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package org.reprap.comms;
import java.io.IOException;
import org.reprap.Device;
import org.reprap.ReprapException;
/**
*
*/
public abstract class IncomingMessage {
/**
* The actual content portion of a packet, not the frilly bits
*/
private byte [] payload;
/**
*
*/
IncomingContext incomingContext;
/**
*
*/
public class InvalidPayloadException extends ReprapException {
private static final long serialVersionUID = -5403970405132990115L;
public InvalidPayloadException() {
super();
}
public InvalidPayloadException(String arg) {
super(arg);
}
}
/**
* Receive a message matching context criteria
* @param incomingContext the context in which to receive messages
* @throws IOException
*/
public IncomingMessage(IncomingContext incomingContext) throws IOException {
this.incomingContext = incomingContext;
Communicator comm = incomingContext.getCommunicator();
comm.receiveMessage(this);
}
/**
* Send a given message and return the incoming response. Re-try
* if there is a comms problem.
* @param message
* @throws IOException
*/
public IncomingMessage(Device device, OutgoingMessage message, long timeout) throws IOException {
Communicator comm = device.getCommunicator();
for(int i=0;i<3;i++) { // Allow 3 retries.
//System.out.println("Retry: " + i);
incomingContext = comm.sendMessage(device, message);
try {
comm.receiveMessage(this, timeout);
} catch (IOException e) {
e.printStackTrace();
System.err.println("IO error/timeout, resending");
// Just to prevent any unexpected spinning
try {
Thread.sleep(1);
} catch (InterruptedException e1) {
e1.printStackTrace();
}
continue;
}
return;
}
// If it's not going to respond, try to continue regardless.
System.err.println("Resend limit exceeded. Failing without reported error.");
}
/**
* Implemented by subclasses to allow them to indicate if they
* understand or expect a given packetType. This is used to
* decide if a received packet should be accepted or possibly discarded.
* @param packetType the type of packet to receive
* @return true if the packetType matches what is expected
*/
protected abstract boolean isExpectedPacketType(byte packetType);
/**
* @return payload
*/
public byte[] getPayload() {
return payload;
}
/**
* Called by the framework to provide data to the IncomingMessage.
* This should not normally be called by a user.
* @param payload The completed message to insert into the IncomingMessage
* @return true is the data was accepted, otherwise false.
*/
public boolean receiveData(byte [] payload) {
// We assume the packet was for us, etc. But we need to
// know it contains the correct contents
if (payload == null || payload.length == 0)
return false;
if (isExpectedPacketType(payload[0])) {
this.payload = (byte[])payload.clone();
return true;
} else {
// That's not what we were after, so discard and wait for more
return false;
}
}
}
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