libstdc++
memory_resource
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1 // <experimental/memory_resource> -*- C++ -*-
2 
3 // Copyright (C) 2015-2016 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>
37 
38 namespace std {
39 namespace experimental {
40 inline namespace fundamentals_v2 {
41 namespace pmr {
42 _GLIBCXX_BEGIN_NAMESPACE_VERSION
43 
44 #define __cpp_lib_experimental_memory_resources 201402L
45 
46  class memory_resource;
47 
48  template <typename _Tp>
49  class polymorphic_allocator;
50 
51  template <typename _Alloc>
52  class __resource_adaptor_imp;
53 
54  template <typename _Alloc>
55  using resource_adaptor = __resource_adaptor_imp<
56  typename allocator_traits<_Alloc>::template rebind_alloc<char>>;
57 
58  template <typename _Tp>
59  struct __uses_allocator_construction_helper;
60 
61  // Global memory resources
62  memory_resource* new_delete_resource() noexcept;
63  memory_resource* null_memory_resource() noexcept;
64 
65  // The default memory resource
66  memory_resource* get_default_resource() noexcept;
67  memory_resource* set_default_resource(memory_resource* __r) noexcept;
68 
69  // Standard memory resources
70 
71  // 8.5 Class memory_resource
72  class memory_resource
73  {
74  protected:
75  static constexpr size_t _S_max_align = alignof(max_align_t);
76 
77  public:
78  virtual ~memory_resource() { }
79 
80  void*
81  allocate(size_t __bytes, size_t __alignment = _S_max_align)
82  { return do_allocate(__bytes, __alignment); }
83 
84  void
85  deallocate(void* __p, size_t __bytes, size_t __alignment = _S_max_align)
86  { return do_deallocate(__p, __bytes, __alignment); }
87 
88  bool
89  is_equal(const memory_resource& __other) const noexcept
90  { return do_is_equal(__other); }
91 
92  protected:
93  virtual void*
94  do_allocate(size_t __bytes, size_t __alignment) = 0;
95 
96  virtual void
97  do_deallocate(void* __p, size_t __bytes, size_t __alignment) = 0;
98 
99  virtual bool
100  do_is_equal(const memory_resource& __other) const noexcept = 0;
101  };
102 
103  inline bool
104  operator==(const memory_resource& __a,
105  const memory_resource& __b) noexcept
106  { return &__a == &__b || __a.is_equal(__b); }
107 
108  inline bool
109  operator!=(const memory_resource& __a,
110  const memory_resource& __b) noexcept
111  { return !(__a == __b); }
112 
113 
114  // 8.6 Class template polymorphic_allocator
115  template <class _Tp>
116  class polymorphic_allocator
117  {
118  using __uses_alloc1_ = __uses_alloc1<memory_resource*>;
119  using __uses_alloc2_ = __uses_alloc2<memory_resource*>;
120 
121  template<typename _Tp1, typename... _Args>
122  void
123  _M_construct(__uses_alloc0, _Tp1* __p, _Args&&... __args)
124  { ::new(__p) _Tp1(std::forward<_Args>(__args)...); }
125 
126  template<typename _Tp1, typename... _Args>
127  void
128  _M_construct(__uses_alloc1_, _Tp1* __p, _Args&&... __args)
129  { ::new(__p) _Tp1(allocator_arg, this->resource(),
130  std::forward<_Args>(__args)...); }
131 
132  template<typename _Tp1, typename... _Args>
133  void
134  _M_construct(__uses_alloc2_, _Tp1* __p, _Args&&... __args)
135  { ::new(__p) _Tp1(std::forward<_Args>(__args)...,
136  this->resource()); }
137 
138  public:
139  using value_type = _Tp;
140 
141  polymorphic_allocator() noexcept
142  : _M_resource(get_default_resource())
143  { }
144 
145  polymorphic_allocator(memory_resource* __r)
146  : _M_resource(__r)
147  { _GLIBCXX_DEBUG_ASSERT(__r); }
148 
149  polymorphic_allocator(const polymorphic_allocator& __other) = default;
150 
151  template <typename _Up>
152  polymorphic_allocator(const polymorphic_allocator<_Up>&
153  __other) noexcept
154  : _M_resource(__other.resource())
155  { }
156 
157  polymorphic_allocator&
158  operator=(const polymorphic_allocator& __rhs) = default;
159 
160  _Tp* allocate(size_t __n)
161  { return static_cast<_Tp*>(_M_resource->allocate(__n * sizeof(_Tp),
162  alignof(_Tp))); }
163 
164  void deallocate(_Tp* __p, size_t __n)
165  { _M_resource->deallocate(__p, __n * sizeof(_Tp), alignof(_Tp)); }
166 
167  template <typename _Tp1, typename... _Args> //used here
168  void construct(_Tp1* __p, _Args&&... __args)
169  {
170  auto __use_tag = __use_alloc<_Tp1, memory_resource*,
171  _Args...>(this->resource());
172  _M_construct(__use_tag, __p, std::forward<_Args>(__args)...);
173  }
174 
175  // Specializations for pair using piecewise construction
176  template <typename _Tp1, typename _Tp2,
177  typename... _Args1, typename... _Args2>
178  void construct(pair<_Tp1, _Tp2>* __p, piecewise_construct_t,
179  tuple<_Args1...> __x,
180  tuple<_Args2...> __y)
181  {
182  auto __x_use_tag =
183  __use_alloc<_Tp1, memory_resource*, _Args1...>(this->resource());
184  auto __y_use_tag =
185  __use_alloc<_Tp2, memory_resource*, _Args2...>(this->resource());
186 
187  ::new(__p) std::pair<_Tp1, _Tp2>(piecewise_construct,
188  _M_construct_p(__x_use_tag, __x),
189  _M_construct_p(__y_use_tag, __y));
190  }
191 
192  template <typename _Tp1, typename _Tp2>
193  void construct(pair<_Tp1,_Tp2>* __p)
194  { this->construct(__p, piecewise_construct, tuple<>(), tuple<>()); }
195 
196  template <typename _Tp1, typename _Tp2, typename _Up, typename _Vp>
197  void construct(pair<_Tp1,_Tp2>* __p, _Up&& __x, _Vp&& __y)
198  { this->construct(__p, piecewise_construct,
199  forward_as_tuple(std::forward<_Up>(__x)),
200  forward_as_tuple(std::forward<_Vp>(__y))); }
201 
202  template <typename _Tp1, typename _Tp2, typename _Up, typename _Vp>
203  void construct(pair<_Tp1,_Tp2>* __p, const std::pair<_Up, _Vp>& __pr)
204  { this->construct(__p, piecewise_construct, forward_as_tuple(__pr.first),
205  forward_as_tuple(__pr.second)); }
206 
207  template <typename _Tp1, typename _Tp2, typename _Up, typename _Vp>
208  void construct(pair<_Tp1,_Tp2>* __p, pair<_Up, _Vp>&& __pr)
209  { this->construct(__p, piecewise_construct,
210  forward_as_tuple(std::forward<_Up>(__pr.first)),
211  forward_as_tuple(std::forward<_Vp>(__pr.second))); }
212 
213  template <typename _Up>
214  void destroy(_Up* __p)
215  { __p->~_Up(); }
216 
217  // Return a default-constructed allocator (no allocator propagation)
218  polymorphic_allocator select_on_container_copy_construction() const
219  { return polymorphic_allocator(); }
220 
221  memory_resource* resource() const
222  { return _M_resource; }
223 
224  private:
225  template<typename _Tuple>
226  _Tuple&&
227  _M_construct_p(__uses_alloc0, _Tuple& __t)
228  { return std::move(__t); }
229 
230  template<typename... _Args>
231  decltype(auto)
232  _M_construct_p(__uses_alloc1_ __ua, tuple<_Args...>& __t)
233  { return tuple_cat(make_tuple(allocator_arg, *(__ua._M_a)),
234  std::move(__t)); }
235 
236  template<typename... _Args>
237  decltype(auto)
238  _M_construct_p(__uses_alloc2_ __ua, tuple<_Args...>& __t)
239  { return tuple_cat(std::move(__t), make_tuple(*(__ua._M_a))); }
240 
241  memory_resource* _M_resource;
242  };
243 
244  template <class _Tp1, class _Tp2>
245  bool operator==(const polymorphic_allocator<_Tp1>& __a,
246  const polymorphic_allocator<_Tp2>& __b) noexcept
247  { return *__a.resource() == *__b.resource(); }
248 
249  template <class _Tp1, class _Tp2>
250  bool operator!=(const polymorphic_allocator<_Tp1>& __a,
251  const polymorphic_allocator<_Tp2>& __b) noexcept
252  { return !(__a == __b); }
253 
254  // 8.7.1 __resource_adaptor_imp
255  template <typename _Alloc>
256  class __resource_adaptor_imp : public memory_resource
257  {
258  static_assert(is_same<char,
259  typename allocator_traits<_Alloc>::value_type>::value,
260  "Allocator's value_type is char");
261  static_assert(is_same<char*,
262  typename allocator_traits<_Alloc>::pointer>::value,
263  "Allocator's pointer type is value_type*");
264  static_assert(is_same<const char*,
265  typename allocator_traits<_Alloc>::const_pointer>::value,
266  "Allocator's const_pointer type is value_type const*");
267  static_assert(is_same<void*,
268  typename allocator_traits<_Alloc>::void_pointer>::value,
269  "Allocator's void_pointer type is void*");
270  static_assert(is_same<const void*,
271  typename allocator_traits<_Alloc>::const_void_pointer>::value,
272  "Allocator's const_void_pointer type is void const*");
273 
274  public:
275  using allocator_type = _Alloc;
276 
277  __resource_adaptor_imp() = default;
278  __resource_adaptor_imp(const __resource_adaptor_imp&) = default;
279  __resource_adaptor_imp(__resource_adaptor_imp&&) = default;
280 
281  explicit __resource_adaptor_imp(const _Alloc& __a2)
282  : _M_alloc(__a2)
283  { }
284 
285  explicit __resource_adaptor_imp(_Alloc&& __a2)
286  : _M_alloc(std::move(__a2))
287  { }
288 
289  __resource_adaptor_imp&
290  operator=(const __resource_adaptor_imp&) = default;
291 
292  allocator_type get_allocator() const noexcept { return _M_alloc; }
293 
294  protected:
295  virtual void*
296  do_allocate(size_t __bytes, size_t __alignment)
297  {
298  using _Aligned_alloc = std::__alloc_rebind<_Alloc, char>;
299  size_t __new_size = _S_aligned_size(__bytes,
300  _S_supported(__alignment) ?
301  __alignment : _S_max_align);
302  return _Aligned_alloc(_M_alloc).allocate(__new_size);
303  }
304 
305  virtual void
306  do_deallocate(void* __p, size_t __bytes, size_t __alignment)
307  {
308  using _Aligned_alloc = std::__alloc_rebind<_Alloc, char>;
309  size_t __new_size = _S_aligned_size(__bytes,
310  _S_supported(__alignment) ?
311  __alignment : _S_max_align);
312  using _Ptr = typename allocator_traits<_Aligned_alloc>::pointer;
313  _Aligned_alloc(_M_alloc).deallocate(static_cast<_Ptr>(__p),
314  __new_size);
315  }
316 
317  virtual bool
318  do_is_equal(const memory_resource& __other) const noexcept
319  {
320  auto __p = dynamic_cast<const __resource_adaptor_imp*>(&__other);
321  return __p ? (_M_alloc == __p->_M_alloc) : false;
322  }
323 
324  private:
325  // Calculate Aligned Size
326  // Returns a size that is larger than or equal to __size and divisible
327  // by __alignment, where __alignment is required to be a power of 2.
328  static size_t
329  _S_aligned_size(size_t __size, size_t __alignment)
330  { return ((__size - 1)|(__alignment - 1)) + 1; }
331 
332  // Determine whether alignment meets one of those preconditions:
333  // 1. Equal to Zero
334  // 2. Is power of two
335  static bool
336  _S_supported (size_t __x)
337  { return ((__x != 0) && !(__x & (__x - 1))); }
338 
339  _Alloc _M_alloc;
340  };
341 
342  // Global memory resources
343 
344  inline memory_resource*
345  new_delete_resource() noexcept
346  {
347  using type = resource_adaptor<std::allocator<char>>;
348  alignas(type) static unsigned char __buf[sizeof(type)];
349  static type* __r = new(__buf) type;
350  return __r;
351  }
352 
353  inline memory_resource*
354  null_memory_resource() noexcept
355  {
356  class type final : public memory_resource
357  {
358  void*
359  do_allocate(size_t, size_t) override
360  { std::__throw_bad_alloc(); }
361 
362  void
363  do_deallocate(void*, size_t, size_t) noexcept override
364  { }
365 
366  bool
367  do_is_equal(const memory_resource& __other) const noexcept override
368  { return this == &__other; }
369  };
370 
371  alignas(type) static unsigned char __buf[sizeof(type)];
372  static type* __r = new(__buf) type;
373  return __r;
374  }
375 
376  // The default memory resource
377 
379  __get_default_resource()
380  {
381  using type = atomic<memory_resource*>;
382  alignas(type) static unsigned char __buf[sizeof(type)];
383  static type* __r = new(__buf) type(new_delete_resource());
384  return *__r;
385  }
386 
387  inline memory_resource*
388  get_default_resource() noexcept
389  { return __get_default_resource().load(); }
390 
391  inline memory_resource*
392  set_default_resource(memory_resource* __r) noexcept
393  {
394  if (__r == nullptr)
395  __r = new_delete_resource();
396  return __get_default_resource().exchange(__r);
397  }
398 
399 _GLIBCXX_END_NAMESPACE_VERSION
400 } // namespace pmr
401 } // namespace fundamentals_v2
402 } // namespace experimental
403 } // namespace std
404 
405 #endif
constexpr _Tp && forward(typename std::remove_reference< _Tp >::type &__t) noexcept
Forward an lvalue.
Definition: move.h:76
_T1 first
second_type is the second bound type
Definition: stl_pair.h:210
Struct holding two objects of arbitrary type.
Definition: stl_pair.h:204
Generic atomic type, primary class template.
Definition: atomic:53
constexpr piecewise_construct_t piecewise_construct
piecewise_construct
Definition: stl_pair.h:79
constexpr auto tuple_cat(_Tpls &&...__tpls) -> typename __tuple_cat_result< _Tpls...>::__type
tuple_cat
Definition: tuple:1530
_T2 second
first is a copy of the first object
Definition: stl_pair.h:211