ros_param_data_source.hpp

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#ifndef __RTT_ROSPARAM__ROS_PARAM_DATA_SOURCE_HPP
#define __RTT_ROSPARAM__ROS_PARAM_DATA_SOURCE_HPP

#include "rtt/internal/DataSource.hpp"
#include "rtt/Logger.hpp"

#include "ros/param.h"

using namespace RTT;

namespace rtt_rosparam {

template<typename T>
class RosParamDataSource
    : public internal::AssignableDataSource<T>
{
  std::string mparam_name_;
  mutable typename internal::DataSource<T>::value_t mcached_data_;

public:

  typedef boost::intrusive_ptr< RosParamDataSource<T> > shared_ptr;

  ~RosParamDataSource()
  {
  }

  RosParamDataSource(std::string param_name_id)
      : mparam_name_(param_name_id),
        mcached_data_()
  {
  }

  typename internal::DataSource<T>::result_t get() const
  {
    (void) evaluate();
    return value();
  }

  bool evaluate() const
  {
    if (!ros::param::getCached(mparam_name_, mcached_data_)) {
      RTT::log(RTT::Error) << "The value of parameter " + mparam_name_ + " could not be fetched." << RTT::endlog();
      return false;
    }
    return true;
  }

  typename internal::DataSource<T>::result_t value() const
  {
    return mcached_data_;
  }

  // There is not referred element, no allocation exists for this data source and it is not an alias.
  // But it needs to return something, because otherwise the .write() calls that require a rvalue()
  // would fail. So we use an internal cache
  typename internal::DataSource<T>::const_reference_t rvalue() const
  {
    return mcached_data_;
  }

  void set( typename internal::AssignableDataSource<T>::param_t t )
  {
    set() = t;
    updated();
  }

  // The referenced element is a cache, since the source of the data is external.
  // After working with the reference, if something was assigned, the data
  // source may need a call to updated() after set()
  typename internal::AssignableDataSource<T>::reference_t set()
  {
    return mcached_data_;
  }

  void updated()
  {
    ros::param::set(mparam_name_, mcached_data_);
  }

  virtual RosParamDataSource<T>* clone() const
  {
    return new RosParamDataSource<T>(this->mparam_name_);
  }

  virtual RosParamDataSource<T>* copy( std::map<const base::DataSourceBase*, base::DataSourceBase*>& already_cloned ) const
  {
    // Just like in ValueDataSource
    if (already_cloned[this] != 0) {
      assert(dynamic_cast<RosParamDataSource<T>*>(already_cloned[this]) == static_cast<RosParamDataSource<T>*>(already_cloned[this]));
      return static_cast<RosParamDataSource<T>*>(already_cloned[this]);
    }
    already_cloned[this] = const_cast<RosParamDataSource<T>*>(this);
    return const_cast<RosParamDataSource<T>*>(this);
  }

}; // class RosParamDataSource

} // namespace rtt_rosparam

#endif // __RTT_ROSPARAM__ROS_PARAM_DATA_SOURCE_HPP