This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
Re: Patch for the allocator.
On Fri, 2004-03-26 at 17:26, Paolo Carlini wrote:
Ok, here's the revised patch with the line width formatting.
Actually, I'm attaching the file, because the patch is bigger than the
file itself.
> Dhruv Matani wrote:
>
> >What's the standard on this?
> >
> Definitely 80 (from C0 to C79, in Emacs terms)
>
> >Can I get this by setting the auto-fill width in emacs?
> >
> >
> Probably is a good idea!
>
> Paolo.
--
-Dhruv Matani.
http://www.geocities.com/dhruvbird/
Proud to be a Vegetarian.
http://www.vegetarianstarterkit.com/
http://www.vegkids.com/vegkids/index.html
// Bitmapped Allocator. -*- C++ -*-
// Copyright (C) 2004 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 2, 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.
// You should have received a copy of the GNU General Public License along
// with this library; see the file COPYING. If not, write to the Free
// Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
// USA.
// As a special exception, you may use this file as part of a free software
// library without restriction. Specifically, if other files instantiate
// templates or use macros or inline functions from this file, or you compile
// this file and link it with other files to produce an executable, this
// file does not by itself cause the resulting executable to be covered by
// the GNU General Public License. This exception does not however
// invalidate any other reasons why the executable file might be covered by
// the GNU General Public License.
#if !defined _BITMAP_ALLOCATOR_H
#define _BITMAP_ALLOCATOR_H 1
#include <cstddef>
//For std::size_t, and ptrdiff_t.
#include <utility>
//For std::pair.
#include <algorithm>
//std::find_if, and std::lower_bound.
#include <vector>
//For the free list of exponentially growing memory blocks. At max,
//size of the vector should be not more than the number of bits in an
//integer or an unsigned integer.
#include <functional>
//For greater_equal, and less_equal.
#include <new>
//For operator new.
#include <bits/gthr.h>
//For __gthread_mutex_t, __gthread_mutex_lock and __gthread_mutex_unlock.
#include <ext/new_allocator.h>
//For __gnu_cxx::new_allocator for std::vector.
//#define _BALLOC_ASSERT(_EXPR) assert(_EXPR)
#define _BALLOC_ASSERT(_EXPR)
#include <cassert>
//#define _BALLOC_SANITY_CHECK
namespace __gnu_cxx
{
namespace
{
#if defined __GTHREADS
bool const __threads_enabled = __gthread_active_p();
#endif
}
#if defined __GTHREADS
class _Mutex
{
__gthread_mutex_t _M_mut;
//Prevent Copying and assignment.
_Mutex(_Mutex const&);
_Mutex& operator=(_Mutex const&);
public:
_Mutex()
{
if (__threads_enabled)
{
#if !defined __GTHREAD_MUTEX_INIT
__GTHREAD_MUTEX_INIT_FUNCTION(&_M_mut);
#else
__gthread_mutex_t __mtemp = __GTHREAD_MUTEX_INIT;
_M_mut = __mtemp;
#endif
}
}
~_Mutex()
{
//Gthreads does not define a Mutex Destruction Function.
}
__gthread_mutex_t *_M_get() { return &_M_mut; }
};
class _Lock
{
_Mutex* _M_pmt;
bool _M_locked;
//Prevent Copying and assignment.
_Lock (_Lock const&);
_Lock& operator= (_Lock const&);
public:
_Lock(_Mutex* __mptr)
: _M_pmt(__mptr), _M_locked(false)
{ this->_M_lock(); }
void
_M_lock()
{
if (__threads_enabled)
{
_M_locked = true;
__gthread_mutex_lock(_M_pmt->_M_get());
}
}
void
_M_unlock()
{
if (__threads_enabled)
{
if (__builtin_expect(_M_locked, true))
{
__gthread_mutex_unlock(_M_pmt->_M_get());
_M_locked = false;
}
}
}
~_Lock() { this->_M_unlock(); }
};
#endif
namespace __aux_balloc
{
static const unsigned int _Bits_Per_Byte = 8;
static const unsigned int _Bits_Per_Block =
sizeof(unsigned int) * _Bits_Per_Byte;
template <typename _Addr_Pair_t>
inline size_t
__balloc_num_blocks (_Addr_Pair_t __ap)
{
return (__ap.second - __ap.first) + 1;
}
template <typename _Addr_Pair_t>
inline size_t
__balloc_num_bit_maps (_Addr_Pair_t __ap)
{
return __balloc_num_blocks(__ap) / _Bits_Per_Block;
}
//T 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); }
};
//T should be a pointer type, and A is the Allocator for the vector.
template <typename _Tp, typename _Alloc>
class _Ffit_finder
: public std::unary_function<typename std::pair<_Tp, _Tp>, bool> {
typedef typename std::vector<std::pair<_Tp, _Tp>, _Alloc> _BPVector;
typedef typename _BPVector::difference_type _Counter_type;
typedef typename std::pair<_Tp, _Tp> _Block_pair;
unsigned int* _M_pbitmap;
unsigned int _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 unsigned integer, which is the
//bitmap to the first free block. Thus, the bitmaps are in exact
//reverse order of the actual memory layout. So, we count down
//the bimaps, 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::__aux_balloc::__balloc_num_bit_maps (__bp);
_BALLOC_ASSERT (*(reinterpret_cast<unsigned int*>(__bp.first) -
(__diff + 1)) <=
__gnu_cxx::__aux_balloc::__balloc_num_blocks (__bp));
if (*(reinterpret_cast<unsigned int*>(__bp.first) - (__diff + 1)) ==
__gnu_cxx::__aux_balloc::__balloc_num_blocks (__bp))
return false;
unsigned int* __rover = reinterpret_cast<unsigned int*>(__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;
}
unsigned int*
_M_get()
{ return _M_pbitmap; }
unsigned int
_M_offset()
{ return _M_data_offset * _Bits_Per_Block; }
};
//T should be a pointer type.
template <typename _Tp, typename _Alloc>
class _Bit_map_counter
{
typedef typename std::vector<std::pair<_Tp, _Tp>, _Alloc> _BPVector;
typedef typename _BPVector::size_type _Index_type;
typedef _Tp pointer;
_BPVector& _M_vbp;
unsigned int* _M_curr_bmap;
unsigned int* _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.
_Bit_map_counter(_BPVector& Rvbp, int __index = -1)
: _M_vbp(Rvbp)
{
this->_M_reset(__index);
}
void
_M_reset(int __index = -1) throw()
{
if (__index == -1)
{
_M_curr_bmap = 0;
_M_curr_index = (_Index_type)-1;
return;
}
_M_curr_index = __index;
_M_curr_bmap = reinterpret_cast<unsigned int*>
(_M_vbp[_M_curr_index].first) - 1;
_BALLOC_ASSERT (__index <= (int)_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)
/ _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_bit_map(unsigned int* __new_internal_marker) throw()
{
_M_curr_bmap = __new_internal_marker;
}
bool
_M_finished() const throw()
{
return (_M_curr_bmap == 0);
}
_Bit_map_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;
}
unsigned int*
_M_get()
{
return _M_curr_bmap;
}
pointer
_M_base()
{ return _M_vbp[_M_curr_index].first; }
unsigned int
_M_offset()
{
return _Bits_Per_Block *
((reinterpret_cast<unsigned int*>(this->_M_base()) - _M_curr_bmap)
- 1);
}
unsigned int
_M_where() { return _M_curr_index; }
};
}
//Generic Version of the bsf instruction.
typedef unsigned int _Bit_map_type;
static inline
unsigned int
_Bit_scan_forward (register _Bit_map_type __num)
{
return static_cast<unsigned int>(__builtin_ctz(__num));
}
struct _OOM_handler
{
static std::new_handler _S_old_handler;
static bool _S_handled_oom;
typedef void (*_FL_clear_proc)(void);
static _FL_clear_proc _S_oom_fcp;
_OOM_handler(_FL_clear_proc __fcp)
{
_S_oom_fcp = __fcp;
_S_old_handler = std::set_new_handler(_S_handle_oom_proc);
_S_handled_oom = false;
}
static
void
_S_handle_oom_proc()
{
_S_oom_fcp();
std::set_new_handler(_S_old_handler);
_S_handled_oom = true;
}
~_OOM_handler()
{
if (!_S_handled_oom)
std::set_new_handler(_S_old_handler);
}
};
std::new_handler _OOM_handler::_S_old_handler;
bool _OOM_handler::_S_handled_oom = false;
_OOM_handler::_FL_clear_proc _OOM_handler::_S_oom_fcp = 0;
class _BA_free_list_store
{
struct _LT_pointer_compare
{
template <typename _Tp>
bool
operator()(_Tp* __pt, _Tp const& __crt) const throw()
{
return *__pt < __crt;
}
};
#if defined __GTHREADS
static _Mutex _S_bfl_mutex;
#endif
static std::vector<unsigned int*> _S_free_list;
typedef std::vector<unsigned int*>::iterator _FLIter;
static
void
_S_validate_free_list(unsigned int *__addr) throw()
{
const unsigned int __max_size = 64;
if (_S_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 >= *_S_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((void*)__addr);
return;
}
else
{
//Deallocate the last block in the list of free lists, and
//insert the new one in it's correct position.
operator delete((void*)_S_free_list.back());
_S_free_list.pop_back();
}
}
//Just add the block to the list of free lists
//unconditionally.
_FLIter __temp = std::lower_bound(_S_free_list.begin(), _S_free_list.end(),
*__addr, _LT_pointer_compare());
//We may insert the new free list before _temp;
_S_free_list.insert(__temp, __addr);
}
static
bool
_S_should_i_give(unsigned int __block_size, unsigned int __required_size) throw()
{
const unsigned int __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:
typedef _BA_free_list_store _BFL_type;
static inline
void
_S_insert_free_list(unsigned int *__addr) throw()
{
#if defined __GTHREADS
_Lock __bfl_lock(&_S_bfl_mutex);
#endif
//Call _S_validate_free_list to decide what should be done with this
//particular free list.
_S_validate_free_list(--__addr);
}
static
unsigned int*
_S_get_free_list(unsigned int __sz) throw (std::bad_alloc)
{
#if defined __GTHREADS
_Lock __bfl_lock(&_S_bfl_mutex);
#endif
_FLIter __temp = std::lower_bound(_S_free_list.begin(), _S_free_list.end(),
__sz, _LT_pointer_compare());
if (__temp == _S_free_list.end() || !_S_should_i_give(**__temp, __sz))
{
//We hold the lock because the OOM_Handler is a stateless
//entity.
_OOM_handler __set_handler(_BFL_type::_S_clear);
unsigned int* __ret_val = reinterpret_cast<unsigned int*>
(operator new(__sz + sizeof(unsigned int)));
*__ret_val = __sz;
return ++__ret_val;
}
else
{
unsigned int* __ret_val = *__temp;
_S_free_list.erase(__temp);
return ++__ret_val;
}
}
//This function just clears the internal Free List, and gives back
//all the memory to the OS.
static
void
_S_clear()
{
#if defined __GTHREADS
_Lock __bfl_lock(&_S_bfl_mutex);
#endif
_FLIter __iter = _S_free_list.begin();
while (__iter != _S_free_list.end())
{
operator delete((void*)*__iter);
++__iter;
}
_S_free_list.clear();
}
};
#if defined __GTHREADS
_Mutex _BA_free_list_store::_S_bfl_mutex;
#endif
std::vector<unsigned int*> _BA_free_list_store::_S_free_list;
//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;
};
};
template <typename _Tp>
class bitmap_allocator : private _BA_free_list_store
{
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;
template <typename _Tp1>
struct rebind
{
typedef bitmap_allocator<_Tp1> other;
};
private:
static const unsigned int _Bits_Per_Byte = 8;
static const unsigned int _Bits_Per_Block =
sizeof(unsigned int) * _Bits_Per_Byte;
static inline
void
_S_bit_allocate(unsigned int *__pbmap, unsigned int __pos) throw()
{
unsigned int __mask = 1 << __pos;
__mask = ~__mask;
*__pbmap &= __mask;
}
static inline
void
_S_bit_free(unsigned int *__pbmap, unsigned int __pos) throw()
{
unsigned int __mask = 1 << __pos;
*__pbmap |= __mask;
}
static inline
void*
_S_memory_get(size_t __sz) throw (std::bad_alloc)
{
return operator new(__sz);
}
static inline
void
_S_memory_put(void *__vptr) throw ()
{
operator delete(__vptr);
}
typedef typename std::pair<pointer, pointer> _Block_pair;
typedef typename __gnu_cxx::new_allocator<_Block_pair> _BPVec_allocator_type;
typedef typename std::vector<_Block_pair, _BPVec_allocator_type> _BPVector;
#if defined _BALLOC_SANITY_CHECK
//Complexity: O(lg(N)). Where, N is the number of block of size
//sizeof(value_type).
static
void
_S_check_for_free_blocks() throw()
{
typedef typename
__gnu_cxx::__aux_balloc::_Ffit_finder<pointer, _BPVec_allocator_type> _FFF;
_FFF __fff;
typedef typename _BPVector::iterator _BPiter;
_BPiter __bpi =
std::find_if(_S_mem_blocks.begin(), _S_mem_blocks.end(),
__gnu_cxx::__aux_balloc::_Functor_Ref<_FFF>(__fff));
_BALLOC_ASSERT(__bpi == _S_mem_blocks.end());
}
#endif
//Complexity: O(1), but internally depends upon the complexity of
//the function _BA_free_list_store::_S_get_free_list. The part
//where the bitmap headers are written is of worst case complexity:
//O(X),where X is the number of blocks of size sizeof(value_type)
//within the newly acquired block. Having a tight bound.
static
void
_S_refill_pool() throw(std::bad_alloc)
{
#if defined _BALLOC_SANITY_CHECK
_S_check_for_free_blocks();
#endif
const unsigned int __num_bit_maps = _S_block_size / _Bits_Per_Block;
const unsigned int __size_to_allocate = sizeof(unsigned int) +
_S_block_size * sizeof(value_type) + __num_bit_maps*sizeof(unsigned int);
unsigned int *__temp =
reinterpret_cast<unsigned int*>
(_BA_free_list_store::_S_get_free_list(__size_to_allocate));
*__temp = 0;
++__temp;
//The Header information goes at the Beginning of the Block.
_Block_pair __bp =
std::make_pair(reinterpret_cast<pointer>(__temp + __num_bit_maps),
reinterpret_cast<pointer>(__temp + __num_bit_maps)
+ _S_block_size - 1);
//Fill the Vector with this information.
_S_mem_blocks.push_back(__bp);
unsigned int __bit_mask = 0; //0 Indicates all Allocated.
__bit_mask = ~__bit_mask; //1 Indicates all Free.
for (unsigned int __i = 0; __i < __num_bit_maps; ++__i)
__temp[__i] = __bit_mask;
//On some implementations, operator new might throw bad_alloc, or
//malloc might fail if the size passed is too large, therefore, we
//limit the size passed to malloc or operator new.
_S_block_size *= 2;
}
static _BPVector _S_mem_blocks;
static unsigned int _S_block_size;
static __gnu_cxx::__aux_balloc::
_Bit_map_counter<pointer,
_BPVec_allocator_type> _S_last_request;
static typename _BPVector::size_type _S_last_dealloc_index;
#if defined __GTHREADS
static _Mutex _S_mut;
#endif
//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 the average. you
//can consider this function to be having a complexity refrred to
//commonly as: Amortized Constant time.
static
pointer
_S_allocate_single_object()
{
#if defined __GTHREADS
_Lock __bit_lock(&_S_mut);
#endif
//The algorithm is something like this: The last_requst 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 dereferenceable if _S_last_request->_M_finished() returns
//true. This would inevitibly 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::__aux_balloc::_Ffit_finder<pointer, _BPVec_allocator_type> _FFF;
_FFF __fff;
typedef typename _BPVector::iterator _BPiter;
_BPiter __bpi =
std::find_if(_S_mem_blocks.begin(), _S_mem_blocks.end(),
__gnu_cxx::__aux_balloc::_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.
unsigned int __nz_bit = _Bit_scan_forward(*__fff._M_get());
_S_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_val = __bpi->first + __fff._M_offset() + __nz_bit;
unsigned int *__puse_count =
reinterpret_cast<unsigned int*>(__bpi->first) -
(__gnu_cxx::__aux_balloc::__balloc_num_bit_maps(*__bpi) + 1);
++(*__puse_count);
return __ret_val;
}
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.
unsigned int __nz_bit = _Bit_scan_forward(*_S_last_request._M_get());
_S_bit_allocate(_S_last_request._M_get(), __nz_bit);
pointer __ret_val =
_S_last_request._M_base() + _S_last_request._M_offset() + __nz_bit;
unsigned int *__puse_count = reinterpret_cast<unsigned int*>
(_S_mem_blocks[_S_last_request._M_where()].first) -
(__gnu_cxx::__aux_balloc::
__balloc_num_bit_maps(_S_mem_blocks[_S_last_request._M_where()]) + 1);
++(*__puse_count);
return __ret_val;
}
//Complexity: O(lg(N)), but the worst case is hit quite often! I
//need to do something about this. I'll be able to work on it, only
//when I have some solid figures from a few real apps.
static
void
_S_deallocate_single_object(pointer __p) throw()
{
#if defined __GTHREADS
_Lock __bit_lock(&_S_mut);
#endif
typedef typename _BPVector::iterator _Iterator;
typedef typename _BPVector::difference_type _Difference_type;
_Difference_type __diff;
int __displacement;
_BALLOC_ASSERT(_S_last_dealloc_index >= 0);
if (__gnu_cxx::__aux_balloc::_Inclusive_between<pointer>(__p)
(_S_mem_blocks[_S_last_dealloc_index]))
{
_BALLOC_ASSERT(_S_last_dealloc_index <= _S_mem_blocks.size() - 1);
//Initial Assumption was correct!
__diff = _S_last_dealloc_index;
__displacement = __p - _S_mem_blocks[__diff].first;
}
else
{
_Iterator _iter =
std::find_if(_S_mem_blocks.begin(), _S_mem_blocks.end(),
__gnu_cxx::__aux_balloc::_Inclusive_between<pointer>(__p));
_BALLOC_ASSERT(_iter != _S_mem_blocks.end());
__diff = _iter - _S_mem_blocks.begin();
__displacement = __p - _S_mem_blocks[__diff].first;
_S_last_dealloc_index = __diff;
}
//Get the position of the iterator that has been found.
const unsigned int __rotate = __displacement % _Bits_Per_Block;
unsigned int* __bit_mapC =
reinterpret_cast<unsigned int*>(_S_mem_blocks[__diff].first) - 1;
__bit_mapC -= (__displacement / _Bits_Per_Block);
_S_bit_free(__bit_mapC, __rotate);
unsigned int *__puse_count = reinterpret_cast<unsigned int*>
(_S_mem_blocks[__diff].first) -
(__gnu_cxx::__aux_balloc::__balloc_num_bit_maps(_S_mem_blocks[__diff]) + 1);
_BALLOC_ASSERT(*__puse_count != 0);
--(*__puse_count);
if (__builtin_expect(*__puse_count == 0, false))
{
_S_block_size /= 2;
//We may safely remove this block.
_Block_pair __bp = _S_mem_blocks[__diff];
_S_insert_free_list(__puse_count);
_S_mem_blocks.erase(_S_mem_blocks.begin() + __diff);
//We 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);
_BALLOC_ASSERT(_S_last_dealloc_index >= 0);
}
}
}
public:
bitmap_allocator() throw()
{ }
bitmap_allocator(const bitmap_allocator&)
{ }
template <typename _Tp1>
bitmap_allocator(const bitmap_allocator<_Tp1>&) throw()
{ }
~bitmap_allocator() throw()
{ }
//Complexity: O(1), but internally the complexity depends upon the
//complexity of the function(s) _S_allocate_single_object and
//_S_memory_get.
pointer
allocate(size_type __n)
{
if (__builtin_expect(__n == 1, true))
return _S_allocate_single_object();
else
return reinterpret_cast<pointer>
(_S_memory_get(__n * sizeof(value_type)));
}
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(__n == 1, true))
_S_deallocate_single_object(__p);
else
_S_memory_put(__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(__p) value_type(__data);
}
void destroy (pointer __p)
{
__p->~value_type();
}
};
template <typename _Tp>
typename bitmap_allocator<_Tp>::_BPVector
bitmap_allocator<_Tp>::_S_mem_blocks;
template <typename _Tp>
unsigned int bitmap_allocator<_Tp>::_S_block_size =
bitmap_allocator<_Tp>::_Bits_Per_Block;
template <typename _Tp>
typename __gnu_cxx::bitmap_allocator<_Tp>::_BPVector::size_type
bitmap_allocator<_Tp>::_S_last_dealloc_index = 0;
template <typename _Tp>
__gnu_cxx::__aux_balloc::_Bit_map_counter
<typename bitmap_allocator<_Tp>::pointer,
typename bitmap_allocator<_Tp>::_BPVec_allocator_type>
bitmap_allocator<_Tp>::_S_last_request(_S_mem_blocks);
#if defined __GTHREADS
template <typename _Tp>
__gnu_cxx::_Mutex
bitmap_allocator<_Tp>::_S_mut;
#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;
}
}
#endif //_BITMAP_ALLOCATOR_H