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{ return std::__to_address(__ptr.operator->()); }
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#else
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template<typename _Ptr>
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constexpr auto
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__to_address(const _Ptr& __ptr) noexcept
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-> decltype(std::pointer_traits<_Ptr>::to_address(__ptr))
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{ return std::pointer_traits<_Ptr>::to_address(__ptr); }
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template<typename _Ptr, typename... _None>
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constexpr auto
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__to_address(const _Ptr& __ptr, _None...) noexcept
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{
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if constexpr (is_base_of_v<__gnu_debug::_Safe_iterator_base, _Ptr>)
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return std::__to_address(__ptr.base().operator->());
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else
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return std::__to_address(__ptr.operator->());
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}
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#define __cpp_lib_to_address 201711L
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/**
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* @brief Obtain address referenced by a pointer to an object
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* @param __ptr A pointer to an object
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* @return @c __ptr
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* @ingroup pointer_abstractions
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*/
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template<typename _Tp>
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constexpr _Tp*
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to_address(_Tp* __ptr) noexcept
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{ return std::__to_address(__ptr); }
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/**
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* @brief Obtain address referenced by a pointer to an object
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* @param __ptr A pointer to an object
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* @return @c pointer_traits<_Ptr>::to_address(__ptr) if that expression is
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well-formed, otherwise @c to_address(__ptr.operator->())
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* @ingroup pointer_abstractions
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*/
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template<typename _Ptr>
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constexpr auto
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to_address(const _Ptr& __ptr) noexcept
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{ return std::__to_address(__ptr); }
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#endif // C++2a
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_GLIBCXX_END_NAMESPACE_VERSION
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} // namespace std
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#endif
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#endif
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