custom PSRAM STL allocator

spram_allocator.h

template <typename T>
class spram_allocator
{
public:
    typedef size_t size_type;
    typedef ptrdiff_t difference_type;
    typedef T* pointer;
    typedef const T* const_pointer;
    typedef T& reference;
    typedef const T& const_reference;
    typedef T value_type;

    spram_allocator(){}
    ~spram_allocator(){}

    template <class U> struct rebind { typedef spram_allocator<U> other; };
    template <class U> spram_allocator(const spram_allocator<U>&){}

    pointer address(reference x) const {return &x;}
    const_pointer address(const_reference x) const {return &x;}
    size_type max_size() const throw() {return size_t(-1) / sizeof(value_type);}

    pointer allocate(size_type n, const void * hint = 0)
    {
        return static_cast<pointer>(ps_malloc(n*sizeof(T)));
    }

    void deallocate(pointer p, size_type n)
    {
        free(p);
    }

    template< class U, class... Args >
    void construct( U* p, Args&&... args )
    {
        ::new((void *) p ) U(std::forward<Args>(args)...);
    }
    
    void destroy(pointer p)
    {
        p->~T();
    }
};

Thank you.

For others:
This works well for putting things like std::vector into PSRam. But, if you want to use it with std::string, you need to add the following to the bottom of the file:

template<class T, class U>
bool operator==(const spram_allocator&, const spram_allocator&) { return true; }

template<class T, class U>
bool operator!=(const spram_allocator&, const spram_allocator&) { return false; }