org.orekit.gnss.metric.ntrip

Interface MessageObserver

public interface MessageObserver

Interface for objects that needs to be notified when new encoded messages are available.

Since:

11.0

Author:

Luc Maisonobe

Method Summary

Modifier and Type	Method and Description
void	messageAvailable(String mountPoint, ParsedMessage message) Notify that an encoded message is available.

Method Detail

messageAvailable

void messageAvailable(String mountPoint,
                      ParsedMessage message)

Notify that an encoded message is available.

Beware that this method will be called from an internal dedicated stream-reading thread. Implementations must take to:

• not perform long processing there to avoid blocking the stream-reading thread
• take care of thread-safety when extracting data from the message

The only filtering that can be specified when adding an observer to a NtripClient is based on message type and mount point. If additional filtering is needed (for example on message content like satellites ids, it must be performed by the observer itself when notified (see example below).

The recommended way to implement this method is to simply build a domain object from the message fields (for example a gnss propagator) and to store it in the observer class as an instance field using a AtomicReference as follows:

 public class GPSProvider implements PVCoordinatesProvider, RTCMMessageObserver {

     private final int                                filteringId;
     private final AtomicReference<GPSPropagator> propagator;

     public void messageAvailable(String mountPoint, ParsedMessage message) {
         MessageXXX msg = (MessageXXX) message;
         GPSPropagator oldPropagator = propagator.get();
         if (msg.getSatId() == filteringId) {
             GPSPropagator newPropagator = new GPSPropagator(msg.get...(),
                                                             msg.get...(),
                                                             msg.get...());
             // only set propagator if no other observer was notified
             // while we were asleep
             propagator.compareAndSet(oldPropagator, newPropagator);
         }
     }

     public TimeStampedPVCoordinates getPVCoordinates(AbsoluteDate date, Frame frame) {
         GPSPropagator lastAvailablePropagator = propagator.get();
         // use the retrieved propagator to compute position-velocity
     }

 }
 

Parameters:

mountPoint - mount point from which the message comes

message - last available message