C++基于现有随机访问迭代器的反向迭代器

我通过继承非常基本的 std：：itrator 模板类(见下文(，为我的自定义容器类实现了一个(非常量(随机访问迭代器。执行此操作所需的只是传入所需的类型。

我无法找到有关如何设置反向迭代器的太多信息，但是我很确定有一种方法可以将现有的迭代器与一些新的typedef一起使用并定义rbegin((和rend((。这就是我被困住的地方。有人可以帮忙吗？

template <class T, class A = std::allocator<T>>
class ring {
public:
    typedef ring<T, A> self_type;
    typedef T value_type;
    typedef A alloc_type;
    typedef ptrdiff_t size_type;
    typedef typename alloc_type::difference_type    difference_type;
    typedef typename alloc_type::pointer            pointer;
    typedef typename alloc_type::reference          reference;
    typedef typename alloc_type::const_pointer      const_pointer;
    typedef typename alloc_type::const_reference    const_reference;
    class iterator;  // we implement iterator as nested class, so no need to typedef it
    iterator begin() { return iterator(this, 0); }
    iterator end() { return iterator(this, size()); }  // the current size (which is one past the end of the array)
    class iterator : public std::iterator<std::random_access_iterator_tag, value_type, difference_type, pointer, reference> {
    private:
        self_type *ring_;  // typedefs defined in ring class apply here
        size_type offset_;
    public:
        iterator(self_type *r, size_type o) : ring_{r}, offset_{o} {}
        reference operator* () const { return (*ring_)[offset_]; }
        pointer operator-> () const { return &(operator*()); }
        iterator& operator++ () {
            ++offset_;
            return *this;
        }
        friend bool operator== (const iterator& it1, const iterator& it2) { return ((it1.ring_ == it2.ring_ && it1.offset_ == it2.offset_)); }
        friend bool operator!= (const iterator& it1, const iterator& it2) { return (!(it1 == it2)); }
        iterator& operator-- () {
            --offset_;
            return *this;
        }
        iterator operator++ (int) {
            iterator clone(*this);  // make a duplicate
            ++offset_;
            return clone;  // return the duplicate
        }
        iterator operator-- (int) {  // has to be return by value
            iterator clone(*this);
            --offset_;
            return clone;
        }
        iterator& operator+=(size_type n) {
            offset_ += n;
            return *this;
        }       
        iterator& operator-=(size_type n) {
            offset_ -= n;
            return *this;
        }
        ...
        reference operator[] (size_type n) const { return (*ring_)[n]; }
    };
};