# std::experimental::pmr::resource_adaptor, std::pmr::experimental::resource_adaptor

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< cpp‎ | experimental

Defined in header `<experimental/memory_resource>` |  |
template< class Alloc > using resource_adaptor = /*resource-adaptor-imp*/< typename std::allocator_traits<Alloc>:: template rebind_alloc<char>>; |  | (library fundamentals TS)
template< class Alloc > class /*resource-adaptor-imp*/ : public memory_resource; // for exposition only |  | (library fundamentals TS)

The alias template `resource_adaptor` adapts the allocator type `Alloc` with a `memory_resource` interface. The allocator is rebound to a `char` value type before it is actually adapted (using the `resource-adaptor-imp` class template), so that adapting specializations of the same allocator template always yields the same type, regardless of the value type the allocator template is originally instantiated with.

`resource_adaptor` is defined in namespace `std::experimental::pmr`, and the base type `memory_resorce` in this page is std::experimental::pmr::memory_resource. | (library fundamentals TS) (until library fundamentals TS v3)
`resource_adaptor` is defined in namespace `std::pmr::experimental`, and the base type `memory_resorce` in this page is std::pmr::memory_resource. | (library fundamentals TS v3)

`resource-adaptor-imp` is a class template whose members are described below. The name `resource-adaptor-imp` is for exposition purposes only and not normative.

In addition to meeting the Allocator requirements, `Alloc` must additionally satisfy the following requirements:

- std::allocator_traits<Alloc>::pointer shall be identical to Alloc::value_type*.
- std::allocator_traits<Alloc>::const_pointer shall be identical to Alloc::value_type const*.
- std::allocator_traits<Alloc>::void_pointer shall be identical to void*.
- std::allocator_traits<Alloc>::const_const_pointer shall be identical to void const*.

### Member types of resource-adaptor-imp

Member type | Definition
`allocator_type` | `Alloc`

### Member functions of resource-adaptor-imp

## resource-adaptor-imp::resource-adaptor-imp

/*resource-adaptor-imp*/() = default; | (1) | (library fundamentals TS)
/*resource-adaptor-imp*/(const /*resource-adaptor-imp*/& other) = default; | (2) | (library fundamentals TS)
/*resource-adaptor-imp*/(/*resource-adaptor-imp*/&& other) = default; | (3) | (library fundamentals TS)
explicit /*resource-adaptor-imp*/(const Alloc& a2); | (4) | (library fundamentals TS)
explicit /*resource-adaptor-imp*/(Alloc&& a2); | (5) | (library fundamentals TS)

1) Default constructor. Default constructs the wrapped allocator.
2) Copy constructor. Copy constructs the wrapped allocator from the allocator wrapped by `other`.
3) Move constructor. Move constructs the wrapped allocator from the allocator wrapped by `other`.
4) Initializes the wrapped allocator with `a2`.
5) Initializes the wrapped allocator with std::move(a2).

#### Parameters

other | - | another `resource-adaptor-imp` object to copy or move from
a2 | - | another `Alloc` object to copy or move from

## resource-adaptor-imp::get_allocator

allocator_type get_allocator() const; |  | (library fundamentals TS)

Returns a copy of the wrapped allocator.

## resource-adaptor-imp::operator=

/*resource-adaptor-imp*/& operator=(const /*resource-adaptor-imp*/& other) = default; |  | (library fundamentals TS)

Defaulted copy assignment operator. Copy assigns the wrapped allocator from that of `other`.

## resource-adaptor-imp::do_allocate

protected: virtual void* do_allocate(std::size_t bytes, std::size_t alignment); |  | (library fundamentals TS)

Allocates memory using the `allocate` member function of the wrapped allocator.

## resource-adaptor-imp::do_deallocate

protected: virtual void do_deallocate(void *p, std::size_t bytes, std::size_t alignment); |  | (library fundamentals TS)

Deallocates the storage pointed to by `p` using the `deallocate` member function of the wrapped allocator.

`p` must have been allocated using the `allocate` member function of an allocator that compares equal to the wrapped allocator, and must not have been subsequently deallocated.

## resource-adaptor-imp::do_is_equal

protected: virtual bool do_is_equal(const memory_resource& other) const noexcept; |  | (library fundamentals TS)

Let `p` be dynamic_cast<const /*resource-adaptor-imp*/*>(&other). If `p` is a null pointer value, returns false. Otherwise, return the result of comparing the allocators wrapped by *p and *this using operator==.

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