CircularArray - Wraps std::array and provides a circular iterator in C++

circular_array.h

#pragma once

#include <algorithm>
#include <array>

template <class T, size_t N>
class CircularArray {
public:
  CircularArray() {}
  CircularArray(const T initValue) { std::fill_n(data_.begin(), data_.size(), initValue); }

  T at(size_t n) { return data_.at(n); }
  std::array<T, N> &data() const { return data_; }
  size_t size() { return v.size(); }

  class iterator : public std::iterator<std::random_access_iterator_tag, T> {
    CircularArray *array;
    ssize_t index;

  public:
    iterator(CircularArray &d, ssize_t idx)
        : array(&d)
        , index(idx) {}
    iterator &operator++() {
      nextIndex();
      return *this;
    }
    iterator operator++(ssize_t) {
      iterator tmp(*array, index);
      nextIndex();
      return tmp;
    }
    iterator operator+(ssize_t off) { return iterator(*array, (index + off) % array->size()); }
    iterator operator-(ssize_t off) {
      return iterator(*array, (index - off + array->size()) % array->size());
    }
    T &operator*() { return (*array).data_[index]; }
    bool operator!=(iterator const &other) { return index != other.index; }

  private:
    void nextIndex() {
      ++index;
      if (index == array->size()) {
        index = 0;
      }
    }
  };

  iterator begin() { return iterator(*this, 0); }

private:
  std::array<T, N> data_;
};