| Home | Libraries | People | FAQ | More

## 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;
      typedef VoidPointer void_pointer;           // Pointer type to be used with the rest of the Interprocess framework.
      typedef unspecified multiallocation_chain;

      // construct/copy/destruct
      rbtree_best_fit(std::size_t, std::size_t);
      ~rbtree_best_fit();

      // public member functions
      void * allocate(std::size_t);
      void deallocate(void *);
      std::size_t get_size() const;
      std::size_t get_free_memory() const;
      void zero_free_memory();
      void grow(std::size_t);
      void shrink_to_fit();
      bool all_memory_deallocated();
      bool check_sanity();
      template<typename T>
        std::pair< T *, bool >
        allocation_command(boost::interprocess::allocation_type, std::size_t,
                           std::size_t, std::size_t &, T * = 0);
      std::pair< void *, bool >
      raw_allocation_command(boost::interprocess::allocation_type, std::size_t,
                             std::size_t, std::size_t &, void * = 0,
                             std::size_t = 1);
      std::size_t size(const void *) const;
      void * allocate_aligned(std::size_t, std::size_t);

      // public static functions
      static std::size_t get_min_size(std::size_t);
      static const std::size_t 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 types

1. typedef MutexFamily mutex_family;

   Shared interprocess_mutex family used for the rest of the Interprocess framework

### `rbtree_best_fit` public construct/copy/destruct

1.     rbtree_best_fit(std::size_t size, std::size_t 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(std::size_t nbytes);

   Allocates bytes, returns 0 if there is not more memory.

2.     void deallocate(void * addr);

   Deallocates previously allocated bytes

3.     std::size_t get_size() const;

   Returns the size of the memory segment.

4.     std::size_t 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(std::size_t 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,
                             std::size_t limit_size, std::size_t preferred_size,
                             std::size_t & received_size, T * reuse_ptr = 0);

11.     std::pair< void *, bool >
        raw_allocation_command(boost::interprocess::allocation_type command,
                               std::size_t limit_object,
                               std::size_t preferred_object,
                               std::size_t & received_object, void * reuse_ptr = 0,
                               std::size_t sizeof_object = 1);

12.     std::size_t size(const void * ptr) const;

    Returns the size of the buffer previously allocated pointed by ptr.

13.     void * allocate_aligned(std::size_t nbytes, std::size_t 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 std::size_t get_min_size(std::size_t extra_hdr_bytes);

   Obtains the minimum size needed by the algorithm.