| // Bitmap Allocator. -*- C++ -*- |
| |
| // Copyright (C) 2004-2020 Free Software Foundation, Inc. |
| // |
| // This file is part of the GNU ISO C++ Library. This library is free |
| // software; you can redistribute it and/or modify it under the |
| // terms of the GNU General Public License as published by the |
| // Free Software Foundation; either version 3, or (at your option) |
| // any later version. |
| |
| // This library is distributed in the hope that it will be useful, |
| // but WITHOUT ANY WARRANTY; without even the implied warranty of |
| // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| // GNU General Public License for more details. |
| |
| // Under Section 7 of GPL version 3, you are granted additional |
| // permissions described in the GCC Runtime Library Exception, version |
| // 3.1, as published by the Free Software Foundation. |
| |
| // You should have received a copy of the GNU General Public License and |
| // a copy of the GCC Runtime Library Exception along with this program; |
| // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see |
| // <http://www.gnu.org/licenses/>. |
| |
| /** @file ext/bitmap_allocator.h |
| * This file is a GNU extension to the Standard C++ Library. |
| */ |
| |
| #ifndef _BITMAP_ALLOCATOR_H |
| #define _BITMAP_ALLOCATOR_H 1 |
| |
| #include <utility> // For std::pair. |
| #include <bits/functexcept.h> // For __throw_bad_alloc(). |
| #include <bits/stl_function.h> // For greater_equal, and less_equal. |
| #include <new> // For operator new. |
| #include <debug/debug.h> // _GLIBCXX_DEBUG_ASSERT |
| #include <ext/concurrence.h> |
| #include <bits/move.h> |
| |
| /** @brief The constant in the expression below is the alignment |
| * required in bytes. |
| */ |
| #define _BALLOC_ALIGN_BYTES 8 |
| |
| namespace __gnu_cxx _GLIBCXX_VISIBILITY(default) |
| { |
| _GLIBCXX_BEGIN_NAMESPACE_VERSION |
| |
| namespace __detail |
| { |
| /** @class __mini_vector bitmap_allocator.h bitmap_allocator.h |
| * |
| * @brief __mini_vector<> is a stripped down version of the |
| * full-fledged std::vector<>. |
| * |
| * It is to be used only for built-in types or PODs. Notable |
| * differences are: |
| * |
| * 1. Not all accessor functions are present. |
| * 2. Used ONLY for PODs. |
| * 3. No Allocator template argument. Uses ::operator new() to get |
| * memory, and ::operator delete() to free it. |
| * Caveat: The dtor does NOT free the memory allocated, so this a |
| * memory-leaking vector! |
| */ |
| template<typename _Tp> |
| class __mini_vector |
| { |
| __mini_vector(const __mini_vector&); |
| __mini_vector& operator=(const __mini_vector&); |
| |
| public: |
| typedef _Tp value_type; |
| typedef _Tp* pointer; |
| typedef _Tp& reference; |
| typedef const _Tp& const_reference; |
| typedef std::size_t size_type; |
| typedef std::ptrdiff_t difference_type; |
| typedef pointer iterator; |
| |
| private: |
| pointer _M_start; |
| pointer _M_finish; |
| pointer _M_end_of_storage; |
| |
| size_type |
| _M_space_left() const throw() |
| { return _M_end_of_storage - _M_finish; } |
| |
| _GLIBCXX_NODISCARD pointer |
| allocate(size_type __n) |
| { return static_cast<pointer>(::operator new(__n * sizeof(_Tp))); } |
| |
| void |
| deallocate(pointer __p, size_type) |
| { ::operator delete(__p); } |
| |
| public: |
| // Members used: size(), push_back(), pop_back(), |
| // insert(iterator, const_reference), erase(iterator), |
| // begin(), end(), back(), operator[]. |
| |
| __mini_vector() |
| : _M_start(0), _M_finish(0), _M_end_of_storage(0) { } |
| |
| size_type |
| size() const throw() |
| { return _M_finish - _M_start; } |
| |
| iterator |
| begin() const throw() |
| { return this->_M_start; } |
| |
| iterator |
| end() const throw() |
| { return this->_M_finish; } |
| |
| reference |
| back() const throw() |
| { return *(this->end() - 1); } |
| |
| reference |
| operator[](const size_type __pos) const throw() |
| { return this->_M_start[__pos]; } |
| |
| void |
| insert(iterator __pos, const_reference __x); |
| |
| void |
| push_back(const_reference __x) |
| { |
| if (this->_M_space_left()) |
| { |
| *this->end() = __x; |
| ++this->_M_finish; |
| } |
| else |
| this->insert(this->end(), __x); |
| } |
| |
| void |
| pop_back() throw() |
| { --this->_M_finish; } |
| |
| void |
| erase(iterator __pos) throw(); |
| |
| void |
| clear() throw() |
| { this->_M_finish = this->_M_start; } |
| }; |
| |
| // Out of line function definitions. |
| template<typename _Tp> |
| void __mini_vector<_Tp>:: |
| insert(iterator __pos, const_reference __x) |
| { |
| if (this->_M_space_left()) |
| { |
| size_type __to_move = this->_M_finish - __pos; |
| iterator __dest = this->end(); |
| iterator __src = this->end() - 1; |
| |
| ++this->_M_finish; |
| while (__to_move) |
| { |
| *__dest = *__src; |
| --__dest; --__src; --__to_move; |
| } |
| *__pos = __x; |
| } |
| else |
| { |
| size_type __new_size = this->size() ? this->size() * 2 : 1; |
| iterator __new_start = this->allocate(__new_size); |
| iterator __first = this->begin(); |
| iterator __start = __new_start; |
| while (__first != __pos) |
| { |
| *__start = *__first; |
| ++__start; ++__first; |
| } |
| *__start = __x; |
| ++__start; |
| while (__first != this->end()) |
| { |
| *__start = *__first; |
| ++__start; ++__first; |
| } |
| if (this->_M_start) |
| this->deallocate(this->_M_start, this->size()); |
| |
| this->_M_start = __new_start; |
| this->_M_finish = __start; |
| this->_M_end_of_storage = this->_M_start + __new_size; |
| } |
| } |
| |
| template<typename _Tp> |
| void __mini_vector<_Tp>:: |
| erase(iterator __pos) throw() |
| { |
| while (__pos + 1 != this->end()) |
| { |
| *__pos = __pos[1]; |
| ++__pos; |
| } |
| --this->_M_finish; |
| } |
| |
| |
| template<typename _Tp> |
| struct __mv_iter_traits |
| { |
| typedef typename _Tp::value_type value_type; |
| typedef typename _Tp::difference_type difference_type; |
| }; |
| |
| template<typename _Tp> |
| struct __mv_iter_traits<_Tp*> |
| { |
| typedef _Tp value_type; |
| typedef std::ptrdiff_t difference_type; |
| }; |
| |
| enum |
| { |
| bits_per_byte = 8, |
| bits_per_block = sizeof(std::size_t) * std::size_t(bits_per_byte) |
| }; |
| |
| template<typename _ForwardIterator, typename _Tp, typename _Compare> |
| _ForwardIterator |
| __lower_bound(_ForwardIterator __first, _ForwardIterator __last, |
| const _Tp& __val, _Compare __comp) |
| { |
| typedef typename __mv_iter_traits<_ForwardIterator>::difference_type |
| _DistanceType; |
| |
| _DistanceType __len = __last - __first; |
| _DistanceType __half; |
| _ForwardIterator __middle; |
| |
| while (__len > 0) |
| { |
| __half = __len >> 1; |
| __middle = __first; |
| __middle += __half; |
| if (__comp(*__middle, __val)) |
| { |
| __first = __middle; |
| ++__first; |
| __len = __len - __half - 1; |
| } |
| else |
| __len = __half; |
| } |
| return __first; |
| } |
| |
| /** @brief The number of Blocks pointed to by the address pair |
| * passed to the function. |
| */ |
| template<typename _AddrPair> |
| inline std::size_t |
| __num_blocks(_AddrPair __ap) |
| { return (__ap.second - __ap.first) + 1; } |
| |
| /** @brief The number of Bit-maps pointed to by the address pair |
| * passed to the function. |
| */ |
| template<typename _AddrPair> |
| inline std::size_t |
| __num_bitmaps(_AddrPair __ap) |
| { return __num_blocks(__ap) / std::size_t(bits_per_block); } |
| |
| // _Tp should be a pointer type. |
| template<typename _Tp> |
| class _Inclusive_between |
| : public std::unary_function<typename std::pair<_Tp, _Tp>, bool> |
| { |
| typedef _Tp pointer; |
| pointer _M_ptr_value; |
| typedef typename std::pair<_Tp, _Tp> _Block_pair; |
| |
| public: |
| _Inclusive_between(pointer __ptr) : _M_ptr_value(__ptr) |
| { } |
| |
| bool |
| operator()(_Block_pair __bp) const throw() |
| { |
| if (std::less_equal<pointer>()(_M_ptr_value, __bp.second) |
| && std::greater_equal<pointer>()(_M_ptr_value, __bp.first)) |
| return true; |
| else |
| return false; |
| } |
| }; |
| |
| // Used to pass a Functor to functions by reference. |
| template<typename _Functor> |
| class _Functor_Ref |
| : public std::unary_function<typename _Functor::argument_type, |
| typename _Functor::result_type> |
| { |
| _Functor& _M_fref; |
| |
| public: |
| typedef typename _Functor::argument_type argument_type; |
| typedef typename _Functor::result_type result_type; |
| |
| _Functor_Ref(_Functor& __fref) : _M_fref(__fref) |
| { } |
| |
| result_type |
| operator()(argument_type __arg) |
| { return _M_fref(__arg); } |
| }; |
| |
| /** @class _Ffit_finder bitmap_allocator.h bitmap_allocator.h |
| * |
| * @brief The class which acts as a predicate for applying the |
| * first-fit memory allocation policy for the bitmap allocator. |
| */ |
| // _Tp should be a pointer type, and _Alloc is the Allocator for |
| // the vector. |
| template<typename _Tp> |
| class _Ffit_finder |
| : public std::unary_function<typename std::pair<_Tp, _Tp>, bool> |
| { |
| typedef typename std::pair<_Tp, _Tp> _Block_pair; |
| typedef typename __detail::__mini_vector<_Block_pair> _BPVector; |
| typedef typename _BPVector::difference_type _Counter_type; |
| |
| std::size_t* _M_pbitmap; |
| _Counter_type _M_data_offset; |
| |
| public: |
| _Ffit_finder() : _M_pbitmap(0), _M_data_offset(0) |
| { } |
| |
| bool |
| operator()(_Block_pair __bp) throw() |
| { |
| using std::size_t; |
| // Set the _rover to the last physical location bitmap, |
| // which is the bitmap which belongs to the first free |
| // block. Thus, the bitmaps are in exact reverse order of |
| // the actual memory layout. So, we count down the bitmaps, |
| // which is the same as moving up the memory. |
| |
| // If the used count stored at the start of the Bit Map headers |
| // is equal to the number of Objects that the current Block can |
| // store, then there is definitely no space for another single |
| // object, so just return false. |
| _Counter_type __diff = __detail::__num_bitmaps(__bp); |
| |
| if (*(reinterpret_cast<size_t*> |
| (__bp.first) - (__diff + 1)) == __detail::__num_blocks(__bp)) |
| return false; |
| |
| size_t* __rover = reinterpret_cast<size_t*>(__bp.first) - 1; |
| |
| for (_Counter_type __i = 0; __i < __diff; ++__i) |
| { |
| _M_data_offset = __i; |
| if (*__rover) |
| { |
| _M_pbitmap = __rover; |
| return true; |
| } |
| --__rover; |
| } |
| return false; |
| } |
| |
| std::size_t* |
| _M_get() const throw() |
| { return _M_pbitmap; } |
| |
| _Counter_type |
| _M_offset() const throw() |
| { return _M_data_offset * std::size_t(bits_per_block); } |
| }; |
| |
| /** @class _Bitmap_counter bitmap_allocator.h bitmap_allocator.h |
| * |
| * @brief The bitmap counter which acts as the bitmap |
| * manipulator, and manages the bit-manipulation functions and |
| * the searching and identification functions on the bit-map. |
| */ |
| // _Tp should be a pointer type. |
| template<typename _Tp> |
| class _Bitmap_counter |
| { |
| typedef typename |
| __detail::__mini_vector<typename std::pair<_Tp, _Tp> > _BPVector; |
| typedef typename _BPVector::size_type _Index_type; |
| typedef _Tp pointer; |
| |
| _BPVector& _M_vbp; |
| std::size_t* _M_curr_bmap; |
| std::size_t* _M_last_bmap_in_block; |
| _Index_type _M_curr_index; |
| |
| public: |
| // Use the 2nd parameter with care. Make sure that such an |
| // entry exists in the vector before passing that particular |
| // index to this ctor. |
| _Bitmap_counter(_BPVector& Rvbp, long __index = -1) : _M_vbp(Rvbp) |
| { this->_M_reset(__index); } |
| |
| void |
| _M_reset(long __index = -1) throw() |
| { |
| if (__index == -1) |
| { |
| _M_curr_bmap = 0; |
| _M_curr_index = static_cast<_Index_type>(-1); |
| return; |
| } |
| |
| _M_curr_index = __index; |
| _M_curr_bmap = reinterpret_cast<std::size_t*> |
| (_M_vbp[_M_curr_index].first) - 1; |
| |
| _GLIBCXX_DEBUG_ASSERT(__index <= (long)_M_vbp.size() - 1); |
| |
| _M_last_bmap_in_block = _M_curr_bmap |
| - ((_M_vbp[_M_curr_index].second |
| - _M_vbp[_M_curr_index].first + 1) |
| / std::size_t(bits_per_block) - 1); |
| } |
| |
| // Dangerous Function! Use with extreme care. Pass to this |
| // function ONLY those values that are known to be correct, |
| // otherwise this will mess up big time. |
| void |
| _M_set_internal_bitmap(std::size_t* __new_internal_marker) throw() |
| { _M_curr_bmap = __new_internal_marker; } |
| |
| bool |
| _M_finished() const throw() |
| { return(_M_curr_bmap == 0); } |
| |
| _Bitmap_counter& |
| operator++() throw() |
| { |
| if (_M_curr_bmap == _M_last_bmap_in_block) |
| { |
| if (++_M_curr_index == _M_vbp.size()) |
| _M_curr_bmap = 0; |
| else |
| this->_M_reset(_M_curr_index); |
| } |
| else |
| --_M_curr_bmap; |
| return *this; |
| } |
| |
| std::size_t* |
| _M_get() const throw() |
| { return _M_curr_bmap; } |
| |
| pointer |
| _M_base() const throw() |
| { return _M_vbp[_M_curr_index].first; } |
| |
| _Index_type |
| _M_offset() const throw() |
| { |
| return std::size_t(bits_per_block) |
| * ((reinterpret_cast<std::size_t*>(this->_M_base()) |
| - _M_curr_bmap) - 1); |
| } |
| |
| _Index_type |
| _M_where() const throw() |
| { return _M_curr_index; } |
| }; |
| |
| /** @brief Mark a memory address as allocated by re-setting the |
| * corresponding bit in the bit-map. |
| */ |
| inline void |
| __bit_allocate(std::size_t* __pbmap, std::size_t __pos) throw() |
| { |
| std::size_t __mask = 1 << __pos; |
| __mask = ~__mask; |
| *__pbmap &= __mask; |
| } |
| |
| /** @brief Mark a memory address as free by setting the |
| * corresponding bit in the bit-map. |
| */ |
| inline void |
| __bit_free(std::size_t* __pbmap, std::size_t __pos) throw() |
| { |
| std::size_t __mask = 1 << __pos; |
| *__pbmap |= __mask; |
| } |
| } // namespace __detail |
| |
| /** @brief Generic Version of the bsf instruction. |
| */ |
| inline std::size_t |
| _Bit_scan_forward(std::size_t __num) |
| { return static_cast<std::size_t>(__builtin_ctzl(__num)); } |
| |
| /** @class free_list bitmap_allocator.h bitmap_allocator.h |
| * |
| * @brief The free list class for managing chunks of memory to be |
| * given to and returned by the bitmap_allocator. |
| */ |
| class free_list |
| { |
| public: |
| typedef std::size_t* value_type; |
| typedef __detail::__mini_vector<value_type> vector_type; |
| typedef vector_type::iterator iterator; |
| typedef __mutex __mutex_type; |
| |
| private: |
| struct _LT_pointer_compare |
| { |
| bool |
| operator()(const std::size_t* __pui, |
| const std::size_t __cui) const throw() |
| { return *__pui < __cui; } |
| }; |
| |
| #if defined __GTHREADS |
| __mutex_type& |
| _M_get_mutex() |
| { |
| static __mutex_type _S_mutex; |
| return _S_mutex; |
| } |
| #endif |
| |
| vector_type& |
| _M_get_free_list() |
| { |
| static vector_type _S_free_list; |
| return _S_free_list; |
| } |
| |
| /** @brief Performs validation of memory based on their size. |
| * |
| * @param __addr The pointer to the memory block to be |
| * validated. |
| * |
| * Validates the memory block passed to this function and |
| * appropriately performs the action of managing the free list of |
| * blocks by adding this block to the free list or deleting this |
| * or larger blocks from the free list. |
| */ |
| void |
| _M_validate(std::size_t* __addr) throw() |
| { |
| vector_type& __free_list = _M_get_free_list(); |
| const vector_type::size_type __max_size = 64; |
| if (__free_list.size() >= __max_size) |
| { |
| // Ok, the threshold value has been reached. We determine |
| // which block to remove from the list of free blocks. |
| if (*__addr >= *__free_list.back()) |
| { |
| // Ok, the new block is greater than or equal to the |
| // last block in the list of free blocks. We just free |
| // the new block. |
| ::operator delete(static_cast<void*>(__addr)); |
| return; |
| } |
| else |
| { |
| // Deallocate the last block in the list of free lists, |
| // and insert the new one in its correct position. |
| ::operator delete(static_cast<void*>(__free_list.back())); |
| __free_list.pop_back(); |
| } |
| } |
| |
| // Just add the block to the list of free lists unconditionally. |
| iterator __temp = __detail::__lower_bound |
| (__free_list.begin(), __free_list.end(), |
| *__addr, _LT_pointer_compare()); |
| |
| // We may insert the new free list before _temp; |
| __free_list.insert(__temp, __addr); |
| } |
| |
| /** @brief Decides whether the wastage of memory is acceptable for |
| * the current memory request and returns accordingly. |
| * |
| * @param __block_size The size of the block available in the free |
| * list. |
| * |
| * @param __required_size The required size of the memory block. |
| * |
| * @return true if the wastage incurred is acceptable, else returns |
| * false. |
| */ |
| bool |
| _M_should_i_give(std::size_t __block_size, |
| std::size_t __required_size) throw() |
| { |
| const std::size_t __max_wastage_percentage = 36; |
| if (__block_size >= __required_size && |
| (((__block_size - __required_size) * 100 / __block_size) |
| < __max_wastage_percentage)) |
| return true; |
| else |
| return false; |
| } |
| |
| public: |
| /** @brief This function returns the block of memory to the |
| * internal free list. |
| * |
| * @param __addr The pointer to the memory block that was given |
| * by a call to the _M_get function. |
| */ |
| inline void |
| _M_insert(std::size_t* __addr) throw() |
| { |
| #if defined __GTHREADS |
| __scoped_lock __bfl_lock(_M_get_mutex()); |
| #endif |
| // Call _M_validate to decide what should be done with |
| // this particular free list. |
| this->_M_validate(reinterpret_cast<std::size_t*>(__addr) - 1); |
| // See discussion as to why this is 1! |
| } |
| |
| /** @brief This function gets a block of memory of the specified |
| * size from the free list. |
| * |
| * @param __sz The size in bytes of the memory required. |
| * |
| * @return A pointer to the new memory block of size at least |
| * equal to that requested. |
| */ |
| std::size_t* |
| _M_get(std::size_t __sz) _GLIBCXX_THROW(std::bad_alloc); |
| |
| /** @brief This function just clears the internal Free List, and |
| * gives back all the memory to the OS. |
| */ |
| void |
| _M_clear(); |
| }; |
| |
| |
| // Forward declare the class. |
| template<typename _Tp> |
| class bitmap_allocator; |
| |
| // Specialize for void: |
| template<> |
| class bitmap_allocator<void> |
| { |
| public: |
| typedef void* pointer; |
| typedef const void* const_pointer; |
| |
| // Reference-to-void members are impossible. |
| typedef void value_type; |
| template<typename _Tp1> |
| struct rebind |
| { |
| typedef bitmap_allocator<_Tp1> other; |
| }; |
| }; |
| |
| /** |
| * @brief Bitmap Allocator, primary template. |
| * @ingroup allocators |
| */ |
| template<typename _Tp> |
| class bitmap_allocator : private free_list |
| { |
| public: |
| typedef std::size_t size_type; |
| typedef std::ptrdiff_t difference_type; |
| typedef _Tp* pointer; |
| typedef const _Tp* const_pointer; |
| typedef _Tp& reference; |
| typedef const _Tp& const_reference; |
| typedef _Tp value_type; |
| typedef free_list::__mutex_type __mutex_type; |
| |
| template<typename _Tp1> |
| struct rebind |
| { |
| typedef bitmap_allocator<_Tp1> other; |
| }; |
| |
| #if __cplusplus >= 201103L |
| // _GLIBCXX_RESOLVE_LIB_DEFECTS |
| // 2103. propagate_on_container_move_assignment |
| typedef std::true_type propagate_on_container_move_assignment; |
| #endif |
| |
| private: |
| template<std::size_t _BSize, std::size_t _AlignSize> |
| struct aligned_size |
| { |
| enum |
| { |
| modulus = _BSize % _AlignSize, |
| value = _BSize + (modulus ? _AlignSize - (modulus) : 0) |
| }; |
| }; |
| |
| struct _Alloc_block |
| { |
| char __M_unused[aligned_size<sizeof(value_type), |
| _BALLOC_ALIGN_BYTES>::value]; |
| }; |
| |
| |
| typedef typename std::pair<_Alloc_block*, _Alloc_block*> _Block_pair; |
| |
| typedef typename __detail::__mini_vector<_Block_pair> _BPVector; |
| typedef typename _BPVector::iterator _BPiter; |
| |
| template<typename _Predicate> |
| static _BPiter |
| _S_find(_Predicate __p) |
| { |
| _BPiter __first = _S_mem_blocks.begin(); |
| while (__first != _S_mem_blocks.end() && !__p(*__first)) |
| ++__first; |
| return __first; |
| } |
| |
| #if defined _GLIBCXX_DEBUG |
| // Complexity: O(lg(N)). Where, N is the number of block of size |
| // sizeof(value_type). |
| void |
| _S_check_for_free_blocks() throw() |
| { |
| typedef typename __detail::_Ffit_finder<_Alloc_block*> _FFF; |
| _BPiter __bpi = _S_find(_FFF()); |
| |
| _GLIBCXX_DEBUG_ASSERT(__bpi == _S_mem_blocks.end()); |
| } |
| #endif |
| |
| /** @brief Responsible for exponentially growing the internal |
| * memory pool. |
| * |
| * @throw std::bad_alloc. If memory cannot be allocated. |
| * |
| * Complexity: O(1), but internally depends upon the |
| * complexity of the function free_list::_M_get. The part where |
| * the bitmap headers are written has complexity: O(X),where X |
| * is the number of blocks of size sizeof(value_type) within |
| * the newly acquired block. Having a tight bound. |
| */ |
| void |
| _S_refill_pool() _GLIBCXX_THROW(std::bad_alloc) |
| { |
| using std::size_t; |
| #if defined _GLIBCXX_DEBUG |
| _S_check_for_free_blocks(); |
| #endif |
| |
| const size_t __num_bitmaps = (_S_block_size |
| / size_t(__detail::bits_per_block)); |
| const size_t __size_to_allocate = sizeof(size_t) |
| + _S_block_size * sizeof(_Alloc_block) |
| + __num_bitmaps * sizeof(size_t); |
| |
| size_t* __temp = |
| reinterpret_cast<size_t*>(this->_M_get(__size_to_allocate)); |
| *__temp = 0; |
| ++__temp; |
| |
| // The Header information goes at the Beginning of the Block. |
| _Block_pair __bp = |
| std::make_pair(reinterpret_cast<_Alloc_block*> |
| (__temp + __num_bitmaps), |
| reinterpret_cast<_Alloc_block*> |
| (__temp + __num_bitmaps) |
| + _S_block_size - 1); |
| |
| // Fill the Vector with this information. |
| _S_mem_blocks.push_back(__bp); |
| |
| for (size_t __i = 0; __i < __num_bitmaps; ++__i) |
| __temp[__i] = ~static_cast<size_t>(0); // 1 Indicates all Free. |
| |
| _S_block_size *= 2; |
| } |
| |
| static _BPVector _S_mem_blocks; |
| static std::size_t _S_block_size; |
| static __detail::_Bitmap_counter<_Alloc_block*> _S_last_request; |
| static typename _BPVector::size_type _S_last_dealloc_index; |
| #if defined __GTHREADS |
| static __mutex_type _S_mut; |
| #endif |
| |
| public: |
| |
| /** @brief Allocates memory for a single object of size |
| * sizeof(_Tp). |
| * |
| * @throw std::bad_alloc. If memory cannot be allocated. |
| * |
| * Complexity: Worst case complexity is O(N), but that |
| * is hardly ever hit. If and when this particular case is |
| * encountered, the next few cases are guaranteed to have a |
| * worst case complexity of O(1)! That's why this function |
| * performs very well on average. You can consider this |
| * function to have a complexity referred to commonly as: |
| * Amortized Constant time. |
| */ |
| pointer |
| _M_allocate_single_object() _GLIBCXX_THROW(std::bad_alloc) |
| { |
| using std::size_t; |
| #if defined __GTHREADS |
| __scoped_lock __bit_lock(_S_mut); |
| #endif |
| |
| // The algorithm is something like this: The last_request |
| // variable points to the last accessed Bit Map. When such a |
| // condition occurs, we try to find a free block in the |
| // current bitmap, or succeeding bitmaps until the last bitmap |
| // is reached. If no free block turns up, we resort to First |
| // Fit method. |
| |
| // WARNING: Do not re-order the condition in the while |
| // statement below, because it relies on C++'s short-circuit |
| // evaluation. The return from _S_last_request->_M_get() will |
| // NOT be dereference able if _S_last_request->_M_finished() |
| // returns true. This would inevitably lead to a NULL pointer |
| // dereference if tinkered with. |
| while (_S_last_request._M_finished() == false |
| && (*(_S_last_request._M_get()) == 0)) |
| _S_last_request.operator++(); |
| |
| if (__builtin_expect(_S_last_request._M_finished() == true, false)) |
| { |
| // Fall Back to First Fit algorithm. |
| typedef typename __detail::_Ffit_finder<_Alloc_block*> _FFF; |
| _FFF __fff; |
| _BPiter __bpi = _S_find(__detail::_Functor_Ref<_FFF>(__fff)); |
| |
| if (__bpi != _S_mem_blocks.end()) |
| { |
| // Search was successful. Ok, now mark the first bit from |
| // the right as 0, meaning Allocated. This bit is obtained |
| // by calling _M_get() on __fff. |
| size_t __nz_bit = _Bit_scan_forward(*__fff._M_get()); |
| __detail::__bit_allocate(__fff._M_get(), __nz_bit); |
| |
| _S_last_request._M_reset(__bpi - _S_mem_blocks.begin()); |
| |
| // Now, get the address of the bit we marked as allocated. |
| pointer __ret = reinterpret_cast<pointer> |
| (__bpi->first + __fff._M_offset() + __nz_bit); |
| size_t* __puse_count = |
| reinterpret_cast<size_t*> |
| (__bpi->first) - (__detail::__num_bitmaps(*__bpi) + 1); |
| |
| ++(*__puse_count); |
| return __ret; |
| } |
| else |
| { |
| // Search was unsuccessful. We Add more memory to the |
| // pool by calling _S_refill_pool(). |
| _S_refill_pool(); |
| |
| // _M_Reset the _S_last_request structure to the first |
| // free block's bit map. |
| _S_last_request._M_reset(_S_mem_blocks.size() - 1); |
| |
| // Now, mark that bit as allocated. |
| } |
| } |
| |
| // _S_last_request holds a pointer to a valid bit map, that |
| // points to a free block in memory. |
| size_t __nz_bit = _Bit_scan_forward(*_S_last_request._M_get()); |
| __detail::__bit_allocate(_S_last_request._M_get(), __nz_bit); |
| |
| pointer __ret = reinterpret_cast<pointer> |
| (_S_last_request._M_base() + _S_last_request._M_offset() + __nz_bit); |
| |
| size_t* __puse_count = reinterpret_cast<size_t*> |
| (_S_mem_blocks[_S_last_request._M_where()].first) |
| - (__detail:: |
| __num_bitmaps(_S_mem_blocks[_S_last_request._M_where()]) + 1); |
| |
| ++(*__puse_count); |
| return __ret; |
| } |
| |
| /** @brief Deallocates memory that belongs to a single object of |
| * size sizeof(_Tp). |
| * |
| * Complexity: O(lg(N)), but the worst case is not hit |
| * often! This is because containers usually deallocate memory |
| * close to each other and this case is handled in O(1) time by |
| * the deallocate function. |
| */ |
| void |
| _M_deallocate_single_object(pointer __p) throw() |
| { |
| using std::size_t; |
| #if defined __GTHREADS |
| __scoped_lock __bit_lock(_S_mut); |
| #endif |
| _Alloc_block* __real_p = reinterpret_cast<_Alloc_block*>(__p); |
| |
| typedef typename _BPVector::iterator _Iterator; |
| typedef typename _BPVector::difference_type _Difference_type; |
| |
| _Difference_type __diff; |
| long __displacement; |
| |
| _GLIBCXX_DEBUG_ASSERT(_S_last_dealloc_index >= 0); |
| |
| __detail::_Inclusive_between<_Alloc_block*> __ibt(__real_p); |
| if (__ibt(_S_mem_blocks[_S_last_dealloc_index])) |
| { |
| _GLIBCXX_DEBUG_ASSERT(_S_last_dealloc_index |
| <= _S_mem_blocks.size() - 1); |
| |
| // Initial Assumption was correct! |
| __diff = _S_last_dealloc_index; |
| __displacement = __real_p - _S_mem_blocks[__diff].first; |
| } |
| else |
| { |
| _Iterator _iter = _S_find(__ibt); |
| |
| _GLIBCXX_DEBUG_ASSERT(_iter != _S_mem_blocks.end()); |
| |
| __diff = _iter - _S_mem_blocks.begin(); |
| __displacement = __real_p - _S_mem_blocks[__diff].first; |
| _S_last_dealloc_index = __diff; |
| } |
| |
| // Get the position of the iterator that has been found. |
| const size_t __rotate = (__displacement |
| % size_t(__detail::bits_per_block)); |
| size_t* __bitmapC = |
| reinterpret_cast<size_t*> |
| (_S_mem_blocks[__diff].first) - 1; |
| __bitmapC -= (__displacement / size_t(__detail::bits_per_block)); |
| |
| __detail::__bit_free(__bitmapC, __rotate); |
| size_t* __puse_count = reinterpret_cast<size_t*> |
| (_S_mem_blocks[__diff].first) |
| - (__detail::__num_bitmaps(_S_mem_blocks[__diff]) + 1); |
| |
| _GLIBCXX_DEBUG_ASSERT(*__puse_count != 0); |
| |
| --(*__puse_count); |
| |
| if (__builtin_expect(*__puse_count == 0, false)) |
| { |
| _S_block_size /= 2; |
| |
| // We can safely remove this block. |
| // _Block_pair __bp = _S_mem_blocks[__diff]; |
| this->_M_insert(__puse_count); |
| _S_mem_blocks.erase(_S_mem_blocks.begin() + __diff); |
| |
| // Reset the _S_last_request variable to reflect the |
| // erased block. We do this to protect future requests |
| // after the last block has been removed from a particular |
| // memory Chunk, which in turn has been returned to the |
| // free list, and hence had been erased from the vector, |
| // so the size of the vector gets reduced by 1. |
| if ((_Difference_type)_S_last_request._M_where() >= __diff--) |
| _S_last_request._M_reset(__diff); |
| |
| // If the Index into the vector of the region of memory |
| // that might hold the next address that will be passed to |
| // deallocated may have been invalidated due to the above |
| // erase procedure being called on the vector, hence we |
| // try to restore this invariant too. |
| if (_S_last_dealloc_index >= _S_mem_blocks.size()) |
| { |
| _S_last_dealloc_index =(__diff != -1 ? __diff : 0); |
| _GLIBCXX_DEBUG_ASSERT(_S_last_dealloc_index >= 0); |
| } |
| } |
| } |
| |
| public: |
| bitmap_allocator() _GLIBCXX_USE_NOEXCEPT |
| { } |
| |
| bitmap_allocator(const bitmap_allocator&) _GLIBCXX_USE_NOEXCEPT |
| { } |
| |
| template<typename _Tp1> |
| bitmap_allocator(const bitmap_allocator<_Tp1>&) _GLIBCXX_USE_NOEXCEPT |
| { } |
| |
| ~bitmap_allocator() _GLIBCXX_USE_NOEXCEPT |
| { } |
| |
| _GLIBCXX_NODISCARD pointer |
| allocate(size_type __n) |
| { |
| if (__n > this->max_size()) |
| std::__throw_bad_alloc(); |
| |
| #if __cpp_aligned_new |
| if (alignof(value_type) > __STDCPP_DEFAULT_NEW_ALIGNMENT__) |
| { |
| const size_type __b = __n * sizeof(value_type); |
| std::align_val_t __al = std::align_val_t(alignof(value_type)); |
| return static_cast<pointer>(::operator new(__b, __al)); |
| } |
| #endif |
| |
| if (__builtin_expect(__n == 1, true)) |
| return this->_M_allocate_single_object(); |
| else |
| { |
| const size_type __b = __n * sizeof(value_type); |
| return reinterpret_cast<pointer>(::operator new(__b)); |
| } |
| } |
| |
| _GLIBCXX_NODISCARD pointer |
| allocate(size_type __n, typename bitmap_allocator<void>::const_pointer) |
| { return allocate(__n); } |
| |
| void |
| deallocate(pointer __p, size_type __n) throw() |
| { |
| if (__builtin_expect(__p != 0, true)) |
| { |
| #if __cpp_aligned_new |
| // Types with extended alignment are handled by operator delete. |
| if (alignof(value_type) > __STDCPP_DEFAULT_NEW_ALIGNMENT__) |
| { |
| ::operator delete(__p, std::align_val_t(alignof(value_type))); |
| return; |
| } |
| #endif |
| |
| if (__builtin_expect(__n == 1, true)) |
| this->_M_deallocate_single_object(__p); |
| else |
| ::operator delete(__p); |
| } |
| } |
| |
| pointer |
| address(reference __r) const _GLIBCXX_NOEXCEPT |
| { return std::__addressof(__r); } |
| |
| const_pointer |
| address(const_reference __r) const _GLIBCXX_NOEXCEPT |
| { return std::__addressof(__r); } |
| |
| size_type |
| max_size() const _GLIBCXX_USE_NOEXCEPT |
| { return size_type(-1) / sizeof(value_type); } |
| |
| #if __cplusplus >= 201103L |
| template<typename _Up, typename... _Args> |
| void |
| construct(_Up* __p, _Args&&... __args) |
| { ::new((void *)__p) _Up(std::forward<_Args>(__args)...); } |
| |
| template<typename _Up> |
| void |
| destroy(_Up* __p) |
| { __p->~_Up(); } |
| #else |
| void |
| construct(pointer __p, const_reference __data) |
| { ::new((void *)__p) value_type(__data); } |
| |
| void |
| destroy(pointer __p) |
| { __p->~value_type(); } |
| #endif |
| }; |
| |
| template<typename _Tp1, typename _Tp2> |
| bool |
| operator==(const bitmap_allocator<_Tp1>&, |
| const bitmap_allocator<_Tp2>&) throw() |
| { return true; } |
| |
| #if __cpp_impl_three_way_comparison < 201907L |
| template<typename _Tp1, typename _Tp2> |
| bool |
| operator!=(const bitmap_allocator<_Tp1>&, |
| const bitmap_allocator<_Tp2>&) throw() |
| { return false; } |
| #endif |
| |
| // Static member definitions. |
| template<typename _Tp> |
| typename bitmap_allocator<_Tp>::_BPVector |
| bitmap_allocator<_Tp>::_S_mem_blocks; |
| |
| template<typename _Tp> |
| std::size_t bitmap_allocator<_Tp>::_S_block_size |
| = 2 * std::size_t(__detail::bits_per_block); |
| |
| template<typename _Tp> |
| typename bitmap_allocator<_Tp>::_BPVector::size_type |
| bitmap_allocator<_Tp>::_S_last_dealloc_index = 0; |
| |
| template<typename _Tp> |
| __detail::_Bitmap_counter |
| <typename bitmap_allocator<_Tp>::_Alloc_block*> |
| bitmap_allocator<_Tp>::_S_last_request(_S_mem_blocks); |
| |
| #if defined __GTHREADS |
| template<typename _Tp> |
| typename bitmap_allocator<_Tp>::__mutex_type |
| bitmap_allocator<_Tp>::_S_mut; |
| #endif |
| |
| _GLIBCXX_END_NAMESPACE_VERSION |
| } // namespace __gnu_cxx |
| |
| #endif |