libstdc++-v3/include/bits/ptr_traits.h

   1 // Pointer Traits -*- C++ -*-
   2
   3 // Copyright (C) 2011-2012 Free Software Foundation, Inc.
   4 //
   5 // This file is part of the GNU ISO C++ Library.  This library is free
   6 // software; you can redistribute it and/or modify it under the
   7 // terms of the GNU General Public License as published by the
   8 // Free Software Foundation; either version 3, or (at your option)
   9 // any later version.
  10
  11 // This library is distributed in the hope that it will be useful,
  12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 // GNU General Public License for more details.
  15
  16 // Under Section 7 of GPL version 3, you are granted additional
  17 // permissions described in the GCC Runtime Library Exception, version
  18 // 3.1, as published by the Free Software Foundation.
  19
  20 // You should have received a copy of the GNU General Public License and
  21 // a copy of the GCC Runtime Library Exception along with this program;
  22 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23 // <http://www.gnu.org/licenses/>.
  24
  25 /** @file bits/ptr_traits.h
  26  *  This is an internal header file, included by other library headers.
  27  *  Do not attempt to use it directly. @headername{memory}
  28  */
  29
  30 #ifndef _PTR_TRAITS_H
  31 #define _PTR_TRAITS_H 1
  32
  33 #if __cplusplus >= 201103L
  34
  35 #include <type_traits> // For _GLIBCXX_HAS_NESTED_TYPE
  36
  37 namespace std _GLIBCXX_VISIBILITY(default)
  38 {
  39 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  40
  41 _GLIBCXX_HAS_NESTED_TYPE(element_type)
  42 _GLIBCXX_HAS_NESTED_TYPE(difference_type)
  43
  44   template<typename _Tp, bool = __has_element_type<_Tp>::value>
  45     struct __ptrtr_elt_type;
  46
  47   template<typename _Tp>
  48     struct __ptrtr_elt_type<_Tp, true>
  49     {
  50       typedef typename _Tp::element_type __type;
  51     };
  52
  53   template<template<typename, typename...> class _SomePtr, typename _Tp,
  54             typename... _Args>
  55     struct __ptrtr_elt_type<_SomePtr<_Tp, _Args...>, false>
  56     {
  57       typedef _Tp __type;
  58     };
  59
  60   template<typename _Tp, bool = __has_difference_type<_Tp>::value>
  61     struct __ptrtr_diff_type
  62     {
  63       typedef typename _Tp::difference_type __type;
  64     };
  65
  66   template<typename _Tp>
  67     struct __ptrtr_diff_type<_Tp, false>
  68     {
  69       typedef ptrdiff_t __type;
  70     };
  71
  72   template<typename _Ptr, typename _Up>
  73     class __ptrtr_rebind_helper
  74     {
  75       template<typename _Ptr2, typename _Up2>
  76         static constexpr bool
  77         _S_chk(typename _Ptr2::template rebind<_Up2>*)
  78         { return true; }
  79
  80       template<typename, typename>
  81         static constexpr bool
  82         _S_chk(...)
  83         { return false; }
  84
  85     public:
  86       static const bool __value = _S_chk<_Ptr, _Up>(nullptr);
  87     };
  88
  89   template<typename _Ptr, typename _Up>
  90     const bool __ptrtr_rebind_helper<_Ptr, _Up>::__value;
  91
  92   template<typename _Tp, typename _Up,
  93            bool = __ptrtr_rebind_helper<_Tp, _Up>::__value>
  94     struct __ptrtr_rebind;
  95
  96   template<typename _Tp, typename _Up>
  97     struct __ptrtr_rebind<_Tp, _Up, true>
  98     {
  99       typedef typename _Tp::template rebind<_Up> __type;
 100     };
 101
 102   template<template<typename, typename...> class _SomePtr, typename _Up,
 103             typename _Tp, typename... _Args>
 104     struct __ptrtr_rebind<_SomePtr<_Tp, _Args...>, _Up, false>
 105     {
 106       typedef _SomePtr<_Up, _Args...> __type;
 107     };
 108
 109   template<typename _Tp, typename = typename remove_cv<_Tp>::type>
 110     struct __ptrtr_not_void
 111     {
 112       typedef _Tp __type;
 113     };
 114
 115   template<typename _Tp>
 116     struct __ptrtr_not_void<_Tp, void>
 117     {
 118       struct __type { };
 119     };
 120
 121   template<typename _Ptr>
 122     class __ptrtr_pointer_to
 123     {
 124       typedef typename __ptrtr_elt_type<_Ptr>::__type   __orig_type;
 125       typedef typename __ptrtr_not_void<__orig_type>::__type __element_type;
 126
 127     public:
 128       static _Ptr pointer_to(__element_type& __e)
 129       { return _Ptr::pointer_to(__e); }
 130     };
 131
 132   /**
 133    * @brief  Uniform interface to all pointer-like types
 134    * @ingroup pointer_abstractions
 135   */
 136   template<typename _Ptr>
 137     struct pointer_traits : __ptrtr_pointer_to<_Ptr>
 138     {
 139       /// The pointer type
 140       typedef _Ptr                                      pointer;
 141       /// The type pointed to
 142       typedef typename __ptrtr_elt_type<_Ptr>::__type   element_type;
 143       /// Type used to represent the difference between two pointers
 144       typedef typename __ptrtr_diff_type<_Ptr>::__type  difference_type;
 145
 146       template<typename _Up>
 147         using rebind = typename __ptrtr_rebind<_Ptr, _Up>::__type;
 148     };
 149
 150   /**
 151    * @brief  Partial specialization for built-in pointers.
 152    * @ingroup pointer_abstractions
 153   */
 154   template<typename _Tp>
 155     struct pointer_traits<_Tp*>
 156     {
 157       /// The pointer type
 158       typedef _Tp* pointer;
 159       /// The type pointed to
 160       typedef _Tp  element_type;
 161       /// Type used to represent the difference between two pointers
 162       typedef ptrdiff_t difference_type;
 163
 164       template<typename _Up>
 165         using rebind = _Up*;
 166
 167       /**
 168        *  @brief  Obtain a pointer to an object
 169        *  @param  __r  A reference to an object of type @c element_type
 170        *  @return @c addressof(__r)
 171       */
 172       static pointer
 173       pointer_to(typename __ptrtr_not_void<element_type>::__type& __r) noexcept
 174       { return std::addressof(__r); }
 175     };
 176
 177 _GLIBCXX_END_NAMESPACE_VERSION
 178 } // namespace std
 179
 180 #endif
 181
 182 #endif