node_output.h

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#ifndef ROS_NODEOUTPUT_H_
#define ROS_NODEOUTPUT_H_

#include "msg.h"

namespace ros {

  /*
   * This class is responsible for controlling the node ouput.
   * It it is the object that is passed to Publishers and services
   */
  class NodeOutput_{
    public:
      virtual int publish(int id, Msg* msg)=0;
  };

  template<class Hardware, int OUTSIZE =512>
  class NodeOutput : public NodeOutput_{

    private:
      Hardware* hardware_;
      bool configured_;
      unsigned char message_out[OUTSIZE];

    public:
      NodeOutput(Hardware* h){
        hardware_ = h;
        configured_ = false;
      }

      NodeOutput(){};

      void setHardware(Hardware* h){
        hardware_  = h;
        configured_=false;
      }
       
      void setConfigured(bool b){
        configured_ =b;
      }
      bool configured(){return configured_;};

      virtual int publish(int id, Msg * msg){
        if(!configured_) return 0;

        /* serialize message */
        int l = msg->serialize(message_out+6);

        /* setup the header */
        message_out[0] = 0xff;
        message_out[1] = 0xff;
        message_out[2] = (unsigned char) id&255;
        message_out[3] = (unsigned char) id>>8;
        message_out[4] = (unsigned char) l&255;
        message_out[5] = ((unsigned char) l>>8);

        /* calculate checksum */
        int chk = 0;
        for(int i =2; i<l+6; i++)
          chk += message_out[i];
        l += 6;
        message_out[l++] = 255 - (chk%256);

        hardware_->write(message_out, l);
        return l;
      }
  };

}

#endif