circular_buffer(capacity_type buffer_capacity, size_type n, const_reference item, const allocator_type& alloc = allocator_type());

template<class T> class Custom
{
  public:

    Custom() :
      time(0.0)
    {}

    double time;
    T data_;
};

boost::circular_buffer<Custom<T>> buffer(10);

int num_elements = 10;
Custom<T> custom;
std::vector<Custom<T>> buffer(10, custom);