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## Class template rbtree_best_fit

boost::interprocess::rbtree_best_fit

## Synopsis

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

    template<typename MutexFamily, typename VoidPointer, std::size_t MemAlignment>
    class rbtree_best_fit {
    public:
      // 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::make_unsigned< difference_type >::type                 size_type;

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

      // 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>
        std::pair< T *, bool >
        allocation_command(boost::interprocess::allocation_type, size_type,
                           size_type, size_type &, T * = 0);
      std::pair< void *, bool >
      raw_allocation_command(boost::interprocess::allocation_type, size_type,
                             size_type, size_type &, void * = 0, 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;
    };

## Description

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();

   Destructor.

### `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>
          std::pair< T *, bool >
          allocation_command(boost::interprocess::allocation_type command,
                             size_type limit_size, size_type preferred_size,
                             size_type & received_size, T * reuse_ptr = 0);

11.     std::pair< void *, bool >
        raw_allocation_command(boost::interprocess::allocation_type command,
                               size_type limit_object, size_type preferred_object,
                               size_type & received_object, void * reuse_ptr = 0,
                               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.