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diff --git a/libstdc++-v3/include/ext/bitmap_allocator.h b/libstdc++-v3/include/ext/bitmap_allocator.h
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+// Bitmap Allocator. -*- C++ -*-
+
+// Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009
+// 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
+// .
+
+/** @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 // For std::size_t, and ptrdiff_t.
+#include // For __throw_bad_alloc().
+#include // For std::pair.
+#include // For greater_equal, and less_equal.
+#include // For operator new.
+#include // _GLIBCXX_DEBUG_ASSERT
+#include
+#include
+
+/** @brief The constant in the expression below is the alignment
+ * required in bytes.
+ */
+#define _BALLOC_ALIGN_BYTES 8
+
+_GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx)
+
+ using std::size_t;
+ using std::ptrdiff_t;
+
+ 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:
+ *
+ * @detail
+ * 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
+ 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 size_t size_type;
+ typedef 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; }
+
+ pointer
+ allocate(size_type __n)
+ { return static_cast(::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)
+ { }
+
+#if 0
+ ~__mini_vector()
+ {
+ if (this->_M_start)
+ {
+ this->deallocate(this->_M_start, this->_M_end_of_storage
+ - this->_M_start);
+ }
+ }
+#endif
+
+ 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
+ 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
+ void __mini_vector<_Tp>::
+ erase(iterator __pos) throw()
+ {
+ while (__pos + 1 != this->end())
+ {
+ *__pos = __pos[1];
+ ++__pos;
+ }
+ --this->_M_finish;
+ }
+
+
+ template
+ struct __mv_iter_traits
+ {
+ typedef typename _Tp::value_type value_type;
+ typedef typename _Tp::difference_type difference_type;
+ };
+
+ template
+ struct __mv_iter_traits<_Tp*>
+ {
+ typedef _Tp value_type;
+ typedef ptrdiff_t difference_type;
+ };
+
+ enum
+ {
+ bits_per_byte = 8,
+ bits_per_block = sizeof(size_t) * size_t(bits_per_byte)
+ };
+
+ template
+ _ForwardIterator
+ __lower_bound(_ForwardIterator __first, _ForwardIterator __last,
+ const _Tp& __val, _Compare __comp)
+ {
+ typedef typename __mv_iter_traits<_ForwardIterator>::value_type
+ _ValueType;
+ 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;
+ }
+
+ template
+ inline _InputIterator
+ __find_if(_InputIterator __first, _InputIterator __last, _Predicate __p)
+ {
+ while (__first != __last && !__p(*__first))
+ ++__first;
+ return __first;
+ }
+
+ /** @brief The number of Blocks pointed to by the address pair
+ * passed to the function.
+ */
+ template
+ inline 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
+ inline size_t
+ __num_bitmaps(_AddrPair __ap)
+ { return __num_blocks(__ap) / size_t(bits_per_block); }
+
+ // _Tp should be a pointer type.
+ template
+ class _Inclusive_between
+ : public std::unary_function, 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()(_M_ptr_value, __bp.second)
+ && std::greater_equal()(_M_ptr_value, __bp.first))
+ return true;
+ else
+ return false;
+ }
+ };
+
+ // Used to pass a Functor to functions by reference.
+ template
+ class _Functor_Ref
+ : public std::unary_function
+ {
+ _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
+ class _Ffit_finder
+ : public std::unary_function, bool>
+ {
+ typedef typename std::pair<_Tp, _Tp> _Block_pair;
+ typedef typename __detail::__mini_vector<_Block_pair> _BPVector;
+ typedef typename _BPVector::difference_type _Counter_type;
+
+ 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()
+ {
+ // 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 =
+ __gnu_cxx::__detail::__num_bitmaps(__bp);
+
+ if (*(reinterpret_cast
+ (__bp.first) - (__diff + 1))
+ == __gnu_cxx::__detail::__num_blocks(__bp))
+ return false;
+
+ size_t* __rover = reinterpret_cast(__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;
+ }
+
+
+ size_t*
+ _M_get() const throw()
+ { return _M_pbitmap; }
+
+ _Counter_type
+ _M_offset() const throw()
+ { return _M_data_offset * 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
+ class _Bitmap_counter
+ {
+ typedef typename __detail::__mini_vector >
+ _BPVector;
+ typedef typename _BPVector::size_type _Index_type;
+ typedef _Tp pointer;
+
+ _BPVector& _M_vbp;
+ size_t* _M_curr_bmap;
+ 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
+ (_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)
+ / 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(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;
+ }
+
+ 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 size_t(bits_per_block)
+ * ((reinterpret_cast(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(size_t* __pbmap, size_t __pos) throw()
+ {
+ 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(size_t* __pbmap, size_t __pos) throw()
+ {
+ size_t __mask = 1 << __pos;
+ *__pbmap |= __mask;
+ }
+ } // namespace __detail
+
+ /** @brief Generic Version of the bsf instruction.
+ */
+ inline size_t
+ _Bit_scan_forward(size_t __num)
+ { return static_cast(__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
+ {
+ typedef size_t* value_type;
+ typedef __detail::__mini_vector vector_type;
+ typedef vector_type::iterator iterator;
+ typedef __mutex __mutex_type;
+
+ struct _LT_pointer_compare
+ {
+ bool
+ operator()(const size_t* __pui,
+ const 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.
+ *
+ * @detail 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(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(__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(__free_list.back()));
+ __free_list.pop_back();
+ }
+ }
+
+ // Just add the block to the list of free lists unconditionally.
+ iterator __temp = __gnu_cxx::__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(size_t __block_size,
+ size_t __required_size) throw()
+ {
+ const 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(size_t* __addr) throw()
+ {
+#if defined __GTHREADS
+ __gnu_cxx::__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(__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.
+ */
+ size_t*
+ _M_get(size_t __sz) 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
+ class bitmap_allocator;
+
+ // Specialize for void:
+ template<>
+ class bitmap_allocator
+ {
+ public:
+ typedef void* pointer;
+ typedef const void* const_pointer;
+
+ // Reference-to-void members are impossible.
+ typedef void value_type;
+ template
+ struct rebind
+ {
+ typedef bitmap_allocator<_Tp1> other;
+ };
+ };
+
+ /**
+ * @brief Bitmap Allocator, primary template.
+ * @ingroup allocators
+ */
+ template
+ class bitmap_allocator : private free_list
+ {
+ public:
+ typedef size_t size_type;
+ typedef 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
+ struct rebind
+ {
+ typedef bitmap_allocator<_Tp1> other;
+ };
+
+ private:
+ template
+ struct aligned_size
+ {
+ enum
+ {
+ modulus = _BSize % _AlignSize,
+ value = _BSize + (modulus ? _AlignSize - (modulus) : 0)
+ };
+ };
+
+ struct _Alloc_block
+ {
+ char __M_unused[aligned_size::value];
+ };
+
+
+ typedef typename std::pair<_Alloc_block*, _Alloc_block*> _Block_pair;
+
+ typedef typename
+ __detail::__mini_vector<_Block_pair> _BPVector;
+
+#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
+ __gnu_cxx::__detail::_Ffit_finder<_Alloc_block*> _FFF;
+ _FFF __fff;
+ typedef typename _BPVector::iterator _BPiter;
+ _BPiter __bpi =
+ __gnu_cxx::__detail::__find_if
+ (_S_mem_blocks.begin(), _S_mem_blocks.end(),
+ __gnu_cxx::__detail::_Functor_Ref<_FFF>(__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 can not be allocated.
+ *
+ * @detail 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() throw(std::bad_alloc)
+ {
+#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
+ (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);
+
+ size_t __bit_mask = 0; // 0 Indicates all Allocated.
+ __bit_mask = ~__bit_mask; // 1 Indicates all Free.
+
+ for (size_t __i = 0; __i < __num_bitmaps; ++__i)
+ __temp[__i] = __bit_mask;
+
+ _S_block_size *= 2;
+ }
+
+
+ static _BPVector _S_mem_blocks;
+ static size_t _S_block_size;
+ static __gnu_cxx::__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 can not be allocated.
+ *
+ * @detail 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() throw(std::bad_alloc)
+ {
+#if defined __GTHREADS
+ __gnu_cxx::__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
+ __gnu_cxx::__detail::_Ffit_finder<_Alloc_block*> _FFF;
+ _FFF __fff;
+ typedef typename _BPVector::iterator _BPiter;
+ _BPiter __bpi =
+ __gnu_cxx::__detail::__find_if
+ (_S_mem_blocks.begin(), _S_mem_blocks.end(),
+ __gnu_cxx::__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
+ (__bpi->first + __fff._M_offset() + __nz_bit);
+ size_t* __puse_count =
+ reinterpret_cast
+ (__bpi->first)
+ - (__gnu_cxx::__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
+ (_S_last_request._M_base() + _S_last_request._M_offset() + __nz_bit);
+
+ size_t* __puse_count = reinterpret_cast
+ (_S_mem_blocks[_S_last_request._M_where()].first)
+ - (__gnu_cxx::__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).
+ *
+ * @detail 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()
+ {
+#if defined __GTHREADS
+ __gnu_cxx::__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);
+
+
+ if (__gnu_cxx::__detail::_Inclusive_between<_Alloc_block*>
+ (__real_p) (_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 = __gnu_cxx::__detail::
+ __find_if(_S_mem_blocks.begin(),
+ _S_mem_blocks.end(),
+ __gnu_cxx::__detail::
+ _Inclusive_between<_Alloc_block*>(__real_p));
+
+ _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
+ (_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
+ (_S_mem_blocks[__diff].first)
+ - (__gnu_cxx::__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() throw()
+ { }
+
+ bitmap_allocator(const bitmap_allocator&)
+ { }
+
+ template
+ bitmap_allocator(const bitmap_allocator<_Tp1>&) throw()
+ { }
+
+ ~bitmap_allocator() throw()
+ { }
+
+ pointer
+ allocate(size_type __n)
+ {
+ if (__builtin_expect(__n > this->max_size(), false))
+ std::__throw_bad_alloc();
+
+ if (__builtin_expect(__n == 1, true))
+ return this->_M_allocate_single_object();
+ else
+ {
+ const size_type __b = __n * sizeof(value_type);
+ return reinterpret_cast(::operator new(__b));
+ }
+ }
+
+ pointer
+ allocate(size_type __n, typename bitmap_allocator::const_pointer)
+ { return allocate(__n); }
+
+ void
+ deallocate(pointer __p, size_type __n) throw()
+ {
+ if (__builtin_expect(__p != 0, true))
+ {
+ if (__builtin_expect(__n == 1, true))
+ this->_M_deallocate_single_object(__p);
+ else
+ ::operator delete(__p);
+ }
+ }
+
+ pointer
+ address(reference __r) const
+ { return &__r; }
+
+ const_pointer
+ address(const_reference __r) const
+ { return &__r; }
+
+ size_type
+ max_size() const throw()
+ { return size_type(-1) / sizeof(value_type); }
+
+ void
+ construct(pointer __p, const_reference __data)
+ { ::new((void *)__p) value_type(__data); }
+
+#ifdef __GXX_EXPERIMENTAL_CXX0X__
+ template
+ void
+ construct(pointer __p, _Args&&... __args)
+ { ::new((void *)__p) _Tp(std::forward<_Args>(__args)...); }
+#endif
+
+ void
+ destroy(pointer __p)
+ { __p->~value_type(); }
+ };
+
+ template
+ bool
+ operator==(const bitmap_allocator<_Tp1>&,
+ const bitmap_allocator<_Tp2>&) throw()
+ { return true; }
+
+ template
+ bool
+ operator!=(const bitmap_allocator<_Tp1>&,
+ const bitmap_allocator<_Tp2>&) throw()
+ { return false; }
+
+ // Static member definitions.
+ template
+ typename bitmap_allocator<_Tp>::_BPVector
+ bitmap_allocator<_Tp>::_S_mem_blocks;
+
+ template
+ size_t bitmap_allocator<_Tp>::_S_block_size =
+ 2 * size_t(__detail::bits_per_block);
+
+ template
+ typename __gnu_cxx::bitmap_allocator<_Tp>::_BPVector::size_type
+ bitmap_allocator<_Tp>::_S_last_dealloc_index = 0;
+
+ template
+ __gnu_cxx::__detail::_Bitmap_counter
+ ::_Alloc_block*>
+ bitmap_allocator<_Tp>::_S_last_request(_S_mem_blocks);
+
+#if defined __GTHREADS
+ template
+ typename bitmap_allocator<_Tp>::__mutex_type
+ bitmap_allocator<_Tp>::_S_mut;
+#endif
+
+_GLIBCXX_END_NAMESPACE
+
+#endif
+