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Class template rbtree_best_fit



// In header: <boost/interprocess/mem_algo/rbtree_best_fit.hpp>

template<typename MutexFamily, typename VoidPointer, std::size_t MemAlignment> 
class rbtree_best_fit {
  // types
  typedef MutexFamily                                                   mutex_family;           // Shared mutex family used for the rest of the Interprocess framework. 
  typedef VoidPointer                                                   void_pointer;           // Pointer type to be used with the rest of the Interprocess framework. 
  typedef unspecified                                                   multiallocation_chain;
  typedef boost::intrusive::pointer_traits< char_ptr >::difference_type difference_type;      
  typedef boost::container::dtl::make_unsigned< difference_type >::type size_type;            

  // construct/copy/destruct
  rbtree_best_fit(size_type, size_type);

  // public member functions
  void * allocate(size_type);
  void deallocate(void *);
  size_type get_size() const;
  size_type get_free_memory() const;
  void zero_free_memory();
  void grow(size_type);
  void shrink_to_fit();
  bool all_memory_deallocated();
  bool check_sanity();
  template<typename T> 
    T * allocation_command(boost::interprocess::allocation_type, size_type, 
                           size_type &, T *&);
  void * raw_allocation_command(boost::interprocess::allocation_type, 
                                size_type, size_type &, void *&, 
                                size_type = 1);
  size_type size(const void *) const;
  void * allocate_aligned(size_type, size_type);

  // public static functions
  static size_type get_min_size(size_type);

  // public data members
  static const size_type PayloadPerAllocation;


This class implements an algorithm that stores the free nodes in a red-black tree to have logarithmic search/insert times.

rbtree_best_fit public construct/copy/destruct

  1. rbtree_best_fit(size_type size, size_type extra_hdr_bytes);

    Constructor. "size" is the total size of the managed memory segment, "extra_hdr_bytes" indicates the extra bytes beginning in the sizeof(rbtree_best_fit) offset that the allocator should not use at all.

  2. ~rbtree_best_fit();

rbtree_best_fit public member functions

  1. void * allocate(size_type nbytes);
    Allocates bytes, returns 0 if there is not more memory.
  2. void deallocate(void * addr);
    Deallocates previously allocated bytes.
  3. size_type get_size() const;
    Returns the size of the memory segment.
  4. size_type get_free_memory() const;
    Returns the number of free bytes of the segment.
  5. void zero_free_memory();

    Initializes to zero all the memory that's not in use. This function is normally used for security reasons.

  6. void grow(size_type extra_size);

    Increases managed memory in extra_size bytes more

  7. void shrink_to_fit();
    Decreases managed memory as much as possible.
  8. bool all_memory_deallocated();
    Returns true if all allocated memory has been deallocated.
  9. bool check_sanity();

    Makes an internal sanity check and returns true if success

  10. template<typename T> 
      T * allocation_command(boost::interprocess::allocation_type command, 
                             size_type limit_size, 
                             size_type & prefer_in_recvd_out_size, T *& reuse);
  11. void * raw_allocation_command(boost::interprocess::allocation_type command, 
                                  size_type limit_object, 
                                  size_type & prefer_in_recvd_out_size, 
                                  void *& reuse_ptr, size_type sizeof_object = 1);
  12. size_type size(const void * ptr) const;
    Returns the size of the buffer previously allocated pointed by ptr.
  13. void * allocate_aligned(size_type nbytes, size_type alignment);

    Allocates aligned bytes, returns 0 if there is not more memory. Alignment must be power of 2

rbtree_best_fit public static functions

  1. static size_type get_min_size(size_type extra_hdr_bytes);
    Obtains the minimum size needed by the algorithm.