libstdc++
memory_resource
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1 // <experimental/memory_resource> -*- C++ -*-
2 
3 // Copyright (C) 2015-2017 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 experimental/memory_resource
26  * This is a TS C++ Library header.
27  */
28 
29 #ifndef _GLIBCXX_EXPERIMENTAL_MEMORY_RESOURCE
30 #define _GLIBCXX_EXPERIMENTAL_MEMORY_RESOURCE 1
31 
32 #include <memory>
33 #include <new>
34 #include <atomic>
35 #include <cstddef>
36 #include <bits/alloc_traits.h>
38 
39 namespace std {
40 namespace experimental {
41 inline namespace fundamentals_v2 {
42 namespace pmr {
43 _GLIBCXX_BEGIN_NAMESPACE_VERSION
44 
45 #define __cpp_lib_experimental_memory_resources 201402L
46 
47  class memory_resource;
48 
49  template <typename _Tp>
50  class polymorphic_allocator;
51 
52  template <typename _Alloc>
53  class __resource_adaptor_imp;
54 
55  template <typename _Alloc>
56  using resource_adaptor = __resource_adaptor_imp<
57  typename allocator_traits<_Alloc>::template rebind_alloc<char>>;
58 
59  template <typename _Tp>
60  struct __uses_allocator_construction_helper;
61 
62  // Global memory resources
63  memory_resource* new_delete_resource() noexcept;
64  memory_resource* null_memory_resource() noexcept;
65 
66  // The default memory resource
67  memory_resource* get_default_resource() noexcept;
68  memory_resource* set_default_resource(memory_resource* __r) noexcept;
69 
70  // Standard memory resources
71 
72  // 8.5 Class memory_resource
73  class memory_resource
74  {
75  protected:
76  static constexpr size_t _S_max_align = alignof(max_align_t);
77 
78  public:
79  virtual ~memory_resource() { }
80 
81  void*
82  allocate(size_t __bytes, size_t __alignment = _S_max_align)
83  { return do_allocate(__bytes, __alignment); }
84 
85  void
86  deallocate(void* __p, size_t __bytes, size_t __alignment = _S_max_align)
87  { return do_deallocate(__p, __bytes, __alignment); }
88 
89  bool
90  is_equal(const memory_resource& __other) const noexcept
91  { return do_is_equal(__other); }
92 
93  protected:
94  virtual void*
95  do_allocate(size_t __bytes, size_t __alignment) = 0;
96 
97  virtual void
98  do_deallocate(void* __p, size_t __bytes, size_t __alignment) = 0;
99 
100  virtual bool
101  do_is_equal(const memory_resource& __other) const noexcept = 0;
102  };
103 
104  inline bool
105  operator==(const memory_resource& __a,
106  const memory_resource& __b) noexcept
107  { return &__a == &__b || __a.is_equal(__b); }
108 
109  inline bool
110  operator!=(const memory_resource& __a,
111  const memory_resource& __b) noexcept
112  { return !(__a == __b); }
113 
114 
115  // 8.6 Class template polymorphic_allocator
116  template <class _Tp>
117  class polymorphic_allocator
118  {
119  using __uses_alloc1_ = __uses_alloc1<memory_resource*>;
120  using __uses_alloc2_ = __uses_alloc2<memory_resource*>;
121 
122  template<typename _Tp1, typename... _Args>
123  void
124  _M_construct(__uses_alloc0, _Tp1* __p, _Args&&... __args)
125  { ::new(__p) _Tp1(std::forward<_Args>(__args)...); }
126 
127  template<typename _Tp1, typename... _Args>
128  void
129  _M_construct(__uses_alloc1_, _Tp1* __p, _Args&&... __args)
130  { ::new(__p) _Tp1(allocator_arg, this->resource(),
131  std::forward<_Args>(__args)...); }
132 
133  template<typename _Tp1, typename... _Args>
134  void
135  _M_construct(__uses_alloc2_, _Tp1* __p, _Args&&... __args)
136  { ::new(__p) _Tp1(std::forward<_Args>(__args)...,
137  this->resource()); }
138 
139  public:
140  using value_type = _Tp;
141 
142  polymorphic_allocator() noexcept
143  : _M_resource(get_default_resource())
144  { }
145 
146  polymorphic_allocator(memory_resource* __r)
147  : _M_resource(__r)
148  { _GLIBCXX_DEBUG_ASSERT(__r); }
149 
150  polymorphic_allocator(const polymorphic_allocator& __other) = default;
151 
152  template <typename _Up>
153  polymorphic_allocator(const polymorphic_allocator<_Up>&
154  __other) noexcept
155  : _M_resource(__other.resource())
156  { }
157 
158  polymorphic_allocator&
159  operator=(const polymorphic_allocator& __rhs) = default;
160 
161  _Tp* allocate(size_t __n)
162  { return static_cast<_Tp*>(_M_resource->allocate(__n * sizeof(_Tp),
163  alignof(_Tp))); }
164 
165  void deallocate(_Tp* __p, size_t __n)
166  { _M_resource->deallocate(__p, __n * sizeof(_Tp), alignof(_Tp)); }
167 
168  template <typename _Tp1, typename... _Args> //used here
169  void construct(_Tp1* __p, _Args&&... __args)
170  {
171  memory_resource* const __resource = this->resource();
172  auto __use_tag
173  = __use_alloc<_Tp1, memory_resource*, _Args...>(__resource);
174  _M_construct(__use_tag, __p, std::forward<_Args>(__args)...);
175  }
176 
177  // Specializations for pair using piecewise construction
178  template <typename _Tp1, typename _Tp2,
179  typename... _Args1, typename... _Args2>
180  void construct(pair<_Tp1, _Tp2>* __p, piecewise_construct_t,
181  tuple<_Args1...> __x,
182  tuple<_Args2...> __y)
183  {
184  memory_resource* const __resource = this->resource();
185  auto __x_use_tag =
186  __use_alloc<_Tp1, memory_resource*, _Args1...>(__resource);
187  auto __y_use_tag =
188  __use_alloc<_Tp2, memory_resource*, _Args2...>(__resource);
189 
191  _M_construct_p(__x_use_tag, __x),
192  _M_construct_p(__y_use_tag, __y));
193  }
194 
195  template <typename _Tp1, typename _Tp2>
196  void construct(pair<_Tp1,_Tp2>* __p)
197  { this->construct(__p, piecewise_construct, tuple<>(), tuple<>()); }
198 
199  template <typename _Tp1, typename _Tp2, typename _Up, typename _Vp>
200  void construct(pair<_Tp1,_Tp2>* __p, _Up&& __x, _Vp&& __y)
201  { this->construct(__p, piecewise_construct,
202  forward_as_tuple(std::forward<_Up>(__x)),
203  forward_as_tuple(std::forward<_Vp>(__y))); }
204 
205  template <typename _Tp1, typename _Tp2, typename _Up, typename _Vp>
206  void construct(pair<_Tp1,_Tp2>* __p, const std::pair<_Up, _Vp>& __pr)
207  { this->construct(__p, piecewise_construct, forward_as_tuple(__pr.first),
208  forward_as_tuple(__pr.second)); }
209 
210  template <typename _Tp1, typename _Tp2, typename _Up, typename _Vp>
211  void construct(pair<_Tp1,_Tp2>* __p, pair<_Up, _Vp>&& __pr)
212  { this->construct(__p, piecewise_construct,
213  forward_as_tuple(std::forward<_Up>(__pr.first)),
214  forward_as_tuple(std::forward<_Vp>(__pr.second))); }
215 
216  template <typename _Up>
217  void destroy(_Up* __p)
218  { __p->~_Up(); }
219 
220  // Return a default-constructed allocator (no allocator propagation)
221  polymorphic_allocator select_on_container_copy_construction() const
222  { return polymorphic_allocator(); }
223 
224  memory_resource* resource() const
225  { return _M_resource; }
226 
227  private:
228  template<typename _Tuple>
229  _Tuple&&
230  _M_construct_p(__uses_alloc0, _Tuple& __t)
231  { return std::move(__t); }
232 
233  template<typename... _Args>
234  decltype(auto)
235  _M_construct_p(__uses_alloc1_ __ua, tuple<_Args...>& __t)
236  { return tuple_cat(make_tuple(allocator_arg, *(__ua._M_a)),
237  std::move(__t)); }
238 
239  template<typename... _Args>
240  decltype(auto)
241  _M_construct_p(__uses_alloc2_ __ua, tuple<_Args...>& __t)
242  { return tuple_cat(std::move(__t), make_tuple(*(__ua._M_a))); }
243 
244  memory_resource* _M_resource;
245  };
246 
247  template <class _Tp1, class _Tp2>
248  bool operator==(const polymorphic_allocator<_Tp1>& __a,
249  const polymorphic_allocator<_Tp2>& __b) noexcept
250  { return *__a.resource() == *__b.resource(); }
251 
252  template <class _Tp1, class _Tp2>
253  bool operator!=(const polymorphic_allocator<_Tp1>& __a,
254  const polymorphic_allocator<_Tp2>& __b) noexcept
255  { return !(__a == __b); }
256 
257  // 8.7.1 __resource_adaptor_imp
258  template <typename _Alloc>
259  class __resource_adaptor_imp : public memory_resource
260  {
261  public:
262  using allocator_type = _Alloc;
263 
264  __resource_adaptor_imp() = default;
265  __resource_adaptor_imp(const __resource_adaptor_imp&) = default;
266  __resource_adaptor_imp(__resource_adaptor_imp&&) = default;
267 
268  explicit __resource_adaptor_imp(const _Alloc& __a2)
269  : _M_alloc(__a2)
270  { }
271 
272  explicit __resource_adaptor_imp(_Alloc&& __a2)
273  : _M_alloc(std::move(__a2))
274  { }
275 
276  __resource_adaptor_imp&
277  operator=(const __resource_adaptor_imp&) = default;
278 
279  allocator_type get_allocator() const { return _M_alloc; }
280 
281  protected:
282  virtual void*
283  do_allocate(size_t __bytes, size_t __alignment)
284  {
285  using _Aligned_alloc = std::__alloc_rebind<_Alloc, char>;
286  size_t __new_size = _S_aligned_size(__bytes,
287  _S_supported(__alignment) ?
288  __alignment : _S_max_align);
289  return _Aligned_alloc(_M_alloc).allocate(__new_size);
290  }
291 
292  virtual void
293  do_deallocate(void* __p, size_t __bytes, size_t __alignment)
294  {
295  using _Aligned_alloc = std::__alloc_rebind<_Alloc, char>;
296  size_t __new_size = _S_aligned_size(__bytes,
297  _S_supported(__alignment) ?
298  __alignment : _S_max_align);
299  using _Ptr = typename allocator_traits<_Aligned_alloc>::pointer;
300  _Aligned_alloc(_M_alloc).deallocate(static_cast<_Ptr>(__p),
301  __new_size);
302  }
303 
304  virtual bool
305  do_is_equal(const memory_resource& __other) const noexcept
306  {
307  auto __p = dynamic_cast<const __resource_adaptor_imp*>(&__other);
308  return __p ? (_M_alloc == __p->_M_alloc) : false;
309  }
310 
311  private:
312  // Calculate Aligned Size
313  // Returns a size that is larger than or equal to __size and divisible
314  // by __alignment, where __alignment is required to be the power of 2.
315  static size_t
316  _S_aligned_size(size_t __size, size_t __alignment)
317  { return ((__size - 1)|(__alignment - 1)) + 1; }
318 
319  // Determine whether alignment meets one of those preconditions:
320  // 1. Equals to Zero
321  // 2. Is power of two
322  static bool
323  _S_supported (size_t __x)
324  { return ((__x != 0) && !(__x & (__x - 1))); }
325 
326  _Alloc _M_alloc;
327  };
328 
329  // Global memory resources
331  __get_default_resource()
332  {
333  static atomic<memory_resource*> _S_default_resource(new_delete_resource());
334  return _S_default_resource;
335  }
336 
337  inline memory_resource*
338  new_delete_resource() noexcept
339  {
340  static resource_adaptor<std::allocator<char>> __r;
341  return static_cast<memory_resource*>(&__r);
342  }
343 
344  template <typename _Alloc>
345  class __null_memory_resource : private memory_resource
346  {
347  protected:
348  void*
349  do_allocate(size_t, size_t)
350  { std::__throw_bad_alloc(); }
351 
352  void
353  do_deallocate(void*, size_t, size_t) noexcept
354  { }
355 
356  bool
357  do_is_equal(const memory_resource& __other) const noexcept
358  { return this == &__other; }
359 
360  friend memory_resource* null_memory_resource() noexcept;
361  };
362 
363  inline memory_resource*
364  null_memory_resource() noexcept
365  {
366  static __null_memory_resource<void> __r;
367  return static_cast<memory_resource*>(&__r);
368  }
369 
370  // The default memory resource
371  inline memory_resource*
372  get_default_resource() noexcept
373  { return __get_default_resource().load(); }
374 
375  inline memory_resource*
376  set_default_resource(memory_resource* __r) noexcept
377  {
378  if (__r == nullptr)
379  __r = new_delete_resource();
380  return __get_default_resource().exchange(__r);
381  }
382 
383 _GLIBCXX_END_NAMESPACE_VERSION
384 } // namespace pmr
385 } // namespace fundamentals_v2
386 } // namespace experimental
387 } // namespace std
388 
389 #endif
_GLIBCXX17_INLINE constexpr piecewise_construct_t piecewise_construct
piecewise_construct
Definition: stl_pair.h:79
ISO C++ entities toplevel namespace is std.
constexpr auto tuple_cat(_Tpls &&... __tpls) -> typename __tuple_cat_result< _Tpls... >::__type
tuple_cat
Definition: tuple:1575
_T1 first
second_type is the second bound type
Definition: stl_pair.h:203
__detected_or_t< value_type *, __pointer, _Alloc > pointer
The allocator&#39;s pointer type.
Generic atomic type, primary class template.
Definition: atomic:58
_T2 second
first is a copy of the first object
Definition: stl_pair.h:204
Struct holding two objects of arbitrary type.
Definition: stl_pair.h:198