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## Class template adaptive_pool

boost::interprocess::adaptive_pool

## Synopsis

    // In header: <boost/interprocess/allocators/adaptive_pool.hpp>

    template<typename T, typename SegmentManager, std::size_t NodesPerBlock,
             std::size_t MaxFreeBlocks, unsigned char OverheadPercent>
    class adaptive_pool {
    public:
      // types
      typedef implementation_defined::segment_manager segment_manager;
      typedef segment_manager::void_pointer           void_pointer;
      typedef implementation_defined::pointer         pointer;
      typedef implementation_defined::const_pointer   const_pointer;
      typedef T                                       value_type;
      typedef unspecified                             reference;
      typedef unspecified                             const_reference;
      typedef segment_manager::size_type              size_type;
      typedef segment_manager::difference_type        difference_type;

      // member classes/structs/unions
      template<typename T2>
      struct rebind {
        // types
        typedef adaptive_pool< T2, SegmentManager, NodesPerBlock, MaxFreeBlocks, OverheadPercent > other;
      };

      // private member functions
      template<typename T2, typename SegmentManager2, std::size_t N2,
               std::size_t F2, unsigned char OP2>
        adaptive_pool &
        operator=(const adaptive_pool< T2, SegmentManager2, N2, F2, OP2 > &);

      // public member functions
      adaptive_pool(segment_manager *);
      adaptive_pool(const adaptive_pool &);
      template<typename T2>
        adaptive_pool(const adaptive_pool< T2, SegmentManager, NodesPerBlock, MaxFreeBlocks, OverheadPercent > &);
      ~adaptive_pool();
      void * get_node_pool() const;
      segment_manager * get_segment_manager() const;
      size_type max_size() const;
      pointer allocate(size_type);
      void deallocate(const pointer &, size_type);
      void deallocate_free_blocks();
      pointer address(reference) const;
      const_pointer address(const_reference) const;
      template<typename U, class ... Args> void construct(U *, Args &&...);
      size_type size(const pointer &) const;
      void allocate_many(size_type, size_type, multiallocation_chain &);
      void allocate_many(const size_type *, size_type, multiallocation_chain &);
      void deallocate_many(multiallocation_chain &);
      pointer allocate_one();
      void allocate_individual(size_type, multiallocation_chain &);
      void deallocate_one(const pointer &);
      void deallocate_individual(multiallocation_chain &);

      // friend functions
      void swap(self_t &, self_t &);
    };

## Description

An STL node allocator that uses a segment manager as memory source. The internal pointer type will of the same type (raw, smart) as "typename SegmentManager::void_pointer" type. This allows placing the allocator in shared memory, memory mapped-files, etc...

This node allocator shares a segregated storage between all instances of adaptive_pool with equal sizeof(T) placed in the same segment group. NodesPerBlock is the number of nodes allocated at once when the allocator needs runs out of nodes. MaxFreeBlocks is the maximum number of totally free blocks that the adaptive node pool will hold. The rest of the totally free blocks will be deallocated with the segment manager.

OverheadPercent is the (approximated) maximum size overhead (1-20%) of the allocator: (memory usable for nodes / total memory allocated from the segment manager)

### `adaptive_pool` private member functions

1.     template<typename T2, typename SegmentManager2, std::size_t N2,
                std::size_t F2, unsigned char OP2>
         adaptive_pool &
         operator=(const adaptive_pool< T2, SegmentManager2, N2, F2, OP2 > &);

   Not assignable from related adaptive_pool

### `adaptive_pool` public member functions

1.     adaptive_pool(segment_manager * segment_mngr);

   Not assignable from other adaptive_pool

   Constructor from a segment manager. If not present, constructs a node pool. Increments the reference count of the associated node pool. Can throw boost::interprocess::bad_alloc

2.     adaptive_pool(const adaptive_pool & other);

   Copy constructor from other adaptive_pool. Increments the reference count of the associated node pool. Never throws

3.     template<typename T2>
         adaptive_pool(const adaptive_pool< T2, SegmentManager, NodesPerBlock, MaxFreeBlocks, OverheadPercent > & other);

   Copy constructor from related adaptive_pool. If not present, constructs a node pool. Increments the reference count of the associated node pool. Can throw boost::interprocess::bad_alloc

4.     ~adaptive_pool();

   Destructor, removes node_pool_t from memory if its reference count reaches to zero. Never throws

5.     void * get_node_pool() const;

   Returns a pointer to the node pool. Never throws

6.     segment_manager * get_segment_manager() const;

   Returns the segment manager. Never throws

7.     size_type max_size() const;

   Returns the number of elements that could be allocated. Never throws

8.     pointer allocate(size_type count);

   Allocate memory for an array of count elements. Throws boost::interprocess::bad_alloc if there is no enough memory

9.     void deallocate(const pointer & ptr, size_type count);

   Deallocate allocated memory. Never throws

10.     void deallocate_free_blocks();

    Deallocates all free blocks of the pool

11.     pointer address(reference value) const;

    Returns address of mutable object. Never throws This function is deprecated and will be removed in the future

12.     const_pointer address(const_reference value) const;

    Returns address of non mutable object. Never throws This function is deprecated and will be removed in the future

13.     template<typename U, class ... Args> void construct(U * p, Args &&... args);

    Requires: Uses-allocator construction of T with allocator argument `uses_segment_manager_t` and additional constructor arguments `std::forward<Args>(args)...` is well-formed. [Note: uses-allocator construction is always well formed for types that do not use allocators. - end note]

    Effects: Construct a T object at p by uses-allocator construction with allocator argument constructible from `segment_manager*` and constructor arguments `std::forward<Args>(args)...`.

    Throws: Nothing unless the constructor for T throws.

14.     size_type size(const pointer & p) const;

    Returns maximum the number of objects the previously allocated memory pointed by p can hold. This size only works for memory allocated with allocate, allocation_command and allocate_many. This function is deprecated and will be removed in the future

15.     void allocate_many(size_type elem_size, size_type num_elements,
                           multiallocation_chain & chain);

    Allocates many elements of size elem_size in a contiguous block of memory. The minimum number to be allocated is min_elements, the preferred and maximum number is preferred_elements. The number of actually allocated elements is will be assigned to received_size. The elements must be deallocated with deallocate(...). This function is deprecated and will be removed in the future

16.     void allocate_many(const size_type * elem_sizes, size_type n_elements,
                           multiallocation_chain & chain);

    Allocates n_elements elements, each one of size elem_sizes[i]in a contiguous block of memory. The elements must be deallocated This function is deprecated and will be removed in the future

17.     void deallocate_many(multiallocation_chain & chain);

    Allocates many elements of size elem_size in a contiguous block of memory. The minimum number to be allocated is min_elements, the preferred and maximum number is preferred_elements. The number of actually allocated elements is will be assigned to received_size. The elements must be deallocated with deallocate(...) This function is deprecated and will be removed in the future

18.     pointer allocate_one();

    Allocates just one object. Memory allocated with this function must be deallocated only with deallocate_one(). Throws boost::interprocess::bad_alloc if there is no enough memory

19.     void allocate_individual(size_type num_elements,
                                 multiallocation_chain & chain);

    Allocates many elements of size == 1 in a contiguous block of memory. The minimum number to be allocated is min_elements, the preferred and maximum number is preferred_elements. The number of actually allocated elements is will be assigned to received_size. Memory allocated with this function must be deallocated only with deallocate_one().

20.     void deallocate_one(const pointer & p);

    Deallocates memory previously allocated with allocate_one(). You should never use deallocate_one to deallocate memory allocated with other functions different from allocate_one(). Never throws

21.     void deallocate_individual(multiallocation_chain & chain);

    Allocates many elements of size == 1 in a contiguous block of memory. The minimum number to be allocated is min_elements, the preferred and maximum number is preferred_elements. The number of actually allocated elements is will be assigned to received_size. Memory allocated with this function must be deallocated only with deallocate_one().

### `adaptive_pool` friend functions

1.     void swap(self_t & alloc1, self_t & alloc2);

   Swaps allocators. Does not throw. If each allocator is placed in a different memory segment, the result is undefined.