Preview: ptr_traits.h
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/opt/rh/gcc-toolset-14/root/usr/include/c++/14/bits/ptr_traits.h
// Pointer Traits -*- C++ -*-
// Copyright (C) 2011-2024 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.
// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
// <http://www.gnu.org/licenses/>.
/** @file bits/ptr_traits.h
* This is an internal header file, included by other library headers.
* Do not attempt to use it directly. @headername{memory}
*/
#ifndef _PTR_TRAITS_H
#define _PTR_TRAITS_H 1
#if __cplusplus >= 201103L
#include <bits/move.h>
#if __cplusplus > 201703L
#include <concepts>
namespace __gnu_debug { struct _Safe_iterator_base; }
#endif
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
/// @cond undocumented
class __undefined;
// For a specialization `SomeTemplate<T, Types...>` the member `type` is T,
// otherwise `type` is `__undefined`.
template<typename _Tp>
struct __get_first_arg
{ using type = __undefined; };
template<template<typename, typename...> class _SomeTemplate, typename _Tp,
typename... _Types>
struct __get_first_arg<_SomeTemplate<_Tp, _Types...>>
{ using type = _Tp; };
// For a specialization `SomeTemplate<T, Args...>` and a type `U` the member
// `type` is `SomeTemplate<U, Args...>`, otherwise there is no member `type`.
template<typename _Tp, typename _Up>
struct __replace_first_arg
{ };
template<template<typename, typename...> class _SomeTemplate, typename _Up,
typename _Tp, typename... _Types>
struct __replace_first_arg<_SomeTemplate<_Tp, _Types...>, _Up>
{ using type = _SomeTemplate<_Up, _Types...>; };
// Detect the element type of a pointer-like type.
template<typename _Ptr, typename = void>
struct __ptr_traits_elem : __get_first_arg<_Ptr>
{ };
// Use _Ptr::element_type if is a valid type.
#if __cpp_concepts
template<typename _Ptr> requires requires { typename _Ptr::element_type; }
struct __ptr_traits_elem<_Ptr, void>
{ using type = typename _Ptr::element_type; };
#else
template<typename _Ptr>
struct __ptr_traits_elem<_Ptr, __void_t<typename _Ptr::element_type>>
{ using type = typename _Ptr::element_type; };
#endif
template<typename _Ptr>
using __ptr_traits_elem_t = typename __ptr_traits_elem<_Ptr>::type;
/// @endcond
// Define pointer_traits<P>::pointer_to.
template<typename _Ptr, typename _Elt, bool = is_void<_Elt>::value>
struct __ptr_traits_ptr_to
{
using pointer = _Ptr;
using element_type = _Elt;
/**
* @brief Obtain a pointer to an object
* @param __r A reference to an object of type `element_type`
* @return `pointer::pointer_to(__r)`
* @pre `pointer::pointer_to(__r)` is a valid expression.
*/
static pointer
pointer_to(element_type& __r)
#if __cpp_lib_concepts
requires requires {
{ pointer::pointer_to(__r) } -> convertible_to<pointer>;
}
#endif
{ return pointer::pointer_to(__r); }
};
// Do not define pointer_traits<P>::pointer_to if element type is void.
template<typename _Ptr, typename _Elt>
struct __ptr_traits_ptr_to<_Ptr, _Elt, true>
{ };
// Partial specialization defining pointer_traits<T*>::pointer_to(T&).
template<typename _Tp>
struct __ptr_traits_ptr_to<_Tp*, _Tp, false>
{
using pointer = _Tp*;
using element_type = _Tp;
/**
* @brief Obtain a pointer to an object
* @param __r A reference to an object of type `element_type`
* @return `addressof(__r)`
*/
static _GLIBCXX20_CONSTEXPR pointer
pointer_to(element_type& __r) noexcept
{ return std::addressof(__r); }
};
template<typename _Ptr, typename _Elt>
struct __ptr_traits_impl : __ptr_traits_ptr_to<_Ptr, _Elt>
{
private:
template<typename _Tp>
using __diff_t = typename _Tp::difference_type;
template<typename _Tp, typename _Up>
using __rebind = __type_identity<typename _Tp::template rebind<_Up>>;
public:
/// The pointer type.
using pointer = _Ptr;
/// The type pointed to.
using element_type = _Elt;
/// The type used to represent the difference between two pointers.
using difference_type = __detected_or_t<ptrdiff_t, __diff_t, _Ptr>;
/// A pointer to a different type.
template<typename _Up>
using rebind = typename __detected_or_t<__replace_first_arg<_Ptr, _Up>,
__rebind, _Ptr, _Up>::type;
};
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// 3545. std::pointer_traits should be SFINAE-friendly
template<typename _Ptr>
struct __ptr_traits_impl<_Ptr, __undefined>
{ };
/**
* @brief Uniform interface to all pointer-like types
* @headerfile memory
* @ingroup pointer_abstractions
* @since C++11
*/
template<typename _Ptr>
struct pointer_traits : __ptr_traits_impl<_Ptr, __ptr_traits_elem_t<_Ptr>>
{ };
/**
* @brief Partial specialization for built-in pointers.
* @headerfile memory
* @ingroup pointer_abstractions
* @since C++11
*/
template<typename _Tp>
struct pointer_traits<_Tp*> : __ptr_traits_ptr_to<_Tp*, _Tp>
{
/// The pointer type
typedef _Tp* pointer;
/// The type pointed to
typedef _Tp element_type;
/// Type used to represent the difference between two pointers
typedef ptrdiff_t difference_type;
/// A pointer to a different type.
template<typename _Up> using rebind = _Up*;
};
/// Convenience alias for rebinding pointers.
template<typename _Ptr, typename _Tp>
using __ptr_rebind = typename pointer_traits<_Ptr>::template rebind<_Tp>;
template<typename _Tp>
constexpr _Tp*
__to_address(_Tp* __ptr) noexcept
{
static_assert(!std::is_function<_Tp>::value, "not a function pointer");
return __ptr;
}
#ifndef __glibcxx_to_address // C++ < 20
template<typename _Ptr>
constexpr typename std::pointer_traits<_Ptr>::element_type*
__to_address(const _Ptr& __ptr)
{ return std::__to_address(__ptr.operator->()); }
#else
template<typename _Ptr>
constexpr auto
__to_address(const _Ptr& __ptr) noexcept
-> decltype(std::pointer_traits<_Ptr>::to_address(__ptr))
{ return std::pointer_traits<_Ptr>::to_address(__ptr); }
template<typename _Ptr, typename... _None>
constexpr auto
__to_address(const _Ptr& __ptr, _None...) noexcept
{
if constexpr (is_base_of_v<__gnu_debug::_Safe_iterator_base, _Ptr>)
return std::__to_address(__ptr.base().operator->());
else
return std::__to_address(__ptr.operator->());
}
/**
* @brief Obtain address referenced by a pointer to an object
* @param __ptr A pointer to an object
* @return @c __ptr
* @ingroup pointer_abstractions
*/
template<typename _Tp>
constexpr _Tp*
to_address(_Tp* __ptr) noexcept
{ return std::__to_address(__ptr); }
/**
* @brief Obtain address referenced by a pointer to an object
* @param __ptr A pointer to an object
* @return @c pointer_traits<_Ptr>::to_address(__ptr) if that expression is
well-formed, otherwise @c to_address(__ptr.operator->())
* @ingroup pointer_abstractions
*/
template<typename _Ptr>
constexpr auto
to_address(const _Ptr& __ptr) noexcept
{ return std::__to_address(__ptr); }
#endif // __glibcxx_to_address
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std
#endif
#endif
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