Class template adaptive_pool

boost::container::adaptive_pool

Synopsis

// In header: <boost/container/adaptive_pool.hpp>

template<typename T, std::size_t NodesPerBlock = ADP_nodes_per_block, 
         std::size_t MaxFreeBlocks = ADP_max_free_blocks, 
         std::size_t OverheadPercent = ADP_overhead_percent> 
class adaptive_pool {
public:
  // types
  typedef unsigned int                                                      allocation_type;
  typedef adaptive_pool< T, NodesPerBlock, MaxFreeBlocks, OverheadPercent > self_t;         
  typedef T                                                                 value_type;     
  typedef T *                                                               pointer;        
  typedef const T *                                                         const_pointer;  
  typedef ::boost::container::dtl::unvoid_ref< T >::type                    reference;      
  typedef ::boost::container::dtl::unvoid_ref< const T >::type              const_reference;
  typedef std::size_t                                                       size_type;      
  typedef std::ptrdiff_t                                                    difference_type;
  typedef boost::container::dtl::version_type< self_t, Version >            version;        

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

  // construct/copy/destruct
  adaptive_pool() noexcept;
  adaptive_pool(const adaptive_pool &) noexcept;
  template<typename T2> 
    adaptive_pool(const adaptive_pool< T2, NodesPerBlock, MaxFreeBlocks, OverheadPercent BOOST_CONTAINER_DOCIGN(BOOST_MOVE_I Version)> &) noexcept;
  adaptive_pool & operator=(const adaptive_pool &) noexcept;
  ~adaptive_pool();

  // public member functions
   BOOST_CONTAINER_DOCIGN(BOOST_STATIC_ASSERT((Version<=2)));
  size_type max_size() const noexcept;
  pointer allocate(size_type, const void * = 0);
  void deallocate(const pointer &, size_type) noexcept;
  pointer allocation_command(allocation_type, size_type, size_type &, 
                             pointer &);
  size_type size(pointer) const noexcept;
  pointer allocate_one();
  void allocate_individual(std::size_t, multiallocation_chain &);
  void deallocate_one(pointer) noexcept;
  void deallocate_individual(multiallocation_chain &) noexcept;
  void allocate_many(size_type, std::size_t, multiallocation_chain &);
  void allocate_many(const size_type *, size_type, multiallocation_chain &);
  void deallocate_many(multiallocation_chain &) noexcept;

  // public static functions
  static void deallocate_free_blocks() noexcept;

  // friend functions
  friend void swap(adaptive_pool &, adaptive_pool &) noexcept;
  friend bool operator==(const adaptive_pool &, const adaptive_pool &) noexcept;
  friend bool operator!=(const adaptive_pool &, const adaptive_pool &) noexcept;

  // private member functions
  pointer priv_allocation_command(allocation_type, std::size_t, size_type &, 
                                  pointer &);

  // public data members
  static const std::size_t nodes_per_block;
  static const std::size_t max_free_blocks;
  static const std::size_t overhead_percent;
  static const std::size_t real_nodes_per_block;
};

Description

An STL node allocator that uses a modified DLMalloc as memory source.

This node allocator shares a segregated storage between all instances of adaptive_pool with equal sizeof(T).

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 to the memory manager.

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

`adaptive_pool` public types

typedef unsigned int allocation_type;

If Version is 1, the allocator is a STL conforming allocator. If Version is 2, the allocator offers advanced expand in place and burst allocation capabilities.

`adaptive_pool` public construct/copy/destruct

```
adaptive_pool() noexcept;
```
Default constructor.

adaptive_pool(const adaptive_pool &) noexcept;

Copy constructor from other adaptive_pool.

template<typename T2> 
  adaptive_pool(const adaptive_pool< T2, NodesPerBlock, MaxFreeBlocks, OverheadPercent BOOST_CONTAINER_DOCIGN(BOOST_MOVE_I Version)> &) noexcept;

Copy constructor from related adaptive_pool.

adaptive_pool & operator=(const adaptive_pool &) noexcept;

Copy assignment from other adaptive_pool.

```
~adaptive_pool();
```
Destructor.

`adaptive_pool` public member functions

 BOOST_CONTAINER_DOCIGN(BOOST_STATIC_ASSERT((Version<=2)));

```
size_type max_size() const noexcept;
```
Returns the number of elements that could be allocated. Never throws
```
pointer allocate(size_type count, const void * = 0);
```
Allocate memory for an array of count elements. Throws bad_alloc if there is no enough memory

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

Deallocate allocated memory. Never throws

pointer allocation_command(allocation_type command, size_type limit_size, 
                           size_type & prefer_in_recvd_out_size, 
                           pointer & reuse);

```
size_type size(pointer p) const noexcept;
```
Returns maximum the number of objects the previously allocated memory pointed by p can hold.
```
pointer allocate_one();
```
Allocates just one object. Memory allocated with this function must be deallocated only with deallocate_one(). Throws bad_alloc if there is no enough memory

void allocate_individual(std::size_t num_elements, 
                         multiallocation_chain & chain);

Allocates many elements of size == 1. Elements must be individually deallocated with deallocate_one()

```
void deallocate_one(pointer p) noexcept;
```
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

void deallocate_individual(multiallocation_chain & chain) noexcept;

void allocate_many(size_type elem_size, std::size_t n_elements, 
                   multiallocation_chain & chain);

Allocates many elements of size elem_size. Elements must be individually deallocated with deallocate()

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] Elements must be individually deallocated with deallocate()

void deallocate_many(multiallocation_chain & chain) noexcept;

`adaptive_pool` public static functions

static void deallocate_free_blocks() noexcept;

Deallocates all free blocks of the pool.

`adaptive_pool` friend functions

```
friend void swap(adaptive_pool &, adaptive_pool &) noexcept;
```
Swaps allocators. Does not throw. If each allocator is placed in a different memory segment, the result is undefined.
```
friend bool operator==(const adaptive_pool &, const adaptive_pool &) noexcept;
```
An allocator always compares to true, as memory allocated with one instance can be deallocated by another instance
```
friend bool operator!=(const adaptive_pool &, const adaptive_pool &) noexcept;
```
An allocator always compares to false, as memory allocated with one instance can be deallocated by another instance

`adaptive_pool` private member functions

pointer priv_allocation_command(allocation_type command, 
                                std::size_t limit_size, 
                                size_type & prefer_in_recvd_out_size, 
                                pointer & reuse_ptr);

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