Boost C++ Libraries

The header <boost/core/pointer_traits.hpp> provides the class template boost::pointer_traits to facilitate use of pointer-like types. The C++11 standard library introduced std::pointer_traits along with an allocator model which supported pointer-like types in addition to plain raw pointers. This implementation also supports C++98.

It also provides the function template boost::to_address to obtain a raw pointer from an object of any pointer-like type.

The following example allocates storage and constructs an object in that storage using an allocator.

template<class Allocator>
void function(Allocator& a)
{
    auto p = a.allocate(1);
    std::allocator_traits<Allocator>::construct(a, boost::to_address(p));
}

namespace boost {

template<class T>
struct pointer_traits {
    typedef T pointer;
    typedef see below element_type;
    typedef see below difference_type;

    template<class U>
    struct rebind_to {
        typedef see below type;
    };

    template<class U>
    using rebind = typename rebind_to<U>::type;

    static pointer pointer_to(element_type& v);
};

template<class T>
struct pointer_traits<T*> {
    typedef T* pointer;
    typedef T element_type;
    typedef std::ptrdiff_t difference_type;

    template<class U>
    struct rebind_to {
        typedef U* type;
    };

    template<class U>
    using rebind = typename rebind_to<U>::type;

    static pointer pointer_to(see below v) noexcept;
};

template<class T>
constexpr T* to_address(T* v) noexcept;

template<class T>
auto to_address(const T& v) noexcept;

} // boost

Member types

typedef see below element_type;

T::element_type if such a type exists; otherwise U if T is a class template instantiation of the form Pointer<U, Args>, where Args is zero or more type arguments; otherwise the member is not defined.

typedef see below difference_type;

T::difference_type if such a type exists; otherwise std::ptrdiff_t.

template<class U> struct rebind_to { typedef see below type; };

type is T::rebind<U> if such a type exists; otherwise, Pointer<V, Args> if T is a class template instantiation of the form Pointer<T, Args>, where Args is zero or more type arguments; otherwise, the member is not defined.

	Note
	When C++11 template aliases are not supported, the type for rebind is T::rebind<U>::other if such a type exists.

Glen Fernandes implemented pointer_traits and to_address with reviews and guidance from Peter Dimov.