libstdc++
memory_resource
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1 // <experimental/memory_resource> -*- C++ -*-
2 
3 // Copyright (C) 2015-2018 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 #pragma GCC system_header
33 
34 #if __cplusplus >= 201402L
35 
36 #include <memory>
37 #include <new>
38 #include <atomic>
39 #include <cstddef>
40 #include <experimental/bits/lfts_config.h>
41 
42 namespace std {
43 _GLIBCXX_BEGIN_NAMESPACE_VERSION
44 
45 namespace experimental {
46 inline namespace fundamentals_v2 {
47 namespace pmr {
48 #define __cpp_lib_experimental_memory_resources 201402L
49 
50  class memory_resource;
51 
52  template <typename _Tp>
53  class polymorphic_allocator;
54 
55  template <typename _Alloc>
56  class __resource_adaptor_imp;
57 
58  template <typename _Alloc>
59  using resource_adaptor = __resource_adaptor_imp<
60  typename allocator_traits<_Alloc>::template rebind_alloc<char>>;
61 
62  template <typename _Tp>
63  struct __uses_allocator_construction_helper;
64 
65  // Global memory resources
66  memory_resource* new_delete_resource() noexcept;
67  memory_resource* null_memory_resource() noexcept;
68 
69  // The default memory resource
70  memory_resource* get_default_resource() noexcept;
71  memory_resource* set_default_resource(memory_resource* __r) noexcept;
72 
73  // Standard memory resources
74 
75  // 8.5 Class memory_resource
76  class memory_resource
77  {
78  protected:
79  static constexpr size_t _S_max_align = alignof(max_align_t);
80 
81  public:
82  virtual ~memory_resource() { }
83 
84  void*
85  allocate(size_t __bytes, size_t __alignment = _S_max_align)
86  { return do_allocate(__bytes, __alignment); }
87 
88  void
89  deallocate(void* __p, size_t __bytes, size_t __alignment = _S_max_align)
90  { return do_deallocate(__p, __bytes, __alignment); }
91 
92  bool
93  is_equal(const memory_resource& __other) const noexcept
94  { return do_is_equal(__other); }
95 
96  protected:
97  virtual void*
98  do_allocate(size_t __bytes, size_t __alignment) = 0;
99 
100  virtual void
101  do_deallocate(void* __p, size_t __bytes, size_t __alignment) = 0;
102 
103  virtual bool
104  do_is_equal(const memory_resource& __other) const noexcept = 0;
105  };
106 
107  inline bool
108  operator==(const memory_resource& __a,
109  const memory_resource& __b) noexcept
110  { return &__a == &__b || __a.is_equal(__b); }
111 
112  inline bool
113  operator!=(const memory_resource& __a,
114  const memory_resource& __b) noexcept
115  { return !(__a == __b); }
116 
117 
118  // 8.6 Class template polymorphic_allocator
119  template <class _Tp>
120  class polymorphic_allocator
121  {
122  using __uses_alloc1_ = __uses_alloc1<memory_resource*>;
123  using __uses_alloc2_ = __uses_alloc2<memory_resource*>;
124 
125  template<typename _Tp1, typename... _Args>
126  void
127  _M_construct(__uses_alloc0, _Tp1* __p, _Args&&... __args)
128  { ::new(__p) _Tp1(std::forward<_Args>(__args)...); }
129 
130  template<typename _Tp1, typename... _Args>
131  void
132  _M_construct(__uses_alloc1_, _Tp1* __p, _Args&&... __args)
133  { ::new(__p) _Tp1(allocator_arg, this->resource(),
134  std::forward<_Args>(__args)...); }
135 
136  template<typename _Tp1, typename... _Args>
137  void
138  _M_construct(__uses_alloc2_, _Tp1* __p, _Args&&... __args)
139  { ::new(__p) _Tp1(std::forward<_Args>(__args)...,
140  this->resource()); }
141 
142  public:
143  using value_type = _Tp;
144 
145  polymorphic_allocator() noexcept
146  : _M_resource(get_default_resource())
147  { }
148 
149  polymorphic_allocator(memory_resource* __r)
150  : _M_resource(__r)
151  { _GLIBCXX_DEBUG_ASSERT(__r); }
152 
153  polymorphic_allocator(const polymorphic_allocator& __other) = default;
154 
155  template <typename _Up>
156  polymorphic_allocator(const polymorphic_allocator<_Up>&
157  __other) noexcept
158  : _M_resource(__other.resource())
159  { }
160 
161  polymorphic_allocator&
162  operator=(const polymorphic_allocator& __rhs) = default;
163 
164  _Tp* allocate(size_t __n)
165  { return static_cast<_Tp*>(_M_resource->allocate(__n * sizeof(_Tp),
166  alignof(_Tp))); }
167 
168  void deallocate(_Tp* __p, size_t __n)
169  { _M_resource->deallocate(__p, __n * sizeof(_Tp), alignof(_Tp)); }
170 
171  template <typename _Tp1, typename... _Args> //used here
172  void construct(_Tp1* __p, _Args&&... __args)
173  {
174  memory_resource* const __resource = this->resource();
175  auto __use_tag
176  = __use_alloc<_Tp1, memory_resource*, _Args...>(__resource);
177  _M_construct(__use_tag, __p, std::forward<_Args>(__args)...);
178  }
179 
180  // Specializations for pair using piecewise construction
181  template <typename _Tp1, typename _Tp2,
182  typename... _Args1, typename... _Args2>
183  void construct(pair<_Tp1, _Tp2>* __p, piecewise_construct_t,
184  tuple<_Args1...> __x,
185  tuple<_Args2...> __y)
186  {
187  memory_resource* const __resource = this->resource();
188  auto __x_use_tag =
189  __use_alloc<_Tp1, memory_resource*, _Args1...>(__resource);
190  auto __y_use_tag =
191  __use_alloc<_Tp2, memory_resource*, _Args2...>(__resource);
192 
193  ::new(__p) std::pair<_Tp1, _Tp2>(piecewise_construct,
194  _M_construct_p(__x_use_tag, __x),
195  _M_construct_p(__y_use_tag, __y));
196  }
197 
198  template <typename _Tp1, typename _Tp2>
199  void construct(pair<_Tp1,_Tp2>* __p)
200  { this->construct(__p, piecewise_construct, tuple<>(), tuple<>()); }
201 
202  template <typename _Tp1, typename _Tp2, typename _Up, typename _Vp>
203  void construct(pair<_Tp1,_Tp2>* __p, _Up&& __x, _Vp&& __y)
204  { this->construct(__p, piecewise_construct,
205  forward_as_tuple(std::forward<_Up>(__x)),
206  forward_as_tuple(std::forward<_Vp>(__y))); }
207 
208  template <typename _Tp1, typename _Tp2, typename _Up, typename _Vp>
209  void construct(pair<_Tp1,_Tp2>* __p, const std::pair<_Up, _Vp>& __pr)
210  { this->construct(__p, piecewise_construct, forward_as_tuple(__pr.first),
211  forward_as_tuple(__pr.second)); }
212 
213  template <typename _Tp1, typename _Tp2, typename _Up, typename _Vp>
214  void construct(pair<_Tp1,_Tp2>* __p, pair<_Up, _Vp>&& __pr)
215  { this->construct(__p, piecewise_construct,
216  forward_as_tuple(std::forward<_Up>(__pr.first)),
217  forward_as_tuple(std::forward<_Vp>(__pr.second))); }
218 
219  template <typename _Up>
220  void destroy(_Up* __p)
221  { __p->~_Up(); }
222 
223  // Return a default-constructed allocator (no allocator propagation)
224  polymorphic_allocator select_on_container_copy_construction() const
225  { return polymorphic_allocator(); }
226 
227  memory_resource* resource() const
228  { return _M_resource; }
229 
230  private:
231  template<typename _Tuple>
232  _Tuple&&
233  _M_construct_p(__uses_alloc0, _Tuple& __t)
234  { return std::move(__t); }
235 
236  template<typename... _Args>
237  decltype(auto)
238  _M_construct_p(__uses_alloc1_ __ua, tuple<_Args...>& __t)
239  { return tuple_cat(make_tuple(allocator_arg, *(__ua._M_a)),
240  std::move(__t)); }
241 
242  template<typename... _Args>
243  decltype(auto)
244  _M_construct_p(__uses_alloc2_ __ua, tuple<_Args...>& __t)
245  { return tuple_cat(std::move(__t), make_tuple(*(__ua._M_a))); }
246 
247  memory_resource* _M_resource;
248  };
249 
250  template <class _Tp1, class _Tp2>
251  bool operator==(const polymorphic_allocator<_Tp1>& __a,
252  const polymorphic_allocator<_Tp2>& __b) noexcept
253  { return *__a.resource() == *__b.resource(); }
254 
255  template <class _Tp1, class _Tp2>
256  bool operator!=(const polymorphic_allocator<_Tp1>& __a,
257  const polymorphic_allocator<_Tp2>& __b) noexcept
258  { return !(__a == __b); }
259 
260  // 8.7.1 __resource_adaptor_imp
261  template <typename _Alloc>
262  class __resource_adaptor_imp : public memory_resource
263  {
264  static_assert(is_same<char,
265  typename allocator_traits<_Alloc>::value_type>::value,
266  "Allocator's value_type is char");
267  static_assert(is_same<char*,
268  typename allocator_traits<_Alloc>::pointer>::value,
269  "Allocator's pointer type is value_type*");
270  static_assert(is_same<const char*,
271  typename allocator_traits<_Alloc>::const_pointer>::value,
272  "Allocator's const_pointer type is value_type const*");
273  static_assert(is_same<void*,
274  typename allocator_traits<_Alloc>::void_pointer>::value,
275  "Allocator's void_pointer type is void*");
276  static_assert(is_same<const void*,
277  typename allocator_traits<_Alloc>::const_void_pointer>::value,
278  "Allocator's const_void_pointer type is void const*");
279 
280  public:
281  using allocator_type = _Alloc;
282 
283  __resource_adaptor_imp() = default;
284  __resource_adaptor_imp(const __resource_adaptor_imp&) = default;
285  __resource_adaptor_imp(__resource_adaptor_imp&&) = default;
286 
287  explicit __resource_adaptor_imp(const _Alloc& __a2)
288  : _M_alloc(__a2)
289  { }
290 
291  explicit __resource_adaptor_imp(_Alloc&& __a2)
292  : _M_alloc(std::move(__a2))
293  { }
294 
295  __resource_adaptor_imp&
296  operator=(const __resource_adaptor_imp&) = default;
297 
298  allocator_type get_allocator() const noexcept { return _M_alloc; }
299 
300  protected:
301  virtual void*
302  do_allocate(size_t __bytes, size_t __alignment)
303  {
304  using _Aligned_alloc = std::__alloc_rebind<_Alloc, char>;
305  size_t __new_size = _S_aligned_size(__bytes,
306  _S_supported(__alignment) ?
307  __alignment : _S_max_align);
308  return _Aligned_alloc(_M_alloc).allocate(__new_size);
309  }
310 
311  virtual void
312  do_deallocate(void* __p, size_t __bytes, size_t __alignment)
313  {
314  using _Aligned_alloc = std::__alloc_rebind<_Alloc, char>;
315  size_t __new_size = _S_aligned_size(__bytes,
316  _S_supported(__alignment) ?
317  __alignment : _S_max_align);
318  using _Ptr = typename allocator_traits<_Aligned_alloc>::pointer;
319  _Aligned_alloc(_M_alloc).deallocate(static_cast<_Ptr>(__p),
320  __new_size);
321  }
322 
323  virtual bool
324  do_is_equal(const memory_resource& __other) const noexcept
325  {
326  auto __p = dynamic_cast<const __resource_adaptor_imp*>(&__other);
327  return __p ? (_M_alloc == __p->_M_alloc) : false;
328  }
329 
330  private:
331  // Calculate Aligned Size
332  // Returns a size that is larger than or equal to __size and divisible
333  // by __alignment, where __alignment is required to be a power of 2.
334  static size_t
335  _S_aligned_size(size_t __size, size_t __alignment)
336  { return ((__size - 1)|(__alignment - 1)) + 1; }
337 
338  // Determine whether alignment meets one of those preconditions:
339  // 1. Equal to Zero
340  // 2. Is power of two
341  static bool
342  _S_supported (size_t __x)
343  { return ((__x != 0) && !(__x & (__x - 1))); }
344 
345  _Alloc _M_alloc;
346  };
347 
348  // Global memory resources
349 
350  inline memory_resource*
351  new_delete_resource() noexcept
352  {
353  using type = resource_adaptor<std::allocator<char>>;
354  alignas(type) static unsigned char __buf[sizeof(type)];
355  static type* __r = new(__buf) type;
356  return __r;
357  }
358 
359  inline memory_resource*
360  null_memory_resource() noexcept
361  {
362  class type final : public memory_resource
363  {
364  void*
365  do_allocate(size_t, size_t) override
366  { std::__throw_bad_alloc(); }
367 
368  void
369  do_deallocate(void*, size_t, size_t) noexcept override
370  { }
371 
372  bool
373  do_is_equal(const memory_resource& __other) const noexcept override
374  { return this == &__other; }
375  };
376 
377  alignas(type) static unsigned char __buf[sizeof(type)];
378  static type* __r = new(__buf) type;
379  return __r;
380  }
381 
382  // The default memory resource
383 
384  inline std::atomic<memory_resource*>&
385  __get_default_resource()
386  {
387  using type = atomic<memory_resource*>;
388  alignas(type) static unsigned char __buf[sizeof(type)];
389  static type* __r = new(__buf) type(new_delete_resource());
390  return *__r;
391  }
392 
393  inline memory_resource*
394  get_default_resource() noexcept
395  { return __get_default_resource().load(); }
396 
397  inline memory_resource*
398  set_default_resource(memory_resource* __r) noexcept
399  {
400  if (__r == nullptr)
401  __r = new_delete_resource();
402  return __get_default_resource().exchange(__r);
403  }
404 } // namespace pmr
405 } // namespace fundamentals_v2
406 } // namespace experimental
407 
408 _GLIBCXX_END_NAMESPACE_VERSION
409 } // namespace std
410 #endif // C++14
411 #endif // _GLIBCXX_EXPERIMENTAL_MEMORY_RESOURCE