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## Struct template allocator_traits

boost::container::allocator_traits

## Synopsis

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

    template<typename Allocator>
    struct allocator_traits {
      // types
      typedef Allocator                             allocator_type;
      typedef allocator_type::value_type            value_type;
      typedef unspecified                           pointer;
      typedef see_documentation                     const_pointer;
      typedef see_documentation                     reference;
      typedef see_documentation                     const_reference;
      typedef see_documentation                     void_pointer;
      typedef see_documentation                     const_void_pointer;
      typedef see_documentation                     difference_type;
      typedef see_documentation                     size_type;
      typedef see_documentation                     propagate_on_container_copy_assignment;
      typedef see_documentation                     propagate_on_container_move_assignment;
      typedef see_documentation                     propagate_on_container_swap;
      typedef see_documentation                     is_always_equal;
      typedef see_documentation                     is_partially_propagable;
      typedef see_documentation                     rebind_alloc;
      typedef allocator_traits< rebind_alloc< T > > rebind_traits;

      // member classes/structs/unions
      template<typename T>
      struct portable_rebind_alloc {
        // types
        typedef see_documentation type;
      };

      // public static functions
      static pointer allocate(Allocator &, size_type);
      static void deallocate(Allocator &, pointer, size_type);
      static pointer allocate(Allocator &, size_type, const_void_pointer);
      template<typename T> static void destroy(Allocator &, T *) noexcept;
      static size_type max_size(const Allocator &) noexcept;
      static Allocator select_on_container_copy_construction(const Allocator &);
      template<typename T, class... Args>
        static void construct(Allocator &, T *, Args &&...);
      static bool storage_is_unpropagable(const Allocator &, pointer) noexcept;
      static bool equal(const Allocator &, const Allocator &) noexcept;
    };

## Description

The class template allocator_traits supplies a uniform interface to all allocator types. This class is a C++03-compatible implementation of std::allocator_traits

### `allocator_traits` public types

1. typedef unspecified pointer;

   Allocator::pointer if such a type exists; otherwise, value_type*

2. typedef see_documentation const_pointer;

   Allocator::const_pointer if such a type exists ; otherwise, pointer_traits<pointer>::rebind<const

3. typedef see_documentation reference;

   Non-standard extension Allocator::reference if such a type exists; otherwise, value_type&

4. typedef see_documentation const_reference;

   Non-standard extension Allocator::const_reference if such a type exists ; otherwise, const value_type&

5. typedef see_documentation void_pointer;

   Allocator::void_pointer if such a type exists ; otherwise, pointer_traits<pointer>::rebind<void>.

6. typedef see_documentation const_void_pointer;

   Allocator::const_void_pointer if such a type exists ; otherwis e, pointer_traits<pointer>::rebind<const

7. typedef see_documentation difference_type;

   Allocator::difference_type if such a type exists ; otherwise, pointer_traits<pointer>::difference_type.

8. typedef see_documentation size_type;

   Allocator::size_type if such a type exists ; otherwise, make_unsigned<difference_type>::type

9. typedef see_documentation propagate_on_container_copy_assignment;

   Allocator::propagate_on_container_copy_assignment if such a type exists, otherwise a type with an internal constant static boolean member `value` == false.

10. typedef see_documentation propagate_on_container_move_assignment;

    Allocator::propagate_on_container_move_assignment if such a type exists, otherwise a type with an internal constant static boolean member `value` == false.

11. typedef see_documentation propagate_on_container_swap;

    Allocator::propagate_on_container_swap if such a type exists, otherwise a type with an internal constant static boolean member `value` == false.

12. typedef see_documentation is_always_equal;

    Allocator::is_always_equal if such a type exists, otherwise a type with an internal constant static boolean member `value` == is_empty<Allocator>::value

13. typedef see_documentation is_partially_propagable;

    Allocator::is_partially_propagable if such a type exists, otherwise a type with an internal constant static boolean member `value` == false Note: Non-standard extension used to implement `small_vector_allocator`.

14. typedef see_documentation rebind_alloc;

    Defines an allocator: Allocator::rebind<T>::other if such a type exists; otherwise, Allocator<T, Args> if Allocator is a class template instantiation of the form Allocator<U, Args>, where Args is zero or more type arguments ; otherwise, the instantiation of rebind_alloc is ill-formed.

    In C++03 compilers `rebind_alloc` is a struct derived from an allocator deduced by previously detailed rules.

15. typedef allocator_traits < rebind_alloc< T > > rebind_traits;

    In C++03 compilers `rebind_traits` is a struct derived from `allocator_traits<OtherAlloc>`, where `OtherAlloc` is the allocator deduced by rules explained in `rebind_alloc`.

### `allocator_traits` public static functions

1.     static pointer allocate(Allocator & a, size_type n);

   Returns: `a.allocate(n)`

2.     static void deallocate(Allocator & a, pointer p, size_type n);

   Returns: `a.deallocate(p, n)`

   Throws: Nothing

3.     static pointer allocate(Allocator & a, size_type n, const_void_pointer p);

   Effects: calls `a.allocate(n, p)` if that call is well-formed; otherwise, invokes `a.allocate(n)`

4.     template<typename T> static void destroy(Allocator & a, T * p) noexcept;

   Effects: calls `a.destroy(p)` if that call is well-formed; otherwise, invokes `p->~T()`.

5.     static size_type max_size(const Allocator & a) noexcept;

   Returns: `a.max_size()` if that expression is well-formed; otherwise, `numeric_limits<size_type>::max()`.

6.     static Allocator select_on_container_copy_construction(const Allocator & a);

   Returns: `a.select_on_container_copy_construction()` if that expression is well-formed; otherwise, a.

7.     template<typename T, class... Args>
         static void construct(Allocator & a, T * p, Args &&... args);

   Effects: calls `a.construct(p, std::forward<Args>(args)...)` if that call is well-formed; otherwise, invokes `::new (static_cast<void*>(p)) T(std::forward<Args>(args)...)`

8.     static bool storage_is_unpropagable(const Allocator & a, pointer p) noexcept;

   Returns: `a.storage_is_unpropagable(p)` if is_partially_propagable::value is true; otherwise, `false`.

9.     static bool equal(const Allocator & a, const Allocator & b) noexcept;

   Returns: `true` if `is_always_equal::value == true`, otherwise, `a == b`.