0,0 → 1,1119 |
// Bitmap Allocator. -*- C++ -*- |
|
// Copyright (C) 2004-2015 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 <functional> // 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) |
{ |
using std::size_t; |
using std::ptrdiff_t; |
|
namespace __detail |
{ |
_GLIBCXX_BEGIN_NAMESPACE_VERSION |
/** @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 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<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 ptrdiff_t difference_type; |
}; |
|
enum |
{ |
bits_per_byte = 8, |
bits_per_block = sizeof(size_t) * 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 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 size_t |
__num_bitmaps(_AddrPair __ap) |
{ return __num_blocks(__ap) / 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; |
|
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 = __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; |
} |
|
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<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; |
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<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) |
/ 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<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(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; |
} |
|
_GLIBCXX_END_NAMESPACE_VERSION |
} // namespace __detail |
|
_GLIBCXX_BEGIN_NAMESPACE_VERSION |
|
/** @brief Generic Version of the bsf instruction. |
*/ |
inline size_t |
_Bit_scan_forward(size_t __num) |
{ return static_cast<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 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 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. |
* |
* 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<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(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 |
__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<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. |
*/ |
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<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 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<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<size_t _BSize, 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 can not 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() 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<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 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 can not 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() throw(std::bad_alloc) |
{ |
#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() |
{ |
#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 |
{ } |
|
pointer |
allocate(size_type __n) |
{ |
if (__n > this->max_size()) |
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<pointer>(::operator new(__b)); |
} |
} |
|
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 (__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; } |
|
template<typename _Tp1, typename _Tp2> |
bool |
operator!=(const bitmap_allocator<_Tp1>&, |
const bitmap_allocator<_Tp2>&) throw() |
{ return false; } |
|
// Static member definitions. |
template<typename _Tp> |
typename bitmap_allocator<_Tp>::_BPVector |
bitmap_allocator<_Tp>::_S_mem_blocks; |
|
template<typename _Tp> |
size_t bitmap_allocator<_Tp>::_S_block_size = |
2 * 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 |
|