static_wait_set.cpp

// Copyright 2021 Open Source Robotics Foundation, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include <memory>
#include <vector>

#include "rclcpp/rclcpp.hpp"
#include "std_msgs/msg/string.hpp"

int main(int argc, char * argv[])
{
  rclcpp::init(argc, argv);

  auto node = std::make_shared<rclcpp::Node>("static_wait_set_example_node");

  auto do_nothing = [](std_msgs::msg::String::UniquePtr) {assert(false);};
  auto sub1 = node->create_subscription<std_msgs::msg::String>("~/chatter", 10, do_nothing);
  auto sub2 = node->create_subscription<std_msgs::msg::String>("~/chatter", 10, do_nothing);
  std::vector<decltype(sub1)> sub_vector = {sub1, sub2};
  auto guard_condition1 = std::make_shared<rclcpp::GuardCondition>();
  auto guard_condition2 = std::make_shared<rclcpp::GuardCondition>();

  rclcpp::StaticWaitSet<2, 2, 0, 0, 0, 0> static_wait_set(
    std::array<rclcpp::StaticWaitSet<2, 2, 0, 0, 0, 0>::SubscriptionEntry, 2>{{{sub1}, {sub2}}},
    std::array<rclcpp::GuardCondition::SharedPtr, 2>{{{guard_condition1}, {guard_condition2}}},
    std::array<rclcpp::TimerBase::SharedPtr, 0>{},
    std::array<rclcpp::ClientBase::SharedPtr, 0>{},
    std::array<rclcpp::ServiceBase::SharedPtr, 0>{},
    std::array<rclcpp::StaticWaitSet<2, 2, 0, 0, 0, 0>::WaitableEntry, 0>{});

  auto wait_and_print_results = [&]() {
      RCLCPP_INFO(node->get_logger(), "Waiting...");
      auto wait_result = static_wait_set.wait(std::chrono::seconds(1));
      if (wait_result.kind() == rclcpp::WaitResultKind::Ready) {
        size_t guard_conditions_num = static_wait_set.get_rcl_wait_set().size_of_guard_conditions;
        size_t subscriptions_num = static_wait_set.get_rcl_wait_set().size_of_subscriptions;

        for (size_t i = 0; i < guard_conditions_num; i++) {
          if (wait_result.get_wait_set().get_rcl_wait_set().guard_conditions[i]) {
            RCLCPP_INFO(node->get_logger(), "guard_condition %zu triggered", i + 1);
          }
        }
        for (size_t i = 0; i < subscriptions_num; i++) {
          if (wait_result.get_wait_set().get_rcl_wait_set().subscriptions[i]) {
            RCLCPP_INFO(node->get_logger(), "subscription %zu triggered", i + 1);
            std_msgs::msg::String msg;
            rclcpp::MessageInfo msg_info;
            if (sub_vector.at(i)->take(msg, msg_info)) {
              RCLCPP_INFO(
                node->get_logger(),
                "subscription %zu: I heard '%s'", i + 1, msg.data.c_str());
            } else {
              RCLCPP_INFO(node->get_logger(), "subscription %zu: No message", i + 1);
            }
          }
        }
      } else if (wait_result.kind() == rclcpp::WaitResultKind::Timeout) {
        RCLCPP_INFO(node->get_logger(), "wait-set waiting failed with timeout");
      } else if (wait_result.kind() == rclcpp::WaitResultKind::Empty) {
        RCLCPP_INFO(node->get_logger(), "wait-set waiting failed because wait-set is empty");
      }
    };

  RCLCPP_INFO(node->get_logger(), "Action: Nothing triggered");
  wait_and_print_results();

  RCLCPP_INFO(node->get_logger(), "Action: Trigger Guard condition 1");
  guard_condition1->trigger();
  wait_and_print_results();

  RCLCPP_INFO(node->get_logger(), "Action: Trigger Guard condition 2");
  guard_condition2->trigger();
  wait_and_print_results();

  RCLCPP_INFO(node->get_logger(), "Action: Message published");
  auto pub = node->create_publisher<std_msgs::msg::String>("~/chatter", 1);
  pub->publish(std_msgs::msg::String().set__data("test"));
  wait_and_print_results();

  // Note the static wait-set does not allow adding or removing entities dynamically.
  // It will result in a compilation error.

  return 0;
}