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The C and C++ Include Header Files
/usr/include/c++/13/ext/bitmap_allocator.h
$ cat -n /usr/include/c++/13/ext/bitmap_allocator.h 1 // Bitmap Allocator. -*- C++ -*- 2 3 // Copyright (C) 2004-2023 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 ext/bitmap_allocator.h 26 * This file is a GNU extension to the Standard C++ Library. 27 */ 28 29 #ifndef _BITMAP_ALLOCATOR_H 30 #define _BITMAP_ALLOCATOR_H 1 31 32 #include <bits/requires_hosted.h> // GNU extensions are currently omitted 33 34 #include <utility> // For std::pair. 35 #include <bits/functexcept.h> // For __throw_bad_alloc(). 36 #include <bits/stl_function.h> // For greater_equal, and less_equal. 37 #include <new> // For operator new. 38 #include <debug/debug.h> // _GLIBCXX_DEBUG_ASSERT 39 #include <ext/concurrence.h> 40 #include <bits/move.h> 41 42 /** @brief The constant in the expression below is the alignment 43 * required in bytes. 44 */ 45 #define _BALLOC_ALIGN_BYTES 8 46 47 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default) 48 { 49 _GLIBCXX_BEGIN_NAMESPACE_VERSION 50 51 namespace __detail 52 { 53 /** @class __mini_vector bitmap_allocator.h bitmap_allocator.h 54 * 55 * @brief __mini_vector<> is a stripped down version of the 56 * full-fledged std::vector<>. 57 * 58 * It is to be used only for built-in types or PODs. Notable 59 * differences are: 60 * 61 * 1. Not all accessor functions are present. 62 * 2. Used ONLY for PODs. 63 * 3. No Allocator template argument. Uses ::operator new() to get 64 * memory, and ::operator delete() to free it. 65 * Caveat: The dtor does NOT free the memory allocated, so this a 66 * memory-leaking vector! 67 */ 68 template<typename _Tp> 69 class __mini_vector 70 { 71 __mini_vector(const __mini_vector&); 72 __mini_vector& operator=(const __mini_vector&); 73 74 public: 75 typedef _Tp value_type; 76 typedef _Tp* pointer; 77 typedef _Tp& reference; 78 typedef const _Tp& const_reference; 79 typedef std::size_t size_type; 80 typedef std::ptrdiff_t difference_type; 81 typedef pointer iterator; 82 83 private: 84 pointer _M_start; 85 pointer _M_finish; 86 pointer _M_end_of_storage; 87 88 size_type 89 _M_space_left() const throw() 90 { return _M_end_of_storage - _M_finish; } 91 92 _GLIBCXX_NODISCARD pointer 93 allocate(size_type __n) 94 { return static_cast<pointer>(::operator new(__n * sizeof(_Tp))); } 95 96 void 97 deallocate(pointer __p, size_type) 98 { ::operator delete(__p); } 99 100 public: 101 // Members used: size(), push_back(), pop_back(), 102 // insert(iterator, const_reference), erase(iterator), 103 // begin(), end(), back(), operator[]. 104 105 __mini_vector() 106 : _M_start(0), _M_finish(0), _M_end_of_storage(0) { } 107 108 size_type 109 size() const throw() 110 { return _M_finish - _M_start; } 111 112 iterator 113 begin() const throw() 114 { return this->_M_start; } 115 116 iterator 117 end() const throw() 118 { return this->_M_finish; } 119 120 reference 121 back() const throw() 122 { return *(this->end() - 1); } 123 124 reference 125 operator[](const size_type __pos) const throw() 126 { return this->_M_start[__pos]; } 127 128 void 129 insert(iterator __pos, const_reference __x); 130 131 void 132 push_back(const_reference __x) 133 { 134 if (this->_M_space_left()) 135 { 136 *this->end() = __x; 137 ++this->_M_finish; 138 } 139 else 140 this->insert(this->end(), __x); 141 } 142 143 void 144 pop_back() throw() 145 { --this->_M_finish; } 146 147 void 148 erase(iterator __pos) throw(); 149 150 void 151 clear() throw() 152 { this->_M_finish = this->_M_start; } 153 }; 154 155 // Out of line function definitions. 156 template<typename _Tp> 157 void __mini_vector<_Tp>:: 158 insert(iterator __pos, const_reference __x) 159 { 160 if (this->_M_space_left()) 161 { 162 size_type __to_move = this->_M_finish - __pos; 163 iterator __dest = this->end(); 164 iterator __src = this->end() - 1; 165 166 ++this->_M_finish; 167 while (__to_move) 168 { 169 *__dest = *__src; 170 --__dest; --__src; --__to_move; 171 } 172 *__pos = __x; 173 } 174 else 175 { 176 size_type __new_size = this->size() ? this->size() * 2 : 1; 177 iterator __new_start = this->allocate(__new_size); 178 iterator __first = this->begin(); 179 iterator __start = __new_start; 180 while (__first != __pos) 181 { 182 *__start = *__first; 183 ++__start; ++__first; 184 } 185 *__start = __x; 186 ++__start; 187 while (__first != this->end()) 188 { 189 *__start = *__first; 190 ++__start; ++__first; 191 } 192 if (this->_M_start) 193 this->deallocate(this->_M_start, this->size()); 194 195 this->_M_start = __new_start; 196 this->_M_finish = __start; 197 this->_M_end_of_storage = this->_M_start + __new_size; 198 } 199 } 200 201 template<typename _Tp> 202 void __mini_vector<_Tp>:: 203 erase(iterator __pos) throw() 204 { 205 while (__pos + 1 != this->end()) 206 { 207 *__pos = __pos[1]; 208 ++__pos; 209 } 210 --this->_M_finish; 211 } 212 213 214 template<typename _Tp> 215 struct __mv_iter_traits 216 { 217 typedef typename _Tp::value_type value_type; 218 typedef typename _Tp::difference_type difference_type; 219 }; 220 221 template<typename _Tp> 222 struct __mv_iter_traits<_Tp*> 223 { 224 typedef _Tp value_type; 225 typedef std::ptrdiff_t difference_type; 226 }; 227 228 enum 229 { 230 bits_per_byte = 8, 231 bits_per_block = sizeof(std::size_t) * std::size_t(bits_per_byte) 232 }; 233 234 template<typename _ForwardIterator, typename _Tp, typename _Compare> 235 _ForwardIterator 236 __lower_bound(_ForwardIterator __first, _ForwardIterator __last, 237 const _Tp& __val, _Compare __comp) 238 { 239 typedef typename __mv_iter_traits<_ForwardIterator>::difference_type 240 _DistanceType; 241 242 _DistanceType __len = __last - __first; 243 _DistanceType __half; 244 _ForwardIterator __middle; 245 246 while (__len > 0) 247 { 248 __half = __len >> 1; 249 __middle = __first; 250 __middle += __half; 251 if (__comp(*__middle, __val)) 252 { 253 __first = __middle; 254 ++__first; 255 __len = __len - __half - 1; 256 } 257 else 258 __len = __half; 259 } 260 return __first; 261 } 262 263 /** @brief The number of Blocks pointed to by the address pair 264 * passed to the function. 265 */ 266 template<typename _AddrPair> 267 inline std::size_t 268 __num_blocks(_AddrPair __ap) 269 { return (__ap.second - __ap.first) + 1; } 270 271 /** @brief The number of Bit-maps pointed to by the address pair 272 * passed to the function. 273 */ 274 template<typename _AddrPair> 275 inline std::size_t 276 __num_bitmaps(_AddrPair __ap) 277 { return __num_blocks(__ap) / std::size_t(bits_per_block); } 278 279 // _Tp should be a pointer type. 280 template<typename _Tp> 281 class _Inclusive_between 282 { 283 typedef _Tp pointer; 284 pointer _M_ptr_value; 285 typedef typename std::pair<_Tp, _Tp> _Block_pair; 286 287 public: 288 _Inclusive_between(pointer __ptr) : _M_ptr_value(__ptr) 289 { } 290 291 bool 292 operator()(_Block_pair __bp) const throw() 293 { 294 if (std::less_equal<pointer>()(_M_ptr_value, __bp.second) 295 && std::greater_equal<pointer>()(_M_ptr_value, __bp.first)) 296 return true; 297 else 298 return false; 299 } 300 }; 301 302 // Used to pass a Functor to functions by reference. 303 template<typename _Functor> 304 class _Functor_Ref 305 { 306 _Functor& _M_fref; 307 308 public: 309 typedef typename _Functor::argument_type argument_type; 310 typedef typename _Functor::result_type result_type; 311 312 _Functor_Ref(_Functor& __fref) : _M_fref(__fref) 313 { } 314 315 result_type 316 operator()(argument_type __arg) 317 { return _M_fref(__arg); } 318 }; 319 320 /** @class _Ffit_finder bitmap_allocator.h bitmap_allocator.h 321 * 322 * @brief The class which acts as a predicate for applying the 323 * first-fit memory allocation policy for the bitmap allocator. 324 */ 325 // _Tp should be a pointer type, and _Alloc is the Allocator for 326 // the vector. 327 template<typename _Tp> 328 class _Ffit_finder 329 { 330 typedef std::pair<_Tp, _Tp> _Block_pair; 331 typedef __detail::__mini_vector<_Block_pair> _BPVector; 332 typedef typename _BPVector::difference_type _Counter_type; 333 334 std::size_t* _M_pbitmap; 335 _Counter_type _M_data_offset; 336 337 public: 338 typedef bool result_type; 339 typedef _Block_pair argument_type; 340 341 _Ffit_finder() : _M_pbitmap(0), _M_data_offset(0) 342 { } 343 344 bool 345 operator()(_Block_pair __bp) throw() 346 { 347 using std::size_t; 348 // Set the _rover to the last physical location bitmap, 349 // which is the bitmap which belongs to the first free 350 // block. Thus, the bitmaps are in exact reverse order of 351 // the actual memory layout. So, we count down the bitmaps, 352 // which is the same as moving up the memory. 353 354 // If the used count stored at the start of the Bit Map headers 355 // is equal to the number of Objects that the current Block can 356 // store, then there is definitely no space for another single 357 // object, so just return false. 358 _Counter_type __diff = __detail::__num_bitmaps(__bp); 359 360 if (*(reinterpret_cast<size_t*> 361 (__bp.first) - (__diff + 1)) == __detail::__num_blocks(__bp)) 362 return false; 363 364 size_t* __rover = reinterpret_cast<size_t*>(__bp.first) - 1; 365 366 for (_Counter_type __i = 0; __i < __diff; ++__i) 367 { 368 _M_data_offset = __i; 369 if (*__rover) 370 { 371 _M_pbitmap = __rover; 372 return true; 373 } 374 --__rover; 375 } 376 return false; 377 } 378 379 std::size_t* 380 _M_get() const throw() 381 { return _M_pbitmap; } 382 383 _Counter_type 384 _M_offset() const throw() 385 { return _M_data_offset * std::size_t(bits_per_block); } 386 }; 387 388 /** @class _Bitmap_counter bitmap_allocator.h bitmap_allocator.h 389 * 390 * @brief The bitmap counter which acts as the bitmap 391 * manipulator, and manages the bit-manipulation functions and 392 * the searching and identification functions on the bit-map. 393 */ 394 // _Tp should be a pointer type. 395 template<typename _Tp> 396 class _Bitmap_counter 397 { 398 typedef typename 399 __detail::__mini_vector<typename std::pair<_Tp, _Tp> > _BPVector; 400 typedef typename _BPVector::size_type _Index_type; 401 typedef _Tp pointer; 402 403 _BPVector& _M_vbp; 404 std::size_t* _M_curr_bmap; 405 std::size_t* _M_last_bmap_in_block; 406 _Index_type _M_curr_index; 407 408 public: 409 // Use the 2nd parameter with care. Make sure that such an 410 // entry exists in the vector before passing that particular 411 // index to this ctor. 412 _Bitmap_counter(_BPVector& Rvbp, long __index = -1) : _M_vbp(Rvbp) 413 { this->_M_reset(__index); } 414 415 void 416 _M_reset(long __index = -1) throw() 417 { 418 if (__index == -1) 419 { 420 _M_curr_bmap = 0; 421 _M_curr_index = static_cast<_Index_type>(-1); 422 return; 423 } 424 425 _M_curr_index = __index; 426 _M_curr_bmap = reinterpret_cast<std::size_t*> 427 (_M_vbp[_M_curr_index].first) - 1; 428 429 _GLIBCXX_DEBUG_ASSERT(__index <= (long)_M_vbp.size() - 1); 430 431 _M_last_bmap_in_block = _M_curr_bmap 432 - ((_M_vbp[_M_curr_index].second 433 - _M_vbp[_M_curr_index].first + 1) 434 / std::size_t(bits_per_block) - 1); 435 } 436 437 // Dangerous Function! Use with extreme care. Pass to this 438 // function ONLY those values that are known to be correct, 439 // otherwise this will mess up big time. 440 void 441 _M_set_internal_bitmap(std::size_t* __new_internal_marker) throw() 442 { _M_curr_bmap = __new_internal_marker; } 443 444 bool 445 _M_finished() const throw() 446 { return(_M_curr_bmap == 0); } 447 448 _Bitmap_counter& 449 operator++() throw() 450 { 451 if (_M_curr_bmap == _M_last_bmap_in_block) 452 { 453 if (++_M_curr_index == _M_vbp.size()) 454 _M_curr_bmap = 0; 455 else 456 this->_M_reset(_M_curr_index); 457 } 458 else 459 --_M_curr_bmap; 460 return *this; 461 } 462 463 std::size_t* 464 _M_get() const throw() 465 { return _M_curr_bmap; } 466 467 pointer 468 _M_base() const throw() 469 { return _M_vbp[_M_curr_index].first; } 470 471 _Index_type 472 _M_offset() const throw() 473 { 474 return std::size_t(bits_per_block) 475 * ((reinterpret_cast<std::size_t*>(this->_M_base()) 476 - _M_curr_bmap) - 1); 477 } 478 479 _Index_type 480 _M_where() const throw() 481 { return _M_curr_index; } 482 }; 483 484 /** @brief Mark a memory address as allocated by re-setting the 485 * corresponding bit in the bit-map. 486 */ 487 inline void 488 __bit_allocate(std::size_t* __pbmap, std::size_t __pos) throw() 489 { 490 std::size_t __mask = 1 << __pos; 491 __mask = ~__mask; 492 *__pbmap &= __mask; 493 } 494 495 /** @brief Mark a memory address as free by setting the 496 * corresponding bit in the bit-map. 497 */ 498 inline void 499 __bit_free(std::size_t* __pbmap, std::size_t __pos) throw() 500 { 501 std::size_t __mask = 1 << __pos; 502 *__pbmap |= __mask; 503 } 504 } // namespace __detail 505 506 /** @brief Generic Version of the bsf instruction. 507 */ 508 inline std::size_t 509 _Bit_scan_forward(std::size_t __num) 510 { return static_cast<std::size_t>(__builtin_ctzl(__num)); } 511 512 /** @class free_list bitmap_allocator.h bitmap_allocator.h 513 * 514 * @brief The free list class for managing chunks of memory to be 515 * given to and returned by the bitmap_allocator. 516 */ 517 class free_list 518 { 519 public: 520 typedef std::size_t* value_type; 521 typedef __detail::__mini_vector<value_type> vector_type; 522 typedef vector_type::iterator iterator; 523 typedef __mutex __mutex_type; 524 525 private: 526 struct _LT_pointer_compare 527 { 528 bool 529 operator()(const std::size_t* __pui, 530 const std::size_t __cui) const throw() 531 { return *__pui < __cui; } 532 }; 533 534 #if defined __GTHREADS 535 __mutex_type& 536 _M_get_mutex() 537 { 538 static __mutex_type _S_mutex; 539 return _S_mutex; 540 } 541 #endif 542 543 vector_type& 544 _M_get_free_list() 545 { 546 static vector_type _S_free_list; 547 return _S_free_list; 548 } 549 550 /** @brief Performs validation of memory based on their size. 551 * 552 * @param __addr The pointer to the memory block to be 553 * validated. 554 * 555 * Validates the memory block passed to this function and 556 * appropriately performs the action of managing the free list of 557 * blocks by adding this block to the free list or deleting this 558 * or larger blocks from the free list. 559 */ 560 void 561 _M_validate(std::size_t* __addr) throw() 562 { 563 vector_type& __free_list = _M_get_free_list(); 564 const vector_type::size_type __max_size = 64; 565 if (__free_list.size() >= __max_size) 566 { 567 // Ok, the threshold value has been reached. We determine 568 // which block to remove from the list of free blocks. 569 if (*__addr >= *__free_list.back()) 570 { 571 // Ok, the new block is greater than or equal to the 572 // last block in the list of free blocks. We just free 573 // the new block. 574 ::operator delete(static_cast<void*>(__addr)); 575 return; 576 } 577 else 578 { 579 // Deallocate the last block in the list of free lists, 580 // and insert the new one in its correct position. 581 ::operator delete(static_cast<void*>(__free_list.back())); 582 __free_list.pop_back(); 583 } 584 } 585 586 // Just add the block to the list of free lists unconditionally. 587 iterator __temp = __detail::__lower_bound 588 (__free_list.begin(), __free_list.end(), 589 *__addr, _LT_pointer_compare()); 590 591 // We may insert the new free list before _temp; 592 __free_list.insert(__temp, __addr); 593 } 594 595 /** @brief Decides whether the wastage of memory is acceptable for 596 * the current memory request and returns accordingly. 597 * 598 * @param __block_size The size of the block available in the free 599 * list. 600 * 601 * @param __required_size The required size of the memory block. 602 * 603 * @return true if the wastage incurred is acceptable, else returns 604 * false. 605 */ 606 bool 607 _M_should_i_give(std::size_t __block_size, 608 std::size_t __required_size) throw() 609 { 610 const std::size_t __max_wastage_percentage = 36; 611 if (__block_size >= __required_size && 612 (((__block_size - __required_size) * 100 / __block_size) 613 < __max_wastage_percentage)) 614 return true; 615 else 616 return false; 617 } 618 619 public: 620 /** @brief This function returns the block of memory to the 621 * internal free list. 622 * 623 * @param __addr The pointer to the memory block that was given 624 * by a call to the _M_get function. 625 */ 626 inline void 627 _M_insert(std::size_t* __addr) throw() 628 { 629 #if defined __GTHREADS 630 __scoped_lock __bfl_lock(_M_get_mutex()); 631 #endif 632 // Call _M_validate to decide what should be done with 633 // this particular free list. 634 this->_M_validate(reinterpret_cast<std::size_t*>(__addr) - 1); 635 // See discussion as to why this is 1! 636 } 637 638 /** @brief This function gets a block of memory of the specified 639 * size from the free list. 640 * 641 * @param __sz The size in bytes of the memory required. 642 * 643 * @return A pointer to the new memory block of size at least 644 * equal to that requested. 645 */ 646 std::size_t* 647 _M_get(std::size_t __sz) _GLIBCXX_THROW(std::bad_alloc); 648 649 /** @brief This function just clears the internal Free List, and 650 * gives back all the memory to the OS. 651 */ 652 void 653 _M_clear(); 654 }; 655 656 657 // Forward declare the class. 658 template<typename _Tp> 659 class bitmap_allocator; 660 661 // Specialize for void: 662 template<> 663 class bitmap_allocator<void> 664 { 665 public: 666 typedef void* pointer; 667 typedef const void* const_pointer; 668 669 // Reference-to-void members are impossible. 670 typedef void value_type; 671 template<typename _Tp1> 672 struct rebind 673 { 674 typedef bitmap_allocator<_Tp1> other; 675 }; 676 }; 677 678 /** 679 * @brief Bitmap Allocator, primary template. 680 * @ingroup allocators 681 */ 682 template<typename _Tp> 683 class bitmap_allocator : private free_list 684 { 685 public: 686 typedef std::size_t size_type; 687 typedef std::ptrdiff_t difference_type; 688 typedef _Tp* pointer; 689 typedef const _Tp* const_pointer; 690 typedef _Tp& reference; 691 typedef const _Tp& const_reference; 692 typedef _Tp value_type; 693 typedef free_list::__mutex_type __mutex_type; 694 695 template<typename _Tp1> 696 struct rebind 697 { 698 typedef bitmap_allocator<_Tp1> other; 699 }; 700 701 #if __cplusplus >= 201103L 702 // _GLIBCXX_RESOLVE_LIB_DEFECTS 703 // 2103. propagate_on_container_move_assignment 704 typedef std::true_type propagate_on_container_move_assignment; 705 #endif 706 707 private: 708 template<std::size_t _BSize, std::size_t _AlignSize> 709 struct aligned_size 710 { 711 enum 712 { 713 modulus = _BSize % _AlignSize, 714 value = _BSize + (modulus ? _AlignSize - (modulus) : 0) 715 }; 716 }; 717 718 struct _Alloc_block 719 { 720 char __M_unused[aligned_size<sizeof(value_type), 721 _BALLOC_ALIGN_BYTES>::value]; 722 }; 723 724 725 typedef typename std::pair<_Alloc_block*, _Alloc_block*> _Block_pair; 726 727 typedef typename __detail::__mini_vector<_Block_pair> _BPVector; 728 typedef typename _BPVector::iterator _BPiter; 729 730 template<typename _Predicate> 731 static _BPiter 732 _S_find(_Predicate __p) 733 { 734 _BPiter __first = _S_mem_blocks.begin(); 735 while (__first != _S_mem_blocks.end() && !__p(*__first)) 736 ++__first; 737 return __first; 738 } 739 740 #if defined _GLIBCXX_DEBUG 741 // Complexity: O(lg(N)). Where, N is the number of block of size 742 // sizeof(value_type). 743 void 744 _S_check_for_free_blocks() throw() 745 { 746 typedef typename __detail::_Ffit_finder<_Alloc_block*> _FFF; 747 _BPiter __bpi = _S_find(_FFF()); 748 749 _GLIBCXX_DEBUG_ASSERT(__bpi == _S_mem_blocks.end()); 750 } 751 #endif 752 753 /** @brief Responsible for exponentially growing the internal 754 * memory pool. 755 * 756 * @throw std::bad_alloc. If memory cannot be allocated. 757 * 758 * Complexity: O(1), but internally depends upon the 759 * complexity of the function free_list::_M_get. The part where 760 * the bitmap headers are written has complexity: O(X),where X 761 * is the number of blocks of size sizeof(value_type) within 762 * the newly acquired block. Having a tight bound. 763 */ 764 void 765 _S_refill_pool() _GLIBCXX_THROW(std::bad_alloc) 766 { 767 using std::size_t; 768 #if defined _GLIBCXX_DEBUG 769 _S_check_for_free_blocks(); 770 #endif 771 772 const size_t __num_bitmaps = (_S_block_size 773 / size_t(__detail::bits_per_block)); 774 const size_t __size_to_allocate = sizeof(size_t) 775 + _S_block_size * sizeof(_Alloc_block) 776 + __num_bitmaps * sizeof(size_t); 777 778 size_t* __temp = 779 reinterpret_cast<size_t*>(this->_M_get(__size_to_allocate)); 780 *__temp = 0; 781 ++__temp; 782 783 // The Header information goes at the Beginning of the Block. 784 _Block_pair __bp = 785 std::make_pair(reinterpret_cast<_Alloc_block*> 786 (__temp + __num_bitmaps), 787 reinterpret_cast<_Alloc_block*> 788 (__temp + __num_bitmaps) 789 + _S_block_size - 1); 790 791 // Fill the Vector with this information. 792 _S_mem_blocks.push_back(__bp); 793 794 for (size_t __i = 0; __i < __num_bitmaps; ++__i) 795 __temp[__i] = ~static_cast<size_t>(0); // 1 Indicates all Free. 796 797 _S_block_size *= 2; 798 } 799 800 static _BPVector _S_mem_blocks; 801 static std::size_t _S_block_size; 802 static __detail::_Bitmap_counter<_Alloc_block*> _S_last_request; 803 static typename _BPVector::size_type _S_last_dealloc_index; 804 #if defined __GTHREADS 805 static __mutex_type _S_mut; 806 #endif 807 808 public: 809 810 /** @brief Allocates memory for a single object of size 811 * sizeof(_Tp). 812 * 813 * @throw std::bad_alloc. If memory cannot be allocated. 814 * 815 * Complexity: Worst case complexity is O(N), but that 816 * is hardly ever hit. If and when this particular case is 817 * encountered, the next few cases are guaranteed to have a 818 * worst case complexity of O(1)! That's why this function 819 * performs very well on average. You can consider this 820 * function to have a complexity referred to commonly as: 821 * Amortized Constant time. 822 */ 823 pointer 824 _M_allocate_single_object() _GLIBCXX_THROW(std::bad_alloc) 825 { 826 using std::size_t; 827 #if defined __GTHREADS 828 __scoped_lock __bit_lock(_S_mut); 829 #endif 830 831 // The algorithm is something like this: The last_request 832 // variable points to the last accessed Bit Map. When such a 833 // condition occurs, we try to find a free block in the 834 // current bitmap, or succeeding bitmaps until the last bitmap 835 // is reached. If no free block turns up, we resort to First 836 // Fit method. 837 838 // WARNING: Do not re-order the condition in the while 839 // statement below, because it relies on C++'s short-circuit 840 // evaluation. The return from _S_last_request->_M_get() will 841 // NOT be dereference able if _S_last_request->_M_finished() 842 // returns true. This would inevitably lead to a NULL pointer 843 // dereference if tinkered with. 844 while (_S_last_request._M_finished() == false 845 && (*(_S_last_request._M_get()) == 0)) 846 _S_last_request.operator++(); 847 848 if (__builtin_expect(_S_last_request._M_finished() == true, false)) 849 { 850 // Fall Back to First Fit algorithm. 851 typedef typename __detail::_Ffit_finder<_Alloc_block*> _FFF; 852 _FFF __fff; 853 _BPiter __bpi = _S_find(__detail::_Functor_Ref<_FFF>(__fff)); 854 855 if (__bpi != _S_mem_blocks.end()) 856 { 857 // Search was successful. Ok, now mark the first bit from 858 // the right as 0, meaning Allocated. This bit is obtained 859 // by calling _M_get() on __fff. 860 size_t __nz_bit = _Bit_scan_forward(*__fff._M_get()); 861 __detail::__bit_allocate(__fff._M_get(), __nz_bit); 862 863 _S_last_request._M_reset(__bpi - _S_mem_blocks.begin()); 864 865 // Now, get the address of the bit we marked as allocated. 866 pointer __ret = reinterpret_cast<pointer> 867 (__bpi->first + __fff._M_offset() + __nz_bit); 868 size_t* __puse_count = 869 reinterpret_cast<size_t*> 870 (__bpi->first) - (__detail::__num_bitmaps(*__bpi) + 1); 871 872 ++(*__puse_count); 873 return __ret; 874 } 875 else 876 { 877 // Search was unsuccessful. We Add more memory to the 878 // pool by calling _S_refill_pool(). 879 _S_refill_pool(); 880 881 // _M_Reset the _S_last_request structure to the first 882 // free block's bit map. 883 _S_last_request._M_reset(_S_mem_blocks.size() - 1); 884 885 // Now, mark that bit as allocated. 886 } 887 } 888 889 // _S_last_request holds a pointer to a valid bit map, that 890 // points to a free block in memory. 891 size_t __nz_bit = _Bit_scan_forward(*_S_last_request._M_get()); 892 __detail::__bit_allocate(_S_last_request._M_get(), __nz_bit); 893 894 pointer __ret = reinterpret_cast<pointer> 895 (_S_last_request._M_base() + _S_last_request._M_offset() + __nz_bit); 896 897 size_t* __puse_count = reinterpret_cast<size_t*> 898 (_S_mem_blocks[_S_last_request._M_where()].first) 899 - (__detail:: 900 __num_bitmaps(_S_mem_blocks[_S_last_request._M_where()]) + 1); 901 902 ++(*__puse_count); 903 return __ret; 904 } 905 906 /** @brief Deallocates memory that belongs to a single object of 907 * size sizeof(_Tp). 908 * 909 * Complexity: O(lg(N)), but the worst case is not hit 910 * often! This is because containers usually deallocate memory 911 * close to each other and this case is handled in O(1) time by 912 * the deallocate function. 913 */ 914 void 915 _M_deallocate_single_object(pointer __p) throw() 916 { 917 using std::size_t; 918 #if defined __GTHREADS 919 __scoped_lock __bit_lock(_S_mut); 920 #endif 921 _Alloc_block* __real_p = reinterpret_cast<_Alloc_block*>(__p); 922 923 typedef typename _BPVector::iterator _Iterator; 924 typedef typename _BPVector::difference_type _Difference_type; 925 926 _Difference_type __diff; 927 long __displacement; 928 929 _GLIBCXX_DEBUG_ASSERT(_S_last_dealloc_index >= 0); 930 931 __detail::_Inclusive_between<_Alloc_block*> __ibt(__real_p); 932 if (__ibt(_S_mem_blocks[_S_last_dealloc_index])) 933 { 934 _GLIBCXX_DEBUG_ASSERT(_S_last_dealloc_index 935 <= _S_mem_blocks.size() - 1); 936 937 // Initial Assumption was correct! 938 __diff = _S_last_dealloc_index; 939 __displacement = __real_p - _S_mem_blocks[__diff].first; 940 } 941 else 942 { 943 _Iterator _iter = _S_find(__ibt); 944 945 _GLIBCXX_DEBUG_ASSERT(_iter != _S_mem_blocks.end()); 946 947 __diff = _iter - _S_mem_blocks.begin(); 948 __displacement = __real_p - _S_mem_blocks[__diff].first; 949 _S_last_dealloc_index = __diff; 950 } 951 952 // Get the position of the iterator that has been found. 953 const size_t __rotate = (__displacement 954 % size_t(__detail::bits_per_block)); 955 size_t* __bitmapC = 956 reinterpret_cast<size_t*> 957 (_S_mem_blocks[__diff].first) - 1; 958 __bitmapC -= (__displacement / size_t(__detail::bits_per_block)); 959 960 __detail::__bit_free(__bitmapC, __rotate); 961 size_t* __puse_count = reinterpret_cast<size_t*> 962 (_S_mem_blocks[__diff].first) 963 - (__detail::__num_bitmaps(_S_mem_blocks[__diff]) + 1); 964 965 _GLIBCXX_DEBUG_ASSERT(*__puse_count != 0); 966 967 --(*__puse_count); 968 969 if (__builtin_expect(*__puse_count == 0, false)) 970 { 971 _S_block_size /= 2; 972 973 // We can safely remove this block. 974 // _Block_pair __bp = _S_mem_blocks[__diff]; 975 this->_M_insert(__puse_count); 976 _S_mem_blocks.erase(_S_mem_blocks.begin() + __diff); 977 978 // Reset the _S_last_request variable to reflect the 979 // erased block. We do this to protect future requests 980 // after the last block has been removed from a particular 981 // memory Chunk, which in turn has been returned to the 982 // free list, and hence had been erased from the vector, 983 // so the size of the vector gets reduced by 1. 984 if ((_Difference_type)_S_last_request._M_where() >= __diff--) 985 _S_last_request._M_reset(__diff); 986 987 // If the Index into the vector of the region of memory 988 // that might hold the next address that will be passed to 989 // deallocated may have been invalidated due to the above 990 // erase procedure being called on the vector, hence we 991 // try to restore this invariant too. 992 if (_S_last_dealloc_index >= _S_mem_blocks.size()) 993 { 994 _S_last_dealloc_index =(__diff != -1 ? __diff : 0); 995 _GLIBCXX_DEBUG_ASSERT(_S_last_dealloc_index >= 0); 996 } 997 } 998 } 999 1000 public: 1001 bitmap_allocator() _GLIBCXX_USE_NOEXCEPT 1002 { } 1003 1004 bitmap_allocator(const bitmap_allocator&) _GLIBCXX_USE_NOEXCEPT 1005 { } 1006 1007 template<typename _Tp1> 1008 bitmap_allocator(const bitmap_allocator<_Tp1>&) _GLIBCXX_USE_NOEXCEPT 1009 { } 1010 1011 ~bitmap_allocator() _GLIBCXX_USE_NOEXCEPT 1012 { } 1013 1014 _GLIBCXX_NODISCARD pointer 1015 allocate(size_type __n) 1016 { 1017 if (__n > this->max_size()) 1018 std::__throw_bad_alloc(); 1019 1020 #if __cpp_aligned_new 1021 if (alignof(value_type) > __STDCPP_DEFAULT_NEW_ALIGNMENT__) 1022 { 1023 const size_type __b = __n * sizeof(value_type); 1024 std::align_val_t __al = std::align_val_t(alignof(value_type)); 1025 return static_cast<pointer>(::operator new(__b, __al)); 1026 } 1027 #endif 1028 1029 if (__builtin_expect(__n == 1, true)) 1030 return this->_M_allocate_single_object(); 1031 else 1032 { 1033 const size_type __b = __n * sizeof(value_type); 1034 return reinterpret_cast<pointer>(::operator new(__b)); 1035 } 1036 } 1037 1038 _GLIBCXX_NODISCARD pointer 1039 allocate(size_type __n, typename bitmap_allocator<void>::const_pointer) 1040 { return allocate(__n); } 1041 1042 void 1043 deallocate(pointer __p, size_type __n) throw() 1044 { 1045 if (__builtin_expect(__p != 0, true)) 1046 { 1047 #if __cpp_aligned_new 1048 // Types with extended alignment are handled by operator delete. 1049 if (alignof(value_type) > __STDCPP_DEFAULT_NEW_ALIGNMENT__) 1050 { 1051 ::operator delete(__p, std::align_val_t(alignof(value_type))); 1052 return; 1053 } 1054 #endif 1055 1056 if (__builtin_expect(__n == 1, true)) 1057 this->_M_deallocate_single_object(__p); 1058 else 1059 ::operator delete(__p); 1060 } 1061 } 1062 1063 pointer 1064 address(reference __r) const _GLIBCXX_NOEXCEPT 1065 { return std::__addressof(__r); } 1066 1067 const_pointer 1068 address(const_reference __r) const _GLIBCXX_NOEXCEPT 1069 { return std::__addressof(__r); } 1070 1071 size_type 1072 max_size() const _GLIBCXX_USE_NOEXCEPT 1073 { return size_type(-1) / sizeof(value_type); } 1074 1075 #if __cplusplus >= 201103L 1076 template<typename _Up, typename... _Args> 1077 void 1078 construct(_Up* __p, _Args&&... __args) 1079 { ::new((void *)__p) _Up(std::forward<_Args>(__args)...); } 1080 1081 template<typename _Up> 1082 void 1083 destroy(_Up* __p) 1084 { __p->~_Up(); } 1085 #else 1086 void 1087 construct(pointer __p, const_reference __data) 1088 { ::new((void *)__p) value_type(__data); } 1089 1090 void 1091 destroy(pointer __p) 1092 { __p->~value_type(); } 1093 #endif 1094 }; 1095 1096 template<typename _Tp1, typename _Tp2> 1097 bool 1098 operator==(const bitmap_allocator<_Tp1>&, 1099 const bitmap_allocator<_Tp2>&) throw() 1100 { return true; } 1101 1102 #if __cpp_impl_three_way_comparison < 201907L 1103 template<typename _Tp1, typename _Tp2> 1104 bool 1105 operator!=(const bitmap_allocator<_Tp1>&, 1106 const bitmap_allocator<_Tp2>&) throw() 1107 { return false; } 1108 #endif 1109 1110 // Static member definitions. 1111 template<typename _Tp> 1112 typename bitmap_allocator<_Tp>::_BPVector 1113 bitmap_allocator<_Tp>::_S_mem_blocks; 1114 1115 template<typename _Tp> 1116 std::size_t bitmap_allocator<_Tp>::_S_block_size 1117 = 2 * std::size_t(__detail::bits_per_block); 1118 1119 template<typename _Tp> 1120 typename bitmap_allocator<_Tp>::_BPVector::size_type 1121 bitmap_allocator<_Tp>::_S_last_dealloc_index = 0; 1122 1123 template<typename _Tp> 1124 __detail::_Bitmap_counter 1125 <typename bitmap_allocator<_Tp>::_Alloc_block*> 1126 bitmap_allocator<_Tp>::_S_last_request(_S_mem_blocks); 1127 1128 #if defined __GTHREADS 1129 template<typename _Tp> 1130 typename bitmap_allocator<_Tp>::__mutex_type 1131 bitmap_allocator<_Tp>::_S_mut; 1132 #endif 1133 1134 _GLIBCXX_END_NAMESPACE_VERSION 1135 } // namespace __gnu_cxx 1136 1137 #endif
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