ROS2与C++入门教程-进程内(intra_process)话题发布和订阅演示2

ROS2与C++入门教程-进程内(intra_process)话题发布和订阅演示2

说明:

• 介绍ros2下实现进程内(intra_process)话题发布和订阅
• 在同一进程内的不同节点,可以通过共享指针方式实现内容读取,减少消息的拷贝开销
• 对于图像之类数据量比较大的节点间处理的效率和性能将大大提高
• 本演示实现两个话题循环处理

步骤:

• 新建一个包cpp_intra_process_topic2

cd ~/dev_ws/src
ros2 pkg create --build-type ament_cmake cpp_intra_process_topic2

• 进入src目录，新建文件cyclic_pipeline.cpp

cd ~/dev_ws/src/cpp_intra_process_topic2/src
touch cyclic_pipeline.cpp

• 内容如下:

#include <chrono>
#include <cinttypes>
#include <cstdio>
#include <memory>
#include <string>
#include <utility>

#include "rclcpp/rclcpp.hpp"
#include "std_msgs/msg/int32.hpp"

using namespace std::chrono_literals;

// This node receives an Int32, waits 1 second, then increments and sends it.
struct IncrementerPipe : public rclcpp::Node
{
  IncrementerPipe(const std::string & name, const std::string & in, const std::string & out)
  : Node(name, rclcpp::NodeOptions().use_intra_process_comms(true))
  {
    // Create a publisher on the output topic.
    pub = this->create_publisher<std_msgs::msg::Int32>(out, 10);
    std::weak_ptr<std::remove_pointer<decltype(pub.get())>::type> captured_pub = pub;
    // Create a subscription on the input topic.
    sub = this->create_subscription<std_msgs::msg::Int32>(
      in,
      10,
      [captured_pub](std_msgs::msg::Int32::UniquePtr msg) {
        auto pub_ptr = captured_pub.lock();
        if (!pub_ptr) {
          return;
        }
        printf(
          "Received message with value:         %d, and address: 0x%" PRIXPTR "\n", msg->data,
          reinterpret_cast<std::uintptr_t>(msg.get()));
        printf("  sleeping for 1 second...\n");
        if (!rclcpp::sleep_for(1s)) {
          return;    // Return if the sleep failed (e.g. on ctrl-c).
        }
        printf("  done.\n");
        msg->data++;    // Increment the message's data.
        printf(
          "Incrementing and sending with value: %d, and address: 0x%" PRIXPTR "\n", msg->data,
          reinterpret_cast<std::uintptr_t>(msg.get()));
        pub_ptr->publish(std::move(msg));    // Send the message along to the output topic.
      });
  }

  rclcpp::Publisher<std_msgs::msg::Int32>::SharedPtr pub;
  rclcpp::Subscription<std_msgs::msg::Int32>::SharedPtr sub;
};

int main(int argc, char * argv[])
{
  setvbuf(stdout, NULL, _IONBF, BUFSIZ);
  rclcpp::init(argc, argv);
  rclcpp::executors::SingleThreadedExecutor executor;

  // Create a simple loop by connecting the in and out topics of two IncrementerPipe's.
  // The expectation is that the address of the message being passed between them never changes.
  auto pipe1 = std::make_shared<IncrementerPipe>("pipe1", "topic1", "topic2");
  auto pipe2 = std::make_shared<IncrementerPipe>("pipe2", "topic2", "topic1");
  rclcpp::sleep_for(1s);  // Wait for subscriptions to be established to avoid race conditions.
  // Publish the first message (kicking off the cycle).
  std::unique_ptr<std_msgs::msg::Int32> msg(new std_msgs::msg::Int32());
  msg->data = 42;
  printf(
    "Published first message with value:  %d, and address: 0x%" PRIXPTR "\n", msg->data,
    reinterpret_cast<std::uintptr_t>(msg.get()));
  pipe1->pub->publish(std::move(msg));

  executor.add_node(pipe1);
  executor.add_node(pipe2);
  executor.spin();

  rclcpp::shutdown();

  return 0;
}

• 编译package.xml
• 在<buildtool_depend>ament_cmake</buildtool_depend>后增加

<build_depend>rclcpp</build_depend>
<build_depend>std_msgs</build_depend>

• 编译CMakelist.txt
• 在find_package(ament_cmake REQUIRED)后增加

find_package(rclcpp REQUIRED)
find_package(std_msgs REQUIRED)

• 生成执行文件

include_directories(include)

add_executable(cyclic_pipeline
  src/cyclic_pipeline.cpp)
target_link_libraries(cyclic_pipeline
  rclcpp::rclcpp
  ${std_msgs_TARGETS})

• 安装相关库文件和执行文件

install(TARGETS
  cyclic_pipeline
  DESTINATION lib/${PROJECT_NAME})

• 编译包

colcon build --symlink-install --packages-select cpp_intra_process_topic2

• 加载工作空间

. install/setup.bash

• 测试:　

ros2 run cpp_intra_process_topic2 cyclic_pipeline

• 效果如下：　

$ ros2 run cpp_intra_process_topic2 cyclic_pipeline
Published first message with value:  42, and address: 0x55DBCB77E6F0
Received message with value:         42, and address: 0x55DBCB77E6F0
  sleeping for 1 second...
  done.
Incrementing and sending with value: 43, and address: 0x55DBCB77E6F0
Received message with value:         43, and address: 0x55DBCB77E6F0
  sleeping for 1 second...
  done.
Incrementing and sending with value: 44, and address: 0x55DBCB77E6F0
Received message with value:         44, and address: 0x55DBCB77E6F0
  sleeping for 1 second...
  done.
Incrementing and sending with value: 45, and address: 0x55DBCB77E6F0
Received message with value:         45, and address: 0x55DBCB77E6F0
  sleeping for 1 second...
  done.

参考:

• 资料1
• 资料2