libstdc++
|
00001 // Bitmap Allocator. -*- C++ -*- 00002 00003 // Copyright (C) 2004-2013 Free Software Foundation, Inc. 00004 // 00005 // This file is part of the GNU ISO C++ Library. This library is free 00006 // software; you can redistribute it and/or modify it under the 00007 // terms of the GNU General Public License as published by the 00008 // Free Software Foundation; either version 3, or (at your option) 00009 // any later version. 00010 00011 // This library is distributed in the hope that it will be useful, 00012 // but WITHOUT ANY WARRANTY; without even the implied warranty of 00013 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 00014 // GNU General Public License for more details. 00015 00016 // Under Section 7 of GPL version 3, you are granted additional 00017 // permissions described in the GCC Runtime Library Exception, version 00018 // 3.1, as published by the Free Software Foundation. 00019 00020 // You should have received a copy of the GNU General Public License and 00021 // a copy of the GCC Runtime Library Exception along with this program; 00022 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 00023 // <http://www.gnu.org/licenses/>. 00024 00025 /** @file ext/bitmap_allocator.h 00026 * This file is a GNU extension to the Standard C++ Library. 00027 */ 00028 00029 #ifndef _BITMAP_ALLOCATOR_H 00030 #define _BITMAP_ALLOCATOR_H 1 00031 00032 #include <utility> // For std::pair. 00033 #include <bits/functexcept.h> // For __throw_bad_alloc(). 00034 #include <functional> // For greater_equal, and less_equal. 00035 #include <new> // For operator new. 00036 #include <debug/debug.h> // _GLIBCXX_DEBUG_ASSERT 00037 #include <ext/concurrence.h> 00038 #include <bits/move.h> 00039 00040 /** @brief The constant in the expression below is the alignment 00041 * required in bytes. 00042 */ 00043 #define _BALLOC_ALIGN_BYTES 8 00044 00045 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default) 00046 { 00047 using std::size_t; 00048 using std::ptrdiff_t; 00049 00050 namespace __detail 00051 { 00052 _GLIBCXX_BEGIN_NAMESPACE_VERSION 00053 /** @class __mini_vector bitmap_allocator.h bitmap_allocator.h 00054 * 00055 * @brief __mini_vector<> is a stripped down version of the 00056 * full-fledged std::vector<>. 00057 * 00058 * It is to be used only for built-in types or PODs. Notable 00059 * differences are: 00060 * 00061 * 1. Not all accessor functions are present. 00062 * 2. Used ONLY for PODs. 00063 * 3. No Allocator template argument. Uses ::operator new() to get 00064 * memory, and ::operator delete() to free it. 00065 * Caveat: The dtor does NOT free the memory allocated, so this a 00066 * memory-leaking vector! 00067 */ 00068 template<typename _Tp> 00069 class __mini_vector 00070 { 00071 __mini_vector(const __mini_vector&); 00072 __mini_vector& operator=(const __mini_vector&); 00073 00074 public: 00075 typedef _Tp value_type; 00076 typedef _Tp* pointer; 00077 typedef _Tp& reference; 00078 typedef const _Tp& const_reference; 00079 typedef size_t size_type; 00080 typedef ptrdiff_t difference_type; 00081 typedef pointer iterator; 00082 00083 private: 00084 pointer _M_start; 00085 pointer _M_finish; 00086 pointer _M_end_of_storage; 00087 00088 size_type 00089 _M_space_left() const throw() 00090 { return _M_end_of_storage - _M_finish; } 00091 00092 pointer 00093 allocate(size_type __n) 00094 { return static_cast<pointer>(::operator new(__n * sizeof(_Tp))); } 00095 00096 void 00097 deallocate(pointer __p, size_type) 00098 { ::operator delete(__p); } 00099 00100 public: 00101 // Members used: size(), push_back(), pop_back(), 00102 // insert(iterator, const_reference), erase(iterator), 00103 // begin(), end(), back(), operator[]. 00104 00105 __mini_vector() 00106 : _M_start(0), _M_finish(0), _M_end_of_storage(0) { } 00107 00108 size_type 00109 size() const throw() 00110 { return _M_finish - _M_start; } 00111 00112 iterator 00113 begin() const throw() 00114 { return this->_M_start; } 00115 00116 iterator 00117 end() const throw() 00118 { return this->_M_finish; } 00119 00120 reference 00121 back() const throw() 00122 { return *(this->end() - 1); } 00123 00124 reference 00125 operator[](const size_type __pos) const throw() 00126 { return this->_M_start[__pos]; } 00127 00128 void 00129 insert(iterator __pos, const_reference __x); 00130 00131 void 00132 push_back(const_reference __x) 00133 { 00134 if (this->_M_space_left()) 00135 { 00136 *this->end() = __x; 00137 ++this->_M_finish; 00138 } 00139 else 00140 this->insert(this->end(), __x); 00141 } 00142 00143 void 00144 pop_back() throw() 00145 { --this->_M_finish; } 00146 00147 void 00148 erase(iterator __pos) throw(); 00149 00150 void 00151 clear() throw() 00152 { this->_M_finish = this->_M_start; } 00153 }; 00154 00155 // Out of line function definitions. 00156 template<typename _Tp> 00157 void __mini_vector<_Tp>:: 00158 insert(iterator __pos, const_reference __x) 00159 { 00160 if (this->_M_space_left()) 00161 { 00162 size_type __to_move = this->_M_finish - __pos; 00163 iterator __dest = this->end(); 00164 iterator __src = this->end() - 1; 00165 00166 ++this->_M_finish; 00167 while (__to_move) 00168 { 00169 *__dest = *__src; 00170 --__dest; --__src; --__to_move; 00171 } 00172 *__pos = __x; 00173 } 00174 else 00175 { 00176 size_type __new_size = this->size() ? this->size() * 2 : 1; 00177 iterator __new_start = this->allocate(__new_size); 00178 iterator __first = this->begin(); 00179 iterator __start = __new_start; 00180 while (__first != __pos) 00181 { 00182 *__start = *__first; 00183 ++__start; ++__first; 00184 } 00185 *__start = __x; 00186 ++__start; 00187 while (__first != this->end()) 00188 { 00189 *__start = *__first; 00190 ++__start; ++__first; 00191 } 00192 if (this->_M_start) 00193 this->deallocate(this->_M_start, this->size()); 00194 00195 this->_M_start = __new_start; 00196 this->_M_finish = __start; 00197 this->_M_end_of_storage = this->_M_start + __new_size; 00198 } 00199 } 00200 00201 template<typename _Tp> 00202 void __mini_vector<_Tp>:: 00203 erase(iterator __pos) throw() 00204 { 00205 while (__pos + 1 != this->end()) 00206 { 00207 *__pos = __pos[1]; 00208 ++__pos; 00209 } 00210 --this->_M_finish; 00211 } 00212 00213 00214 template<typename _Tp> 00215 struct __mv_iter_traits 00216 { 00217 typedef typename _Tp::value_type value_type; 00218 typedef typename _Tp::difference_type difference_type; 00219 }; 00220 00221 template<typename _Tp> 00222 struct __mv_iter_traits<_Tp*> 00223 { 00224 typedef _Tp value_type; 00225 typedef ptrdiff_t difference_type; 00226 }; 00227 00228 enum 00229 { 00230 bits_per_byte = 8, 00231 bits_per_block = sizeof(size_t) * size_t(bits_per_byte) 00232 }; 00233 00234 template<typename _ForwardIterator, typename _Tp, typename _Compare> 00235 _ForwardIterator 00236 __lower_bound(_ForwardIterator __first, _ForwardIterator __last, 00237 const _Tp& __val, _Compare __comp) 00238 { 00239 typedef typename __mv_iter_traits<_ForwardIterator>::difference_type 00240 _DistanceType; 00241 00242 _DistanceType __len = __last - __first; 00243 _DistanceType __half; 00244 _ForwardIterator __middle; 00245 00246 while (__len > 0) 00247 { 00248 __half = __len >> 1; 00249 __middle = __first; 00250 __middle += __half; 00251 if (__comp(*__middle, __val)) 00252 { 00253 __first = __middle; 00254 ++__first; 00255 __len = __len - __half - 1; 00256 } 00257 else 00258 __len = __half; 00259 } 00260 return __first; 00261 } 00262 00263 /** @brief The number of Blocks pointed to by the address pair 00264 * passed to the function. 00265 */ 00266 template<typename _AddrPair> 00267 inline size_t 00268 __num_blocks(_AddrPair __ap) 00269 { return (__ap.second - __ap.first) + 1; } 00270 00271 /** @brief The number of Bit-maps pointed to by the address pair 00272 * passed to the function. 00273 */ 00274 template<typename _AddrPair> 00275 inline size_t 00276 __num_bitmaps(_AddrPair __ap) 00277 { return __num_blocks(__ap) / size_t(bits_per_block); } 00278 00279 // _Tp should be a pointer type. 00280 template<typename _Tp> 00281 class _Inclusive_between 00282 : public std::unary_function<typename std::pair<_Tp, _Tp>, bool> 00283 { 00284 typedef _Tp pointer; 00285 pointer _M_ptr_value; 00286 typedef typename std::pair<_Tp, _Tp> _Block_pair; 00287 00288 public: 00289 _Inclusive_between(pointer __ptr) : _M_ptr_value(__ptr) 00290 { } 00291 00292 bool 00293 operator()(_Block_pair __bp) const throw() 00294 { 00295 if (std::less_equal<pointer>()(_M_ptr_value, __bp.second) 00296 && std::greater_equal<pointer>()(_M_ptr_value, __bp.first)) 00297 return true; 00298 else 00299 return false; 00300 } 00301 }; 00302 00303 // Used to pass a Functor to functions by reference. 00304 template<typename _Functor> 00305 class _Functor_Ref 00306 : public std::unary_function<typename _Functor::argument_type, 00307 typename _Functor::result_type> 00308 { 00309 _Functor& _M_fref; 00310 00311 public: 00312 typedef typename _Functor::argument_type argument_type; 00313 typedef typename _Functor::result_type result_type; 00314 00315 _Functor_Ref(_Functor& __fref) : _M_fref(__fref) 00316 { } 00317 00318 result_type 00319 operator()(argument_type __arg) 00320 { return _M_fref(__arg); } 00321 }; 00322 00323 /** @class _Ffit_finder bitmap_allocator.h bitmap_allocator.h 00324 * 00325 * @brief The class which acts as a predicate for applying the 00326 * first-fit memory allocation policy for the bitmap allocator. 00327 */ 00328 // _Tp should be a pointer type, and _Alloc is the Allocator for 00329 // the vector. 00330 template<typename _Tp> 00331 class _Ffit_finder 00332 : public std::unary_function<typename std::pair<_Tp, _Tp>, bool> 00333 { 00334 typedef typename std::pair<_Tp, _Tp> _Block_pair; 00335 typedef typename __detail::__mini_vector<_Block_pair> _BPVector; 00336 typedef typename _BPVector::difference_type _Counter_type; 00337 00338 size_t* _M_pbitmap; 00339 _Counter_type _M_data_offset; 00340 00341 public: 00342 _Ffit_finder() : _M_pbitmap(0), _M_data_offset(0) 00343 { } 00344 00345 bool 00346 operator()(_Block_pair __bp) throw() 00347 { 00348 // Set the _rover to the last physical location bitmap, 00349 // which is the bitmap which belongs to the first free 00350 // block. Thus, the bitmaps are in exact reverse order of 00351 // the actual memory layout. So, we count down the bitmaps, 00352 // which is the same as moving up the memory. 00353 00354 // If the used count stored at the start of the Bit Map headers 00355 // is equal to the number of Objects that the current Block can 00356 // store, then there is definitely no space for another single 00357 // object, so just return false. 00358 _Counter_type __diff = __detail::__num_bitmaps(__bp); 00359 00360 if (*(reinterpret_cast<size_t*> 00361 (__bp.first) - (__diff + 1)) == __detail::__num_blocks(__bp)) 00362 return false; 00363 00364 size_t* __rover = reinterpret_cast<size_t*>(__bp.first) - 1; 00365 00366 for (_Counter_type __i = 0; __i < __diff; ++__i) 00367 { 00368 _M_data_offset = __i; 00369 if (*__rover) 00370 { 00371 _M_pbitmap = __rover; 00372 return true; 00373 } 00374 --__rover; 00375 } 00376 return false; 00377 } 00378 00379 size_t* 00380 _M_get() const throw() 00381 { return _M_pbitmap; } 00382 00383 _Counter_type 00384 _M_offset() const throw() 00385 { return _M_data_offset * size_t(bits_per_block); } 00386 }; 00387 00388 /** @class _Bitmap_counter bitmap_allocator.h bitmap_allocator.h 00389 * 00390 * @brief The bitmap counter which acts as the bitmap 00391 * manipulator, and manages the bit-manipulation functions and 00392 * the searching and identification functions on the bit-map. 00393 */ 00394 // _Tp should be a pointer type. 00395 template<typename _Tp> 00396 class _Bitmap_counter 00397 { 00398 typedef typename 00399 __detail::__mini_vector<typename std::pair<_Tp, _Tp> > _BPVector; 00400 typedef typename _BPVector::size_type _Index_type; 00401 typedef _Tp pointer; 00402 00403 _BPVector& _M_vbp; 00404 size_t* _M_curr_bmap; 00405 size_t* _M_last_bmap_in_block; 00406 _Index_type _M_curr_index; 00407 00408 public: 00409 // Use the 2nd parameter with care. Make sure that such an 00410 // entry exists in the vector before passing that particular 00411 // index to this ctor. 00412 _Bitmap_counter(_BPVector& Rvbp, long __index = -1) : _M_vbp(Rvbp) 00413 { this->_M_reset(__index); } 00414 00415 void 00416 _M_reset(long __index = -1) throw() 00417 { 00418 if (__index == -1) 00419 { 00420 _M_curr_bmap = 0; 00421 _M_curr_index = static_cast<_Index_type>(-1); 00422 return; 00423 } 00424 00425 _M_curr_index = __index; 00426 _M_curr_bmap = reinterpret_cast<size_t*> 00427 (_M_vbp[_M_curr_index].first) - 1; 00428 00429 _GLIBCXX_DEBUG_ASSERT(__index <= (long)_M_vbp.size() - 1); 00430 00431 _M_last_bmap_in_block = _M_curr_bmap 00432 - ((_M_vbp[_M_curr_index].second 00433 - _M_vbp[_M_curr_index].first + 1) 00434 / size_t(bits_per_block) - 1); 00435 } 00436 00437 // Dangerous Function! Use with extreme care. Pass to this 00438 // function ONLY those values that are known to be correct, 00439 // otherwise this will mess up big time. 00440 void 00441 _M_set_internal_bitmap(size_t* __new_internal_marker) throw() 00442 { _M_curr_bmap = __new_internal_marker; } 00443 00444 bool 00445 _M_finished() const throw() 00446 { return(_M_curr_bmap == 0); } 00447 00448 _Bitmap_counter& 00449 operator++() throw() 00450 { 00451 if (_M_curr_bmap == _M_last_bmap_in_block) 00452 { 00453 if (++_M_curr_index == _M_vbp.size()) 00454 _M_curr_bmap = 0; 00455 else 00456 this->_M_reset(_M_curr_index); 00457 } 00458 else 00459 --_M_curr_bmap; 00460 return *this; 00461 } 00462 00463 size_t* 00464 _M_get() const throw() 00465 { return _M_curr_bmap; } 00466 00467 pointer 00468 _M_base() const throw() 00469 { return _M_vbp[_M_curr_index].first; } 00470 00471 _Index_type 00472 _M_offset() const throw() 00473 { 00474 return size_t(bits_per_block) 00475 * ((reinterpret_cast<size_t*>(this->_M_base()) 00476 - _M_curr_bmap) - 1); 00477 } 00478 00479 _Index_type 00480 _M_where() const throw() 00481 { return _M_curr_index; } 00482 }; 00483 00484 /** @brief Mark a memory address as allocated by re-setting the 00485 * corresponding bit in the bit-map. 00486 */ 00487 inline void 00488 __bit_allocate(size_t* __pbmap, size_t __pos) throw() 00489 { 00490 size_t __mask = 1 << __pos; 00491 __mask = ~__mask; 00492 *__pbmap &= __mask; 00493 } 00494 00495 /** @brief Mark a memory address as free by setting the 00496 * corresponding bit in the bit-map. 00497 */ 00498 inline void 00499 __bit_free(size_t* __pbmap, size_t __pos) throw() 00500 { 00501 size_t __mask = 1 << __pos; 00502 *__pbmap |= __mask; 00503 } 00504 00505 _GLIBCXX_END_NAMESPACE_VERSION 00506 } // namespace __detail 00507 00508 _GLIBCXX_BEGIN_NAMESPACE_VERSION 00509 00510 /** @brief Generic Version of the bsf instruction. 00511 */ 00512 inline size_t 00513 _Bit_scan_forward(size_t __num) 00514 { return static_cast<size_t>(__builtin_ctzl(__num)); } 00515 00516 /** @class free_list bitmap_allocator.h bitmap_allocator.h 00517 * 00518 * @brief The free list class for managing chunks of memory to be 00519 * given to and returned by the bitmap_allocator. 00520 */ 00521 class free_list 00522 { 00523 public: 00524 typedef size_t* value_type; 00525 typedef __detail::__mini_vector<value_type> vector_type; 00526 typedef vector_type::iterator iterator; 00527 typedef __mutex __mutex_type; 00528 00529 private: 00530 struct _LT_pointer_compare 00531 { 00532 bool 00533 operator()(const size_t* __pui, 00534 const size_t __cui) const throw() 00535 { return *__pui < __cui; } 00536 }; 00537 00538 #if defined __GTHREADS 00539 __mutex_type& 00540 _M_get_mutex() 00541 { 00542 static __mutex_type _S_mutex; 00543 return _S_mutex; 00544 } 00545 #endif 00546 00547 vector_type& 00548 _M_get_free_list() 00549 { 00550 static vector_type _S_free_list; 00551 return _S_free_list; 00552 } 00553 00554 /** @brief Performs validation of memory based on their size. 00555 * 00556 * @param __addr The pointer to the memory block to be 00557 * validated. 00558 * 00559 * Validates the memory block passed to this function and 00560 * appropriately performs the action of managing the free list of 00561 * blocks by adding this block to the free list or deleting this 00562 * or larger blocks from the free list. 00563 */ 00564 void 00565 _M_validate(size_t* __addr) throw() 00566 { 00567 vector_type& __free_list = _M_get_free_list(); 00568 const vector_type::size_type __max_size = 64; 00569 if (__free_list.size() >= __max_size) 00570 { 00571 // Ok, the threshold value has been reached. We determine 00572 // which block to remove from the list of free blocks. 00573 if (*__addr >= *__free_list.back()) 00574 { 00575 // Ok, the new block is greater than or equal to the 00576 // last block in the list of free blocks. We just free 00577 // the new block. 00578 ::operator delete(static_cast<void*>(__addr)); 00579 return; 00580 } 00581 else 00582 { 00583 // Deallocate the last block in the list of free lists, 00584 // and insert the new one in its correct position. 00585 ::operator delete(static_cast<void*>(__free_list.back())); 00586 __free_list.pop_back(); 00587 } 00588 } 00589 00590 // Just add the block to the list of free lists unconditionally. 00591 iterator __temp = __detail::__lower_bound 00592 (__free_list.begin(), __free_list.end(), 00593 *__addr, _LT_pointer_compare()); 00594 00595 // We may insert the new free list before _temp; 00596 __free_list.insert(__temp, __addr); 00597 } 00598 00599 /** @brief Decides whether the wastage of memory is acceptable for 00600 * the current memory request and returns accordingly. 00601 * 00602 * @param __block_size The size of the block available in the free 00603 * list. 00604 * 00605 * @param __required_size The required size of the memory block. 00606 * 00607 * @return true if the wastage incurred is acceptable, else returns 00608 * false. 00609 */ 00610 bool 00611 _M_should_i_give(size_t __block_size, 00612 size_t __required_size) throw() 00613 { 00614 const size_t __max_wastage_percentage = 36; 00615 if (__block_size >= __required_size && 00616 (((__block_size - __required_size) * 100 / __block_size) 00617 < __max_wastage_percentage)) 00618 return true; 00619 else 00620 return false; 00621 } 00622 00623 public: 00624 /** @brief This function returns the block of memory to the 00625 * internal free list. 00626 * 00627 * @param __addr The pointer to the memory block that was given 00628 * by a call to the _M_get function. 00629 */ 00630 inline void 00631 _M_insert(size_t* __addr) throw() 00632 { 00633 #if defined __GTHREADS 00634 __scoped_lock __bfl_lock(_M_get_mutex()); 00635 #endif 00636 // Call _M_validate to decide what should be done with 00637 // this particular free list. 00638 this->_M_validate(reinterpret_cast<size_t*>(__addr) - 1); 00639 // See discussion as to why this is 1! 00640 } 00641 00642 /** @brief This function gets a block of memory of the specified 00643 * size from the free list. 00644 * 00645 * @param __sz The size in bytes of the memory required. 00646 * 00647 * @return A pointer to the new memory block of size at least 00648 * equal to that requested. 00649 */ 00650 size_t* 00651 _M_get(size_t __sz) throw(std::bad_alloc); 00652 00653 /** @brief This function just clears the internal Free List, and 00654 * gives back all the memory to the OS. 00655 */ 00656 void 00657 _M_clear(); 00658 }; 00659 00660 00661 // Forward declare the class. 00662 template<typename _Tp> 00663 class bitmap_allocator; 00664 00665 // Specialize for void: 00666 template<> 00667 class bitmap_allocator<void> 00668 { 00669 public: 00670 typedef void* pointer; 00671 typedef const void* const_pointer; 00672 00673 // Reference-to-void members are impossible. 00674 typedef void value_type; 00675 template<typename _Tp1> 00676 struct rebind 00677 { 00678 typedef bitmap_allocator<_Tp1> other; 00679 }; 00680 }; 00681 00682 /** 00683 * @brief Bitmap Allocator, primary template. 00684 * @ingroup allocators 00685 */ 00686 template<typename _Tp> 00687 class bitmap_allocator : private free_list 00688 { 00689 public: 00690 typedef size_t size_type; 00691 typedef ptrdiff_t difference_type; 00692 typedef _Tp* pointer; 00693 typedef const _Tp* const_pointer; 00694 typedef _Tp& reference; 00695 typedef const _Tp& const_reference; 00696 typedef _Tp value_type; 00697 typedef free_list::__mutex_type __mutex_type; 00698 00699 template<typename _Tp1> 00700 struct rebind 00701 { 00702 typedef bitmap_allocator<_Tp1> other; 00703 }; 00704 00705 #if __cplusplus >= 201103L 00706 // _GLIBCXX_RESOLVE_LIB_DEFECTS 00707 // 2103. propagate_on_container_move_assignment 00708 typedef std::true_type propagate_on_container_move_assignment; 00709 #endif 00710 00711 private: 00712 template<size_t _BSize, size_t _AlignSize> 00713 struct aligned_size 00714 { 00715 enum 00716 { 00717 modulus = _BSize % _AlignSize, 00718 value = _BSize + (modulus ? _AlignSize - (modulus) : 0) 00719 }; 00720 }; 00721 00722 struct _Alloc_block 00723 { 00724 char __M_unused[aligned_size<sizeof(value_type), 00725 _BALLOC_ALIGN_BYTES>::value]; 00726 }; 00727 00728 00729 typedef typename std::pair<_Alloc_block*, _Alloc_block*> _Block_pair; 00730 00731 typedef typename __detail::__mini_vector<_Block_pair> _BPVector; 00732 typedef typename _BPVector::iterator _BPiter; 00733 00734 template<typename _Predicate> 00735 static _BPiter 00736 _S_find(_Predicate __p) 00737 { 00738 _BPiter __first = _S_mem_blocks.begin(); 00739 while (__first != _S_mem_blocks.end() && !__p(*__first)) 00740 ++__first; 00741 return __first; 00742 } 00743 00744 #if defined _GLIBCXX_DEBUG 00745 // Complexity: O(lg(N)). Where, N is the number of block of size 00746 // sizeof(value_type). 00747 void 00748 _S_check_for_free_blocks() throw() 00749 { 00750 typedef typename __detail::_Ffit_finder<_Alloc_block*> _FFF; 00751 _BPiter __bpi = _S_find(_FFF()); 00752 00753 _GLIBCXX_DEBUG_ASSERT(__bpi == _S_mem_blocks.end()); 00754 } 00755 #endif 00756 00757 /** @brief Responsible for exponentially growing the internal 00758 * memory pool. 00759 * 00760 * @throw std::bad_alloc. If memory can not be allocated. 00761 * 00762 * Complexity: O(1), but internally depends upon the 00763 * complexity of the function free_list::_M_get. The part where 00764 * the bitmap headers are written has complexity: O(X),where X 00765 * is the number of blocks of size sizeof(value_type) within 00766 * the newly acquired block. Having a tight bound. 00767 */ 00768 void 00769 _S_refill_pool() throw(std::bad_alloc) 00770 { 00771 #if defined _GLIBCXX_DEBUG 00772 _S_check_for_free_blocks(); 00773 #endif 00774 00775 const size_t __num_bitmaps = (_S_block_size 00776 / size_t(__detail::bits_per_block)); 00777 const size_t __size_to_allocate = sizeof(size_t) 00778 + _S_block_size * sizeof(_Alloc_block) 00779 + __num_bitmaps * sizeof(size_t); 00780 00781 size_t* __temp = 00782 reinterpret_cast<size_t*>(this->_M_get(__size_to_allocate)); 00783 *__temp = 0; 00784 ++__temp; 00785 00786 // The Header information goes at the Beginning of the Block. 00787 _Block_pair __bp = 00788 std::make_pair(reinterpret_cast<_Alloc_block*> 00789 (__temp + __num_bitmaps), 00790 reinterpret_cast<_Alloc_block*> 00791 (__temp + __num_bitmaps) 00792 + _S_block_size - 1); 00793 00794 // Fill the Vector with this information. 00795 _S_mem_blocks.push_back(__bp); 00796 00797 for (size_t __i = 0; __i < __num_bitmaps; ++__i) 00798 __temp[__i] = ~static_cast<size_t>(0); // 1 Indicates all Free. 00799 00800 _S_block_size *= 2; 00801 } 00802 00803 static _BPVector _S_mem_blocks; 00804 static size_t _S_block_size; 00805 static __detail::_Bitmap_counter<_Alloc_block*> _S_last_request; 00806 static typename _BPVector::size_type _S_last_dealloc_index; 00807 #if defined __GTHREADS 00808 static __mutex_type _S_mut; 00809 #endif 00810 00811 public: 00812 00813 /** @brief Allocates memory for a single object of size 00814 * sizeof(_Tp). 00815 * 00816 * @throw std::bad_alloc. If memory can not be allocated. 00817 * 00818 * Complexity: Worst case complexity is O(N), but that 00819 * is hardly ever hit. If and when this particular case is 00820 * encountered, the next few cases are guaranteed to have a 00821 * worst case complexity of O(1)! That's why this function 00822 * performs very well on average. You can consider this 00823 * function to have a complexity referred to commonly as: 00824 * Amortized Constant time. 00825 */ 00826 pointer 00827 _M_allocate_single_object() throw(std::bad_alloc) 00828 { 00829 #if defined __GTHREADS 00830 __scoped_lock __bit_lock(_S_mut); 00831 #endif 00832 00833 // The algorithm is something like this: The last_request 00834 // variable points to the last accessed Bit Map. When such a 00835 // condition occurs, we try to find a free block in the 00836 // current bitmap, or succeeding bitmaps until the last bitmap 00837 // is reached. If no free block turns up, we resort to First 00838 // Fit method. 00839 00840 // WARNING: Do not re-order the condition in the while 00841 // statement below, because it relies on C++'s short-circuit 00842 // evaluation. The return from _S_last_request->_M_get() will 00843 // NOT be dereference able if _S_last_request->_M_finished() 00844 // returns true. This would inevitably lead to a NULL pointer 00845 // dereference if tinkered with. 00846 while (_S_last_request._M_finished() == false 00847 && (*(_S_last_request._M_get()) == 0)) 00848 _S_last_request.operator++(); 00849 00850 if (__builtin_expect(_S_last_request._M_finished() == true, false)) 00851 { 00852 // Fall Back to First Fit algorithm. 00853 typedef typename __detail::_Ffit_finder<_Alloc_block*> _FFF; 00854 _FFF __fff; 00855 _BPiter __bpi = _S_find(__detail::_Functor_Ref<_FFF>(__fff)); 00856 00857 if (__bpi != _S_mem_blocks.end()) 00858 { 00859 // Search was successful. Ok, now mark the first bit from 00860 // the right as 0, meaning Allocated. This bit is obtained 00861 // by calling _M_get() on __fff. 00862 size_t __nz_bit = _Bit_scan_forward(*__fff._M_get()); 00863 __detail::__bit_allocate(__fff._M_get(), __nz_bit); 00864 00865 _S_last_request._M_reset(__bpi - _S_mem_blocks.begin()); 00866 00867 // Now, get the address of the bit we marked as allocated. 00868 pointer __ret = reinterpret_cast<pointer> 00869 (__bpi->first + __fff._M_offset() + __nz_bit); 00870 size_t* __puse_count = 00871 reinterpret_cast<size_t*> 00872 (__bpi->first) - (__detail::__num_bitmaps(*__bpi) + 1); 00873 00874 ++(*__puse_count); 00875 return __ret; 00876 } 00877 else 00878 { 00879 // Search was unsuccessful. We Add more memory to the 00880 // pool by calling _S_refill_pool(). 00881 _S_refill_pool(); 00882 00883 // _M_Reset the _S_last_request structure to the first 00884 // free block's bit map. 00885 _S_last_request._M_reset(_S_mem_blocks.size() - 1); 00886 00887 // Now, mark that bit as allocated. 00888 } 00889 } 00890 00891 // _S_last_request holds a pointer to a valid bit map, that 00892 // points to a free block in memory. 00893 size_t __nz_bit = _Bit_scan_forward(*_S_last_request._M_get()); 00894 __detail::__bit_allocate(_S_last_request._M_get(), __nz_bit); 00895 00896 pointer __ret = reinterpret_cast<pointer> 00897 (_S_last_request._M_base() + _S_last_request._M_offset() + __nz_bit); 00898 00899 size_t* __puse_count = reinterpret_cast<size_t*> 00900 (_S_mem_blocks[_S_last_request._M_where()].first) 00901 - (__detail:: 00902 __num_bitmaps(_S_mem_blocks[_S_last_request._M_where()]) + 1); 00903 00904 ++(*__puse_count); 00905 return __ret; 00906 } 00907 00908 /** @brief Deallocates memory that belongs to a single object of 00909 * size sizeof(_Tp). 00910 * 00911 * Complexity: O(lg(N)), but the worst case is not hit 00912 * often! This is because containers usually deallocate memory 00913 * close to each other and this case is handled in O(1) time by 00914 * the deallocate function. 00915 */ 00916 void 00917 _M_deallocate_single_object(pointer __p) throw() 00918 { 00919 #if defined __GTHREADS 00920 __scoped_lock __bit_lock(_S_mut); 00921 #endif 00922 _Alloc_block* __real_p = reinterpret_cast<_Alloc_block*>(__p); 00923 00924 typedef typename _BPVector::iterator _Iterator; 00925 typedef typename _BPVector::difference_type _Difference_type; 00926 00927 _Difference_type __diff; 00928 long __displacement; 00929 00930 _GLIBCXX_DEBUG_ASSERT(_S_last_dealloc_index >= 0); 00931 00932 __detail::_Inclusive_between<_Alloc_block*> __ibt(__real_p); 00933 if (__ibt(_S_mem_blocks[_S_last_dealloc_index])) 00934 { 00935 _GLIBCXX_DEBUG_ASSERT(_S_last_dealloc_index 00936 <= _S_mem_blocks.size() - 1); 00937 00938 // Initial Assumption was correct! 00939 __diff = _S_last_dealloc_index; 00940 __displacement = __real_p - _S_mem_blocks[__diff].first; 00941 } 00942 else 00943 { 00944 _Iterator _iter = _S_find(__ibt); 00945 00946 _GLIBCXX_DEBUG_ASSERT(_iter != _S_mem_blocks.end()); 00947 00948 __diff = _iter - _S_mem_blocks.begin(); 00949 __displacement = __real_p - _S_mem_blocks[__diff].first; 00950 _S_last_dealloc_index = __diff; 00951 } 00952 00953 // Get the position of the iterator that has been found. 00954 const size_t __rotate = (__displacement 00955 % size_t(__detail::bits_per_block)); 00956 size_t* __bitmapC = 00957 reinterpret_cast<size_t*> 00958 (_S_mem_blocks[__diff].first) - 1; 00959 __bitmapC -= (__displacement / size_t(__detail::bits_per_block)); 00960 00961 __detail::__bit_free(__bitmapC, __rotate); 00962 size_t* __puse_count = reinterpret_cast<size_t*> 00963 (_S_mem_blocks[__diff].first) 00964 - (__detail::__num_bitmaps(_S_mem_blocks[__diff]) + 1); 00965 00966 _GLIBCXX_DEBUG_ASSERT(*__puse_count != 0); 00967 00968 --(*__puse_count); 00969 00970 if (__builtin_expect(*__puse_count == 0, false)) 00971 { 00972 _S_block_size /= 2; 00973 00974 // We can safely remove this block. 00975 // _Block_pair __bp = _S_mem_blocks[__diff]; 00976 this->_M_insert(__puse_count); 00977 _S_mem_blocks.erase(_S_mem_blocks.begin() + __diff); 00978 00979 // Reset the _S_last_request variable to reflect the 00980 // erased block. We do this to protect future requests 00981 // after the last block has been removed from a particular 00982 // memory Chunk, which in turn has been returned to the 00983 // free list, and hence had been erased from the vector, 00984 // so the size of the vector gets reduced by 1. 00985 if ((_Difference_type)_S_last_request._M_where() >= __diff--) 00986 _S_last_request._M_reset(__diff); 00987 00988 // If the Index into the vector of the region of memory 00989 // that might hold the next address that will be passed to 00990 // deallocated may have been invalidated due to the above 00991 // erase procedure being called on the vector, hence we 00992 // try to restore this invariant too. 00993 if (_S_last_dealloc_index >= _S_mem_blocks.size()) 00994 { 00995 _S_last_dealloc_index =(__diff != -1 ? __diff : 0); 00996 _GLIBCXX_DEBUG_ASSERT(_S_last_dealloc_index >= 0); 00997 } 00998 } 00999 } 01000 01001 public: 01002 bitmap_allocator() _GLIBCXX_USE_NOEXCEPT 01003 { } 01004 01005 bitmap_allocator(const bitmap_allocator&) _GLIBCXX_USE_NOEXCEPT 01006 { } 01007 01008 template<typename _Tp1> 01009 bitmap_allocator(const bitmap_allocator<_Tp1>&) _GLIBCXX_USE_NOEXCEPT 01010 { } 01011 01012 ~bitmap_allocator() _GLIBCXX_USE_NOEXCEPT 01013 { } 01014 01015 pointer 01016 allocate(size_type __n) 01017 { 01018 if (__n > this->max_size()) 01019 std::__throw_bad_alloc(); 01020 01021 if (__builtin_expect(__n == 1, true)) 01022 return this->_M_allocate_single_object(); 01023 else 01024 { 01025 const size_type __b = __n * sizeof(value_type); 01026 return reinterpret_cast<pointer>(::operator new(__b)); 01027 } 01028 } 01029 01030 pointer 01031 allocate(size_type __n, typename bitmap_allocator<void>::const_pointer) 01032 { return allocate(__n); } 01033 01034 void 01035 deallocate(pointer __p, size_type __n) throw() 01036 { 01037 if (__builtin_expect(__p != 0, true)) 01038 { 01039 if (__builtin_expect(__n == 1, true)) 01040 this->_M_deallocate_single_object(__p); 01041 else 01042 ::operator delete(__p); 01043 } 01044 } 01045 01046 pointer 01047 address(reference __r) const _GLIBCXX_NOEXCEPT 01048 { return std::__addressof(__r); } 01049 01050 const_pointer 01051 address(const_reference __r) const _GLIBCXX_NOEXCEPT 01052 { return std::__addressof(__r); } 01053 01054 size_type 01055 max_size() const _GLIBCXX_USE_NOEXCEPT 01056 { return size_type(-1) / sizeof(value_type); } 01057 01058 #if __cplusplus >= 201103L 01059 template<typename _Up, typename... _Args> 01060 void 01061 construct(_Up* __p, _Args&&... __args) 01062 { ::new((void *)__p) _Up(std::forward<_Args>(__args)...); } 01063 01064 template<typename _Up> 01065 void 01066 destroy(_Up* __p) 01067 { __p->~_Up(); } 01068 #else 01069 void 01070 construct(pointer __p, const_reference __data) 01071 { ::new((void *)__p) value_type(__data); } 01072 01073 void 01074 destroy(pointer __p) 01075 { __p->~value_type(); } 01076 #endif 01077 }; 01078 01079 template<typename _Tp1, typename _Tp2> 01080 bool 01081 operator==(const bitmap_allocator<_Tp1>&, 01082 const bitmap_allocator<_Tp2>&) throw() 01083 { return true; } 01084 01085 template<typename _Tp1, typename _Tp2> 01086 bool 01087 operator!=(const bitmap_allocator<_Tp1>&, 01088 const bitmap_allocator<_Tp2>&) throw() 01089 { return false; } 01090 01091 // Static member definitions. 01092 template<typename _Tp> 01093 typename bitmap_allocator<_Tp>::_BPVector 01094 bitmap_allocator<_Tp>::_S_mem_blocks; 01095 01096 template<typename _Tp> 01097 size_t bitmap_allocator<_Tp>::_S_block_size = 01098 2 * size_t(__detail::bits_per_block); 01099 01100 template<typename _Tp> 01101 typename bitmap_allocator<_Tp>::_BPVector::size_type 01102 bitmap_allocator<_Tp>::_S_last_dealloc_index = 0; 01103 01104 template<typename _Tp> 01105 __detail::_Bitmap_counter 01106 <typename bitmap_allocator<_Tp>::_Alloc_block*> 01107 bitmap_allocator<_Tp>::_S_last_request(_S_mem_blocks); 01108 01109 #if defined __GTHREADS 01110 template<typename _Tp> 01111 typename bitmap_allocator<_Tp>::__mutex_type 01112 bitmap_allocator<_Tp>::_S_mut; 01113 #endif 01114 01115 _GLIBCXX_END_NAMESPACE_VERSION 01116 } // namespace __gnu_cxx 01117 01118 #endif 01119