libstdc++
extptr_allocator.h
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1 // <extptr_allocator.h> -*- C++ -*-
2 
3 // Copyright (C) 2008-2024 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
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22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23 // <http://www.gnu.org/licenses/>.
24 
25 /**
26  * @file ext/extptr_allocator.h
27  * This file is a GNU extension to the Standard C++ Library.
28  *
29  * @author Bob Walters
30  *
31  * An example allocator which uses an alternative pointer type from
32  * bits/pointer.h. Supports test cases which confirm container support
33  * for alternative pointers.
34  */
35 
36 #ifndef _EXTPTR_ALLOCATOR_H
37 #define _EXTPTR_ALLOCATOR_H 1
38 
39 #include <bits/requires_hosted.h> // GNU extensions are currently omitted
40 
41 #include <memory>
42 #include <ext/numeric_traits.h>
43 #include <ext/pointer.h>
44 
45 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
46 {
47 _GLIBCXX_BEGIN_NAMESPACE_VERSION
48 
49  /**
50  * @brief An example allocator which uses a non-standard pointer type.
51  * @ingroup allocators
52  *
53  * This allocator specifies that containers use a 'relative pointer' as it's
54  * pointer type. (See ext/pointer.h) Memory allocation in this example
55  * is still performed using std::allocator.
56  */
57  template<typename _Tp>
59  {
60  public:
61  typedef std::size_t size_type;
62  typedef std::ptrdiff_t difference_type;
63 
64  // Note the non-standard pointer types.
68 
69  typedef _Tp& reference;
70  typedef const _Tp& const_reference;
71  typedef _Tp value_type;
72 
73  template<typename _Up>
74  struct rebind
75  { typedef _ExtPtr_allocator<_Up> other; };
76 
77  _ExtPtr_allocator() _GLIBCXX_USE_NOEXCEPT
78  : _M_real_alloc() { }
79 
80  _ExtPtr_allocator(const _ExtPtr_allocator& __rarg) _GLIBCXX_USE_NOEXCEPT
81  : _M_real_alloc(__rarg._M_real_alloc) { }
82 
83  template<typename _Up>
85  _GLIBCXX_USE_NOEXCEPT
86  : _M_real_alloc(__rarg._M_getUnderlyingImp()) { }
87 
88  ~_ExtPtr_allocator() _GLIBCXX_USE_NOEXCEPT
89  { }
90 
91  pointer address(reference __x) const _GLIBCXX_NOEXCEPT
92  { return std::__addressof(__x); }
93 
94  const_pointer address(const_reference __x) const _GLIBCXX_NOEXCEPT
95  { return std::__addressof(__x); }
96 
97  _GLIBCXX_NODISCARD pointer allocate(size_type __n, const void* = 0)
98  { return _M_real_alloc.allocate(__n); }
99 
100  void deallocate(pointer __p, size_type __n)
101  { _M_real_alloc.deallocate(__p.get(), __n); }
102 
103  size_type max_size() const _GLIBCXX_USE_NOEXCEPT
104  { return __numeric_traits<size_type>::__max / sizeof(_Tp); }
105 
106 #if __cplusplus >= 201103L
107  template<typename _Up, typename... _Args>
108  void
109  construct(_Up* __p, _Args&&... __args)
110  { ::new((void *)__p) _Up(std::forward<_Args>(__args)...); }
111 
112  template<typename... _Args>
113  void
114  construct(pointer __p, _Args&&... __args)
115  { construct(__p.get(), std::forward<_Args>(__args)...); }
116 
117  template<typename _Up>
118  void
119  destroy(_Up* __p)
120  { __p->~_Up(); }
121 
122  void destroy(pointer __p)
123  { destroy(__p.get()); }
124 
125 #else
126 
127  void construct(pointer __p, const _Tp& __val)
128  { ::new(__p.get()) _Tp(__val); }
129 
130  void destroy(pointer __p)
131  { __p->~_Tp(); }
132 #endif
133 
134  template<typename _Up>
135  inline bool
136  operator==(const _ExtPtr_allocator<_Up>& __rarg) const
137  { return _M_real_alloc == __rarg._M_getUnderlyingImp(); }
138 
139  inline bool
140  operator==(const _ExtPtr_allocator& __rarg) const
141  { return _M_real_alloc == __rarg._M_real_alloc; }
142 
143 #if __cpp_impl_three_way_comparison < 201907L
144  template<typename _Up>
145  inline bool
146  operator!=(const _ExtPtr_allocator<_Up>& __rarg) const
147  { return _M_real_alloc != __rarg._M_getUnderlyingImp(); }
148 
149  inline bool
150  operator!=(const _ExtPtr_allocator& __rarg) const
151  { return _M_real_alloc != __rarg._M_real_alloc; }
152 #endif
153 
154  template<typename _Up>
155  inline friend void
157 
158  // A method specific to this implementation.
159  const std::allocator<_Tp>&
160  _M_getUnderlyingImp() const
161  { return _M_real_alloc; }
162 
163  private:
164  std::allocator<_Tp> _M_real_alloc;
165  };
166 
167  // _ExtPtr_allocator<void> specialization.
168  template<>
169  class _ExtPtr_allocator<void>
170  {
171  public:
172  typedef std::size_t size_type;
173  typedef std::ptrdiff_t difference_type;
174  typedef void value_type;
175 
176  // Note the non-standard pointer types
179  const_pointer;
180 
181  _ExtPtr_allocator() { }
182 
183  template<typename _Up>
184  _ExtPtr_allocator(const _ExtPtr_allocator<_Up>&) { }
185 
186  template<typename _Up>
187  struct rebind
188  { typedef _ExtPtr_allocator<_Up> other; };
189 
190  private:
191  std::allocator<void> _M_real_alloc;
192  };
193 
194  template<typename _Tp>
195  inline void
196  swap(_ExtPtr_allocator<_Tp>& __larg, _ExtPtr_allocator<_Tp>& __rarg)
197  {
198  std::allocator<_Tp> __tmp( __rarg._M_real_alloc );
199  __rarg._M_real_alloc = __larg._M_real_alloc;
200  __larg._M_real_alloc = __tmp;
201  }
202 
203 _GLIBCXX_END_NAMESPACE_VERSION
204 } // namespace
205 
206 #endif /* _EXTPTR_ALLOCATOR_H */
constexpr _Tp * __addressof(_Tp &__r) noexcept
Same as C++11 std::addressof.
Definition: move.h:51
GNU extensions for public use.
The standard allocator, as per C++03 [20.4.1].
Definition: allocator.h:129
An example allocator which uses a non-standard pointer type.