libstdc++
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00001 // Bitmap Allocator. -*- C++ -*- 00002 00003 // Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 00004 // Free Software Foundation, Inc. 00005 // 00006 // This file is part of the GNU ISO C++ Library. This library is free 00007 // software; you can redistribute it and/or modify it under the 00008 // terms of the GNU General Public License as published by the 00009 // Free Software Foundation; either version 3, or (at your option) 00010 // any later version. 00011 00012 // This library is distributed in the hope that it will be useful, 00013 // but WITHOUT ANY WARRANTY; without even the implied warranty of 00014 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 00015 // GNU General Public License for more details. 00016 00017 // Under Section 7 of GPL version 3, you are granted additional 00018 // permissions described in the GCC Runtime Library Exception, version 00019 // 3.1, as published by the Free Software Foundation. 00020 00021 // You should have received a copy of the GNU General Public License and 00022 // a copy of the GCC Runtime Library Exception along with this program; 00023 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 00024 // <http://www.gnu.org/licenses/>. 00025 00026 /** @file ext/bitmap_allocator.h 00027 * This file is a GNU extension to the Standard C++ Library. 00028 */ 00029 00030 #ifndef _BITMAP_ALLOCATOR_H 00031 #define _BITMAP_ALLOCATOR_H 1 00032 00033 #include <cstddef> // For std::size_t, and ptrdiff_t. 00034 #include <bits/functexcept.h> // For __throw_bad_alloc(). 00035 #include <utility> // For std::pair. 00036 #include <functional> // For greater_equal, and less_equal. 00037 #include <new> // For operator new. 00038 #include <debug/debug.h> // _GLIBCXX_DEBUG_ASSERT 00039 #include <ext/concurrence.h> 00040 #include <bits/move.h> 00041 00042 /** @brief The constant in the expression below is the alignment 00043 * required in bytes. 00044 */ 00045 #define _BALLOC_ALIGN_BYTES 8 00046 00047 _GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx) 00048 00049 using std::size_t; 00050 using std::ptrdiff_t; 00051 00052 namespace __detail 00053 { 00054 /** @class __mini_vector bitmap_allocator.h bitmap_allocator.h 00055 * 00056 * @brief __mini_vector<> is a stripped down version of the 00057 * full-fledged std::vector<>. 00058 * 00059 * It is to be used only for built-in types or PODs. Notable 00060 * differences are: 00061 * 00062 * @detail 00063 * 1. Not all accessor functions are present. 00064 * 2. Used ONLY for PODs. 00065 * 3. No Allocator template argument. Uses ::operator new() to get 00066 * memory, and ::operator delete() to free it. 00067 * Caveat: The dtor does NOT free the memory allocated, so this a 00068 * memory-leaking vector! 00069 */ 00070 template<typename _Tp> 00071 class __mini_vector 00072 { 00073 __mini_vector(const __mini_vector&); 00074 __mini_vector& operator=(const __mini_vector&); 00075 00076 public: 00077 typedef _Tp value_type; 00078 typedef _Tp* pointer; 00079 typedef _Tp& reference; 00080 typedef const _Tp& const_reference; 00081 typedef size_t size_type; 00082 typedef ptrdiff_t difference_type; 00083 typedef pointer iterator; 00084 00085 private: 00086 pointer _M_start; 00087 pointer _M_finish; 00088 pointer _M_end_of_storage; 00089 00090 size_type 00091 _M_space_left() const throw() 00092 { return _M_end_of_storage - _M_finish; } 00093 00094 pointer 00095 allocate(size_type __n) 00096 { return static_cast<pointer>(::operator new(__n * sizeof(_Tp))); } 00097 00098 void 00099 deallocate(pointer __p, size_type) 00100 { ::operator delete(__p); } 00101 00102 public: 00103 // Members used: size(), push_back(), pop_back(), 00104 // insert(iterator, const_reference), erase(iterator), 00105 // begin(), end(), back(), operator[]. 00106 00107 __mini_vector() : _M_start(0), _M_finish(0), 00108 _M_end_of_storage(0) 00109 { } 00110 00111 #if 0 00112 ~__mini_vector() 00113 { 00114 if (this->_M_start) 00115 { 00116 this->deallocate(this->_M_start, this->_M_end_of_storage 00117 - this->_M_start); 00118 } 00119 } 00120 #endif 00121 00122 size_type 00123 size() const throw() 00124 { return _M_finish - _M_start; } 00125 00126 iterator 00127 begin() const throw() 00128 { return this->_M_start; } 00129 00130 iterator 00131 end() const throw() 00132 { return this->_M_finish; } 00133 00134 reference 00135 back() const throw() 00136 { return *(this->end() - 1); } 00137 00138 reference 00139 operator[](const size_type __pos) const throw() 00140 { return this->_M_start[__pos]; } 00141 00142 void 00143 insert(iterator __pos, const_reference __x); 00144 00145 void 00146 push_back(const_reference __x) 00147 { 00148 if (this->_M_space_left()) 00149 { 00150 *this->end() = __x; 00151 ++this->_M_finish; 00152 } 00153 else 00154 this->insert(this->end(), __x); 00155 } 00156 00157 void 00158 pop_back() throw() 00159 { --this->_M_finish; } 00160 00161 void 00162 erase(iterator __pos) throw(); 00163 00164 void 00165 clear() throw() 00166 { this->_M_finish = this->_M_start; } 00167 }; 00168 00169 // Out of line function definitions. 00170 template<typename _Tp> 00171 void __mini_vector<_Tp>:: 00172 insert(iterator __pos, const_reference __x) 00173 { 00174 if (this->_M_space_left()) 00175 { 00176 size_type __to_move = this->_M_finish - __pos; 00177 iterator __dest = this->end(); 00178 iterator __src = this->end() - 1; 00179 00180 ++this->_M_finish; 00181 while (__to_move) 00182 { 00183 *__dest = *__src; 00184 --__dest; --__src; --__to_move; 00185 } 00186 *__pos = __x; 00187 } 00188 else 00189 { 00190 size_type __new_size = this->size() ? this->size() * 2 : 1; 00191 iterator __new_start = this->allocate(__new_size); 00192 iterator __first = this->begin(); 00193 iterator __start = __new_start; 00194 while (__first != __pos) 00195 { 00196 *__start = *__first; 00197 ++__start; ++__first; 00198 } 00199 *__start = __x; 00200 ++__start; 00201 while (__first != this->end()) 00202 { 00203 *__start = *__first; 00204 ++__start; ++__first; 00205 } 00206 if (this->_M_start) 00207 this->deallocate(this->_M_start, this->size()); 00208 00209 this->_M_start = __new_start; 00210 this->_M_finish = __start; 00211 this->_M_end_of_storage = this->_M_start + __new_size; 00212 } 00213 } 00214 00215 template<typename _Tp> 00216 void __mini_vector<_Tp>:: 00217 erase(iterator __pos) throw() 00218 { 00219 while (__pos + 1 != this->end()) 00220 { 00221 *__pos = __pos[1]; 00222 ++__pos; 00223 } 00224 --this->_M_finish; 00225 } 00226 00227 00228 template<typename _Tp> 00229 struct __mv_iter_traits 00230 { 00231 typedef typename _Tp::value_type value_type; 00232 typedef typename _Tp::difference_type difference_type; 00233 }; 00234 00235 template<typename _Tp> 00236 struct __mv_iter_traits<_Tp*> 00237 { 00238 typedef _Tp value_type; 00239 typedef ptrdiff_t difference_type; 00240 }; 00241 00242 enum 00243 { 00244 bits_per_byte = 8, 00245 bits_per_block = sizeof(size_t) * size_t(bits_per_byte) 00246 }; 00247 00248 template<typename _ForwardIterator, typename _Tp, typename _Compare> 00249 _ForwardIterator 00250 __lower_bound(_ForwardIterator __first, _ForwardIterator __last, 00251 const _Tp& __val, _Compare __comp) 00252 { 00253 typedef typename __mv_iter_traits<_ForwardIterator>::value_type 00254 _ValueType; 00255 typedef typename __mv_iter_traits<_ForwardIterator>::difference_type 00256 _DistanceType; 00257 00258 _DistanceType __len = __last - __first; 00259 _DistanceType __half; 00260 _ForwardIterator __middle; 00261 00262 while (__len > 0) 00263 { 00264 __half = __len >> 1; 00265 __middle = __first; 00266 __middle += __half; 00267 if (__comp(*__middle, __val)) 00268 { 00269 __first = __middle; 00270 ++__first; 00271 __len = __len - __half - 1; 00272 } 00273 else 00274 __len = __half; 00275 } 00276 return __first; 00277 } 00278 00279 template<typename _InputIterator, typename _Predicate> 00280 inline _InputIterator 00281 __find_if(_InputIterator __first, _InputIterator __last, _Predicate __p) 00282 { 00283 while (__first != __last && !__p(*__first)) 00284 ++__first; 00285 return __first; 00286 } 00287 00288 /** @brief The number of Blocks pointed to by the address pair 00289 * passed to the function. 00290 */ 00291 template<typename _AddrPair> 00292 inline size_t 00293 __num_blocks(_AddrPair __ap) 00294 { return (__ap.second - __ap.first) + 1; } 00295 00296 /** @brief The number of Bit-maps pointed to by the address pair 00297 * passed to the function. 00298 */ 00299 template<typename _AddrPair> 00300 inline size_t 00301 __num_bitmaps(_AddrPair __ap) 00302 { return __num_blocks(__ap) / size_t(bits_per_block); } 00303 00304 // _Tp should be a pointer type. 00305 template<typename _Tp> 00306 class _Inclusive_between 00307 : public std::unary_function<typename std::pair<_Tp, _Tp>, bool> 00308 { 00309 typedef _Tp pointer; 00310 pointer _M_ptr_value; 00311 typedef typename std::pair<_Tp, _Tp> _Block_pair; 00312 00313 public: 00314 _Inclusive_between(pointer __ptr) : _M_ptr_value(__ptr) 00315 { } 00316 00317 bool 00318 operator()(_Block_pair __bp) const throw() 00319 { 00320 if (std::less_equal<pointer>()(_M_ptr_value, __bp.second) 00321 && std::greater_equal<pointer>()(_M_ptr_value, __bp.first)) 00322 return true; 00323 else 00324 return false; 00325 } 00326 }; 00327 00328 // Used to pass a Functor to functions by reference. 00329 template<typename _Functor> 00330 class _Functor_Ref 00331 : public std::unary_function<typename _Functor::argument_type, 00332 typename _Functor::result_type> 00333 { 00334 _Functor& _M_fref; 00335 00336 public: 00337 typedef typename _Functor::argument_type argument_type; 00338 typedef typename _Functor::result_type result_type; 00339 00340 _Functor_Ref(_Functor& __fref) : _M_fref(__fref) 00341 { } 00342 00343 result_type 00344 operator()(argument_type __arg) 00345 { return _M_fref(__arg); } 00346 }; 00347 00348 /** @class _Ffit_finder bitmap_allocator.h bitmap_allocator.h 00349 * 00350 * @brief The class which acts as a predicate for applying the 00351 * first-fit memory allocation policy for the bitmap allocator. 00352 */ 00353 // _Tp should be a pointer type, and _Alloc is the Allocator for 00354 // the vector. 00355 template<typename _Tp> 00356 class _Ffit_finder 00357 : public std::unary_function<typename std::pair<_Tp, _Tp>, bool> 00358 { 00359 typedef typename std::pair<_Tp, _Tp> _Block_pair; 00360 typedef typename __detail::__mini_vector<_Block_pair> _BPVector; 00361 typedef typename _BPVector::difference_type _Counter_type; 00362 00363 size_t* _M_pbitmap; 00364 _Counter_type _M_data_offset; 00365 00366 public: 00367 _Ffit_finder() : _M_pbitmap(0), _M_data_offset(0) 00368 { } 00369 00370 bool 00371 operator()(_Block_pair __bp) throw() 00372 { 00373 // Set the _rover to the last physical location bitmap, 00374 // which is the bitmap which belongs to the first free 00375 // block. Thus, the bitmaps are in exact reverse order of 00376 // the actual memory layout. So, we count down the bitmaps, 00377 // which is the same as moving up the memory. 00378 00379 // If the used count stored at the start of the Bit Map headers 00380 // is equal to the number of Objects that the current Block can 00381 // store, then there is definitely no space for another single 00382 // object, so just return false. 00383 _Counter_type __diff = 00384 __gnu_cxx::__detail::__num_bitmaps(__bp); 00385 00386 if (*(reinterpret_cast<size_t*> 00387 (__bp.first) - (__diff + 1)) 00388 == __gnu_cxx::__detail::__num_blocks(__bp)) 00389 return false; 00390 00391 size_t* __rover = reinterpret_cast<size_t*>(__bp.first) - 1; 00392 00393 for (_Counter_type __i = 0; __i < __diff; ++__i) 00394 { 00395 _M_data_offset = __i; 00396 if (*__rover) 00397 { 00398 _M_pbitmap = __rover; 00399 return true; 00400 } 00401 --__rover; 00402 } 00403 return false; 00404 } 00405 00406 00407 size_t* 00408 _M_get() const throw() 00409 { return _M_pbitmap; } 00410 00411 _Counter_type 00412 _M_offset() const throw() 00413 { return _M_data_offset * size_t(bits_per_block); } 00414 }; 00415 00416 00417 /** @class _Bitmap_counter bitmap_allocator.h bitmap_allocator.h 00418 * 00419 * @brief The bitmap counter which acts as the bitmap 00420 * manipulator, and manages the bit-manipulation functions and 00421 * the searching and identification functions on the bit-map. 00422 */ 00423 // _Tp should be a pointer type. 00424 template<typename _Tp> 00425 class _Bitmap_counter 00426 { 00427 typedef typename __detail::__mini_vector<typename std::pair<_Tp, _Tp> > 00428 _BPVector; 00429 typedef typename _BPVector::size_type _Index_type; 00430 typedef _Tp pointer; 00431 00432 _BPVector& _M_vbp; 00433 size_t* _M_curr_bmap; 00434 size_t* _M_last_bmap_in_block; 00435 _Index_type _M_curr_index; 00436 00437 public: 00438 // Use the 2nd parameter with care. Make sure that such an 00439 // entry exists in the vector before passing that particular 00440 // index to this ctor. 00441 _Bitmap_counter(_BPVector& Rvbp, long __index = -1) : _M_vbp(Rvbp) 00442 { this->_M_reset(__index); } 00443 00444 void 00445 _M_reset(long __index = -1) throw() 00446 { 00447 if (__index == -1) 00448 { 00449 _M_curr_bmap = 0; 00450 _M_curr_index = static_cast<_Index_type>(-1); 00451 return; 00452 } 00453 00454 _M_curr_index = __index; 00455 _M_curr_bmap = reinterpret_cast<size_t*> 00456 (_M_vbp[_M_curr_index].first) - 1; 00457 00458 _GLIBCXX_DEBUG_ASSERT(__index <= (long)_M_vbp.size() - 1); 00459 00460 _M_last_bmap_in_block = _M_curr_bmap 00461 - ((_M_vbp[_M_curr_index].second 00462 - _M_vbp[_M_curr_index].first + 1) 00463 / size_t(bits_per_block) - 1); 00464 } 00465 00466 // Dangerous Function! Use with extreme care. Pass to this 00467 // function ONLY those values that are known to be correct, 00468 // otherwise this will mess up big time. 00469 void 00470 _M_set_internal_bitmap(size_t* __new_internal_marker) throw() 00471 { _M_curr_bmap = __new_internal_marker; } 00472 00473 bool 00474 _M_finished() const throw() 00475 { return(_M_curr_bmap == 0); } 00476 00477 _Bitmap_counter& 00478 operator++() throw() 00479 { 00480 if (_M_curr_bmap == _M_last_bmap_in_block) 00481 { 00482 if (++_M_curr_index == _M_vbp.size()) 00483 _M_curr_bmap = 0; 00484 else 00485 this->_M_reset(_M_curr_index); 00486 } 00487 else 00488 --_M_curr_bmap; 00489 return *this; 00490 } 00491 00492 size_t* 00493 _M_get() const throw() 00494 { return _M_curr_bmap; } 00495 00496 pointer 00497 _M_base() const throw() 00498 { return _M_vbp[_M_curr_index].first; } 00499 00500 _Index_type 00501 _M_offset() const throw() 00502 { 00503 return size_t(bits_per_block) 00504 * ((reinterpret_cast<size_t*>(this->_M_base()) 00505 - _M_curr_bmap) - 1); 00506 } 00507 00508 _Index_type 00509 _M_where() const throw() 00510 { return _M_curr_index; } 00511 }; 00512 00513 /** @brief Mark a memory address as allocated by re-setting the 00514 * corresponding bit in the bit-map. 00515 */ 00516 inline void 00517 __bit_allocate(size_t* __pbmap, size_t __pos) throw() 00518 { 00519 size_t __mask = 1 << __pos; 00520 __mask = ~__mask; 00521 *__pbmap &= __mask; 00522 } 00523 00524 /** @brief Mark a memory address as free by setting the 00525 * corresponding bit in the bit-map. 00526 */ 00527 inline void 00528 __bit_free(size_t* __pbmap, size_t __pos) throw() 00529 { 00530 size_t __mask = 1 << __pos; 00531 *__pbmap |= __mask; 00532 } 00533 } // namespace __detail 00534 00535 /** @brief Generic Version of the bsf instruction. 00536 */ 00537 inline size_t 00538 _Bit_scan_forward(size_t __num) 00539 { return static_cast<size_t>(__builtin_ctzl(__num)); } 00540 00541 /** @class free_list bitmap_allocator.h bitmap_allocator.h 00542 * 00543 * @brief The free list class for managing chunks of memory to be 00544 * given to and returned by the bitmap_allocator. 00545 */ 00546 class free_list 00547 { 00548 typedef size_t* value_type; 00549 typedef __detail::__mini_vector<value_type> vector_type; 00550 typedef vector_type::iterator iterator; 00551 typedef __mutex __mutex_type; 00552 00553 struct _LT_pointer_compare 00554 { 00555 bool 00556 operator()(const size_t* __pui, 00557 const size_t __cui) const throw() 00558 { return *__pui < __cui; } 00559 }; 00560 00561 #if defined __GTHREADS 00562 __mutex_type& 00563 _M_get_mutex() 00564 { 00565 static __mutex_type _S_mutex; 00566 return _S_mutex; 00567 } 00568 #endif 00569 00570 vector_type& 00571 _M_get_free_list() 00572 { 00573 static vector_type _S_free_list; 00574 return _S_free_list; 00575 } 00576 00577 /** @brief Performs validation of memory based on their size. 00578 * 00579 * @param __addr The pointer to the memory block to be 00580 * validated. 00581 * 00582 * @detail Validates the memory block passed to this function and 00583 * appropriately performs the action of managing the free list of 00584 * blocks by adding this block to the free list or deleting this 00585 * or larger blocks from the free list. 00586 */ 00587 void 00588 _M_validate(size_t* __addr) throw() 00589 { 00590 vector_type& __free_list = _M_get_free_list(); 00591 const vector_type::size_type __max_size = 64; 00592 if (__free_list.size() >= __max_size) 00593 { 00594 // Ok, the threshold value has been reached. We determine 00595 // which block to remove from the list of free blocks. 00596 if (*__addr >= *__free_list.back()) 00597 { 00598 // Ok, the new block is greater than or equal to the 00599 // last block in the list of free blocks. We just free 00600 // the new block. 00601 ::operator delete(static_cast<void*>(__addr)); 00602 return; 00603 } 00604 else 00605 { 00606 // Deallocate the last block in the list of free lists, 00607 // and insert the new one in its correct position. 00608 ::operator delete(static_cast<void*>(__free_list.back())); 00609 __free_list.pop_back(); 00610 } 00611 } 00612 00613 // Just add the block to the list of free lists unconditionally. 00614 iterator __temp = __gnu_cxx::__detail::__lower_bound 00615 (__free_list.begin(), __free_list.end(), 00616 *__addr, _LT_pointer_compare()); 00617 00618 // We may insert the new free list before _temp; 00619 __free_list.insert(__temp, __addr); 00620 } 00621 00622 /** @brief Decides whether the wastage of memory is acceptable for 00623 * the current memory request and returns accordingly. 00624 * 00625 * @param __block_size The size of the block available in the free 00626 * list. 00627 * 00628 * @param __required_size The required size of the memory block. 00629 * 00630 * @return true if the wastage incurred is acceptable, else returns 00631 * false. 00632 */ 00633 bool 00634 _M_should_i_give(size_t __block_size, 00635 size_t __required_size) throw() 00636 { 00637 const size_t __max_wastage_percentage = 36; 00638 if (__block_size >= __required_size && 00639 (((__block_size - __required_size) * 100 / __block_size) 00640 < __max_wastage_percentage)) 00641 return true; 00642 else 00643 return false; 00644 } 00645 00646 public: 00647 /** @brief This function returns the block of memory to the 00648 * internal free list. 00649 * 00650 * @param __addr The pointer to the memory block that was given 00651 * by a call to the _M_get function. 00652 */ 00653 inline void 00654 _M_insert(size_t* __addr) throw() 00655 { 00656 #if defined __GTHREADS 00657 __gnu_cxx::__scoped_lock __bfl_lock(_M_get_mutex()); 00658 #endif 00659 // Call _M_validate to decide what should be done with 00660 // this particular free list. 00661 this->_M_validate(reinterpret_cast<size_t*>(__addr) - 1); 00662 // See discussion as to why this is 1! 00663 } 00664 00665 /** @brief This function gets a block of memory of the specified 00666 * size from the free list. 00667 * 00668 * @param __sz The size in bytes of the memory required. 00669 * 00670 * @return A pointer to the new memory block of size at least 00671 * equal to that requested. 00672 */ 00673 size_t* 00674 _M_get(size_t __sz) throw(std::bad_alloc); 00675 00676 /** @brief This function just clears the internal Free List, and 00677 * gives back all the memory to the OS. 00678 */ 00679 void 00680 _M_clear(); 00681 }; 00682 00683 00684 // Forward declare the class. 00685 template<typename _Tp> 00686 class bitmap_allocator; 00687 00688 // Specialize for void: 00689 template<> 00690 class bitmap_allocator<void> 00691 { 00692 public: 00693 typedef void* pointer; 00694 typedef const void* const_pointer; 00695 00696 // Reference-to-void members are impossible. 00697 typedef void value_type; 00698 template<typename _Tp1> 00699 struct rebind 00700 { 00701 typedef bitmap_allocator<_Tp1> other; 00702 }; 00703 }; 00704 00705 /** 00706 * @brief Bitmap Allocator, primary template. 00707 * @ingroup allocators 00708 */ 00709 template<typename _Tp> 00710 class bitmap_allocator : private free_list 00711 { 00712 public: 00713 typedef size_t size_type; 00714 typedef ptrdiff_t difference_type; 00715 typedef _Tp* pointer; 00716 typedef const _Tp* const_pointer; 00717 typedef _Tp& reference; 00718 typedef const _Tp& const_reference; 00719 typedef _Tp value_type; 00720 typedef free_list::__mutex_type __mutex_type; 00721 00722 template<typename _Tp1> 00723 struct rebind 00724 { 00725 typedef bitmap_allocator<_Tp1> other; 00726 }; 00727 00728 private: 00729 template<size_t _BSize, size_t _AlignSize> 00730 struct aligned_size 00731 { 00732 enum 00733 { 00734 modulus = _BSize % _AlignSize, 00735 value = _BSize + (modulus ? _AlignSize - (modulus) : 0) 00736 }; 00737 }; 00738 00739 struct _Alloc_block 00740 { 00741 char __M_unused[aligned_size<sizeof(value_type), 00742 _BALLOC_ALIGN_BYTES>::value]; 00743 }; 00744 00745 00746 typedef typename std::pair<_Alloc_block*, _Alloc_block*> _Block_pair; 00747 00748 typedef typename 00749 __detail::__mini_vector<_Block_pair> _BPVector; 00750 00751 #if defined _GLIBCXX_DEBUG 00752 // Complexity: O(lg(N)). Where, N is the number of block of size 00753 // sizeof(value_type). 00754 void 00755 _S_check_for_free_blocks() throw() 00756 { 00757 typedef typename 00758 __gnu_cxx::__detail::_Ffit_finder<_Alloc_block*> _FFF; 00759 _FFF __fff; 00760 typedef typename _BPVector::iterator _BPiter; 00761 _BPiter __bpi = 00762 __gnu_cxx::__detail::__find_if 00763 (_S_mem_blocks.begin(), _S_mem_blocks.end(), 00764 __gnu_cxx::__detail::_Functor_Ref<_FFF>(__fff)); 00765 00766 _GLIBCXX_DEBUG_ASSERT(__bpi == _S_mem_blocks.end()); 00767 } 00768 #endif 00769 00770 /** @brief Responsible for exponentially growing the internal 00771 * memory pool. 00772 * 00773 * @throw std::bad_alloc. If memory can not be allocated. 00774 * 00775 * @detail Complexity: O(1), but internally depends upon the 00776 * complexity of the function free_list::_M_get. The part where 00777 * the bitmap headers are written has complexity: O(X),where X 00778 * is the number of blocks of size sizeof(value_type) within 00779 * the newly acquired block. Having a tight bound. 00780 */ 00781 void 00782 _S_refill_pool() throw(std::bad_alloc) 00783 { 00784 #if defined _GLIBCXX_DEBUG 00785 _S_check_for_free_blocks(); 00786 #endif 00787 00788 const size_t __num_bitmaps = (_S_block_size 00789 / size_t(__detail::bits_per_block)); 00790 const size_t __size_to_allocate = sizeof(size_t) 00791 + _S_block_size * sizeof(_Alloc_block) 00792 + __num_bitmaps * sizeof(size_t); 00793 00794 size_t* __temp = 00795 reinterpret_cast<size_t*> 00796 (this->_M_get(__size_to_allocate)); 00797 *__temp = 0; 00798 ++__temp; 00799 00800 // The Header information goes at the Beginning of the Block. 00801 _Block_pair __bp = 00802 std::make_pair(reinterpret_cast<_Alloc_block*> 00803 (__temp + __num_bitmaps), 00804 reinterpret_cast<_Alloc_block*> 00805 (__temp + __num_bitmaps) 00806 + _S_block_size - 1); 00807 00808 // Fill the Vector with this information. 00809 _S_mem_blocks.push_back(__bp); 00810 00811 size_t __bit_mask = 0; // 0 Indicates all Allocated. 00812 __bit_mask = ~__bit_mask; // 1 Indicates all Free. 00813 00814 for (size_t __i = 0; __i < __num_bitmaps; ++__i) 00815 __temp[__i] = __bit_mask; 00816 00817 _S_block_size *= 2; 00818 } 00819 00820 00821 static _BPVector _S_mem_blocks; 00822 static size_t _S_block_size; 00823 static __gnu_cxx::__detail:: 00824 _Bitmap_counter<_Alloc_block*> _S_last_request; 00825 static typename _BPVector::size_type _S_last_dealloc_index; 00826 #if defined __GTHREADS 00827 static __mutex_type _S_mut; 00828 #endif 00829 00830 public: 00831 00832 /** @brief Allocates memory for a single object of size 00833 * sizeof(_Tp). 00834 * 00835 * @throw std::bad_alloc. If memory can not be allocated. 00836 * 00837 * @detail Complexity: Worst case complexity is O(N), but that 00838 * is hardly ever hit. If and when this particular case is 00839 * encountered, the next few cases are guaranteed to have a 00840 * worst case complexity of O(1)! That's why this function 00841 * performs very well on average. You can consider this 00842 * function to have a complexity referred to commonly as: 00843 * Amortized Constant time. 00844 */ 00845 pointer 00846 _M_allocate_single_object() throw(std::bad_alloc) 00847 { 00848 #if defined __GTHREADS 00849 __gnu_cxx::__scoped_lock __bit_lock(_S_mut); 00850 #endif 00851 00852 // The algorithm is something like this: The last_request 00853 // variable points to the last accessed Bit Map. When such a 00854 // condition occurs, we try to find a free block in the 00855 // current bitmap, or succeeding bitmaps until the last bitmap 00856 // is reached. If no free block turns up, we resort to First 00857 // Fit method. 00858 00859 // WARNING: Do not re-order the condition in the while 00860 // statement below, because it relies on C++'s short-circuit 00861 // evaluation. The return from _S_last_request->_M_get() will 00862 // NOT be dereference able if _S_last_request->_M_finished() 00863 // returns true. This would inevitably lead to a NULL pointer 00864 // dereference if tinkered with. 00865 while (_S_last_request._M_finished() == false 00866 && (*(_S_last_request._M_get()) == 0)) 00867 { 00868 _S_last_request.operator++(); 00869 } 00870 00871 if (__builtin_expect(_S_last_request._M_finished() == true, false)) 00872 { 00873 // Fall Back to First Fit algorithm. 00874 typedef typename 00875 __gnu_cxx::__detail::_Ffit_finder<_Alloc_block*> _FFF; 00876 _FFF __fff; 00877 typedef typename _BPVector::iterator _BPiter; 00878 _BPiter __bpi = 00879 __gnu_cxx::__detail::__find_if 00880 (_S_mem_blocks.begin(), _S_mem_blocks.end(), 00881 __gnu_cxx::__detail::_Functor_Ref<_FFF>(__fff)); 00882 00883 if (__bpi != _S_mem_blocks.end()) 00884 { 00885 // Search was successful. Ok, now mark the first bit from 00886 // the right as 0, meaning Allocated. This bit is obtained 00887 // by calling _M_get() on __fff. 00888 size_t __nz_bit = _Bit_scan_forward(*__fff._M_get()); 00889 __detail::__bit_allocate(__fff._M_get(), __nz_bit); 00890 00891 _S_last_request._M_reset(__bpi - _S_mem_blocks.begin()); 00892 00893 // Now, get the address of the bit we marked as allocated. 00894 pointer __ret = reinterpret_cast<pointer> 00895 (__bpi->first + __fff._M_offset() + __nz_bit); 00896 size_t* __puse_count = 00897 reinterpret_cast<size_t*> 00898 (__bpi->first) 00899 - (__gnu_cxx::__detail::__num_bitmaps(*__bpi) + 1); 00900 00901 ++(*__puse_count); 00902 return __ret; 00903 } 00904 else 00905 { 00906 // Search was unsuccessful. We Add more memory to the 00907 // pool by calling _S_refill_pool(). 00908 _S_refill_pool(); 00909 00910 // _M_Reset the _S_last_request structure to the first 00911 // free block's bit map. 00912 _S_last_request._M_reset(_S_mem_blocks.size() - 1); 00913 00914 // Now, mark that bit as allocated. 00915 } 00916 } 00917 00918 // _S_last_request holds a pointer to a valid bit map, that 00919 // points to a free block in memory. 00920 size_t __nz_bit = _Bit_scan_forward(*_S_last_request._M_get()); 00921 __detail::__bit_allocate(_S_last_request._M_get(), __nz_bit); 00922 00923 pointer __ret = reinterpret_cast<pointer> 00924 (_S_last_request._M_base() + _S_last_request._M_offset() + __nz_bit); 00925 00926 size_t* __puse_count = reinterpret_cast<size_t*> 00927 (_S_mem_blocks[_S_last_request._M_where()].first) 00928 - (__gnu_cxx::__detail:: 00929 __num_bitmaps(_S_mem_blocks[_S_last_request._M_where()]) + 1); 00930 00931 ++(*__puse_count); 00932 return __ret; 00933 } 00934 00935 /** @brief Deallocates memory that belongs to a single object of 00936 * size sizeof(_Tp). 00937 * 00938 * @detail Complexity: O(lg(N)), but the worst case is not hit 00939 * often! This is because containers usually deallocate memory 00940 * close to each other and this case is handled in O(1) time by 00941 * the deallocate function. 00942 */ 00943 void 00944 _M_deallocate_single_object(pointer __p) throw() 00945 { 00946 #if defined __GTHREADS 00947 __gnu_cxx::__scoped_lock __bit_lock(_S_mut); 00948 #endif 00949 _Alloc_block* __real_p = reinterpret_cast<_Alloc_block*>(__p); 00950 00951 typedef typename _BPVector::iterator _Iterator; 00952 typedef typename _BPVector::difference_type _Difference_type; 00953 00954 _Difference_type __diff; 00955 long __displacement; 00956 00957 _GLIBCXX_DEBUG_ASSERT(_S_last_dealloc_index >= 0); 00958 00959 00960 if (__gnu_cxx::__detail::_Inclusive_between<_Alloc_block*> 00961 (__real_p) (_S_mem_blocks[_S_last_dealloc_index])) 00962 { 00963 _GLIBCXX_DEBUG_ASSERT(_S_last_dealloc_index 00964 <= _S_mem_blocks.size() - 1); 00965 00966 // Initial Assumption was correct! 00967 __diff = _S_last_dealloc_index; 00968 __displacement = __real_p - _S_mem_blocks[__diff].first; 00969 } 00970 else 00971 { 00972 _Iterator _iter = __gnu_cxx::__detail:: 00973 __find_if(_S_mem_blocks.begin(), 00974 _S_mem_blocks.end(), 00975 __gnu_cxx::__detail:: 00976 _Inclusive_between<_Alloc_block*>(__real_p)); 00977 00978 _GLIBCXX_DEBUG_ASSERT(_iter != _S_mem_blocks.end()); 00979 00980 __diff = _iter - _S_mem_blocks.begin(); 00981 __displacement = __real_p - _S_mem_blocks[__diff].first; 00982 _S_last_dealloc_index = __diff; 00983 } 00984 00985 // Get the position of the iterator that has been found. 00986 const size_t __rotate = (__displacement 00987 % size_t(__detail::bits_per_block)); 00988 size_t* __bitmapC = 00989 reinterpret_cast<size_t*> 00990 (_S_mem_blocks[__diff].first) - 1; 00991 __bitmapC -= (__displacement / size_t(__detail::bits_per_block)); 00992 00993 __detail::__bit_free(__bitmapC, __rotate); 00994 size_t* __puse_count = reinterpret_cast<size_t*> 00995 (_S_mem_blocks[__diff].first) 00996 - (__gnu_cxx::__detail::__num_bitmaps(_S_mem_blocks[__diff]) + 1); 00997 00998 _GLIBCXX_DEBUG_ASSERT(*__puse_count != 0); 00999 01000 --(*__puse_count); 01001 01002 if (__builtin_expect(*__puse_count == 0, false)) 01003 { 01004 _S_block_size /= 2; 01005 01006 // We can safely remove this block. 01007 // _Block_pair __bp = _S_mem_blocks[__diff]; 01008 this->_M_insert(__puse_count); 01009 _S_mem_blocks.erase(_S_mem_blocks.begin() + __diff); 01010 01011 // Reset the _S_last_request variable to reflect the 01012 // erased block. We do this to protect future requests 01013 // after the last block has been removed from a particular 01014 // memory Chunk, which in turn has been returned to the 01015 // free list, and hence had been erased from the vector, 01016 // so the size of the vector gets reduced by 1. 01017 if ((_Difference_type)_S_last_request._M_where() >= __diff--) 01018 _S_last_request._M_reset(__diff); 01019 01020 // If the Index into the vector of the region of memory 01021 // that might hold the next address that will be passed to 01022 // deallocated may have been invalidated due to the above 01023 // erase procedure being called on the vector, hence we 01024 // try to restore this invariant too. 01025 if (_S_last_dealloc_index >= _S_mem_blocks.size()) 01026 { 01027 _S_last_dealloc_index =(__diff != -1 ? __diff : 0); 01028 _GLIBCXX_DEBUG_ASSERT(_S_last_dealloc_index >= 0); 01029 } 01030 } 01031 } 01032 01033 public: 01034 bitmap_allocator() throw() 01035 { } 01036 01037 bitmap_allocator(const bitmap_allocator&) 01038 { } 01039 01040 template<typename _Tp1> 01041 bitmap_allocator(const bitmap_allocator<_Tp1>&) throw() 01042 { } 01043 01044 ~bitmap_allocator() throw() 01045 { } 01046 01047 pointer 01048 allocate(size_type __n) 01049 { 01050 if (__builtin_expect(__n > this->max_size(), false)) 01051 std::__throw_bad_alloc(); 01052 01053 if (__builtin_expect(__n == 1, true)) 01054 return this->_M_allocate_single_object(); 01055 else 01056 { 01057 const size_type __b = __n * sizeof(value_type); 01058 return reinterpret_cast<pointer>(::operator new(__b)); 01059 } 01060 } 01061 01062 pointer 01063 allocate(size_type __n, typename bitmap_allocator<void>::const_pointer) 01064 { return allocate(__n); } 01065 01066 void 01067 deallocate(pointer __p, size_type __n) throw() 01068 { 01069 if (__builtin_expect(__p != 0, true)) 01070 { 01071 if (__builtin_expect(__n == 1, true)) 01072 this->_M_deallocate_single_object(__p); 01073 else 01074 ::operator delete(__p); 01075 } 01076 } 01077 01078 pointer 01079 address(reference __r) const 01080 { return &__r; } 01081 01082 const_pointer 01083 address(const_reference __r) const 01084 { return &__r; } 01085 01086 size_type 01087 max_size() const throw() 01088 { return size_type(-1) / sizeof(value_type); } 01089 01090 void 01091 construct(pointer __p, const_reference __data) 01092 { ::new((void *)__p) value_type(__data); } 01093 01094 #ifdef __GXX_EXPERIMENTAL_CXX0X__ 01095 template<typename... _Args> 01096 void 01097 construct(pointer __p, _Args&&... __args) 01098 { ::new((void *)__p) _Tp(std::forward<_Args>(__args)...); } 01099 #endif 01100 01101 void 01102 destroy(pointer __p) 01103 { __p->~value_type(); } 01104 }; 01105 01106 template<typename _Tp1, typename _Tp2> 01107 bool 01108 operator==(const bitmap_allocator<_Tp1>&, 01109 const bitmap_allocator<_Tp2>&) throw() 01110 { return true; } 01111 01112 template<typename _Tp1, typename _Tp2> 01113 bool 01114 operator!=(const bitmap_allocator<_Tp1>&, 01115 const bitmap_allocator<_Tp2>&) throw() 01116 { return false; } 01117 01118 // Static member definitions. 01119 template<typename _Tp> 01120 typename bitmap_allocator<_Tp>::_BPVector 01121 bitmap_allocator<_Tp>::_S_mem_blocks; 01122 01123 template<typename _Tp> 01124 size_t bitmap_allocator<_Tp>::_S_block_size = 01125 2 * size_t(__detail::bits_per_block); 01126 01127 template<typename _Tp> 01128 typename __gnu_cxx::bitmap_allocator<_Tp>::_BPVector::size_type 01129 bitmap_allocator<_Tp>::_S_last_dealloc_index = 0; 01130 01131 template<typename _Tp> 01132 __gnu_cxx::__detail::_Bitmap_counter 01133 <typename bitmap_allocator<_Tp>::_Alloc_block*> 01134 bitmap_allocator<_Tp>::_S_last_request(_S_mem_blocks); 01135 01136 #if defined __GTHREADS 01137 template<typename _Tp> 01138 typename bitmap_allocator<_Tp>::__mutex_type 01139 bitmap_allocator<_Tp>::_S_mut; 01140 #endif 01141 01142 _GLIBCXX_END_NAMESPACE 01143 01144 #endif 01145