Function const_buffer

3rd/asio-1.24.0/include/asio/buffer.hpp:255–261

#if defined(ASIO_ENABLE_BUFFER_DEBUGGING)
  const_buffer(const void* data, std::size_t size,
      asio::detail::function<void()> debug_check)
    : data_(data),
      size_(size),
      debug_check_(debug_check)
  {
  }

  const asio::detail::function<void()>& get_debug_check() const
  {