use rclcpp serialized messages to write data

rosbag2_cpp/CMakeLists.txt

@@ -36,6 +36,7 @@ endif()
 find_package(ament_cmake REQUIRED)
 find_package(ament_index_cpp REQUIRED)
 find_package(pluginlib REQUIRED)
+find_package(rclcpp REQUIRED)
 find_package(rcpputils REQUIRED)
 find_package(rcutils REQUIRED)
 find_package(rmw REQUIRED)
@@ -65,6 +66,7 @@ add_library(${PROJECT_NAME} SHARED
 ament_target_dependencies(${PROJECT_NAME}
   ament_index_cpp
   pluginlib
+  rclcpp
   rcpputils
   rcutils
   rmw
@@ -103,7 +105,9 @@ install(
 ament_export_include_directories(include)
 ament_export_libraries(${PROJECT_NAME})
 ament_export_targets(export_${PROJECT_NAME})
-ament_export_dependencies(pluginlib
+ament_export_dependencies(
+  pluginlib
+  rclcpp
   rmw
   rmw_implementation
   rosbag2_storage

rosbag2_cpp/include/rosbag2_cpp/reader.hpp

@@ -20,6 +20,9 @@
 #include <string>
 #include <vector>
 
+#include "rclcpp/serialization.hpp"
+#include "rclcpp/serialized_message.hpp"
+
 #include "rosbag2_cpp/converter_options.hpp"
 #include "rosbag2_cpp/readers/sequential_reader.hpp"
 #include "rosbag2_cpp/visibility_control.hpp"
@@ -110,6 +113,28 @@ class ROSBAG2_CPP_PUBLIC Reader final
    */
   std::shared_ptr<rosbag2_storage::SerializedBagMessage> read_next();
 
+  /**
+   * Read next message from storage. Will throw if no more messages are available.
+   * The message will be serialized in the format given to `open`.
+   *
+   * Expected usage:
+   * if (writer.has_next()) message = writer.read_next();
+   *
+   * \return next message in non-serialized form
+   * \throws runtime_error if the Reader is not open.
+   */
+  template<class MessageT>
+  MessageT read_next()
+  {
+    MessageT msg;
+    auto bag_message = read_next();
+    rclcpp::SerializedMessage extracted_serialized_msg(*bag_message->serialized_data);
+    rclcpp::Serialization<MessageT> serialization;
+    serialization.deserialize_message(&extracted_serialized_msg, &msg);
+
+    return msg;
+  }
+
   /**
     * Ask bagfile for its full metadata.
     *

rosbag2_cpp/include/rosbag2_cpp/writer.hpp

@@ -21,6 +21,10 @@
 #include <unordered_map>
 #include <vector>
 
+#include "rclcpp/serialization.hpp"
+#include "rclcpp/serialized_message.hpp"
+#include "rclcpp/time.hpp"
+
 #include "rosbag2_cpp/converter_options.hpp"
 #include "rosbag2_cpp/visibility_control.hpp"
 #include "rosbag2_cpp/writers/sequential_writer.hpp"
@@ -112,7 +116,7 @@ class ROSBAG2_CPP_PUBLIC Writer final
 
   /**
    * Write a message to a bagfile.
-   * Opposing a call to \sa write without topic metadata, the topic will be created.
+   * The topic will be created if it has not been created already.
    *
    * \param message to be written to the bagfile
    * \param topic_name the string of the topic this messages belongs to
@@ -126,6 +130,45 @@ class ROSBAG2_CPP_PUBLIC Writer final
     const std::string & type_name,
     const std::string & serialization_format = "cdr");
 
+  /**
+   * Write a serialized message to a bagfile.
+   * The topic will be created if it has not been created already.
+   *
+   * \param message rclcpp::SerializedMessage The serialized message to be written to the bagfile
+   * \param topic_name the string of the topic this messages belongs to
+   * \param type_name the string of the type associated with this message
+   * \param time The time stamp of the message
+   * \throws runtime_error if the Writer is not open.
+   */
+  void write(
+    const rclcpp::SerializedMessage & message,
+    const std::string & topic_name,
+    const std::string & type_name,
+    const rclcpp::Time & time);
+
+  /**
+   * Write a non-serialized message to a bagfile.
+   * The topic will be created if it has not been created already.
+   *
+   * \param message MessageT The serialized message to be written to the bagfile
+   * \param topic_name the string of the topic this messages belongs to
+   * \param type_name the string of the type associated with this message
+   * \param time The time stamp of the message
+   * \throws runtime_error if the Writer is not open.
+   */
+  template<class MessageT>
+  void write(
+    const MessageT & message,
+    const std::string & topic_name,
+    const rclcpp::Time & time)
+  {
+    rclcpp::SerializedMessage serialized_msg;
+
+    rclcpp::Serialization<MessageT> serialization;
+    serialization.serialize_message(&message, &serialized_msg);
+    return write(serialized_msg, topic_name, rosidl_generator_traits::name<MessageT>(), time);
+  }
+
   writer_interfaces::BaseWriterInterface & get_implementation_handle() const
   {
     return *writer_impl_;

rosbag2_cpp/package.xml

@@ -12,6 +12,7 @@
 
   <depend>ament_index_cpp</depend>
   <depend>pluginlib</depend>
+  <depend>rclcpp</depend>
   <depend>rcutils</depend>
   <depend>rcpputils</depend>
   <depend>rmw</depend>

rosbag2_cpp/src/rosbag2_cpp/writer.cpp

@@ -21,13 +21,18 @@
 #include <string>
 #include <utility>
 
+#include "rclcpp/serialized_message.hpp"
+#include "rclcpp/time.hpp"
+
 #include "rosbag2_cpp/info.hpp"
 #include "rosbag2_cpp/writer_interfaces/base_writer_interface.hpp"
 
 #include "rosbag2_storage/serialized_bag_message.hpp"
 #include "rosbag2_storage/storage_options.hpp"
 #include "rosbag2_storage/topic_metadata.hpp"
 
+#include "rmw/rmw.h"
+
 namespace rosbag2_cpp
 {
 
@@ -97,4 +102,24 @@ void Writer::write(
   write(message);
 }
 
+void Writer::write(
+  const rclcpp::SerializedMessage & message,
+  const std::string & topic_name,
+  const std::string & type_name,
+  const rclcpp::Time & time)
+{
+  auto serialized_bag_message = std::make_shared<rosbag2_storage::SerializedBagMessage>();
+  serialized_bag_message->topic_name = topic_name;
+  serialized_bag_message->time_stamp = time.nanoseconds();
+
+  // temporary store the payload in a shared_ptr.
+  // add custom no-op deleter to avoid deep copying data.
+  serialized_bag_message->serialized_data = std::shared_ptr<rcutils_uint8_array_t>(
+    const_cast<rcutils_uint8_array_t *>(&message.get_rcl_serialized_message()),
+    [](rcutils_uint8_array_t * /* data */) {});
+
+  return write(
+    serialized_bag_message, topic_name, type_name, rmw_get_serialization_format());
+}
+
 }  // namespace rosbag2_cpp

rosbag2_tests/test/rosbag2_tests/test_rosbag2_cpp_api.cpp

@@ -18,6 +18,7 @@
 #include <string>
 #include <vector>
 
+#include "rclcpp/clock.hpp"
 #include "rclcpp/serialization.hpp"
 #include "rclcpp/serialized_message.hpp"
 
@@ -74,6 +75,14 @@ TEST(TestRosbag2CPPAPI, minimal_writer_example)
     bag_message->topic_name = "/my/other/topic";
     writer.write(bag_message, "/my/other/topic", "test_msgs/msg/BasicTypes");
 
+    // yet another alternative, writing the rclcpp::SerializedMessage directly
+    writer.write(
+      serialized_msg, "/yet/another/topic", "test_msgs/msg/BasicTypes",
+      rclcpp::Clock().now());
+
+    // writing a non-serialized message
+    writer.write(test_msg, "/a/ros2/message", rclcpp::Clock().now());
+
     // close on scope exit
   }
 
@@ -92,9 +101,23 @@ TEST(TestRosbag2CPPAPI, minimal_writer_example)
 
       EXPECT_EQ(test_msg, extracted_test_msg);
     }
-    ASSERT_EQ(2u, topics.size());
+    ASSERT_EQ(4u, topics.size());
     EXPECT_EQ("/my/test/topic", topics[0]);
     EXPECT_EQ("/my/other/topic", topics[1]);
+    EXPECT_EQ("/yet/another/topic", topics[2]);
+    EXPECT_EQ("/a/ros2/message", topics[3]);
+
+    // close on scope exit
+  }
+
+  // alternative reader
+  {
+    rosbag2_cpp::Reader reader;
+    reader.open(rosbag_directory.string());
+    while (reader.has_next()) {
+      TestMsgT extracted_test_msg = reader.read_next<TestMsgT>();
+      EXPECT_EQ(test_msg, extracted_test_msg);
+    }
 
     // close on scope exit
   }