Class initiate_spawn

3rd/asio-1.24.0/include/asio/impl/spawn.hpp:1120–1207

template <typename Executor>
class initiate_spawn
{
public:
  typedef Executor executor_type;

  explicit initiate_spawn(const executor_type& ex)
    : executor_(ex)
  {
  }

  executor_type get_executor() const ASIO_NOEXCEPT
  {
    return executor_;
  }

  template <typename Handler, typename F>
  void operator()(ASIO_MOVE_ARG(Handler) handler,
      ASIO_MOVE_ARG(F) f) const
  {
    typedef typename decay<Handler>::type handler_type;
    typedef typename decay<F>::type function_type;
    typedef spawn_cancellation_handler<
      handler_type, Executor> cancel_handler_type;

    typename associated_cancellation_slot<handler_type>::type slot
      = asio::get_associated_cancellation_slot(handler);

    cancel_handler_type* cancel_handler = slot.is_connected()
      ? &slot.template emplace<cancel_handler_type>(handler, executor_)
      : 0;

    cancellation_slot proxy_slot(
        cancel_handler
          ? cancel_handler->slot()
          : cancellation_slot());

    cancellation_state cancel_state(proxy_slot);

    (dispatch)(executor_,
        spawned_thread_resumer(
          default_spawned_thread_type::spawn(
            spawn_entry_point<Executor, function_type, handler_type>(
              executor_, ASIO_MOVE_CAST(F)(f),
              ASIO_MOVE_CAST(Handler)(handler)),
            proxy_slot, cancel_state)));
  }

#if defined(ASIO_HAS_BOOST_CONTEXT_FIBER)

  template <typename Handler, typename StackAllocator, typename F>
  void operator()(ASIO_MOVE_ARG(Handler) handler, allocator_arg_t,
      ASIO_MOVE_ARG(StackAllocator) stack_allocator,
      ASIO_MOVE_ARG(F) f) const
  {
    typedef typename decay<Handler>::type handler_type;
    typedef typename decay<F>::type function_type;
    typedef spawn_cancellation_handler<
      handler_type, Executor> cancel_handler_type;