154 lines
4.7 KiB
C++
154 lines
4.7 KiB
C++
// Pointer Traits -*- C++ -*-
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// Copyright (C) 2011-2016 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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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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// Given Template<T, ...> return T, otherwise invalid.
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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 _Template, typename _Tp,
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typename... _Types>
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struct __get_first_arg<_Template<_Tp, _Types...>>
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{ using type = _Tp; };
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template<typename _Tp>
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using __get_first_arg_t = typename __get_first_arg<_Tp>::type;
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// Given Template<T, ...> and U return Template<U, ...>, otherwise invalid.
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template<typename _Tp, typename _Up>
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struct __replace_first_arg
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{ using type = __undefined; };
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template<template<typename, typename...> class _Template, typename _Up,
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typename _Tp, typename... _Types>
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struct __replace_first_arg<_Template<_Tp, _Types...>, _Up>
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{ using type = _Template<_Up, _Types...>; };
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template<typename _Tp, typename _Up>
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using __replace_first_arg_t = typename __replace_first_arg<_Tp, _Up>::type;
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template<typename _Tp>
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using __make_not_void
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= typename conditional<is_void<_Tp>::value, __undefined, _Tp>::type;
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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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*/
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template<typename _Ptr>
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struct pointer_traits
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{
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private:
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template<typename _Tp>
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using __element_type = typename _Tp::element_type;
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template<typename _Tp>
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using __difference_type = typename _Tp::difference_type;
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template<typename _Tp, typename _Up>
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using __rebind = 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
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= __detected_or_t_<__get_first_arg_t, __element_type, _Ptr>;
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/// The type used to represent the difference between two pointers.
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using difference_type
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= __detected_or_t<ptrdiff_t, __difference_type, _Ptr>;
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/// A pointer to a different type.
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template<typename _Up>
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using rebind
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= __detected_or_t_<__replace_first_arg_t, __rebind, _Ptr, _Up>;
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static _Ptr
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pointer_to(__make_not_void<element_type>& __e)
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{ return _Ptr::pointer_to(__e); }
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static_assert(!is_same<element_type, __undefined>::value,
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"pointer type defines element_type or is like SomePointer<T, Args>");
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static_assert(!is_same<rebind<element_type>, __undefined>::value,
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"pointer type defines rebind<U> or is like SomePointer<T, Args>");
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};
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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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*/
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template<typename _Tp>
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struct pointer_traits<_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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template<typename _Up>
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using rebind = _Up*;
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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 @c element_type
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* @return @c addressof(__r)
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*/
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static pointer
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pointer_to(__make_not_void<element_type>& __r) noexcept
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{ return std::addressof(__r); }
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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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_GLIBCXX_END_NAMESPACE_VERSION
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} // namespace std
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#endif
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#endif
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