1 // Bitmap Allocator. -*- C++ -*-
3 // Copyright (C) 2004, 2005 Free Software Foundation, Inc.
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)
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.
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,
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.
30 /** @file ext/bitmap_allocator.h
31 * This file is a GNU extension to the Standard C++ Library.
34 #ifndef _BITMAP_ALLOCATOR_H
35 #define _BITMAP_ALLOCATOR_H 1
37 // For std::size_t, and ptrdiff_t.
40 // For __throw_bad_alloc().
41 #include <bits/functexcept.h>
46 // For greater_equal, and less_equal.
52 // For __gthread_mutex_t, __gthread_mutex_lock and __gthread_mutex_unlock.
53 #include <bits/gthr.h>
55 // Define this to enable error checking withing the allocator
56 // itself(to debug the allocator itself).
57 //#define _BALLOC_SANITY_CHECK
59 /** @brief The constant in the expression below is the alignment
62 #define _BALLOC_ALIGN_BYTES 8
64 #if defined _BALLOC_SANITY_CHECK
66 #define _BALLOC_ASSERT(_EXPR) assert(_EXPR)
68 #define _BALLOC_ASSERT(_EXPR)
74 #if defined __GTHREADS
77 /** @brief If true, then the application being compiled will be
78 * using threads, so use mutexes as a synchronization primitive,
79 * else do no use any synchronization primitives.
81 bool const __threads_enabled = __gthread_active_p();
85 #if defined __GTHREADS
86 /** @class _Mutex bitmap_allocator.h bitmap_allocator.h
88 * @brief _Mutex is an OO-Wrapper for __gthread_mutex_t.
90 * It does not allow you to copy or assign an already initialized
91 * mutex. This is used merely as a convenience for the locking
96 __gthread_mutex_t _M_mut;
98 // Prevent Copying and assignment.
99 _Mutex(_Mutex const&);
100 _Mutex& operator=(_Mutex const&);
105 if (__threads_enabled)
107 #if !defined __GTHREAD_MUTEX_INIT
108 __GTHREAD_MUTEX_INIT_FUNCTION(&_M_mut);
110 __gthread_mutex_t __mtemp = __GTHREAD_MUTEX_INIT;
118 // Gthreads does not define a Mutex Destruction Function.
122 _M_get() { return &_M_mut; }
125 /** @class _Lock bitmap_allocator.h bitmap_allocator.h
127 * @brief _Lock is a simple manual locking class which allows you to
128 * manually lock and unlock a mutex associated with the lock.
130 * There is no automatic locking or unlocking happening without the
131 * programmer's explicit instructions. This class unlocks the mutex
132 * ONLY if it has not been locked. However, this check does not
133 * apply for locking, and wayward use may cause dead-locks.
140 // Prevent Copying and assignment.
142 _Lock& operator=(_Lock const&);
145 _Lock(_Mutex* __mptr)
146 : _M_pmt(__mptr), _M_locked(false)
152 if (__threads_enabled)
155 __gthread_mutex_lock(_M_pmt->_M_get());
162 if (__threads_enabled)
164 if (__builtin_expect(_M_locked, true))
166 __gthread_mutex_unlock(_M_pmt->_M_get());
175 /** @class _Auto_Lock bitmap_allocator.h bitmap_allocator.h
177 * @brief _Auto_Lock locks the associated mutex on construction, and
178 * unlocks on destruction.
180 * There are no checks performed, and this class follows the RAII
186 // Prevent Copying and assignment.
187 _Auto_Lock(_Auto_Lock const&);
188 _Auto_Lock& operator=(_Auto_Lock const&);
193 if (__threads_enabled)
194 __gthread_mutex_lock(_M_pmt->_M_get());
200 if (__threads_enabled)
201 __gthread_mutex_unlock(_M_pmt->_M_get());
205 _Auto_Lock(_Mutex* __mptr) : _M_pmt(__mptr)
208 ~_Auto_Lock() { this->_M_unlock(); }
214 /** @class __mini_vector bitmap_allocator.h bitmap_allocator.h
216 * @brief __mini_vector<> is a stripped down version of the
217 * full-fledged std::vector<>.
219 * It is to be used only for built-in types or PODs. Notable
223 * 1. Not all accessor functions are present.
224 * 2. Used ONLY for PODs.
225 * 3. No Allocator template argument. Uses ::operator new() to get
226 * memory, and ::operator delete() to free it.
227 * Caveat: The dtor does NOT free the memory allocated, so this a
228 * memory-leaking vector!
230 template<typename _Tp>
233 __mini_vector(const __mini_vector&);
234 __mini_vector& operator=(const __mini_vector&);
237 typedef _Tp value_type;
238 typedef _Tp* pointer;
239 typedef _Tp& reference;
240 typedef const _Tp& const_reference;
241 typedef std::size_t size_type;
242 typedef std::ptrdiff_t difference_type;
243 typedef pointer iterator;
248 pointer _M_end_of_storage;
251 _M_space_left() const throw()
252 { return _M_end_of_storage - _M_finish; }
255 allocate(size_type __n)
256 { return static_cast<pointer>(::operator new(__n * sizeof(_Tp))); }
259 deallocate(pointer __p, size_type)
260 { ::operator delete(__p); }
263 // Members used: size(), push_back(), pop_back(),
264 // insert(iterator, const_reference), erase(iterator),
265 // begin(), end(), back(), operator[].
267 __mini_vector() : _M_start(0), _M_finish(0),
276 this->deallocate(this->_M_start, this->_M_end_of_storage
284 { return _M_finish - _M_start; }
287 begin() const throw()
288 { return this->_M_start; }
292 { return this->_M_finish; }
296 { return *(this->end() - 1); }
299 operator[](const size_type __pos) const throw()
300 { return this->_M_start[__pos]; }
303 insert(iterator __pos, const_reference __x);
306 push_back(const_reference __x)
308 if (this->_M_space_left())
314 this->insert(this->end(), __x);
319 { --this->_M_finish; }
322 erase(iterator __pos) throw();
326 { this->_M_finish = this->_M_start; }
329 // Out of line function definitions.
330 template<typename _Tp>
331 void __mini_vector<_Tp>::
332 insert(iterator __pos, const_reference __x)
334 if (this->_M_space_left())
336 size_type __to_move = this->_M_finish - __pos;
337 iterator __dest = this->end();
338 iterator __src = this->end() - 1;
344 --__dest; --__src; --__to_move;
350 size_type __new_size = this->size() ? this->size() * 2 : 1;
351 iterator __new_start = this->allocate(__new_size);
352 iterator __first = this->begin();
353 iterator __start = __new_start;
354 while (__first != __pos)
357 ++__start; ++__first;
361 while (__first != this->end())
364 ++__start; ++__first;
367 this->deallocate(this->_M_start, this->size());
369 this->_M_start = __new_start;
370 this->_M_finish = __start;
371 this->_M_end_of_storage = this->_M_start + __new_size;
375 template<typename _Tp>
376 void __mini_vector<_Tp>::
377 erase(iterator __pos) throw()
379 while (__pos + 1 != this->end())
388 template<typename _Tp>
389 struct __mv_iter_traits
391 typedef typename _Tp::value_type value_type;
392 typedef typename _Tp::difference_type difference_type;
395 template<typename _Tp>
396 struct __mv_iter_traits<_Tp*>
398 typedef _Tp value_type;
399 typedef std::ptrdiff_t difference_type;
405 bits_per_block = sizeof(size_t) * size_t(bits_per_byte)
408 template<typename _ForwardIterator, typename _Tp, typename _Compare>
410 __lower_bound(_ForwardIterator __first, _ForwardIterator __last,
411 const _Tp& __val, _Compare __comp)
413 typedef typename __mv_iter_traits<_ForwardIterator>::value_type
415 typedef typename __mv_iter_traits<_ForwardIterator>::difference_type
418 _DistanceType __len = __last - __first;
419 _DistanceType __half;
420 _ForwardIterator __middle;
427 if (__comp(*__middle, __val))
431 __len = __len - __half - 1;
439 template<typename _InputIterator, typename _Predicate>
440 inline _InputIterator
441 __find_if(_InputIterator __first, _InputIterator __last, _Predicate __p)
443 while (__first != __last && !__p(*__first))
448 /** @brief The number of Blocks pointed to by the address pair
449 * passed to the function.
451 template<typename _AddrPair>
453 __num_blocks(_AddrPair __ap)
454 { return (__ap.second - __ap.first) + 1; }
456 /** @brief The number of Bit-maps pointed to by the address pair
457 * passed to the function.
459 template<typename _AddrPair>
461 __num_bitmaps(_AddrPair __ap)
462 { return __num_blocks(__ap) / size_t(bits_per_block); }
464 // _Tp should be a pointer type.
465 template<typename _Tp>
466 class _Inclusive_between
467 : public std::unary_function<typename std::pair<_Tp, _Tp>, bool>
470 pointer _M_ptr_value;
471 typedef typename std::pair<_Tp, _Tp> _Block_pair;
474 _Inclusive_between(pointer __ptr) : _M_ptr_value(__ptr)
478 operator()(_Block_pair __bp) const throw()
480 if (std::less_equal<pointer>()(_M_ptr_value, __bp.second)
481 && std::greater_equal<pointer>()(_M_ptr_value, __bp.first))
488 // Used to pass a Functor to functions by reference.
489 template<typename _Functor>
491 : public std::unary_function<typename _Functor::argument_type,
492 typename _Functor::result_type>
497 typedef typename _Functor::argument_type argument_type;
498 typedef typename _Functor::result_type result_type;
500 _Functor_Ref(_Functor& __fref) : _M_fref(__fref)
504 operator()(argument_type __arg)
505 { return _M_fref(__arg); }
508 /** @class _Ffit_finder bitmap_allocator.h bitmap_allocator.h
510 * @brief The class which acts as a predicate for applying the
511 * first-fit memory allocation policy for the bitmap allocator.
513 // _Tp should be a pointer type, and _Alloc is the Allocator for
515 template<typename _Tp>
517 : public std::unary_function<typename std::pair<_Tp, _Tp>, bool>
519 typedef typename std::pair<_Tp, _Tp> _Block_pair;
520 typedef typename balloc::__mini_vector<_Block_pair> _BPVector;
521 typedef typename _BPVector::difference_type _Counter_type;
524 _Counter_type _M_data_offset;
527 _Ffit_finder() : _M_pbitmap(0), _M_data_offset(0)
531 operator()(_Block_pair __bp) throw()
533 // Set the _rover to the last physical location bitmap,
534 // which is the bitmap which belongs to the first free
535 // block. Thus, the bitmaps are in exact reverse order of
536 // the actual memory layout. So, we count down the bimaps,
537 // which is the same as moving up the memory.
539 // If the used count stored at the start of the Bit Map headers
540 // is equal to the number of Objects that the current Block can
541 // store, then there is definitely no space for another single
542 // object, so just return false.
543 _Counter_type __diff =
544 __gnu_cxx::balloc::__num_bitmaps(__bp);
546 if (*(reinterpret_cast<size_t*>
547 (__bp.first) - (__diff + 1))
548 == __gnu_cxx::balloc::__num_blocks(__bp))
551 size_t* __rover = reinterpret_cast<size_t*>(__bp.first) - 1;
553 for (_Counter_type __i = 0; __i < __diff; ++__i)
555 _M_data_offset = __i;
558 _M_pbitmap = __rover;
568 _M_get() const throw()
569 { return _M_pbitmap; }
572 _M_offset() const throw()
573 { return _M_data_offset * size_t(bits_per_block); }
577 /** @class _Bitmap_counter bitmap_allocator.h bitmap_allocator.h
579 * @brief The bitmap counter which acts as the bitmap
580 * manipulator, and manages the bit-manipulation functions and
581 * the searching and identification functions on the bit-map.
583 // _Tp should be a pointer type.
584 template<typename _Tp>
585 class _Bitmap_counter
587 typedef typename balloc::__mini_vector<typename std::pair<_Tp, _Tp> >
589 typedef typename _BPVector::size_type _Index_type;
593 size_t* _M_curr_bmap;
594 size_t* _M_last_bmap_in_block;
595 _Index_type _M_curr_index;
598 // Use the 2nd parameter with care. Make sure that such an
599 // entry exists in the vector before passing that particular
600 // index to this ctor.
601 _Bitmap_counter(_BPVector& Rvbp, long __index = -1) : _M_vbp(Rvbp)
602 { this->_M_reset(__index); }
605 _M_reset(long __index = -1) throw()
610 _M_curr_index = static_cast<_Index_type>(-1);
614 _M_curr_index = __index;
615 _M_curr_bmap = reinterpret_cast<size_t*>
616 (_M_vbp[_M_curr_index].first) - 1;
618 _BALLOC_ASSERT(__index <= (long)_M_vbp.size() - 1);
620 _M_last_bmap_in_block = _M_curr_bmap
621 - ((_M_vbp[_M_curr_index].second
622 - _M_vbp[_M_curr_index].first + 1)
623 / size_t(bits_per_block) - 1);
626 // Dangerous Function! Use with extreme care. Pass to this
627 // function ONLY those values that are known to be correct,
628 // otherwise this will mess up big time.
630 _M_set_internal_bitmap(size_t* __new_internal_marker) throw()
631 { _M_curr_bmap = __new_internal_marker; }
634 _M_finished() const throw()
635 { return(_M_curr_bmap == 0); }
640 if (_M_curr_bmap == _M_last_bmap_in_block)
642 if (++_M_curr_index == _M_vbp.size())
645 this->_M_reset(_M_curr_index);
653 _M_get() const throw()
654 { return _M_curr_bmap; }
657 _M_base() const throw()
658 { return _M_vbp[_M_curr_index].first; }
661 _M_offset() const throw()
663 return size_t(bits_per_block)
664 * ((reinterpret_cast<size_t*>(this->_M_base())
665 - _M_curr_bmap) - 1);
669 _M_where() const throw()
670 { return _M_curr_index; }
673 /** @brief Mark a memory address as allocated by re-setting the
674 * corresponding bit in the bit-map.
677 __bit_allocate(size_t* __pbmap, size_t __pos) throw()
679 size_t __mask = 1 << __pos;
684 /** @brief Mark a memory address as free by setting the
685 * corresponding bit in the bit-map.
688 __bit_free(size_t* __pbmap, size_t __pos) throw()
690 size_t __mask = 1 << __pos;
693 } // namespace balloc
695 /** @brief Generic Version of the bsf instruction.
698 _Bit_scan_forward(size_t __num)
699 { return static_cast<size_t>(__builtin_ctzl(__num)); }
701 /** @class free_list bitmap_allocator.h bitmap_allocator.h
703 * @brief The free list class for managing chunks of memory to be
704 * given to and returned by the bitmap_allocator.
708 typedef size_t* value_type;
709 typedef balloc::__mini_vector<value_type> vector_type;
710 typedef vector_type::iterator iterator;
712 struct _LT_pointer_compare
715 operator()(const size_t* __pui,
716 const size_t __cui) const throw()
717 { return *__pui < __cui; }
720 #if defined __GTHREADS
724 static _Mutex _S_mutex;
732 static vector_type _S_free_list;
736 /** @brief Performs validation of memory based on their size.
738 * @param __addr The pointer to the memory block to be
741 * @detail Validates the memory block passed to this function and
742 * appropriately performs the action of managing the free list of
743 * blocks by adding this block to the free list or deleting this
744 * or larger blocks from the free list.
747 _M_validate(size_t* __addr) throw()
749 vector_type& __free_list = _M_get_free_list();
750 const vector_type::size_type __max_size = 64;
751 if (__free_list.size() >= __max_size)
753 // Ok, the threshold value has been reached. We determine
754 // which block to remove from the list of free blocks.
755 if (*__addr >= *__free_list.back())
757 // Ok, the new block is greater than or equal to the
758 // last block in the list of free blocks. We just free
760 ::operator delete(static_cast<void*>(__addr));
765 // Deallocate the last block in the list of free lists,
766 // and insert the new one in it's correct position.
767 ::operator delete(static_cast<void*>(__free_list.back()));
768 __free_list.pop_back();
772 // Just add the block to the list of free lists unconditionally.
773 iterator __temp = __gnu_cxx::balloc::__lower_bound
774 (__free_list.begin(), __free_list.end(),
775 *__addr, _LT_pointer_compare());
777 // We may insert the new free list before _temp;
778 __free_list.insert(__temp, __addr);
781 /** @brief Decides whether the wastage of memory is acceptable for
782 * the current memory request and returns accordingly.
784 * @param __block_size The size of the block available in the free
787 * @param __required_size The required size of the memory block.
789 * @return true if the wastage incurred is acceptable, else returns
793 _M_should_i_give(size_t __block_size,
794 size_t __required_size) throw()
796 const size_t __max_wastage_percentage = 36;
797 if (__block_size >= __required_size &&
798 (((__block_size - __required_size) * 100 / __block_size)
799 < __max_wastage_percentage))
806 /** @brief This function returns the block of memory to the
807 * internal free list.
809 * @param __addr The pointer to the memory block that was given
810 * by a call to the _M_get function.
813 _M_insert(size_t* __addr) throw()
815 #if defined __GTHREADS
816 _Auto_Lock __bfl_lock(_M_get_mutex());
818 // Call _M_validate to decide what should be done with
819 // this particular free list.
820 this->_M_validate(reinterpret_cast<size_t*>(__addr) - 1);
821 // See discussion as to why this is 1!
824 /** @brief This function gets a block of memory of the specified
825 * size from the free list.
827 * @param __sz The size in bytes of the memory required.
829 * @return A pointer to the new memory block of size at least
830 * equal to that requested.
833 _M_get(size_t __sz) throw(std::bad_alloc);
835 /** @brief This function just clears the internal Free List, and
836 * gives back all the memory to the OS.
843 // Forward declare the class.
844 template<typename _Tp>
845 class bitmap_allocator;
847 // Specialize for void:
849 class bitmap_allocator<void>
852 typedef void* pointer;
853 typedef const void* const_pointer;
855 // Reference-to-void members are impossible.
856 typedef void value_type;
857 template<typename _Tp1>
860 typedef bitmap_allocator<_Tp1> other;
864 template<typename _Tp>
865 class bitmap_allocator : private free_list
868 typedef std::size_t size_type;
869 typedef std::ptrdiff_t difference_type;
870 typedef _Tp* pointer;
871 typedef const _Tp* const_pointer;
872 typedef _Tp& reference;
873 typedef const _Tp& const_reference;
874 typedef _Tp value_type;
875 template<typename _Tp1>
878 typedef bitmap_allocator<_Tp1> other;
882 template<size_t _BSize, size_t _AlignSize>
887 modulus = _BSize % _AlignSize,
888 value = _BSize + (modulus ? _AlignSize - (modulus) : 0)
894 char __M_unused[aligned_size<sizeof(value_type),
895 _BALLOC_ALIGN_BYTES>::value];
899 typedef typename std::pair<_Alloc_block*, _Alloc_block*> _Block_pair;
902 balloc::__mini_vector<_Block_pair> _BPVector;
904 #if defined _BALLOC_SANITY_CHECK
905 // Complexity: O(lg(N)). Where, N is the number of block of size
906 // sizeof(value_type).
908 _S_check_for_free_blocks() throw()
911 __gnu_cxx::balloc::_Ffit_finder<_Alloc_block*> _FFF;
913 typedef typename _BPVector::iterator _BPiter;
915 __gnu_cxx::balloc::__find_if
916 (_S_mem_blocks.begin(), _S_mem_blocks.end(),
917 __gnu_cxx::balloc::_Functor_Ref<_FFF>(__fff));
919 _BALLOC_ASSERT(__bpi == _S_mem_blocks.end());
923 /** @brief Responsible for exponentially growing the internal
926 * @throw std::bad_alloc. If memory can not be allocated.
928 * @detail Complexity: O(1), but internally depends upon the
929 * complexity of the function free_list::_M_get. The part where
930 * the bitmap headers are written has complexity: O(X),where X
931 * is the number of blocks of size sizeof(value_type) within
932 * the newly acquired block. Having a tight bound.
935 _S_refill_pool() throw(std::bad_alloc)
937 #if defined _BALLOC_SANITY_CHECK
938 _S_check_for_free_blocks();
941 const size_t __num_bitmaps = (_S_block_size
942 / size_t(balloc::bits_per_block));
943 const size_t __size_to_allocate = sizeof(size_t)
944 + _S_block_size * sizeof(_Alloc_block)
945 + __num_bitmaps * sizeof(size_t);
948 reinterpret_cast<size_t*>
949 (this->_M_get(__size_to_allocate));
953 // The Header information goes at the Beginning of the Block.
955 std::make_pair(reinterpret_cast<_Alloc_block*>
956 (__temp + __num_bitmaps),
957 reinterpret_cast<_Alloc_block*>
958 (__temp + __num_bitmaps)
959 + _S_block_size - 1);
961 // Fill the Vector with this information.
962 _S_mem_blocks.push_back(__bp);
964 size_t __bit_mask = 0; // 0 Indicates all Allocated.
965 __bit_mask = ~__bit_mask; // 1 Indicates all Free.
967 for (size_t __i = 0; __i < __num_bitmaps; ++__i)
968 __temp[__i] = __bit_mask;
974 static _BPVector _S_mem_blocks;
975 static size_t _S_block_size;
976 static __gnu_cxx::balloc::
977 _Bitmap_counter<_Alloc_block*> _S_last_request;
978 static typename _BPVector::size_type _S_last_dealloc_index;
979 #if defined __GTHREADS
980 static _Mutex _S_mut;
985 /** @brief Allocates memory for a single object of size
988 * @throw std::bad_alloc. If memory can not be allocated.
990 * @detail Complexity: Worst case complexity is O(N), but that
991 * is hardly ever hit. If and when this particular case is
992 * encountered, the next few cases are guaranteed to have a
993 * worst case complexity of O(1)! That's why this function
994 * performs very well on average. You can consider this
995 * function to have a complexity referred to commonly as:
996 * Amortized Constant time.
999 _M_allocate_single_object() throw(std::bad_alloc)
1001 #if defined __GTHREADS
1002 _Auto_Lock __bit_lock(&_S_mut);
1005 // The algorithm is something like this: The last_request
1006 // variable points to the last accessed Bit Map. When such a
1007 // condition occurs, we try to find a free block in the
1008 // current bitmap, or succeeding bitmaps until the last bitmap
1009 // is reached. If no free block turns up, we resort to First
1012 // WARNING: Do not re-order the condition in the while
1013 // statement below, because it relies on C++'s short-circuit
1014 // evaluation. The return from _S_last_request->_M_get() will
1015 // NOT be dereference able if _S_last_request->_M_finished()
1016 // returns true. This would inevitably lead to a NULL pointer
1017 // dereference if tinkered with.
1018 while (_S_last_request._M_finished() == false
1019 && (*(_S_last_request._M_get()) == 0))
1021 _S_last_request.operator++();
1024 if (__builtin_expect(_S_last_request._M_finished() == true, false))
1026 // Fall Back to First Fit algorithm.
1028 __gnu_cxx::balloc::_Ffit_finder<_Alloc_block*> _FFF;
1030 typedef typename _BPVector::iterator _BPiter;
1032 __gnu_cxx::balloc::__find_if
1033 (_S_mem_blocks.begin(), _S_mem_blocks.end(),
1034 __gnu_cxx::balloc::_Functor_Ref<_FFF>(__fff));
1036 if (__bpi != _S_mem_blocks.end())
1038 // Search was successful. Ok, now mark the first bit from
1039 // the right as 0, meaning Allocated. This bit is obtained
1040 // by calling _M_get() on __fff.
1041 size_t __nz_bit = _Bit_scan_forward(*__fff._M_get());
1042 balloc::__bit_allocate(__fff._M_get(), __nz_bit);
1044 _S_last_request._M_reset(__bpi - _S_mem_blocks.begin());
1046 // Now, get the address of the bit we marked as allocated.
1047 pointer __ret = reinterpret_cast<pointer>
1048 (__bpi->first + __fff._M_offset() + __nz_bit);
1049 size_t* __puse_count =
1050 reinterpret_cast<size_t*>
1052 - (__gnu_cxx::balloc::__num_bitmaps(*__bpi) + 1);
1059 // Search was unsuccessful. We Add more memory to the
1060 // pool by calling _S_refill_pool().
1063 // _M_Reset the _S_last_request structure to the first
1064 // free block's bit map.
1065 _S_last_request._M_reset(_S_mem_blocks.size() - 1);
1067 // Now, mark that bit as allocated.
1071 // _S_last_request holds a pointer to a valid bit map, that
1072 // points to a free block in memory.
1073 size_t __nz_bit = _Bit_scan_forward(*_S_last_request._M_get());
1074 balloc::__bit_allocate(_S_last_request._M_get(), __nz_bit);
1076 pointer __ret = reinterpret_cast<pointer>
1077 (_S_last_request._M_base() + _S_last_request._M_offset() + __nz_bit);
1079 size_t* __puse_count = reinterpret_cast<size_t*>
1080 (_S_mem_blocks[_S_last_request._M_where()].first)
1081 - (__gnu_cxx::balloc::
1082 __num_bitmaps(_S_mem_blocks[_S_last_request._M_where()]) + 1);
1088 /** @brief Deallocates memory that belongs to a single object of
1091 * @detail Complexity: O(lg(N)), but the worst case is not hit
1092 * often! This is because containers usually deallocate memory
1093 * close to each other and this case is handled in O(1) time by
1094 * the deallocate function.
1097 _M_deallocate_single_object(pointer __p) throw()
1099 #if defined __GTHREADS
1100 _Auto_Lock __bit_lock(&_S_mut);
1102 _Alloc_block* __real_p = reinterpret_cast<_Alloc_block*>(__p);
1104 typedef typename _BPVector::iterator _Iterator;
1105 typedef typename _BPVector::difference_type _Difference_type;
1107 _Difference_type __diff;
1108 long __displacement;
1110 _BALLOC_ASSERT(_S_last_dealloc_index >= 0);
1113 if (__gnu_cxx::balloc::_Inclusive_between<_Alloc_block*>
1115 (_S_mem_blocks[_S_last_dealloc_index]))
1117 _BALLOC_ASSERT(_S_last_dealloc_index <= _S_mem_blocks.size() - 1);
1119 // Initial Assumption was correct!
1120 __diff = _S_last_dealloc_index;
1121 __displacement = __real_p - _S_mem_blocks[__diff].first;
1127 __find_if(_S_mem_blocks.begin(),
1128 _S_mem_blocks.end(),
1130 _Inclusive_between<_Alloc_block*>(__real_p));
1132 _BALLOC_ASSERT(_iter != _S_mem_blocks.end());
1134 __diff = _iter - _S_mem_blocks.begin();
1135 __displacement = __real_p - _S_mem_blocks[__diff].first;
1136 _S_last_dealloc_index = __diff;
1139 // Get the position of the iterator that has been found.
1140 const size_t __rotate = (__displacement
1141 % size_t(balloc::bits_per_block));
1143 reinterpret_cast<size_t*>
1144 (_S_mem_blocks[__diff].first) - 1;
1145 __bitmapC -= (__displacement / size_t(balloc::bits_per_block));
1147 balloc::__bit_free(__bitmapC, __rotate);
1148 size_t* __puse_count = reinterpret_cast<size_t*>
1149 (_S_mem_blocks[__diff].first)
1150 - (__gnu_cxx::balloc::__num_bitmaps(_S_mem_blocks[__diff]) + 1);
1152 _BALLOC_ASSERT(*__puse_count != 0);
1156 if (__builtin_expect(*__puse_count == 0, false))
1160 // We can safely remove this block.
1161 // _Block_pair __bp = _S_mem_blocks[__diff];
1162 this->_M_insert(__puse_count);
1163 _S_mem_blocks.erase(_S_mem_blocks.begin() + __diff);
1165 // Reset the _S_last_request variable to reflect the
1166 // erased block. We do this to protect future requests
1167 // after the last block has been removed from a particular
1168 // memory Chunk, which in turn has been returned to the
1169 // free list, and hence had been erased from the vector,
1170 // so the size of the vector gets reduced by 1.
1171 if ((_Difference_type)_S_last_request._M_where() >= __diff--)
1172 _S_last_request._M_reset(__diff);
1174 // If the Index into the vector of the region of memory
1175 // that might hold the next address that will be passed to
1176 // deallocated may have been invalidated due to the above
1177 // erase procedure being called on the vector, hence we
1178 // try to restore this invariant too.
1179 if (_S_last_dealloc_index >= _S_mem_blocks.size())
1181 _S_last_dealloc_index =(__diff != -1 ? __diff : 0);
1182 _BALLOC_ASSERT(_S_last_dealloc_index >= 0);
1188 bitmap_allocator() throw()
1191 bitmap_allocator(const bitmap_allocator&)
1194 template<typename _Tp1>
1195 bitmap_allocator(const bitmap_allocator<_Tp1>&) throw()
1198 ~bitmap_allocator() throw()
1202 allocate(size_type __n)
1204 if (__builtin_expect(__n > this->max_size(), false))
1205 std::__throw_bad_alloc();
1207 if (__builtin_expect(__n == 1, true))
1208 return this->_M_allocate_single_object();
1211 const size_type __b = __n * sizeof(value_type);
1212 return reinterpret_cast<pointer>(::operator new(__b));
1217 allocate(size_type __n, typename bitmap_allocator<void>::const_pointer)
1218 { return allocate(__n); }
1221 deallocate(pointer __p, size_type __n) throw()
1223 if (__builtin_expect(__p != 0, true))
1225 if (__builtin_expect(__n == 1, true))
1226 this->_M_deallocate_single_object(__p);
1228 ::operator delete(__p);
1233 address(reference __r) const
1237 address(const_reference __r) const
1241 max_size() const throw()
1242 { return size_type(-1) / sizeof(value_type); }
1245 construct(pointer __p, const_reference __data)
1246 { ::new(__p) value_type(__data); }
1249 destroy(pointer __p)
1250 { __p->~value_type(); }
1253 template<typename _Tp1, typename _Tp2>
1255 operator==(const bitmap_allocator<_Tp1>&,
1256 const bitmap_allocator<_Tp2>&) throw()
1259 template<typename _Tp1, typename _Tp2>
1261 operator!=(const bitmap_allocator<_Tp1>&,
1262 const bitmap_allocator<_Tp2>&) throw()
1265 // Static member definitions.
1266 template<typename _Tp>
1267 typename bitmap_allocator<_Tp>::_BPVector
1268 bitmap_allocator<_Tp>::_S_mem_blocks;
1270 template<typename _Tp>
1271 size_t bitmap_allocator<_Tp>::_S_block_size =
1272 2 * size_t(balloc::bits_per_block);
1274 template<typename _Tp>
1275 typename __gnu_cxx::bitmap_allocator<_Tp>::_BPVector::size_type
1276 bitmap_allocator<_Tp>::_S_last_dealloc_index = 0;
1278 template<typename _Tp>
1279 __gnu_cxx::balloc::_Bitmap_counter
1280 <typename bitmap_allocator<_Tp>::_Alloc_block*>
1281 bitmap_allocator<_Tp>::_S_last_request(_S_mem_blocks);
1283 #if defined __GTHREADS
1284 template<typename _Tp>
1286 bitmap_allocator<_Tp>::_S_mut;
1294 // LocalWords: namespace GTHREADS bool const gthread endif Mutex mutex