shape_shifter.h

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#ifndef TOPIC_TOOLS_SHAPE_SHIFTER_H
#define TOPIC_TOOLS_SHAPE_SHIFTER_H
 
#include "ros/ros.h"
#include "ros/console.h"
#include "ros/assert.h"
#include <vector>
#include <string>
#include <string.h>
 
#include <ros/message_traits.h>
#include "macros.h"
 
namespace topic_tools
{
 
class ShapeShifterException : public ros::Exception
{
public:
  ShapeShifterException(const std::string& msg)
    : ros::Exception(msg)  {}
};
 
 
class TOPIC_TOOLS_DECL ShapeShifter
{
public:
  typedef boost::shared_ptr<ShapeShifter> Ptr;
  typedef boost::shared_ptr<ShapeShifter const> ConstPtr;
 
  static bool uses_old_API_;
 
  // Constructor and destructor
  ShapeShifter();
  virtual ~ShapeShifter();
 
  // Helpers for inspecting shapeshifter
  std::string const& getDataType()          const;
  std::string const& getMD5Sum()            const;
  std::string const& getMessageDefinition() const;
 
  void morph(const std::string& md5sum, const std::string& datatype, const std::string& msg_def,
             const std::string& latching);
 
  // Helper for advertising
  ros::Publisher advertise(ros::NodeHandle& nh, const std::string& topic, uint32_t queue_size_, bool latch=false, 
                           const ros::SubscriberStatusCallback &connect_cb=ros::SubscriberStatusCallback()) const;
 
  template<class M> 
  boost::shared_ptr<M> instantiate() const;
 
  template<typename Stream>
  void write(Stream& stream) const;
 
  template<typename Stream>
  void read(Stream& stream);
 
  uint32_t size() const;
 
private:
 
  std::string md5, datatype, msg_def, latching;
  bool typed;
 
  std::vector<uint8_t> msgBuf;
};
  
}
 
 
// Message traits allow shape shifter to work with the new serialization API
namespace ros {
namespace message_traits {
 
template <> struct IsMessage<topic_tools::ShapeShifter> : TrueType { };
template <> struct IsMessage<const topic_tools::ShapeShifter> : TrueType { };
 
template<>
struct MD5Sum<topic_tools::ShapeShifter>
{
  static const char* value(const topic_tools::ShapeShifter& m) { return m.getMD5Sum().c_str(); }
 
  // Used statically, a shapeshifter appears to be of any type
  static const char* value() { return "*"; }
};
 
template<>
struct DataType<topic_tools::ShapeShifter>
{
  static const char* value(const topic_tools::ShapeShifter& m) { return m.getDataType().c_str(); }
 
  // Used statically, a shapeshifter appears to be of any type
  static const char* value() { return "*"; }
};
 
template<>
struct Definition<topic_tools::ShapeShifter>
{
  static const char* value(const topic_tools::ShapeShifter& m) { return m.getMessageDefinition().c_str(); }
};
 
} // namespace message_traits
 
 
namespace serialization
{
 
template<>
struct Serializer<topic_tools::ShapeShifter>
{
  template<typename Stream>
  inline static void write(Stream& stream, const topic_tools::ShapeShifter& m) {
    m.write(stream);
  }
 
  template<typename Stream>
  inline static void read(Stream& stream, topic_tools::ShapeShifter& m)
  {
    m.read(stream);
  }
 
  inline static uint32_t serializedLength(const topic_tools::ShapeShifter& m) {
    return m.size();
  }
};
 
 
template<>
struct PreDeserialize<topic_tools::ShapeShifter>
{
  static void notify(const PreDeserializeParams<topic_tools::ShapeShifter>& params)
  {
    std::string md5      = (*params.connection_header)["md5sum"];
    std::string datatype = (*params.connection_header)["type"];
    std::string msg_def  = (*params.connection_header)["message_definition"];
    std::string latching  = (*params.connection_header)["latching"];
 
    params.message->morph(md5, datatype, msg_def, latching);
  }
};
 
} // namespace serialization
 
} //namespace ros
 
 
 
// Template implementations:
 
namespace topic_tools
{
 
  //
  //  only used in testing, seemingly
  //
template<class M> 
boost::shared_ptr<M> ShapeShifter::instantiate() const
{
  if (!typed)
    throw ShapeShifterException("Tried to instantiate message from an untyped shapeshifter.");
  
  if (ros::message_traits::datatype<M>() != getDataType())
    throw ShapeShifterException("Tried to instantiate message without matching datatype.");
  
  if (ros::message_traits::md5sum<M>() != getMD5Sum())
    throw ShapeShifterException("Tried to instantiate message without matching md5sum.");
  
  boost::shared_ptr<M> p(boost::make_shared<M>());
 
  // The IStream never modifies its data, and nothing else has access to this
  // object, so the const_cast here is ok
  ros::serialization::IStream s(const_cast<unsigned char*>(msgBuf.data()),
                                msgBuf.size());
  ros::serialization::deserialize(s, *p);
 
  return p;
}
 
template<typename Stream>
void ShapeShifter::write(Stream& stream) const {
  if (msgBuf.size() > 0)
    memcpy(stream.advance(msgBuf.size()), msgBuf.data(), msgBuf.size());
}
 
template<typename Stream>
void ShapeShifter::read(Stream& stream)
{
  stream.getLength();
  stream.getData();
 
  // stash this message in our buffer
  msgBuf.resize(stream.getLength());
  memcpy(msgBuf.data(), stream.getData(), stream.getLength());
}
 
} // namespace topic_tools
 
 
#endif