libstdc++-v3/include/experimental/memory_resource

   1 // <experimental/memory_resource> -*- C++ -*-
   2
   3 // Copyright (C) 2015-2019 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>                       // align, uses_allocator, __uses_alloc
  33 #include <experimental/utility>         // pair, experimental::erased_type
  34 #include <atomic>                       // atomic
  35 #include <new>                          // placement new
  36 #include <cstddef>                      // max_align_t
  37 #include <ext/new_allocator.h>
  38 #include <debug/assertions.h>
  39
  40 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
  41 {
  42 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  43   template<typename _Tp> class malloc_allocator;
  44 _GLIBCXX_END_NAMESPACE_VERSION
  45 } // namespace __gnu_cxx
  46
  47 namespace std {
  48 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  49
  50 namespace experimental {
  51 inline namespace fundamentals_v2 {
  52 namespace pmr {
  53 #define __cpp_lib_experimental_memory_resources 201402L
  54
  55   // Standard memory resources
  56
  57   // 8.5 Class memory_resource
  58   class memory_resource;
  59
  60   // 8.6 Class template polymorphic_allocator
  61   template<typename _Tp>
  62     class polymorphic_allocator;
  63
  64   template<typename _Alloc, typename _Resource = memory_resource>
  65     class __resource_adaptor_imp;
  66
  67   // 8.7 Alias template resource_adaptor
  68   template<typename _Alloc>
  69     using resource_adaptor = __resource_adaptor_imp<
  70       typename allocator_traits<_Alloc>::template rebind_alloc<char>>;
  71
  72   // 8.8 Global memory resources
  73   memory_resource* new_delete_resource() noexcept;
  74   memory_resource* null_memory_resource() noexcept;
  75   memory_resource* get_default_resource() noexcept;
  76   memory_resource* set_default_resource(memory_resource* __r) noexcept;
  77
  78   // TODO 8.9 Pool resource classes
  79
  80   class memory_resource
  81   {
  82     static constexpr size_t _S_max_align = alignof(max_align_t);
  83
  84   public:
  85     memory_resource() = default;
  86     memory_resource(const memory_resource&) = default;
  87     virtual ~memory_resource() = default;
  88
  89     memory_resource& operator=(const memory_resource&) = default;
  90
  91     _GLIBCXX_NODISCARD void*
  92     allocate(size_t __bytes, size_t __alignment = _S_max_align)
  93     { return do_allocate(__bytes, __alignment); }
  94
  95     void
  96     deallocate(void* __p, size_t __bytes, size_t __alignment = _S_max_align)
  97     { return do_deallocate(__p, __bytes, __alignment); }
  98
  99     bool
 100     is_equal(const memory_resource& __other) const noexcept
 101     { return do_is_equal(__other); }
 102
 103   protected:
 104     virtual void*
 105     do_allocate(size_t __bytes, size_t __alignment) = 0;
 106
 107     virtual void
 108     do_deallocate(void* __p, size_t __bytes, size_t __alignment) = 0;
 109
 110     virtual bool
 111     do_is_equal(const memory_resource& __other) const noexcept = 0;
 112   };
 113
 114   inline bool
 115   operator==(const memory_resource& __a, const memory_resource& __b) noexcept
 116   { return &__a == &__b || __a.is_equal(__b); }
 117
 118   inline bool
 119   operator!=(const memory_resource& __a, const memory_resource& __b) noexcept
 120   { return !(__a == __b); }
 121
 122
 123   template<typename _Tp>
 124     class polymorphic_allocator
 125     {
 126     public:
 127       using value_type = _Tp;
 128
 129       polymorphic_allocator() noexcept
 130       : _M_resource(get_default_resource())
 131       { }
 132
 133       polymorphic_allocator(memory_resource* __r)
 134       : _M_resource(__r)
 135       { _GLIBCXX_DEBUG_ASSERT(__r); }
 136
 137       polymorphic_allocator(const polymorphic_allocator& __other) = default;
 138
 139       template <typename _Up>
 140         polymorphic_allocator(const polymorphic_allocator<_Up>&
 141                               __other) noexcept
 142         : _M_resource(__other.resource())
 143         { }
 144
 145       polymorphic_allocator&
 146         operator=(const polymorphic_allocator& __rhs) = default;
 147
 148       _GLIBCXX_NODISCARD _Tp* allocate(size_t __n)
 149       { return static_cast<_Tp*>(_M_resource->allocate(__n * sizeof(_Tp),
 150                                                        alignof(_Tp))); }
 151
 152       void
 153       deallocate(_Tp* __p, size_t __n)
 154       { _M_resource->deallocate(__p, __n * sizeof(_Tp), alignof(_Tp)); }
 155
 156       template <typename _Tp1, typename... _Args> //used here
 157         void
 158         construct(_Tp1* __p, _Args&&... __args)
 159         {
 160           std::__uses_allocator_construct(this->resource(), __p,
 161                                           std::forward<_Args>(__args)...);
 162         }
 163
 164       // Specializations for pair using piecewise construction
 165       template <typename _Tp1, typename _Tp2,
 166                typename... _Args1, typename... _Args2>
 167         void
 168         construct(pair<_Tp1, _Tp2>* __p, piecewise_construct_t,
 169                   tuple<_Args1...> __x, tuple<_Args2...> __y)
 170         {
 171           memory_resource* const __resource = this->resource();
 172           auto __x_use_tag =
 173             std::__use_alloc<_Tp1, memory_resource*, _Args1...>(__resource);
 174           auto __y_use_tag =
 175             std::__use_alloc<_Tp2, memory_resource*, _Args2...>(__resource);
 176
 177           ::new(__p) std::pair<_Tp1, _Tp2>(piecewise_construct,
 178                                            _M_construct_p(__x_use_tag, __x),
 179                                            _M_construct_p(__y_use_tag, __y));
 180         }
 181
 182       template <typename _Tp1, typename _Tp2>
 183         void
 184         construct(pair<_Tp1,_Tp2>* __p)
 185         { this->construct(__p, piecewise_construct, tuple<>(), tuple<>()); }
 186
 187       template <typename _Tp1, typename _Tp2, typename _Up, typename _Vp>
 188         void
 189         construct(pair<_Tp1,_Tp2>* __p, _Up&& __x, _Vp&& __y)
 190         {
 191           this->construct(__p, piecewise_construct,
 192                           forward_as_tuple(std::forward<_Up>(__x)),
 193                           forward_as_tuple(std::forward<_Vp>(__y)));
 194         }
 195
 196       template <typename _Tp1, typename _Tp2, typename _Up, typename _Vp>
 197         void
 198         construct(pair<_Tp1,_Tp2>* __p, const std::pair<_Up, _Vp>& __pr)
 199         {
 200           this->construct(__p, piecewise_construct,
 201                           forward_as_tuple(__pr.first),
 202                           forward_as_tuple(__pr.second));
 203         }
 204
 205       template <typename _Tp1, typename _Tp2, typename _Up, typename _Vp>
 206         void
 207         construct(pair<_Tp1,_Tp2>* __p, pair<_Up, _Vp>&& __pr)
 208         {
 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
 214       template <typename _Up>
 215         void
 216         destroy(_Up* __p)
 217         { __p->~_Up(); }
 218
 219       // Return a default-constructed allocator (no allocator propagation)
 220       polymorphic_allocator
 221       select_on_container_copy_construction() const
 222       { return polymorphic_allocator(); }
 223
 224       memory_resource* resource() const { return _M_resource; }
 225
 226     private:
 227       using __uses_alloc1_ = __uses_alloc1<memory_resource*>;
 228       using __uses_alloc2_ = __uses_alloc2<memory_resource*>;
 229
 230       template<typename _Tuple>
 231         _Tuple&&
 232         _M_construct_p(__uses_alloc0, _Tuple& __t)
 233         { return std::move(__t); }
 234
 235       template<typename... _Args>
 236         decltype(auto)
 237         _M_construct_p(__uses_alloc1_ __ua, tuple<_Args...>& __t)
 238         { return tuple_cat(make_tuple(allocator_arg, *(__ua._M_a)),
 239                            std::move(__t)); }
 240
 241       template<typename... _Args>
 242         decltype(auto)
 243         _M_construct_p(__uses_alloc2_ __ua, tuple<_Args...>& __t)
 244         { return tuple_cat(std::move(__t), make_tuple(*(__ua._M_a))); }
 245
 246       memory_resource* _M_resource;
 247     };
 248
 249   template <class _Tp1, class _Tp2>
 250     bool
 251     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
 257     operator!=(const polymorphic_allocator<_Tp1>& __a,
 258                const polymorphic_allocator<_Tp2>& __b) noexcept
 259     { return !(__a == __b); }
 260
 261
 262   class __resource_adaptor_common
 263   {
 264     template<typename, typename> friend class __resource_adaptor_imp;
 265
 266     struct _AlignMgr
 267     {
 268       _AlignMgr(size_t __nbytes, size_t __align)
 269       : _M_nbytes(__nbytes), _M_align(__align)
 270       { }
 271
 272       // Total size that needs to be allocated.
 273       size_t
 274       _M_alloc_size() const { return _M_buf_size() + _M_token_size(); }
 275
 276       void*
 277       _M_adjust(void* __ptr) const
 278       {
 279         const auto __orig_ptr = static_cast<char*>(__ptr);
 280         size_t __space = _M_buf_size();
 281         // Align the pointer within the buffer:
 282         std::align(_M_align, _M_nbytes, __ptr, __space);
 283         const auto __aligned_ptr = static_cast<char*>(__ptr);
 284         const auto __token_size = _M_token_size();
 285         // Store token immediately after the aligned block:
 286         char* const __end = __aligned_ptr + _M_nbytes;
 287         if (__token_size == 1)
 288           _S_write<unsigned char>(__end, __aligned_ptr - __orig_ptr);
 289         else if (__token_size == sizeof(short))
 290           _S_write<unsigned short>(__end, __aligned_ptr - __orig_ptr);
 291         else if (__token_size == sizeof(int) && sizeof(int) < sizeof(char*))
 292           _S_write<unsigned int>(__end, __aligned_ptr - __orig_ptr);
 293         else // (__token_size == sizeof(char*))
 294           // Just store the original pointer:
 295           _S_write<char*>(__end, __orig_ptr);
 296         return __aligned_ptr;
 297       }
 298
 299       char*
 300       _M_unadjust(char* __ptr) const
 301       {
 302         const char* const __end = __ptr + _M_nbytes;
 303         char* __orig_ptr;
 304         const auto __token_size = _M_token_size();
 305         // Read the token and restore the original pointer:
 306         if (__token_size == 1)
 307           __orig_ptr = __ptr - _S_read<unsigned char>(__end);
 308         else if (__token_size == sizeof(short))
 309           __orig_ptr = __ptr - _S_read<unsigned short>(__end);
 310         else if (__token_size == sizeof(int)
 311             && sizeof(int) < sizeof(char*))
 312           __orig_ptr = __ptr - _S_read<unsigned int>(__end);
 313         else // (__token_size == sizeof(char*))
 314           __orig_ptr = _S_read<char*>(__end);
 315         // The adjustment is always less than the requested alignment,
 316         // so if that isn't true now then either the wrong size was passed
 317         // to deallocate or the token was overwritten by a buffer overflow:
 318         __glibcxx_assert(static_cast<size_t>(__ptr - __orig_ptr) < _M_align);
 319         return __orig_ptr;
 320       }
 321
 322     private:
 323       size_t _M_nbytes;
 324       size_t _M_align;
 325
 326       // Number of bytes needed to fit block of given size and alignment.
 327       size_t
 328       _M_buf_size() const { return _M_nbytes + _M_align - 1; }
 329
 330       // Number of additional bytes needed to write the token.
 331       int
 332       _M_token_size() const
 333       {
 334         if (_M_align <= (1ul << __CHAR_BIT__))
 335           return 1;
 336         if (_M_align <= (1ul << (sizeof(short) * __CHAR_BIT__)))
 337           return sizeof(short);
 338         if (_M_align <= (1ull << (sizeof(int) * __CHAR_BIT__)))
 339           return sizeof(int);
 340         return sizeof(char*);
 341       }
 342
 343       template<typename _Tp>
 344         static void
 345         _S_write(void* __to, _Tp __val)
 346         { __builtin_memcpy(__to, &__val, sizeof(_Tp)); }
 347
 348       template<typename _Tp>
 349         static _Tp
 350         _S_read(const void* __from)
 351         {
 352           _Tp __val;
 353           __builtin_memcpy(&__val, __from, sizeof(_Tp));
 354           return __val;
 355         }
 356     };
 357
 358     template<typename _Alloc>
 359       struct __guaranteed_alignment : std::integral_constant<size_t, 1> { };
 360
 361     template<typename _Tp>
 362       struct __guaranteed_alignment<__gnu_cxx::new_allocator<_Tp>>
 363       : std::alignment_of<std::max_align_t>::type { };
 364
 365     template<typename _Tp>
 366       struct __guaranteed_alignment<__gnu_cxx::malloc_allocator<_Tp>>
 367       : std::alignment_of<std::max_align_t>::type { };
 368
 369 #if _GLIBCXX_USE_ALLOCATOR_NEW
 370     template<typename _Tp>
 371       struct __guaranteed_alignment<std::allocator<_Tp>>
 372       : std::alignment_of<std::max_align_t>::type { };
 373 #endif
 374   };
 375
 376   // 8.7.1 __resource_adaptor_imp
 377   template<typename _Alloc, typename _Resource>
 378     class __resource_adaptor_imp
 379     : public _Resource, private __resource_adaptor_common
 380     {
 381       using memory_resource = _Resource;
 382
 383       static_assert(is_same<char,
 384           typename allocator_traits<_Alloc>::value_type>::value,
 385           "Allocator's value_type is char");
 386       static_assert(is_same<char*,
 387           typename allocator_traits<_Alloc>::pointer>::value,
 388           "Allocator's pointer type is value_type*");
 389       static_assert(is_same<const char*,
 390           typename allocator_traits<_Alloc>::const_pointer>::value,
 391           "Allocator's const_pointer type is value_type const*");
 392       static_assert(is_same<void*,
 393           typename allocator_traits<_Alloc>::void_pointer>::value,
 394           "Allocator's void_pointer type is void*");
 395       static_assert(is_same<const void*,
 396           typename allocator_traits<_Alloc>::const_void_pointer>::value,
 397           "Allocator's const_void_pointer type is void const*");
 398
 399     public:
 400       using allocator_type = _Alloc;
 401
 402       __resource_adaptor_imp() = default;
 403       __resource_adaptor_imp(const __resource_adaptor_imp&) = default;
 404       __resource_adaptor_imp(__resource_adaptor_imp&&) = default;
 405
 406       explicit __resource_adaptor_imp(const _Alloc& __a2)
 407       : _M_alloc(__a2)
 408       { }
 409
 410       explicit __resource_adaptor_imp(_Alloc&& __a2)
 411       : _M_alloc(std::move(__a2))
 412       { }
 413
 414       __resource_adaptor_imp&
 415       operator=(const __resource_adaptor_imp&) = default;
 416
 417       allocator_type get_allocator() const noexcept { return _M_alloc; }
 418
 419     protected:
 420       virtual void*
 421       do_allocate(size_t __bytes, size_t __alignment) override
 422       {
 423         if (__alignment <= __guaranteed_alignment<_Alloc>::value)
 424           {
 425             if (__bytes < __alignment)
 426               __bytes = __alignment;
 427             return _M_alloc.allocate(__bytes);
 428           }
 429
 430
 431         const _AlignMgr __mgr(__bytes, __alignment);
 432         // Assume _M_alloc returns 1-byte aligned memory, so allocate enough
 433         // space to fit a block of the right size and alignment, plus some
 434         // extra bytes to store a token for retrieving the original pointer.
 435         return __mgr._M_adjust(_M_alloc.allocate(__mgr._M_alloc_size()));
 436       }
 437
 438       virtual void
 439       do_deallocate(void* __p, size_t __bytes, size_t __alignment) noexcept
 440       override
 441       {
 442         auto __ptr = static_cast<char*>(__p);
 443         if (__alignment <= __guaranteed_alignment<_Alloc>::value)
 444           {
 445             if (__bytes < __alignment)
 446               __bytes = __alignment;
 447             _M_alloc.deallocate(__ptr, __bytes);
 448             return;
 449           }
 450
 451         const _AlignMgr __mgr(__bytes, __alignment);
 452         // Use the stored token to retrieve the original pointer to deallocate.
 453         _M_alloc.deallocate(__mgr._M_unadjust(__ptr), __mgr._M_alloc_size());
 454       }
 455
 456       virtual bool
 457       do_is_equal(const memory_resource& __other) const noexcept override
 458       {
 459         if (auto __p = dynamic_cast<const __resource_adaptor_imp*>(&__other))
 460           return _M_alloc == __p->_M_alloc;
 461         return false;
 462       }
 463
 464     private:
 465       _Alloc _M_alloc{};
 466     };
 467
 468   // Global memory resources
 469
 470   inline memory_resource*
 471   new_delete_resource() noexcept
 472   {
 473     using type = resource_adaptor<__gnu_cxx::new_allocator<char>>;
 474     alignas(type) static unsigned char __buf[sizeof(type)];
 475     static type* __r = new(__buf) type;
 476     return __r;
 477   }
 478
 479   inline memory_resource*
 480   null_memory_resource() noexcept
 481   {
 482     class type final : public memory_resource
 483     {
 484       void*
 485       do_allocate(size_t, size_t) override
 486       { std::__throw_bad_alloc(); }
 487
 488       void
 489       do_deallocate(void*, size_t, size_t) noexcept override
 490       { }
 491
 492       bool
 493       do_is_equal(const memory_resource& __other) const noexcept override
 494       { return this == &__other; }
 495     };
 496
 497     alignas(type) static unsigned char __buf[sizeof(type)];
 498     static type* __r = new(__buf) type;
 499     return __r;
 500   }
 501
 502   // The default memory resource
 503
 504   inline std::atomic<memory_resource*>&
 505   __get_default_resource()
 506   {
 507     using type = atomic<memory_resource*>;
 508     alignas(type) static unsigned char __buf[sizeof(type)];
 509     static type* __r = new(__buf) type(new_delete_resource());
 510     return *__r;
 511   }
 512
 513   inline memory_resource*
 514   get_default_resource() noexcept
 515   { return __get_default_resource().load(); }
 516
 517   inline memory_resource*
 518   set_default_resource(memory_resource* __r) noexcept
 519   {
 520     if (__r == nullptr)
 521       __r = new_delete_resource();
 522     return __get_default_resource().exchange(__r);
 523   }
 524
 525 } // namespace pmr
 526 } // namespace fundamentals_v2
 527 } // namespace experimental
 528
 529 _GLIBCXX_END_NAMESPACE_VERSION
 530 } // namespace std
 531 #endif // _GLIBCXX_EXPERIMENTAL_MEMORY_RESOURCE