C++Cartographer加载配置文件过程介绍

  std::tie(node_options, trajectory_options) =
      LoadOptions(FLAGS_configuration_directory, FLAGS_configuration_basename);

std::tuple<NodeOptions, TrajectoryOptions> LoadOptions(
    const std::string& configuration_directory,
    const std::string& configuration_basename) {
  // 获取配置文件所在的目录
  auto file_resolver =
      absl::make_unique<cartographer::common::ConfigurationFileResolver>(std::vector<std::string>{configuration_directory});
  // 读取配置文件内容到code中
  const std::string code =
      file_resolver->GetFileContentOrDie(configuration_basename);
  // 根据给定的字符串, 生成一个lua字典
  cartographer::common::LuaParameterDictionary lua_parameter_dictionary(
      code, std::move(file_resolver));
  // 创建元组tuple,元组定义了一个有固定数目元素的容器, 其中的每个元素类型都可以不相同
  // 将配置文件的内容填充进NodeOptions与TrajectoryOptions, 并返回
  return std::make_tuple(CreateNodeOptions(&lua_parameter_dictionary),
                         CreateTrajectoryOptions(&lua_parameter_dictionary));
}

void CheckTrajectoryOptions(const TrajectoryOptions& options) {
  CHECK_GE(options.num_subdivisions_per_laser_scan, 1);
  CHECK_GE(options.num_laser_scans + options.num_multi_echo_laser_scans +
               options.num_point_clouds,
           1)
      << "Configuration error: 'num_laser_scans', "
         "'num_multi_echo_laser_scans' and 'num_point_clouds' are "
         "all zero, but at least one is required.";
}

NodeOptions CreateNodeOptions(
    ::cartographer::common::LuaParameterDictionary* const
        lua_parameter_dictionary) {
  NodeOptions options;
  options.map_builder_options =
      ::cartographer::mapping::CreateMapBuilderOptions(
          lua_parameter_dictionary->GetDictionary("map_builder").get());
  options.map_frame = lua_parameter_dictionary->GetString("map_frame");
  options.lookup_transform_timeout_sec =
      lua_parameter_dictionary->GetDouble("lookup_transform_timeout_sec");
  options.submap_publish_period_sec =
      lua_parameter_dictionary->GetDouble("submap_publish_period_sec");
  options.pose_publish_period_sec =
      lua_parameter_dictionary->GetDouble("pose_publish_period_sec");
  options.trajectory_publish_period_sec =
      lua_parameter_dictionary->GetDouble("trajectory_publish_period_sec");
  if (lua_parameter_dictionary->HasKey("publish_to_tf")) {
    options.publish_to_tf =
        lua_parameter_dictionary->GetBool("publish_to_tf");
  }
  if (lua_parameter_dictionary->HasKey("publish_tracked_pose")) {
    options.publish_tracked_pose =
        lua_parameter_dictionary->GetBool("publish_tracked_pose");
  }
  if (lua_parameter_dictionary->HasKey("use_pose_extrapolator")) {
    options.use_pose_extrapolator =
        lua_parameter_dictionary->GetBool("use_pose_extrapolator");
  }
  return options;
}

class ConfigurationFileResolver : public FileResolver{
 public:
  // c++11: explicit关键字 的作用就是防止类构造函数的隐式自动转换
  explicit ConfigurationFileResolver(
      const std::vector<std::string>& configuration_files_directories);
  std::string GetFullPathOrDie(const std::string& basename) override;
  std::string GetFileContentOrDie(const std::string& basename) override;
 private:
  std::vector<std::string> configuration_files_directories_;
};

class FileResolver {
 public:
  virtual ~FileResolver() {}
  virtual std::string GetFullPathOrDie(const std::string& basename) = 0;
  virtual std::string GetFileContentOrDie(const std::string& basename) = 0;
};

ConfigurationFileResolver::ConfigurationFileResolver(
    const std::vector<std::string>& configuration_files_directories)
    : configuration_files_directories_(configuration_files_directories) {
  configuration_files_directories_.push_back(kConfigurationFilesDirectory);
}

namespace cartographer {
namespace common {
constexpr char kConfigurationFilesDirectory[] =
    "@CARTOGRAPHER_CONFIGURATION_FILES_DIRECTORY@";
constexpr char kSourceDirectory[] = "@PROJECT_SOURCE_DIR@";
}  // namespace common
}  // namespace cartographer

  if (lua_parameter_dictionary->HasKey("th")) {
    options.th =
        lua_parameter_dictionary->GetDouble("th");
  }