bitmap_allocator.h

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	    else
	      __len = __half;
	  }
	return __first;
      }

    template<typename _InputIterator, typename _Predicate>
      inline _InputIterator
      __find_if(_InputIterator __first, _InputIterator __last, _Predicate __p)
      {
	while (__first != __last && !__p(*__first))
	  ++__first;
	return __first;
      }

    /** @brief The number of Blocks pointed to by the address pair
     *  passed to the function.
     */
    template<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 balloc::__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 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::balloc::__num_bitmaps(__bp);

	  if (*(reinterpret_cast<size_t*>
		(__bp.first) - (__diff + 1))
	      == __gnu_cxx::balloc::__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 balloc::__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;
	  
	  _BALLOC_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;
    }
  } // namespace balloc

  /** @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
  {
    typedef size_t* value_type;
    typedef balloc::__mini_vector<value_type> vector_type;
    typedef vector_type::iterator iterator;

    struct _LT_pointer_compare
    {
      bool
      operator()(const size_t* __pui, 
		 const size_t __cui) const throw()
      { return *__pui < __cui; }
    };

#if defined __GTHREADS
    _Mutex*
    _M_get_mutex()
    {
      static _Mutex _S_mutex;
      return &_S_mutex;
    }
#endif

    vector_type&
    _M_get_free_list()
    {
      static vector_type _S_free_list;
      return _S_free_list;
    }

    /** @brief  Performs validation of memory based on their size.
     *
     *  @param  __addr The pointer to the memory block to be
     *  validated.
     *
     *  @detail  Validates the memory block passed to this function and
     *  appropriately performs the action of managing the free list of
     *  blocks by adding this block to the free list or deleting this
     *  or larger blocks from the free list.
     */
    void
    _M_validate(size_t* __addr) throw()
    {
      vector_type& __free_list = _M_get_free_list();
      const vector_type::size_type __max_size = 64;
      if (__free_list.size() >= __max_size)
	{
	  // Ok, the threshold value has been reached.  We determine
	  // which block to remove from the list of free blocks.
	  if (*__addr >= *__free_list.back())
	    {
	      // Ok, the new block is greater than or equal to the
	      // last block in the list of free blocks. We just free
	      // the new block.
	      ::operator delete(static_cast<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(static_cast<void*>(__free_list.back()));
	      __free_list.pop_back();
	    }
	}
	  
      // Just add the block to the list of free lists unconditionally.
      iterator __temp = __gnu_cxx::balloc::__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
      _Auto_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;
	};
    };

  template<typename _Tp>