void start_io()

in include/unifex/linux/io_epoll_context.hpp [551:596]

• 40 lines of code
• 9 McCabe index (conditional complexity)

    void start_io() noexcept {
      UNIFEX_ASSERT(context_.is_running_on_io_thread());

      auto result = readv(fd_, buffer_, 1);

      if (result == -EAGAIN || result == -EWOULDBLOCK || result == -EPERM) {
        if constexpr (is_stop_ever_possible) {
          stopCallback_.construct(
              get_stop_token(receiver_), cancel_callback{*this});
        }
        UNIFEX_ASSERT(static_cast<completion_base*>(this)->enqueued_.load() == 0);
        static_cast<completion_base*>(this)->execute_ = &operation::on_read_complete;
        epoll_event event;
        event.data.ptr = static_cast<completion_base*>(this);
        event.events = EPOLLIN | EPOLLRDHUP | EPOLLHUP;
        (void)epoll_ctl(context_.epollFd_.get(), EPOLL_CTL_ADD, fd_, &event);
        return;
      }

      auto oldState = state_.fetch_add(
          io_epoll_context::read_sender::operation<Receiver>::io_flag,
          std::memory_order_acq_rel);
      if ((oldState & io_epoll_context::read_sender::operation<Receiver>::cancel_pending_mask) != 0) {
        // io has been cancelled by a remote thread.
        // The other thread is responsible for enqueueing the operation completion
        return;
      }

      if (result == -ECANCELED) {
        unifex::set_done(std::move(receiver_));
      } else if (result >= 0) {
        if constexpr (is_nothrow_receiver_of_v<Receiver, ssize_t>) {
          unifex::set_value(std::move(receiver_), ssize_t(result));
        } else {
          UNIFEX_TRY {
            unifex::set_value(std::move(receiver_), ssize_t(result));
          } UNIFEX_CATCH (...) {
            unifex::set_error(std::move(receiver_), std::current_exception());
          }
        }
      } else {
        unifex::set_error(
            std::move(receiver_),
            std::error_code{-int(result), std::system_category()});
      }
    }