# bitmap_allocator.h

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    00001 // Bitmap Allocator. -*- C++ -*-
    00002
    00003 // Copyright (C) 2004, 2005, 2006 Free Software Foundation, Inc.
    00004 //
    00005 // This file is part of the GNU ISO C++ Library.  This library is free
    00006 // software; you can redistribute it and/or modify it under the
    00007 // terms of the GNU General Public License as published by the
    00008 // Free Software Foundation; either version 2, or (at your option)
    00009 // any later version.
    00010
    00011 // This library is distributed in the hope that it will be useful,
    00012 // but WITHOUT ANY WARRANTY; without even the implied warranty of
    00013 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    00014 // GNU General Public License for more details.
    00015
    00016 // You should have received a copy of the GNU General Public License along
    00017 // with this library; see the file COPYING.  If not, write to the Free
    00018 // Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
    00019 // USA.
    00020
    00021 // As a special exception, you may use this file as part of a free software
    00022 // library without restriction.  Specifically, if other files instantiate
    00023 // templates or use macros or inline functions from this file, or you compile
    00024 // this file and link it with other files to produce an executable, this
    00025 // file does not by itself cause the resulting executable to be covered by
    00026 // the GNU General Public License.  This exception does not however
    00027 // invalidate any other reasons why the executable file might be covered by
    00028 // the GNU General Public License.
    00029
    00030 /** @file ext/bitmap_allocator.h
    00031  *  This file is a GNU extension to the Standard C++ Library.
    00032  */
    00033
    00034 #ifndef _BITMAP_ALLOCATOR_H
    00035 #define _BITMAP_ALLOCATOR_H 1
    00036
    00037 #include <cstddef> // For std::size_t, and ptrdiff_t.
    00038 #include <bits/functexcept.h> // For __throw_bad_alloc().
    00039 #include <utility> // For std::pair.
    00040 #include <functional> // For greater_equal, and less_equal.
    00041 #include <new> // For operator new.
    00042 #include <debug/debug.h> // _GLIBCXX_DEBUG_ASSERT
    00043 #include <ext/concurrence.h>
    00044
    00045
    00046 /** @brief The constant in the expression below is the alignment
    00047  * required in bytes.
    00048  */
    00049 #define _BALLOC_ALIGN_BYTES 8
    00050
    00051 _GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx)
    00052
    00053   using std::size_t;
    00054   using std::ptrdiff_t;
    00055
    00056   namespace __detail
    00057   {
    00058     /** @class  __mini_vector bitmap_allocator.h bitmap_allocator.h
    00059      *
    00060      *  @brief  __mini_vector<> is a stripped down version of the
    00061      *  full-fledged std::vector<>.
    00062      *
    00063      *  It is to be used only for built-in types or PODs. Notable
    00064      *  differences are:
    00065      *
    00066      *  @detail
    00067      *  1. Not all accessor functions are present.
    00068      *  2. Used ONLY for PODs.
    00069      *  3. No Allocator template argument. Uses ::operator new() to get
    00070      *  memory, and ::operator delete() to free it.
    00071      *  Caveat: The dtor does NOT free the memory allocated, so this a
    00072      *  memory-leaking vector!
    00073      */
    00074     template<typename _Tp>
    00075       class __mini_vector
    00076       {
    00077     __mini_vector(const __mini_vector&);
    00078     __mini_vector& operator=(const __mini_vector&);
    00079
    00080       public:
    00081     typedef _Tp value_type;
    00082     typedef _Tp* pointer;
    00083     typedef _Tp& reference;
    00084     typedef const _Tp& const_reference;
    00085     typedef size_t size_type;
    00086     typedef ptrdiff_t difference_type;
    00087     typedef pointer iterator;
    00088
    00089       private:
    00090     pointer _M_start;
    00091     pointer _M_finish;
    00092     pointer _M_end_of_storage;
    00093
    00094     size_type
    00095     _M_space_left() const throw()
    00096     { return _M_end_of_storage - _M_finish; }
    00097
    00098     pointer
    00099     allocate(size_type __n)
    00100     { return static_cast<pointer>(::operator new(__n * sizeof(_Tp))); }
    00101
    00102     void
    00103     deallocate(pointer __p, size_type)
    00104     { ::operator delete(__p); }
    00105
    00106       public:
    00107     // Members used: size(), push_back(), pop_back(),
    00108     // insert(iterator, const_reference), erase(iterator),
    00109     // begin(), end(), back(), operator[].
    00110
    00111     __mini_vector() : _M_start(0), _M_finish(0),
    00112               _M_end_of_storage(0)
    00113     { }
    00114
    00115 #if 0
    00116     ~__mini_vector()
    00117     {
    00118       if (this->_M_start)
    00119         {
    00120           this->deallocate(this->_M_start, this->_M_end_of_storage
    00121                    - this->_M_start);
    00122         }
    00123     }
    00124 #endif
    00125
    00126     size_type
    00127     size() const throw()
    00128     { return _M_finish - _M_start; }
    00129
    00130     iterator
    00131     begin() const throw()
    00132     { return this->_M_start; }
    00133
    00134     iterator
    00135     end() const throw()
    00136     { return this->_M_finish; }
    00137
    00138     reference
    00139     back() const throw()
    00140     { return *(this->end() - 1); }
    00141
    00142     reference
    00143     operator[](const size_type __pos) const throw()
    00144     { return this->_M_start[__pos]; }
    00145
    00146     void
    00147     insert(iterator __pos, const_reference __x);
    00148
    00149     void
    00150     push_back(const_reference __x)
    00151     {
    00152       if (this->_M_space_left())
    00153         {
    00154           *this->end() = __x;
    00155           ++this->_M_finish;
    00156         }
    00157       else
    00158         this->insert(this->end(), __x);
    00159     }
    00160
    00161     void
    00162     pop_back() throw()
    00163     { --this->_M_finish; }
    00164
    00165     void
    00166     erase(iterator __pos) throw();
    00167
    00168     void
    00169     clear() throw()
    00170     { this->_M_finish = this->_M_start; }
    00171       };
    00172
    00173     // Out of line function definitions.
    00174     template<typename _Tp>
    00175       void __mini_vector<_Tp>::
    00176       insert(iterator __pos, const_reference __x)
    00177       {
    00178     if (this->_M_space_left())
    00179       {
    00180         size_type __to_move = this->_M_finish - __pos;
    00181         iterator __dest = this->end();
    00182         iterator __src = this->end() - 1;
    00183
    00184         ++this->_M_finish;
    00185         while (__to_move)
    00186           {
    00187         *__dest = *__src;
    00188         --__dest; --__src; --__to_move;
    00189           }
    00190         *__pos = __x;
    00191       }
    00192     else
    00193       {
    00194         size_type __new_size = this->size() ? this->size() * 2 : 1;
    00195         iterator __new_start = this->allocate(__new_size);
    00196         iterator __first = this->begin();
    00197         iterator __start = __new_start;
    00198         while (__first != __pos)
    00199           {
    00200         *__start = *__first;
    00201         ++__start; ++__first;
    00202           }
    00203         *__start = __x;
    00204         ++__start;
    00205         while (__first != this->end())
    00206           {
    00207         *__start = *__first;
    00208         ++__start; ++__first;
    00209           }
    00210         if (this->_M_start)
    00211           this->deallocate(this->_M_start, this->size());
    00212
    00213         this->_M_start = __new_start;
    00214         this->_M_finish = __start;
    00215         this->_M_end_of_storage = this->_M_start + __new_size;
    00216       }
    00217       }
    00218
    00219     template<typename _Tp>
    00220       void __mini_vector<_Tp>::
    00221       erase(iterator __pos) throw()
    00222       {
    00223     while (__pos + 1 != this->end())
    00224       {
    00225         *__pos = __pos[1];
    00226         ++__pos;
    00227       }
    00228     --this->_M_finish;
    00229       }
    00230
    00231
    00232     template<typename _Tp>
    00233       struct __mv_iter_traits
    00234       {
    00235     typedef typename _Tp::value_type value_type;
    00236     typedef typename _Tp::difference_type difference_type;
    00237       };
    00238
    00239     template<typename _Tp>
    00240       struct __mv_iter_traits<_Tp*>
    00241       {
    00242     typedef _Tp value_type;
    00243     typedef ptrdiff_t difference_type;
    00244       };
    00245
    00246     enum
    00247       {
    00248     bits_per_byte = 8,
    00249     bits_per_block = sizeof(size_t) * size_t(bits_per_byte)
    00250       };
    00251
    00252     template<typename _ForwardIterator, typename _Tp, typename _Compare>
    00253       _ForwardIterator
    00254       __lower_bound(_ForwardIterator __first, _ForwardIterator __last,
    00255             const _Tp& __val, _Compare __comp)
    00256       {
    00257     typedef typename __mv_iter_traits<_ForwardIterator>::value_type
    00258       _ValueType;
    00259     typedef typename __mv_iter_traits<_ForwardIterator>::difference_type
    00260       _DistanceType;
    00261
    00262     _DistanceType __len = __last - __first;
    00263     _DistanceType __half;
    00264     _ForwardIterator __middle;
    00265
    00266     while (__len > 0)
    00267       {
    00268         __half = __len >> 1;
    00269         __middle = __first;
    00270         __middle += __half;
    00271         if (__comp(*__middle, __val))
    00272           {
    00273         __first = __middle;
    00274         ++__first;
    00275         __len = __len - __half - 1;
    00276           }
    00277         else
    00278           __len = __half;
    00279       }
    00280     return __first;
    00281       }
    00282
    00283     template<typename _InputIterator, typename _Predicate>
    00284       inline _InputIterator
    00285       __find_if(_InputIterator __first, _InputIterator __last, _Predicate __p)
    00286       {
    00287     while (__first != __last && !__p(*__first))
    00288       ++__first;
    00289     return __first;
    00290       }
    00291
    00292     /** @brief The number of Blocks pointed to by the address pair
    00293      *  passed to the function.
    00294      */
    00295     template<typename _AddrPair>
    00296       inline size_t
    00297       __num_blocks(_AddrPair __ap)
    00298       { return (__ap.second - __ap.first) + 1; }
    00299
    00300     /** @brief The number of Bit-maps pointed to by the address pair
    00301      *  passed to the function.
    00302      */
    00303     template<typename _AddrPair>
    00304       inline size_t
    00305       __num_bitmaps(_AddrPair __ap)
    00306       { return __num_blocks(__ap) / size_t(bits_per_block); }
    00307
    00308     // _Tp should be a pointer type.
    00309     template<typename _Tp>
    00310       class _Inclusive_between
    00311       : public std::unary_function<typename std::pair<_Tp, _Tp>, bool>
    00312       {
    00313     typedef _Tp pointer;
    00314     pointer _M_ptr_value;
    00315     typedef typename std::pair<_Tp, _Tp> _Block_pair;
    00316
    00317       public:
    00318     _Inclusive_between(pointer __ptr) : _M_ptr_value(__ptr)
    00319     { }
    00320
    00321     bool
    00322     operator()(_Block_pair __bp) const throw()
    00323     {
    00324       if (std::less_equal<pointer>()(_M_ptr_value, __bp.second)
    00325           && std::greater_equal<pointer>()(_M_ptr_value, __bp.first))
    00326         return true;
    00327       else
    00328         return false;
    00329     }
    00330       };
    00331
    00332     // Used to pass a Functor to functions by reference.
    00333     template<typename _Functor>
    00334       class _Functor_Ref
    00335       : public std::unary_function<typename _Functor::argument_type,
    00336                    typename _Functor::result_type>
    00337       {
    00338     _Functor& _M_fref;
    00339
    00340       public:
    00341     typedef typename _Functor::argument_type argument_type;
    00342     typedef typename _Functor::result_type result_type;
    00343
    00344     _Functor_Ref(_Functor& __fref) : _M_fref(__fref)
    00345     { }
    00346
    00347     result_type
    00348     operator()(argument_type __arg)
    00349     { return _M_fref(__arg); }
    00350       };
    00351
    00352     /** @class  _Ffit_finder bitmap_allocator.h bitmap_allocator.h
    00353      *
    00354      *  @brief  The class which acts as a predicate for applying the
    00355      *  first-fit memory allocation policy for the bitmap allocator.
    00356      */
    00357     // _Tp should be a pointer type, and _Alloc is the Allocator for
    00358     // the vector.
    00359     template<typename _Tp>
    00360       class _Ffit_finder
    00361       : public std::unary_function<typename std::pair<_Tp, _Tp>, bool>
    00362       {
    00363     typedef typename std::pair<_Tp, _Tp> _Block_pair;
    00364     typedef typename __detail::__mini_vector<_Block_pair> _BPVector;
    00365     typedef typename _BPVector::difference_type _Counter_type;
    00366
    00367     size_t* _M_pbitmap;
    00368     _Counter_type _M_data_offset;
    00369
    00370       public:
    00371     _Ffit_finder() : _M_pbitmap(0), _M_data_offset(0)
    00372     { }
    00373
    00374     bool
    00375     operator()(_Block_pair __bp) throw()
    00376     {
    00377       // Set the _rover to the last physical location bitmap,
    00378       // which is the bitmap which belongs to the first free
    00379       // block. Thus, the bitmaps are in exact reverse order of
    00380       // the actual memory layout. So, we count down the bimaps,
    00381       // which is the same as moving up the memory.
    00382
    00383       // If the used count stored at the start of the Bit Map headers
    00384       // is equal to the number of Objects that the current Block can
    00385       // store, then there is definitely no space for another single
    00386       // object, so just return false.
    00387       _Counter_type __diff =
    00388         __gnu_cxx::__detail::__num_bitmaps(__bp);
    00389
    00390       if (*(reinterpret_cast<size_t*>
    00391         (__bp.first) - (__diff + 1))
    00392           == __gnu_cxx::__detail::__num_blocks(__bp))
    00393         return false;
    00394
    00395       size_t* __rover = reinterpret_cast<size_t*>(__bp.first) - 1;
    00396
    00397       for (_Counter_type __i = 0; __i < __diff; ++__i)
    00398         {
    00399           _M_data_offset = __i;
    00400           if (*__rover)
    00401         {
    00402           _M_pbitmap = __rover;
    00403           return true;
    00404         }
    00405           --__rover;
    00406         }
    00407       return false;
    00408     }
    00409
    00410
    00411     size_t*
    00412     _M_get() const throw()
    00413     { return _M_pbitmap; }
    00414
    00415     _Counter_type
    00416     _M_offset() const throw()
    00417     { return _M_data_offset * size_t(bits_per_block); }
    00418       };
    00419
    00420
    00421     /** @class  _Bitmap_counter bitmap_allocator.h bitmap_allocator.h
    00422      *
    00423      *  @brief  The bitmap counter which acts as the bitmap
    00424      *  manipulator, and manages the bit-manipulation functions and
    00425      *  the searching and identification functions on the bit-map.
    00426      */
    00427     // _Tp should be a pointer type.
    00428     template<typename _Tp>
    00429       class _Bitmap_counter
    00430       {
    00431     typedef typename __detail::__mini_vector<typename std::pair<_Tp, _Tp> >
    00432     _BPVector;
    00433     typedef typename _BPVector::size_type _Index_type;
    00434     typedef _Tp pointer;
    00435
    00436     _BPVector& _M_vbp;
    00437     size_t* _M_curr_bmap;
    00438     size_t* _M_last_bmap_in_block;
    00439     _Index_type _M_curr_index;
    00440
    00441       public:
    00442     // Use the 2nd parameter with care. Make sure that such an
    00443     // entry exists in the vector before passing that particular
    00444     // index to this ctor.
    00445     _Bitmap_counter(_BPVector& Rvbp, long __index = -1) : _M_vbp(Rvbp)
    00446     { this->_M_reset(__index); }
    00447
    00448     void
    00449     _M_reset(long __index = -1) throw()
    00450     {
    00451       if (__index == -1)
    00452         {
    00453           _M_curr_bmap = 0;
    00454           _M_curr_index = static_cast<_Index_type>(-1);
    00455           return;
    00456         }
    00457
    00458       _M_curr_index = __index;
    00459       _M_curr_bmap = reinterpret_cast<size_t*>
    00460         (_M_vbp[_M_curr_index].first) - 1;
    00461
    00462       _GLIBCXX_DEBUG_ASSERT(__index <= (long)_M_vbp.size() - 1);
    00463
    00464       _M_last_bmap_in_block = _M_curr_bmap
    00465         - ((_M_vbp[_M_curr_index].second
    00466         - _M_vbp[_M_curr_index].first + 1)
    00467            / size_t(bits_per_block) - 1);
    00468     }
    00469
    00470     // Dangerous Function! Use with extreme care. Pass to this
    00471     // function ONLY those values that are known to be correct,
    00472     // otherwise this will mess up big time.
    00473     void
    00474     _M_set_internal_bitmap(size_t* __new_internal_marker) throw()
    00475     { _M_curr_bmap = __new_internal_marker; }
    00476
    00477     bool
    00478     _M_finished() const throw()
    00479     { return(_M_curr_bmap == 0); }
    00480
    00481     _Bitmap_counter&
    00482     operator++() throw()
    00483     {
    00484       if (_M_curr_bmap == _M_last_bmap_in_block)
    00485         {
    00486           if (++_M_curr_index == _M_vbp.size())
    00487         _M_curr_bmap = 0;
    00488           else
    00489         this->_M_reset(_M_curr_index);
    00490         }
    00491       else
    00492         --_M_curr_bmap;
    00493       return *this;
    00494     }
    00495
    00496     size_t*
    00497     _M_get() const throw()
    00498     { return _M_curr_bmap; }
    00499
    00500     pointer
    00501     _M_base() const throw()
    00502     { return _M_vbp[_M_curr_index].first; }
    00503
    00504     _Index_type
    00505     _M_offset() const throw()
    00506     {
    00507       return size_t(bits_per_block)
    00508         * ((reinterpret_cast<size_t*>(this->_M_base())
    00509         - _M_curr_bmap) - 1);
    00510     }
    00511
    00512     _Index_type
    00513     _M_where() const throw()
    00514     { return _M_curr_index; }
    00515       };
    00516
    00517     /** @brief  Mark a memory address as allocated by re-setting the
    00518      *  corresponding bit in the bit-map.
    00519      */
    00520     inline void
    00521     __bit_allocate(size_t* __pbmap, size_t __pos) throw()
    00522     {
    00523       size_t __mask = 1 << __pos;
    00524       __mask = ~__mask;
    00525       *__pbmap &= __mask;
    00526     }
    00527
    00528     /** @brief  Mark a memory address as free by setting the
    00529      *  corresponding bit in the bit-map.
    00530      */
    00531     inline void
    00532     __bit_free(size_t* __pbmap, size_t __pos) throw()
    00533     {
    00534       size_t __mask = 1 << __pos;
    00535       *__pbmap |= __mask;
    00536     }
    00537   } // namespace __detail
    00538
    00539   /** @brief  Generic Version of the bsf instruction.
    00540    */
    00541   inline size_t
    00542   _Bit_scan_forward(size_t __num)
    00543   { return static_cast<size_t>(__builtin_ctzl(__num)); }
    00544
    00545   /** @class  free_list bitmap_allocator.h bitmap_allocator.h
    00546    *
    00547    *  @brief  The free list class for managing chunks of memory to be
    00548    *  given to and returned by the bitmap_allocator.
    00549    */
    00550   class free_list
    00551   {
    00552     typedef size_t*                 value_type;
    00553     typedef __detail::__mini_vector<value_type> vector_type;
    00554     typedef vector_type::iterator       iterator;
    00555     typedef __mutex             __mutex_type;
    00556
    00557     struct _LT_pointer_compare
    00558     {
    00559       bool
    00560       operator()(const size_t* __pui,
    00561          const size_t __cui) const throw()
    00562       { return *__pui < __cui; }
    00563     };
    00564
    00565 #if defined __GTHREADS
    00566     __mutex_type&
    00567     _M_get_mutex()
    00568     {
    00569       static __mutex_type _S_mutex;
    00570       return _S_mutex;
    00571     }
    00572 #endif
    00573
    00574     vector_type&
    00575     _M_get_free_list()
    00576     {
    00577       static vector_type _S_free_list;
    00578       return _S_free_list;
    00579     }
    00580
    00581     /** @brief  Performs validation of memory based on their size.
    00582      *
    00583      *  @param  __addr The pointer to the memory block to be
    00584      *  validated.
    00585      *
    00586      *  @detail  Validates the memory block passed to this function and
    00587      *  appropriately performs the action of managing the free list of
    00588      *  blocks by adding this block to the free list or deleting this
    00589      *  or larger blocks from the free list.
    00590      */
    00591     void
    00592     _M_validate(size_t* __addr) throw()
    00593     {
    00594       vector_type& __free_list = _M_get_free_list();
    00595       const vector_type::size_type __max_size = 64;
    00596       if (__free_list.size() >= __max_size)
    00597     {
    00598       // Ok, the threshold value has been reached.  We determine
    00599       // which block to remove from the list of free blocks.
    00600       if (*__addr >= *__free_list.back())
    00601         {
    00602           // Ok, the new block is greater than or equal to the
    00603           // last block in the list of free blocks. We just free
    00604           // the new block.
    00605           ::operator delete(static_cast<void*>(__addr));
    00606           return;
    00607         }
    00608       else
    00609         {
    00610           // Deallocate the last block in the list of free lists,
    00611           // and insert the new one in it's correct position.
    00612           ::operator delete(static_cast<void*>(__free_list.back()));
    00613           __free_list.pop_back();
    00614         }
    00615     }
    00616
    00617       // Just add the block to the list of free lists unconditionally.
    00618       iterator __temp = __gnu_cxx::__detail::__lower_bound
    00619     (__free_list.begin(), __free_list.end(),
    00620      *__addr, _LT_pointer_compare());
    00621
    00622       // We may insert the new free list before _temp;
    00623       __free_list.insert(__temp, __addr);
    00624     }
    00625
    00626     /** @brief  Decides whether the wastage of memory is acceptable for
    00627      *  the current memory request and returns accordingly.
    00628      *
    00629      *  @param __block_size The size of the block available in the free
    00630      *  list.
    00631      *
    00632      *  @param __required_size The required size of the memory block.
    00633      *
    00634      *  @return true if the wastage incurred is acceptable, else returns
    00635      *  false.
    00636      */
    00637     bool
    00638     _M_should_i_give(size_t __block_size,
    00639              size_t __required_size) throw()
    00640     {
    00641       const size_t __max_wastage_percentage = 36;
    00642       if (__block_size >= __required_size &&
    00643       (((__block_size - __required_size) * 100 / __block_size)
    00644        < __max_wastage_percentage))
    00645     return true;
    00646       else
    00647     return false;
    00648     }
    00649
    00650   public:
    00651     /** @brief This function returns the block of memory to the
    00652      *  internal free list.
    00653      *
    00654      *  @param  __addr The pointer to the memory block that was given
    00655      *  by a call to the _M_get function.
    00656      */
    00657     inline void
    00658     _M_insert(size_t* __addr) throw()
    00659     {
    00660 #if defined __GTHREADS
    00661       __gnu_cxx::__scoped_lock __bfl_lock(_M_get_mutex());
    00662 #endif
    00663       // Call _M_validate to decide what should be done with
    00664       // this particular free list.
    00665       this->_M_validate(reinterpret_cast<size_t*>(__addr) - 1);
    00666       // See discussion as to why this is 1!
    00667     }
    00668
    00669     /** @brief  This function gets a block of memory of the specified
    00670      *  size from the free list.
    00671      *
    00672      *  @param  __sz The size in bytes of the memory required.
    00673      *
    00674      *  @return  A pointer to the new memory block of size at least
    00675      *  equal to that requested.
    00676      */
    00677     size_t*
    00678     _M_get(size_t __sz) throw(std::bad_alloc);
    00679
    00680     /** @brief  This function just clears the internal Free List, and
    00681      *  gives back all the memory to the OS.
    00682      */
    00683     void
    00684     _M_clear();
    00685   };
    00686
    00687
    00688   // Forward declare the class.
    00689   template<typename _Tp>
    00690     class bitmap_allocator;
    00691
    00692   // Specialize for void:
    00693   template<>
    00694     class bitmap_allocator<void>
    00695     {
    00696     public:
    00697       typedef void*       pointer;
    00698       typedef const void* const_pointer;
    00699
    00700       // Reference-to-void members are impossible.
    00701       typedef void  value_type;
    00702       template<typename _Tp1>
    00703         struct rebind
    00704     {
    00705       typedef bitmap_allocator<_Tp1> other;
    00706     };
    00707     };
    00708
    00709   template<typename _Tp>
    00710     class bitmap_allocator : private free_list
    00711     {
    00712     public:
    00713       typedef size_t            size_type;
    00714       typedef ptrdiff_t         difference_type;
    00715       typedef _Tp*              pointer;
    00716       typedef const _Tp*        const_pointer;
    00717       typedef _Tp&              reference;
    00718       typedef const _Tp&        const_reference;
    00719       typedef _Tp               value_type;
    00720       typedef free_list::__mutex_type   __mutex_type;
    00721
    00722       template<typename _Tp1>
    00723         struct rebind
    00724     {
    00725       typedef bitmap_allocator<_Tp1> other;
    00726     };
    00727
    00728     private:
    00729       template<size_t _BSize, size_t _AlignSize>
    00730         struct aligned_size
    00731     {
    00732       enum
    00733         {
    00734           modulus = _BSize % _AlignSize,
    00735           value = _BSize + (modulus ? _AlignSize - (modulus) : 0)
    00736         };
    00737     };
    00738
    00739       struct _Alloc_block
    00740       {
    00741     char __M_unused[aligned_size<sizeof(value_type),
    00742             _BALLOC_ALIGN_BYTES>::value];
    00743       };
    00744
    00745
    00746       typedef typename std::pair<_Alloc_block*, _Alloc_block*> _Block_pair;
    00747
    00748       typedef typename
    00749       __detail::__mini_vector<_Block_pair> _BPVector;
    00750
    00751 #if defined _GLIBCXX_DEBUG
    00752       // Complexity: O(lg(N)). Where, N is the number of block of size
    00753       // sizeof(value_type).
    00754       void
    00755       _S_check_for_free_blocks() throw()
    00756       {
    00757     typedef typename
    00758       __gnu_cxx::__detail::_Ffit_finder<_Alloc_block*> _FFF;
    00759     _FFF __fff;
    00760     typedef typename _BPVector::iterator _BPiter;
    00761     _BPiter __bpi =
    00762       __gnu_cxx::__detail::__find_if
    00763       (_S_mem_blocks.begin(), _S_mem_blocks.end(),
    00764        __gnu_cxx::__detail::_Functor_Ref<_FFF>(__fff));
    00765
    00766     _GLIBCXX_DEBUG_ASSERT(__bpi == _S_mem_blocks.end());
    00767       }
    00768 #endif
    00769
    00770       /** @brief  Responsible for exponentially growing the internal
    00771        *  memory pool.
    00772        *
    00773        *  @throw  std::bad_alloc. If memory can not be allocated.
    00774        *
    00775        *  @detail  Complexity: O(1), but internally depends upon the
    00776        *  complexity of the function free_list::_M_get. The part where
    00777        *  the bitmap headers are written has complexity: O(X),where X
    00778        *  is the number of blocks of size sizeof(value_type) within
    00779        *  the newly acquired block. Having a tight bound.
    00780        */
    00781       void
    00782       _S_refill_pool() throw(std::bad_alloc)
    00783       {
    00784 #if defined _GLIBCXX_DEBUG
    00785     _S_check_for_free_blocks();
    00786 #endif
    00787
    00788     const size_t __num_bitmaps = (_S_block_size
    00789                       / size_t(__detail::bits_per_block));
    00790     const size_t __size_to_allocate = sizeof(size_t)
    00791       + _S_block_size * sizeof(_Alloc_block)
    00792       + __num_bitmaps * sizeof(size_t);
    00793
    00794     size_t* __temp =
    00795       reinterpret_cast<size_t*>
    00796       (this->_M_get(__size_to_allocate));
    00797     *__temp = 0;
    00798     ++__temp;
    00799
    00800     // The Header information goes at the Beginning of the Block.
    00801     _Block_pair __bp =
    00802       std::make_pair(reinterpret_cast<_Alloc_block*>
    00803              (__temp + __num_bitmaps),
    00804              reinterpret_cast<_Alloc_block*>
    00805              (__temp + __num_bitmaps)
    00806              + _S_block_size - 1);
    00807
    00808     // Fill the Vector with this information.
    00809     _S_mem_blocks.push_back(__bp);
    00810
    00811     size_t __bit_mask = 0; // 0 Indicates all Allocated.
    00812     __bit_mask = ~__bit_mask; // 1 Indicates all Free.
    00813
    00814     for (size_t __i = 0; __i < __num_bitmaps; ++__i)
    00815       __temp[__i] = __bit_mask;
    00816
    00817     _S_block_size *= 2;
    00818       }
    00819
    00820
    00821       static _BPVector _S_mem_blocks;
    00822       static size_t _S_block_size;
    00823       static __gnu_cxx::__detail::
    00824       _Bitmap_counter<_Alloc_block*> _S_last_request;
    00825       static typename _BPVector::size_type _S_last_dealloc_index;
    00826 #if defined __GTHREADS
    00827       static __mutex_type _S_mut;
    00828 #endif
    00829
    00830     public:
    00831
    00832       /** @brief  Allocates memory for a single object of size
    00833        *  sizeof(_Tp).
    00834        *
    00835        *  @throw  std::bad_alloc. If memory can not be allocated.
    00836        *
    00837        *  @detail  Complexity: Worst case complexity is O(N), but that
    00838        *  is hardly ever hit. If and when this particular case is
    00839        *  encountered, the next few cases are guaranteed to have a
    00840        *  worst case complexity of O(1)!  That's why this function
    00841        *  performs very well on average. You can consider this
    00842        *  function to have a complexity referred to commonly as:
    00843        *  Amortized Constant time.
    00844        */
    00845       pointer
    00846       _M_allocate_single_object() throw(std::bad_alloc)
    00847       {
    00848 #if defined __GTHREADS
    00849     __gnu_cxx::__scoped_lock __bit_lock(_S_mut);
    00850 #endif
    00851
    00852     // The algorithm is something like this: The last_request
    00853     // variable points to the last accessed Bit Map. When such a
    00854     // condition occurs, we try to find a free block in the
    00855     // current bitmap, or succeeding bitmaps until the last bitmap
    00856     // is reached. If no free block turns up, we resort to First
    00857     // Fit method.
    00858
    00859     // WARNING: Do not re-order the condition in the while
    00860     // statement below, because it relies on C++'s short-circuit
    00861     // evaluation. The return from _S_last_request->_M_get() will
    00862     // NOT be dereference able if _S_last_request->_M_finished()
    00863     // returns true. This would inevitably lead to a NULL pointer
    00864     // dereference if tinkered with.
    00865     while (_S_last_request._M_finished() == false
    00866            && (*(_S_last_request._M_get()) == 0))
    00867       {
    00868         _S_last_request.operator++();
    00869       }
    00870
    00871     if (__builtin_expect(_S_last_request._M_finished() == true, false))
    00872       {
    00873         // Fall Back to First Fit algorithm.
    00874         typedef typename
    00875           __gnu_cxx::__detail::_Ffit_finder<_Alloc_block*> _FFF;
    00876         _FFF __fff;
    00877         typedef typename _BPVector::iterator _BPiter;
    00878         _BPiter __bpi =
    00879           __gnu_cxx::__detail::__find_if
    00880           (_S_mem_blocks.begin(), _S_mem_blocks.end(),
    00881            __gnu_cxx::__detail::_Functor_Ref<_FFF>(__fff));
    00882
    00883         if (__bpi != _S_mem_blocks.end())
    00884           {
    00885         // Search was successful. Ok, now mark the first bit from
    00886         // the right as 0, meaning Allocated. This bit is obtained
    00887         // by calling _M_get() on __fff.
    00888         size_t __nz_bit = _Bit_scan_forward(*__fff._M_get());
    00889         __detail::__bit_allocate(__fff._M_get(), __nz_bit);
    00890
    00891         _S_last_request._M_reset(__bpi - _S_mem_blocks.begin());
    00892
    00893         // Now, get the address of the bit we marked as allocated.
    00894         pointer __ret = reinterpret_cast<pointer>
    00895           (__bpi->first + __fff._M_offset() + __nz_bit);
    00896         size_t* __puse_count =
    00897           reinterpret_cast<size_t*>
    00898           (__bpi->first)
    00899           - (__gnu_cxx::__detail::__num_bitmaps(*__bpi) + 1);
    00900
    00901         ++(*__puse_count);
    00902         return __ret;
    00903           }
    00904         else
    00905           {
    00906         // Search was unsuccessful. We Add more memory to the
    00907         // pool by calling _S_refill_pool().
    00908         _S_refill_pool();
    00909
    00910         // _M_Reset the _S_last_request structure to the first
    00911         // free block's bit map.
    00912         _S_last_request._M_reset(_S_mem_blocks.size() - 1);
    00913
    00914         // Now, mark that bit as allocated.
    00915           }
    00916       }
    00917
    00918     // _S_last_request holds a pointer to a valid bit map, that
    00919     // points to a free block in memory.
    00920     size_t __nz_bit = _Bit_scan_forward(*_S_last_request._M_get());
    00921     __detail::__bit_allocate(_S_last_request._M_get(), __nz_bit);
    00922
    00923     pointer __ret = reinterpret_cast<pointer>
    00924       (_S_last_request._M_base() + _S_last_request._M_offset() + __nz_bit);
    00925
    00926     size_t* __puse_count = reinterpret_cast<size_t*>
    00927       (_S_mem_blocks[_S_last_request._M_where()].first)
    00928       - (__gnu_cxx::__detail::
    00929          __num_bitmaps(_S_mem_blocks[_S_last_request._M_where()]) + 1);
    00930
    00931     ++(*__puse_count);
    00932     return __ret;
    00933       }
    00934
    00935       /** @brief  Deallocates memory that belongs to a single object of
    00936        *  size sizeof(_Tp).
    00937        *
    00938        *  @detail  Complexity: O(lg(N)), but the worst case is not hit
    00939        *  often!  This is because containers usually deallocate memory
    00940        *  close to each other and this case is handled in O(1) time by
    00941        *  the deallocate function.
    00942        */
    00943       void
    00944       _M_deallocate_single_object(pointer __p) throw()
    00945       {
    00946 #if defined __GTHREADS
    00947     __gnu_cxx::__scoped_lock __bit_lock(_S_mut);
    00948 #endif
    00949     _Alloc_block* __real_p = reinterpret_cast<_Alloc_block*>(__p);
    00950
    00951     typedef typename _BPVector::iterator _Iterator;
    00952     typedef typename _BPVector::difference_type _Difference_type;
    00953
    00954     _Difference_type __diff;
    00955     long __displacement;
    00956
    00957     _GLIBCXX_DEBUG_ASSERT(_S_last_dealloc_index >= 0);
    00958
    00959
    00960     if (__gnu_cxx::__detail::_Inclusive_between<_Alloc_block*>
    00961         (__real_p) (_S_mem_blocks[_S_last_dealloc_index]))
    00962       {
    00963         _GLIBCXX_DEBUG_ASSERT(_S_last_dealloc_index
    00964                   <= _S_mem_blocks.size() - 1);
    00965
    00966         // Initial Assumption was correct!
    00967         __diff = _S_last_dealloc_index;
    00968         __displacement = __real_p - _S_mem_blocks[__diff].first;
    00969       }
    00970     else
    00971       {
    00972         _Iterator _iter = __gnu_cxx::__detail::
    00973 	      __find_if(_S_mem_blocks.begin(),
    00974             _S_mem_blocks.end(),
    00975             __gnu_cxx::__detail::
    00976             _Inclusive_between<_Alloc_block*>(__real_p));
    00977
    00978         _GLIBCXX_DEBUG_ASSERT(_iter != _S_mem_blocks.end());
    00979
    00980         __diff = _iter - _S_mem_blocks.begin();
    00981         __displacement = __real_p - _S_mem_blocks[__diff].first;
    00982         _S_last_dealloc_index = __diff;
    00983       }
    00984
    00985     // Get the position of the iterator that has been found.
    00986     const size_t __rotate = (__displacement
    00987                  % size_t(__detail::bits_per_block));
    00988     size_t* __bitmapC =
    00989       reinterpret_cast<size_t*>
    00990       (_S_mem_blocks[__diff].first) - 1;
    00991     __bitmapC -= (__displacement / size_t(__detail::bits_per_block));
    00992
    00993     __detail::__bit_free(__bitmapC, __rotate);
    00994     size_t* __puse_count = reinterpret_cast<size_t*>
    00995       (_S_mem_blocks[__diff].first)
    00996       - (__gnu_cxx::__detail::__num_bitmaps(_S_mem_blocks[__diff]) + 1);
    00997
    00998     _GLIBCXX_DEBUG_ASSERT(*__puse_count != 0);
    00999
    01000     --(*__puse_count);
    01001
    01002     if (__builtin_expect(*__puse_count == 0, false))
    01003       {
    01004         _S_block_size /= 2;
    01005
    01006         // We can safely remove this block.
    01007         // _Block_pair __bp = _S_mem_blocks[__diff];
    01008         this->_M_insert(__puse_count);
    01009         _S_mem_blocks.erase(_S_mem_blocks.begin() + __diff);
    01010
    01011         // Reset the _S_last_request variable to reflect the
    01012         // erased block. We do this to protect future requests
    01013         // after the last block has been removed from a particular
    01014         // memory Chunk, which in turn has been returned to the
    01015         // free list, and hence had been erased from the vector,
    01016         // so the size of the vector gets reduced by 1.
    01017         if ((_Difference_type)_S_last_request._M_where() >= __diff--)
    01018           _S_last_request._M_reset(__diff);
    01019
    01020         // If the Index into the vector of the region of memory
    01021         // that might hold the next address that will be passed to
    01022         // deallocated may have been invalidated due to the above
    01023         // erase procedure being called on the vector, hence we
    01024         // try to restore this invariant too.
    01025         if (_S_last_dealloc_index >= _S_mem_blocks.size())
    01026           {
    01027         _S_last_dealloc_index =(__diff != -1 ? __diff : 0);
    01028         _GLIBCXX_DEBUG_ASSERT(_S_last_dealloc_index >= 0);
    01029           }
    01030       }
    01031       }
    01032
    01033     public:
    01034       bitmap_allocator() throw()
    01035       { }
    01036
    01037       bitmap_allocator(const bitmap_allocator&)
    01038       { }
    01039
    01040       template<typename _Tp1>
    01041         bitmap_allocator(const bitmap_allocator<_Tp1>&) throw()
    01042         { }
    01043
    01044       ~bitmap_allocator() throw()
    01045       { }
    01046
    01047       pointer
    01048       allocate(size_type __n)
    01049       {
    01050     if (__builtin_expect(__n > this->max_size(), false))
    01051       std::__throw_bad_alloc();
    01052
    01053     if (__builtin_expect(__n == 1, true))
    01054       return this->_M_allocate_single_object();
    01055     else
    01056       {
    01057         const size_type __b = __n * sizeof(value_type);
    01058         return reinterpret_cast<pointer>(::operator new(__b));
    01059       }
    01060       }
    01061
    01062       pointer
    01063       allocate(size_type __n, typename bitmap_allocator<void>::const_pointer)
    01064       { return allocate(__n); }
    01065
    01066       void
    01067       deallocate(pointer __p, size_type __n) throw()
    01068       {
    01069     if (__builtin_expect(__p != 0, true))
    01070       {
    01071         if (__builtin_expect(__n == 1, true))
    01072           this->_M_deallocate_single_object(__p);
    01073         else
    01074           ::operator delete(__p);
    01075       }
    01076       }
    01077
    01078       pointer
    01079       address(reference __r) const
    01080       { return &__r; }
    01081
    01082       const_pointer
    01083       address(const_reference __r) const
    01084       { return &__r; }
    01085
    01086       size_type
    01087       max_size() const throw()
    01088       { return size_type(-1) / sizeof(value_type); }
    01089
    01090       void
    01091       construct(pointer __p, const_reference __data)
    01092       { ::new(__p) value_type(__data); }
    01093
    01094       void
    01095       destroy(pointer __p)
    01096       { __p->~value_type(); }
    01097     };
    01098
    01099   template<typename _Tp1, typename _Tp2>
    01100     bool
    01101     operator==(const bitmap_allocator<_Tp1>&,
    01102            const bitmap_allocator<_Tp2>&) throw()
    01103     { return true; }
    01104
    01105   template<typename _Tp1, typename _Tp2>
    01106     bool
    01107     operator!=(const bitmap_allocator<_Tp1>&,
    01108            const bitmap_allocator<_Tp2>&) throw()
    01109   { return false; }
    01110
    01111   // Static member definitions.
    01112   template<typename _Tp>
    01113     typename bitmap_allocator<_Tp>::_BPVector
    01114     bitmap_allocator<_Tp>::_S_mem_blocks;
    01115
    01116   template<typename _Tp>
    01117     size_t bitmap_allocator<_Tp>::_S_block_size =
    01118     2 * size_t(__detail::bits_per_block);
    01119
    01120   template<typename _Tp>
    01121     typename __gnu_cxx::bitmap_allocator<_Tp>::_BPVector::size_type
    01122     bitmap_allocator<_Tp>::_S_last_dealloc_index = 0;
    01123
    01124   template<typename _Tp>
    01125     __gnu_cxx::__detail::_Bitmap_counter
    01126   <typename bitmap_allocator<_Tp>::_Alloc_block*>
    01127     bitmap_allocator<_Tp>::_S_last_request(_S_mem_blocks);
    01128
    01129 #if defined __GTHREADS
    01130   template<typename _Tp>
    01131     typename bitmap_allocator<_Tp>::__mutex_type
    01132     bitmap_allocator<_Tp>::_S_mut;
    01133 #endif
    01134
    01135 _GLIBCXX_END_NAMESPACE
    01136
    01137 #endif
    01138