1// Bitmap Allocator. -*- C++ -*- 2 3// Copyright (C) 2004, 2005, 2006 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 2, 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// You should have received a copy of the GNU General Public License along 17// with this library; see the file COPYING. If not, write to the Free 18// Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, 19// USA. 20 21// As a special exception, you may use this file as part of a free software 22// library without restriction. Specifically, if other files instantiate 23// templates or use macros or inline functions from this file, or you compile 24// this file and link it with other files to produce an executable, this 25// file does not by itself cause the resulting executable to be covered by 26// the GNU General Public License. This exception does not however 27// invalidate any other reasons why the executable file might be covered by 28// the GNU General Public License. 29 30/** @file ext/bitmap_allocator.h 31 * This file is a GNU extension to the Standard C++ Library. 32 */ 33 34#ifndef _BITMAP_ALLOCATOR_H 35#define _BITMAP_ALLOCATOR_H 1 36 37#include <cstddef> // For std::size_t, and ptrdiff_t. 38#include <bits/functexcept.h> // For __throw_bad_alloc(). 39#include <utility> // For std::pair. 40#include <functional> // For greater_equal, and less_equal. 41#include <new> // For operator new. 42#include <debug/debug.h> // _GLIBCXX_DEBUG_ASSERT 43#include <ext/concurrence.h> 44 45 46/** @brief The constant in the expression below is the alignment 47 * required in bytes. 48 */ 49#define _BALLOC_ALIGN_BYTES 8 50 51_GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx) 52 53 using std::size_t; 54 using std::ptrdiff_t; 55 56 namespace __detail 57 { 58 /** @class __mini_vector bitmap_allocator.h bitmap_allocator.h 59 * 60 * @brief __mini_vector<> is a stripped down version of the 61 * full-fledged std::vector<>. 62 * 63 * It is to be used only for built-in types or PODs. Notable 64 * differences are: 65 * 66 * @detail 67 * 1. Not all accessor functions are present. 68 * 2. Used ONLY for PODs. 69 * 3. No Allocator template argument. Uses ::operator new() to get 70 * memory, and ::operator delete() to free it. 71 * Caveat: The dtor does NOT free the memory allocated, so this a 72 * memory-leaking vector! 73 */ 74 template<typename _Tp> 75 class __mini_vector 76 { 77 __mini_vector(const __mini_vector&); 78 __mini_vector& operator=(const __mini_vector&); 79 80 public: 81 typedef _Tp value_type; 82 typedef _Tp* pointer; 83 typedef _Tp& reference; 84 typedef const _Tp& const_reference; 85 typedef size_t size_type; 86 typedef ptrdiff_t difference_type; 87 typedef pointer iterator; 88 89 private: 90 pointer _M_start; 91 pointer _M_finish; 92 pointer _M_end_of_storage; 93 94 size_type 95 _M_space_left() const throw() 96 { return _M_end_of_storage - _M_finish; } 97 98 pointer 99 allocate(size_type __n) 100 { return static_cast<pointer>(::operator new(__n * sizeof(_Tp))); } 101 102 void 103 deallocate(pointer __p, size_type) 104 { ::operator delete(__p); } 105 106 public: 107 // Members used: size(), push_back(), pop_back(), 108 // insert(iterator, const_reference), erase(iterator), 109 // begin(), end(), back(), operator[]. 110 111 __mini_vector() : _M_start(0), _M_finish(0), 112 _M_end_of_storage(0) 113 { } 114 115#if 0 116 ~__mini_vector() 117 { 118 if (this->_M_start) 119 { 120 this->deallocate(this->_M_start, this->_M_end_of_storage 121 - this->_M_start); 122 } 123 } 124#endif 125 126 size_type 127 size() const throw() 128 { return _M_finish - _M_start; } 129 130 iterator 131 begin() const throw() 132 { return this->_M_start; } 133 134 iterator 135 end() const throw() 136 { return this->_M_finish; } 137 138 reference 139 back() const throw() 140 { return *(this->end() - 1); } 141 142 reference 143 operator[](const size_type __pos) const throw() 144 { return this->_M_start[__pos]; } 145 146 void 147 insert(iterator __pos, const_reference __x); 148 149 void 150 push_back(const_reference __x) 151 { 152 if (this->_M_space_left()) 153 { 154 *this->end() = __x; 155 ++this->_M_finish; 156 } 157 else 158 this->insert(this->end(), __x); 159 } 160 161 void 162 pop_back() throw() 163 { --this->_M_finish; } 164 165 void 166 erase(iterator __pos) throw(); 167 168 void 169 clear() throw() 170 { this->_M_finish = this->_M_start; } 171 }; 172 173 // Out of line function definitions. 174 template<typename _Tp> 175 void __mini_vector<_Tp>:: 176 insert(iterator __pos, const_reference __x) 177 { 178 if (this->_M_space_left()) 179 { 180 size_type __to_move = this->_M_finish - __pos; 181 iterator __dest = this->end(); 182 iterator __src = this->end() - 1; 183 184 ++this->_M_finish; 185 while (__to_move) 186 { 187 *__dest = *__src; 188 --__dest; --__src; --__to_move; 189 } 190 *__pos = __x; 191 } 192 else 193 { 194 size_type __new_size = this->size() ? this->size() * 2 : 1; 195 iterator __new_start = this->allocate(__new_size); 196 iterator __first = this->begin(); 197 iterator __start = __new_start; 198 while (__first != __pos) 199 { 200 *__start = *__first; 201 ++__start; ++__first; 202 } 203 *__start = __x; 204 ++__start; 205 while (__first != this->end()) 206 { 207 *__start = *__first; 208 ++__start; ++__first; 209 } 210 if (this->_M_start) 211 this->deallocate(this->_M_start, this->size()); 212 213 this->_M_start = __new_start; 214 this->_M_finish = __start; 215 this->_M_end_of_storage = this->_M_start + __new_size; 216 } 217 } 218 219 template<typename _Tp> 220 void __mini_vector<_Tp>:: 221 erase(iterator __pos) throw() 222 { 223 while (__pos + 1 != this->end()) 224 { 225 *__pos = __pos[1]; 226 ++__pos; 227 } 228 --this->_M_finish; 229 } 230 231 232 template<typename _Tp> 233 struct __mv_iter_traits 234 { 235 typedef typename _Tp::value_type value_type; 236 typedef typename _Tp::difference_type difference_type; 237 }; 238 239 template<typename _Tp> 240 struct __mv_iter_traits<_Tp*> 241 { 242 typedef _Tp value_type; 243 typedef ptrdiff_t difference_type; 244 }; 245 246 enum 247 { 248 bits_per_byte = 8, 249 bits_per_block = sizeof(size_t) * size_t(bits_per_byte) 250 }; 251 252 template<typename _ForwardIterator, typename _Tp, typename _Compare> 253 _ForwardIterator 254 __lower_bound(_ForwardIterator __first, _ForwardIterator __last, 255 const _Tp& __val, _Compare __comp) 256 { 257 typedef typename __mv_iter_traits<_ForwardIterator>::value_type 258 _ValueType; 259 typedef typename __mv_iter_traits<_ForwardIterator>::difference_type 260 _DistanceType; 261 262 _DistanceType __len = __last - __first; 263 _DistanceType __half; 264 _ForwardIterator __middle; 265 266 while (__len > 0) 267 { 268 __half = __len >> 1; 269 __middle = __first; 270 __middle += __half; 271 if (__comp(*__middle, __val)) 272 { 273 __first = __middle; 274 ++__first; 275 __len = __len - __half - 1; 276 } 277 else 278 __len = __half; 279 } 280 return __first; 281 } 282 283 template<typename _InputIterator, typename _Predicate> 284 inline _InputIterator 285 __find_if(_InputIterator __first, _InputIterator __last, _Predicate __p) 286 { 287 while (__first != __last && !__p(*__first)) 288 ++__first; 289 return __first; 290 } 291 292 /** @brief The number of Blocks pointed to by the address pair 293 * passed to the function. 294 */ 295 template<typename _AddrPair> 296 inline size_t 297 __num_blocks(_AddrPair __ap) 298 { return (__ap.second - __ap.first) + 1; } 299 300 /** @brief The number of Bit-maps pointed to by the address pair 301 * passed to the function. 302 */ 303 template<typename _AddrPair> 304 inline size_t 305 __num_bitmaps(_AddrPair __ap) 306 { return __num_blocks(__ap) / size_t(bits_per_block); } 307 308 // _Tp should be a pointer type. 309 template<typename _Tp> 310 class _Inclusive_between 311 : public std::unary_function<typename std::pair<_Tp, _Tp>, bool> 312 { 313 typedef _Tp pointer; 314 pointer _M_ptr_value; 315 typedef typename std::pair<_Tp, _Tp> _Block_pair; 316 317 public: 318 _Inclusive_between(pointer __ptr) : _M_ptr_value(__ptr) 319 { } 320 321 bool 322 operator()(_Block_pair __bp) const throw() 323 { 324 if (std::less_equal<pointer>()(_M_ptr_value, __bp.second) 325 && std::greater_equal<pointer>()(_M_ptr_value, __bp.first)) 326 return true; 327 else 328 return false; 329 } 330 }; 331 332 // Used to pass a Functor to functions by reference. 333 template<typename _Functor> 334 class _Functor_Ref 335 : public std::unary_function<typename _Functor::argument_type, 336 typename _Functor::result_type> 337 { 338 _Functor& _M_fref; 339 340 public: 341 typedef typename _Functor::argument_type argument_type; 342 typedef typename _Functor::result_type result_type; 343 344 _Functor_Ref(_Functor& __fref) : _M_fref(__fref) 345 { } 346 347 result_type 348 operator()(argument_type __arg) 349 { return _M_fref(__arg); } 350 }; 351 352 /** @class _Ffit_finder bitmap_allocator.h bitmap_allocator.h 353 * 354 * @brief The class which acts as a predicate for applying the 355 * first-fit memory allocation policy for the bitmap allocator. 356 */ 357 // _Tp should be a pointer type, and _Alloc is the Allocator for 358 // the vector. 359 template<typename _Tp> 360 class _Ffit_finder 361 : public std::unary_function<typename std::pair<_Tp, _Tp>, bool> 362 { 363 typedef typename std::pair<_Tp, _Tp> _Block_pair; 364 typedef typename __detail::__mini_vector<_Block_pair> _BPVector; 365 typedef typename _BPVector::difference_type _Counter_type; 366 367 size_t* _M_pbitmap; 368 _Counter_type _M_data_offset; 369 370 public: 371 _Ffit_finder() : _M_pbitmap(0), _M_data_offset(0) 372 { } 373 374 bool 375 operator()(_Block_pair __bp) throw() 376 { 377 // Set the _rover to the last physical location bitmap, 378 // which is the bitmap which belongs to the first free 379 // block. Thus, the bitmaps are in exact reverse order of 380 // the actual memory layout. So, we count down the bimaps, 381 // which is the same as moving up the memory. 382 383 // If the used count stored at the start of the Bit Map headers 384 // is equal to the number of Objects that the current Block can 385 // store, then there is definitely no space for another single 386 // object, so just return false. 387 _Counter_type __diff = 388 __gnu_cxx::__detail::__num_bitmaps(__bp); 389 390 if (*(reinterpret_cast<size_t*> 391 (__bp.first) - (__diff + 1)) 392 == __gnu_cxx::__detail::__num_blocks(__bp)) 393 return false; 394 395 size_t* __rover = reinterpret_cast<size_t*>(__bp.first) - 1; 396 397 for (_Counter_type __i = 0; __i < __diff; ++__i) 398 { 399 _M_data_offset = __i; 400 if (*__rover) 401 { 402 _M_pbitmap = __rover; 403 return true; 404 } 405 --__rover; 406 } 407 return false; 408 } 409 410 411 size_t* 412 _M_get() const throw() 413 { return _M_pbitmap; } 414 415 _Counter_type 416 _M_offset() const throw() 417 { return _M_data_offset * size_t(bits_per_block); } 418 }; 419 420 421 /** @class _Bitmap_counter bitmap_allocator.h bitmap_allocator.h 422 * 423 * @brief The bitmap counter which acts as the bitmap 424 * manipulator, and manages the bit-manipulation functions and 425 * the searching and identification functions on the bit-map. 426 */ 427 // _Tp should be a pointer type. 428 template<typename _Tp> 429 class _Bitmap_counter 430 { 431 typedef typename __detail::__mini_vector<typename std::pair<_Tp, _Tp> > 432 _BPVector; 433 typedef typename _BPVector::size_type _Index_type; 434 typedef _Tp pointer; 435 436 _BPVector& _M_vbp; 437 size_t* _M_curr_bmap; 438 size_t* _M_last_bmap_in_block; 439 _Index_type _M_curr_index; 440 441 public: 442 // Use the 2nd parameter with care. Make sure that such an 443 // entry exists in the vector before passing that particular 444 // index to this ctor. 445 _Bitmap_counter(_BPVector& Rvbp, long __index = -1) : _M_vbp(Rvbp) 446 { this->_M_reset(__index); } 447 448 void 449 _M_reset(long __index = -1) throw() 450 { 451 if (__index == -1) 452 { 453 _M_curr_bmap = 0; 454 _M_curr_index = static_cast<_Index_type>(-1); 455 return; 456 } 457 458 _M_curr_index = __index; 459 _M_curr_bmap = reinterpret_cast<size_t*> 460 (_M_vbp[_M_curr_index].first) - 1; 461 462 _GLIBCXX_DEBUG_ASSERT(__index <= (long)_M_vbp.size() - 1); 463 464 _M_last_bmap_in_block = _M_curr_bmap 465 - ((_M_vbp[_M_curr_index].second 466 - _M_vbp[_M_curr_index].first + 1) 467 / size_t(bits_per_block) - 1); 468 } 469 470 // Dangerous Function! Use with extreme care. Pass to this 471 // function ONLY those values that are known to be correct, 472 // otherwise this will mess up big time. 473 void 474 _M_set_internal_bitmap(size_t* __new_internal_marker) throw() 475 { _M_curr_bmap = __new_internal_marker; } 476 477 bool 478 _M_finished() const throw() 479 { return(_M_curr_bmap == 0); } 480 481 _Bitmap_counter& 482 operator++() throw() 483 { 484 if (_M_curr_bmap == _M_last_bmap_in_block) 485 { 486 if (++_M_curr_index == _M_vbp.size()) 487 _M_curr_bmap = 0; 488 else 489 this->_M_reset(_M_curr_index); 490 } 491 else 492 --_M_curr_bmap; 493 return *this; 494 } 495 496 size_t* 497 _M_get() const throw() 498 { return _M_curr_bmap; } 499 500 pointer 501 _M_base() const throw() 502 { return _M_vbp[_M_curr_index].first; } 503 504 _Index_type 505 _M_offset() const throw() 506 { 507 return size_t(bits_per_block) 508 * ((reinterpret_cast<size_t*>(this->_M_base()) 509 - _M_curr_bmap) - 1); 510 } 511 512 _Index_type 513 _M_where() const throw() 514 { return _M_curr_index; } 515 }; 516 517 /** @brief Mark a memory address as allocated by re-setting the 518 * corresponding bit in the bit-map. 519 */ 520 inline void 521 __bit_allocate(size_t* __pbmap, size_t __pos) throw() 522 { 523 size_t __mask = 1 << __pos; 524 __mask = ~__mask; 525 *__pbmap &= __mask; 526 } 527 528 /** @brief Mark a memory address as free by setting the 529 * corresponding bit in the bit-map. 530 */ 531 inline void 532 __bit_free(size_t* __pbmap, size_t __pos) throw() 533 { 534 size_t __mask = 1 << __pos; 535 *__pbmap |= __mask; 536 } 537 } // namespace __detail 538 539 /** @brief Generic Version of the bsf instruction. 540 */ 541 inline size_t 542 _Bit_scan_forward(size_t __num) 543 { return static_cast<size_t>(__builtin_ctzl(__num)); } 544 545 /** @class free_list bitmap_allocator.h bitmap_allocator.h 546 * 547 * @brief The free list class for managing chunks of memory to be 548 * given to and returned by the bitmap_allocator. 549 */ 550 class free_list 551 { 552 typedef size_t* value_type; 553 typedef __detail::__mini_vector<value_type> vector_type; 554 typedef vector_type::iterator iterator; 555protected: 556 typedef __mutex __mutex_type; 557private: 558 559 struct _LT_pointer_compare 560 { 561 bool 562 operator()(const size_t* __pui, 563 const size_t __cui) const throw() 564 { return *__pui < __cui; } 565 }; 566 567#if defined __GTHREADS 568 __mutex_type& 569 _M_get_mutex() 570 { 571 static __mutex_type _S_mutex; 572 return _S_mutex; 573 } 574#endif 575 576 vector_type& 577 _M_get_free_list() 578 { 579 static vector_type _S_free_list; 580 return _S_free_list; 581 } 582 583 /** @brief Performs validation of memory based on their size. 584 * 585 * @param __addr The pointer to the memory block to be 586 * validated. 587 * 588 * @detail Validates the memory block passed to this function and 589 * appropriately performs the action of managing the free list of 590 * blocks by adding this block to the free list or deleting this 591 * or larger blocks from the free list. 592 */ 593 void 594 _M_validate(size_t* __addr) throw() 595 { 596 vector_type& __free_list = _M_get_free_list(); 597 const vector_type::size_type __max_size = 64; 598 if (__free_list.size() >= __max_size) 599 { 600 // Ok, the threshold value has been reached. We determine 601 // which block to remove from the list of free blocks. 602 if (*__addr >= *__free_list.back()) 603 { 604 // Ok, the new block is greater than or equal to the 605 // last block in the list of free blocks. We just free 606 // the new block. 607 ::operator delete(static_cast<void*>(__addr)); 608 return; 609 } 610 else 611 { 612 // Deallocate the last block in the list of free lists, 613 // and insert the new one in it's correct position. 614 ::operator delete(static_cast<void*>(__free_list.back())); 615 __free_list.pop_back(); 616 } 617 } 618 619 // Just add the block to the list of free lists unconditionally. 620 iterator __temp = __gnu_cxx::__detail::__lower_bound 621 (__free_list.begin(), __free_list.end(), 622 *__addr, _LT_pointer_compare()); 623 624 // We may insert the new free list before _temp; 625 __free_list.insert(__temp, __addr); 626 } 627 628 /** @brief Decides whether the wastage of memory is acceptable for 629 * the current memory request and returns accordingly. 630 * 631 * @param __block_size The size of the block available in the free 632 * list. 633 * 634 * @param __required_size The required size of the memory block. 635 * 636 * @return true if the wastage incurred is acceptable, else returns 637 * false. 638 */ 639 bool 640 _M_should_i_give(size_t __block_size, 641 size_t __required_size) throw() 642 { 643 const size_t __max_wastage_percentage = 36; 644 if (__block_size >= __required_size && 645 (((__block_size - __required_size) * 100 / __block_size) 646 < __max_wastage_percentage)) 647 return true; 648 else 649 return false; 650 } 651 652 public: 653 /** @brief This function returns the block of memory to the 654 * internal free list. 655 * 656 * @param __addr The pointer to the memory block that was given 657 * by a call to the _M_get function. 658 */ 659 inline void 660 _M_insert(size_t* __addr) throw() 661 { 662#if defined __GTHREADS 663 __gnu_cxx::__scoped_lock __bfl_lock(_M_get_mutex()); 664#endif 665 // Call _M_validate to decide what should be done with 666 // this particular free list. 667 this->_M_validate(reinterpret_cast<size_t*>(__addr) - 1); 668 // See discussion as to why this is 1! 669 } 670 671 /** @brief This function gets a block of memory of the specified 672 * size from the free list. 673 * 674 * @param __sz The size in bytes of the memory required. 675 * 676 * @return A pointer to the new memory block of size at least 677 * equal to that requested. 678 */ 679 size_t* 680 _M_get(size_t __sz) throw(std::bad_alloc); 681 682 /** @brief This function just clears the internal Free List, and 683 * gives back all the memory to the OS. 684 */ 685 void 686 _M_clear(); 687 }; 688 689 690 // Forward declare the class. 691 template<typename _Tp> 692 class bitmap_allocator; 693 694 // Specialize for void: 695 template<> 696 class bitmap_allocator<void> 697 { 698 public: 699 typedef void* pointer; 700 typedef const void* const_pointer; 701 702 // Reference-to-void members are impossible. 703 typedef void value_type; 704 template<typename _Tp1> 705 struct rebind 706 { 707 typedef bitmap_allocator<_Tp1> other; 708 }; 709 }; 710 711 template<typename _Tp> 712 class bitmap_allocator : private free_list 713 { 714 public: 715 typedef size_t size_type; 716 typedef ptrdiff_t difference_type; 717 typedef _Tp* pointer; 718 typedef const _Tp* const_pointer; 719 typedef _Tp& reference; 720 typedef const _Tp& const_reference; 721 typedef _Tp value_type; 722 typedef free_list::__mutex_type __mutex_type; 723 724 template<typename _Tp1> 725 struct rebind 726 { 727 typedef bitmap_allocator<_Tp1> other; 728 }; 729 730 private: 731 template<size_t _BSize, size_t _AlignSize> 732 struct aligned_size 733 { 734 enum 735 { 736 modulus = _BSize % _AlignSize, 737 value = _BSize + (modulus ? _AlignSize - (modulus) : 0) 738 }; 739 }; 740 741 struct _Alloc_block 742 { 743 char __M_unused[aligned_size<sizeof(value_type), 744 _BALLOC_ALIGN_BYTES>::value]; 745 }; 746 747 748 typedef typename std::pair<_Alloc_block*, _Alloc_block*> _Block_pair; 749 750 typedef typename 751 __detail::__mini_vector<_Block_pair> _BPVector; 752 753#if defined _GLIBCXX_DEBUG 754 // Complexity: O(lg(N)). Where, N is the number of block of size 755 // sizeof(value_type). 756 void 757 _S_check_for_free_blocks() throw() 758 { 759 typedef typename 760 __gnu_cxx::__detail::_Ffit_finder<_Alloc_block*> _FFF; 761 _FFF __fff; 762 typedef typename _BPVector::iterator _BPiter; 763 _BPiter __bpi = 764 __gnu_cxx::__detail::__find_if 765 (_S_mem_blocks.begin(), _S_mem_blocks.end(), 766 __gnu_cxx::__detail::_Functor_Ref<_FFF>(__fff)); 767 768 _GLIBCXX_DEBUG_ASSERT(__bpi == _S_mem_blocks.end()); 769 } 770#endif 771 772 /** @brief Responsible for exponentially growing the internal 773 * memory pool. 774 * 775 * @throw std::bad_alloc. If memory can not be allocated. 776 * 777 * @detail Complexity: O(1), but internally depends upon the 778 * complexity of the function free_list::_M_get. The part where 779 * the bitmap headers are written has complexity: O(X),where X 780 * is the number of blocks of size sizeof(value_type) within 781 * the newly acquired block. Having a tight bound. 782 */ 783 void 784 _S_refill_pool() throw(std::bad_alloc) 785 { 786#if defined _GLIBCXX_DEBUG 787 _S_check_for_free_blocks(); 788#endif 789 790 const size_t __num_bitmaps = (_S_block_size 791 / size_t(__detail::bits_per_block)); 792 const size_t __size_to_allocate = sizeof(size_t) 793 + _S_block_size * sizeof(_Alloc_block) 794 + __num_bitmaps * sizeof(size_t); 795 796 size_t* __temp = 797 reinterpret_cast<size_t*> 798 (this->_M_get(__size_to_allocate)); 799 *__temp = 0; 800 ++__temp; 801 802 // The Header information goes at the Beginning of the Block. 803 _Block_pair __bp = 804 std::make_pair(reinterpret_cast<_Alloc_block*> 805 (__temp + __num_bitmaps), 806 reinterpret_cast<_Alloc_block*> 807 (__temp + __num_bitmaps) 808 + _S_block_size - 1); 809 810 // Fill the Vector with this information. 811 _S_mem_blocks.push_back(__bp); 812 813 size_t __bit_mask = 0; // 0 Indicates all Allocated. 814 __bit_mask = ~__bit_mask; // 1 Indicates all Free. 815 816 for (size_t __i = 0; __i < __num_bitmaps; ++__i) 817 __temp[__i] = __bit_mask; 818 819 _S_block_size *= 2; 820 } 821 822 823 static _BPVector _S_mem_blocks; 824 static size_t _S_block_size; 825 static __gnu_cxx::__detail:: 826 _Bitmap_counter<_Alloc_block*> _S_last_request; 827 static typename _BPVector::size_type _S_last_dealloc_index; 828#if defined __GTHREADS 829 static __mutex_type _S_mut; 830#endif 831 832 public: 833 834 /** @brief Allocates memory for a single object of size 835 * sizeof(_Tp). 836 * 837 * @throw std::bad_alloc. If memory can not be allocated. 838 * 839 * @detail Complexity: Worst case complexity is O(N), but that 840 * is hardly ever hit. If and when this particular case is 841 * encountered, the next few cases are guaranteed to have a 842 * worst case complexity of O(1)! That's why this function 843 * performs very well on average. You can consider this 844 * function to have a complexity referred to commonly as: 845 * Amortized Constant time. 846 */ 847 pointer 848 _M_allocate_single_object() throw(std::bad_alloc) 849 { 850#if defined __GTHREADS 851 __gnu_cxx::__scoped_lock __bit_lock(_S_mut); 852#endif 853 854 // The algorithm is something like this: The last_request 855 // variable points to the last accessed Bit Map. When such a 856 // condition occurs, we try to find a free block in the 857 // current bitmap, or succeeding bitmaps until the last bitmap 858 // is reached. If no free block turns up, we resort to First 859 // Fit method. 860 861 // WARNING: Do not re-order the condition in the while 862 // statement below, because it relies on C++'s short-circuit 863 // evaluation. The return from _S_last_request->_M_get() will 864 // NOT be dereference able if _S_last_request->_M_finished() 865 // returns true. This would inevitably lead to a NULL pointer 866 // dereference if tinkered with. 867 while (_S_last_request._M_finished() == false 868 && (*(_S_last_request._M_get()) == 0)) 869 { 870 _S_last_request.operator++(); 871 } 872 873 if (__builtin_expect(_S_last_request._M_finished() == true, false)) 874 { 875 // Fall Back to First Fit algorithm. 876 typedef typename 877 __gnu_cxx::__detail::_Ffit_finder<_Alloc_block*> _FFF; 878 _FFF __fff; 879 typedef typename _BPVector::iterator _BPiter; 880 _BPiter __bpi = 881 __gnu_cxx::__detail::__find_if 882 (_S_mem_blocks.begin(), _S_mem_blocks.end(), 883 __gnu_cxx::__detail::_Functor_Ref<_FFF>(__fff)); 884 885 if (__bpi != _S_mem_blocks.end()) 886 { 887 // Search was successful. Ok, now mark the first bit from 888 // the right as 0, meaning Allocated. This bit is obtained 889 // by calling _M_get() on __fff. 890 size_t __nz_bit = _Bit_scan_forward(*__fff._M_get()); 891 __detail::__bit_allocate(__fff._M_get(), __nz_bit); 892 893 _S_last_request._M_reset(__bpi - _S_mem_blocks.begin()); 894 895 // Now, get the address of the bit we marked as allocated. 896 pointer __ret = reinterpret_cast<pointer> 897 (__bpi->first + __fff._M_offset() + __nz_bit); 898 size_t* __puse_count = 899 reinterpret_cast<size_t*> 900 (__bpi->first) 901 - (__gnu_cxx::__detail::__num_bitmaps(*__bpi) + 1); 902 903 ++(*__puse_count); 904 return __ret; 905 } 906 else 907 { 908 // Search was unsuccessful. We Add more memory to the 909 // pool by calling _S_refill_pool(). 910 _S_refill_pool(); 911 912 // _M_Reset the _S_last_request structure to the first 913 // free block's bit map. 914 _S_last_request._M_reset(_S_mem_blocks.size() - 1); 915 916 // Now, mark that bit as allocated. 917 } 918 } 919 920 // _S_last_request holds a pointer to a valid bit map, that 921 // points to a free block in memory. 922 size_t __nz_bit = _Bit_scan_forward(*_S_last_request._M_get()); 923 __detail::__bit_allocate(_S_last_request._M_get(), __nz_bit); 924 925 pointer __ret = reinterpret_cast<pointer> 926 (_S_last_request._M_base() + _S_last_request._M_offset() + __nz_bit); 927 928 size_t* __puse_count = reinterpret_cast<size_t*> 929 (_S_mem_blocks[_S_last_request._M_where()].first) 930 - (__gnu_cxx::__detail:: 931 __num_bitmaps(_S_mem_blocks[_S_last_request._M_where()]) + 1); 932 933 ++(*__puse_count); 934 return __ret; 935 } 936 937 /** @brief Deallocates memory that belongs to a single object of 938 * size sizeof(_Tp). 939 * 940 * @detail Complexity: O(lg(N)), but the worst case is not hit 941 * often! This is because containers usually deallocate memory 942 * close to each other and this case is handled in O(1) time by 943 * the deallocate function. 944 */ 945 void 946 _M_deallocate_single_object(pointer __p) throw() 947 { 948#if defined __GTHREADS 949 __gnu_cxx::__scoped_lock __bit_lock(_S_mut); 950#endif 951 _Alloc_block* __real_p = reinterpret_cast<_Alloc_block*>(__p); 952 953 typedef typename _BPVector::iterator _Iterator; 954 typedef typename _BPVector::difference_type _Difference_type; 955 956 _Difference_type __diff; 957 long __displacement; 958 959 _GLIBCXX_DEBUG_ASSERT(_S_last_dealloc_index >= 0); 960 961 962 if (__gnu_cxx::__detail::_Inclusive_between<_Alloc_block*> 963 (__real_p) (_S_mem_blocks[_S_last_dealloc_index])) 964 { 965 _GLIBCXX_DEBUG_ASSERT(_S_last_dealloc_index 966 <= _S_mem_blocks.size() - 1); 967 968 // Initial Assumption was correct! 969 __diff = _S_last_dealloc_index; 970 __displacement = __real_p - _S_mem_blocks[__diff].first; 971 } 972 else 973 { 974 _Iterator _iter = __gnu_cxx::__detail:: 975 __find_if(_S_mem_blocks.begin(), 976 _S_mem_blocks.end(), 977 __gnu_cxx::__detail:: 978 _Inclusive_between<_Alloc_block*>(__real_p)); 979 980 _GLIBCXX_DEBUG_ASSERT(_iter != _S_mem_blocks.end()); 981 982 __diff = _iter - _S_mem_blocks.begin(); 983 __displacement = __real_p - _S_mem_blocks[__diff].first; 984 _S_last_dealloc_index = __diff; 985 } 986 987 // Get the position of the iterator that has been found. 988 const size_t __rotate = (__displacement 989 % size_t(__detail::bits_per_block)); 990 size_t* __bitmapC = 991 reinterpret_cast<size_t*> 992 (_S_mem_blocks[__diff].first) - 1; 993 __bitmapC -= (__displacement / size_t(__detail::bits_per_block)); 994 995 __detail::__bit_free(__bitmapC, __rotate); 996 size_t* __puse_count = reinterpret_cast<size_t*> 997 (_S_mem_blocks[__diff].first) 998 - (__gnu_cxx::__detail::__num_bitmaps(_S_mem_blocks[__diff]) + 1); 999 1000 _GLIBCXX_DEBUG_ASSERT(*__puse_count != 0); 1001 1002 --(*__puse_count); 1003 1004 if (__builtin_expect(*__puse_count == 0, false)) 1005 { 1006 _S_block_size /= 2; 1007 1008 // We can safely remove this block. 1009 // _Block_pair __bp = _S_mem_blocks[__diff]; 1010 this->_M_insert(__puse_count); 1011 _S_mem_blocks.erase(_S_mem_blocks.begin() + __diff); 1012 1013 // Reset the _S_last_request variable to reflect the 1014 // erased block. We do this to protect future requests 1015 // after the last block has been removed from a particular 1016 // memory Chunk, which in turn has been returned to the 1017 // free list, and hence had been erased from the vector, 1018 // so the size of the vector gets reduced by 1. 1019 if ((_Difference_type)_S_last_request._M_where() >= __diff--) 1020 _S_last_request._M_reset(__diff); 1021 1022 // If the Index into the vector of the region of memory 1023 // that might hold the next address that will be passed to 1024 // deallocated may have been invalidated due to the above 1025 // erase procedure being called on the vector, hence we 1026 // try to restore this invariant too. 1027 if (_S_last_dealloc_index >= _S_mem_blocks.size()) 1028 { 1029 _S_last_dealloc_index =(__diff != -1 ? __diff : 0); 1030 _GLIBCXX_DEBUG_ASSERT(_S_last_dealloc_index >= 0); 1031 } 1032 } 1033 } 1034 1035 public: 1036 bitmap_allocator() throw() 1037 { } 1038 1039 bitmap_allocator(const bitmap_allocator&) 1040 { } 1041 1042 template<typename _Tp1> 1043 bitmap_allocator(const bitmap_allocator<_Tp1>&) throw() 1044 { } 1045 1046 ~bitmap_allocator() throw() 1047 { } 1048 1049 pointer 1050 allocate(size_type __n) 1051 { 1052 if (__builtin_expect(__n > this->max_size(), false)) 1053 std::__throw_bad_alloc(); 1054 1055 if (__builtin_expect(__n == 1, true)) 1056 return this->_M_allocate_single_object(); 1057 else 1058 { 1059 const size_type __b = __n * sizeof(value_type); 1060 return reinterpret_cast<pointer>(::operator new(__b)); 1061 } 1062 } 1063 1064 pointer 1065 allocate(size_type __n, typename bitmap_allocator<void>::const_pointer) 1066 { return allocate(__n); } 1067 1068 void 1069 deallocate(pointer __p, size_type __n) throw() 1070 { 1071 if (__builtin_expect(__p != 0, true)) 1072 { 1073 if (__builtin_expect(__n == 1, true)) 1074 this->_M_deallocate_single_object(__p); 1075 else 1076 ::operator delete(__p); 1077 } 1078 } 1079 1080 pointer 1081 address(reference __r) const 1082 { return &__r; } 1083 1084 const_pointer 1085 address(const_reference __r) const 1086 { return &__r; } 1087 1088 size_type 1089 max_size() const throw() 1090 { return size_type(-1) / sizeof(value_type); } 1091 1092 void 1093 construct(pointer __p, const_reference __data) 1094 { ::new(__p) value_type(__data); } 1095 1096 void 1097 destroy(pointer __p) 1098 { __p->~value_type(); } 1099 }; 1100 1101 template<typename _Tp1, typename _Tp2> 1102 bool 1103 operator==(const bitmap_allocator<_Tp1>&, 1104 const bitmap_allocator<_Tp2>&) throw() 1105 { return true; } 1106 1107 template<typename _Tp1, typename _Tp2> 1108 bool 1109 operator!=(const bitmap_allocator<_Tp1>&, 1110 const bitmap_allocator<_Tp2>&) throw() 1111 { return false; } 1112 1113 // Static member definitions. 1114 template<typename _Tp> 1115 typename bitmap_allocator<_Tp>::_BPVector 1116 bitmap_allocator<_Tp>::_S_mem_blocks; 1117 1118 template<typename _Tp> 1119 size_t bitmap_allocator<_Tp>::_S_block_size = 1120 2 * size_t(__detail::bits_per_block); 1121 1122 template<typename _Tp> 1123 typename __gnu_cxx::bitmap_allocator<_Tp>::_BPVector::size_type 1124 bitmap_allocator<_Tp>::_S_last_dealloc_index = 0; 1125 1126 template<typename _Tp> 1127 __gnu_cxx::__detail::_Bitmap_counter 1128 <typename bitmap_allocator<_Tp>::_Alloc_block*> 1129 bitmap_allocator<_Tp>::_S_last_request(_S_mem_blocks); 1130 1131#if defined __GTHREADS 1132 template<typename _Tp> 1133 typename bitmap_allocator<_Tp>::__mutex_type 1134 bitmap_allocator<_Tp>::_S_mut; 1135#endif 1136 1137_GLIBCXX_END_NAMESPACE 1138 1139#endif 1140 1141