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274 lines
8.6 KiB
Java
274 lines
8.6 KiB
Java
// MCASTRouterA.java
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package protocol; // protocol package
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import java.util.*; // import Java utility classes
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import support.*; // import Jasper support classes
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/**
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This is the class that supports a router for broad/uni/multicast.
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@author Kenneth J. Turner
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@version 1.0 (22nd July 2010, KJT): initial version
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*/
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public class MCASTRouter implements ProtocolEntity {
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/** Service send offer */
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private final static String SEND = "Forward message for router ";
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/** Current router letter */
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public char currentRouter;
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/** Service provider events */
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private Vector<ProtocolEvent> serviceEvents;
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/** Service data unit output */
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private Vector<MCASTSdu> sdus;
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/** Service entity name */
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private String serviceName;
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/**
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Constructor for sources/sinks.
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@param serviceName service name
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*/
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public MCASTRouter(String serviceName) {
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this.serviceName = serviceName; // set service name
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currentRouter = lastOf(serviceName); // set current router letter
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initialise(); // initialise service entity
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}
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/**
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Find the SDU with the given destinations.
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@param destinations destinations
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@return the corresponding SDU (or null if none)
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*/
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public MCASTSdu findSDU(String destinations) {
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MCASTSdu result = null; // initialise SDU result
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for (int i = 0; i < sdus.size(); i++) { // go through SDUs
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MCASTSdu sdu = sdus.get(i); // get SDU
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if (sdu.destinations.equals(destinations)) { // destinations found?
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result = sdu; // save result
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break; // exit loop
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}
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}
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return(result); // return SDU
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}
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/**
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Get first character of string.
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@param string string to extract from
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@return first character of string
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*/
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public char firstOf(String string) {
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char letter = '?'; // initialise letter
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if (string != null) { // non-null string?
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int length = string.length(); // get string length
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if (length > 0) // non-empty string?
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letter = string.charAt(0); // get first character
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}
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return(letter); // return first character
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}
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/**
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Return the service name.
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@return service name
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*/
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public String getName() {
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return(serviceName); // return service name
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}
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/**
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Return the service data units.
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@return service data units
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*/
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public Vector<MCASTSdu> getSDUs() {
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return(sdus); // return service data units
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}
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/**
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Return services currently offered.
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@return list of services
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*/
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public Vector<String> getServices() {
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Vector<String> list = new Vector<String>(); // initialise service list
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if (sdus != null && sdus.size() > 0) { // SDUs from service user?
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for (int i = 0; i < sdus.size(); i++) { // go through SDUs
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MCASTSdu sdu = sdus.get(i); // get SDU
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String destinations = sdu.destinations; // get SDU destinations
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String destination = ""; // initialise destination
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for (int j = 0; j < destinations.length(); j++) { // go through dests.
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if (j > 0) // not first destination?
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destination += ", "; // append comma
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destination += destinations.charAt(j);// append destination
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}
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char router = firstOf(destination); // get router letter
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if (router != currentRouter) // not current router?
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list.addElement(SEND + destination); // add send to list
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}
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}
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return(list); // return service list
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}
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/**
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Initialise the service entity.
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*/
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public void initialise() {
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serviceEvents = new Vector<ProtocolEvent>();// initialise service events
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sdus = new Vector<MCASTSdu>(); // initialise SDUs
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}
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/**
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Get last character of string.
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@param string string to extract from
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@return last character of string
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*/
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public char lastOf(String string) {
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char letter = '?'; // initialise letter
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if (string != null) { // non-null string?
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int length = string.length(); // get string length
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if (length > 0) // non-empty string?
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letter = string.charAt(length - 1); // get last character
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}
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return(letter); // return last character
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}
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/**
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Check if the destination router is more than one hop from the current router
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(i.e. is not the next router letter.
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@param destination entity destination
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@return true/false if destination is not/is adjacent
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*/
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public boolean laterRouter(ProtocolEntity destination) {
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int currentIndex = (int) currentRouter; // get current router index
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int destinationIndex = // get destination router index
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(int) ((MCASTRouter) destination).currentRouter;
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return(destinationIndex > currentIndex + 1);// return router letter check
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}
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/**
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Return the next router to reach the destination. This is a very restricted
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routing table for the purposes of this example.
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@param destination entity destination
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@return next entity destination
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*/
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public ProtocolEntity nextRouter(ProtocolEntity destination) {
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char destinationLetter = // get destination router letter
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((MCASTRouter) destination).currentRouter;
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char nextLetter = destinationLetter; // assume destination by default
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switch (currentRouter) { // route based on current router
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case 'A': // at router A?
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switch (destinationLetter) { // check destination index
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case 'D': // to router D?
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nextLetter = 'C'; // via C
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break;
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case 'E': // to router E?
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nextLetter = 'C'; // via C
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break;
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}
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break;
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}
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return(MCAST.getEntity(nextLetter)); // return next router entity
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}
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/**
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Perform service. Note that the current implementation works for a particular
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topology but is not general. When there are multiple destinations, the
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router forward to the first two of these. A more general implementation
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would embody particular knowledge about routing.
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@param service service request
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@return resulting service events
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*/
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public Vector<ProtocolEvent> performService(String service) {
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serviceEvents = new Vector<ProtocolEvent>();// initialise service events
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if (service.startsWith(SEND)) { // send request?
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String destinations = // get destinations
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service.substring(SEND.length());
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String destination = // remove destination commas
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destinations.replaceAll(", ", ""); // get destination(s)
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MCASTSdu sdu = findSDU(destination); // find corresponding SDU
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char router = firstOf(destination); // get destination router letter
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serviceEvents.addElement( // add forward comment
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MCAST.comment(this, "forward"));
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transmitPDU(sdu, router); // transmit SDU
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sdus.remove(sdu); // remove SDU from SDUs
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}
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return(serviceEvents); // return service events
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}
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/**
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Receive an SDU.
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@param sdu SDU
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@return resulting service events
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*/
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public Vector<ProtocolEvent> receivePDU(PDU sdu) {
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serviceEvents = new Vector<ProtocolEvent>();// initialise service events
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if (sdu != null) { // non-empty SDU?
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String destinations = // get SDU destination(s)
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((MCASTSdu) sdu).destinations;
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if (destinations.length() > 1) { // more than one destination?
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String message = ((MCASTSdu) sdu).sdu; // get SDU message
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sdu = // get SDU for first destination
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new MCASTSdu(destinations.substring(0, 1), message);
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sdus.addElement((MCASTSdu) sdu); // store SDU
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sdu = // get SDU for later dests.
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new MCASTSdu(destinations.substring(1), message);
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sdus.addElement((MCASTSdu) sdu); // store SDU
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}
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else // one destination
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sdus.addElement((MCASTSdu) sdu); // store SDU
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}
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return(serviceEvents); // return service events
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}
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/**
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Send an SDU to the given destination letter.
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@param sdu SDU
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@param destination destination letter
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*/
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public void transmitPDU(PDU sdu, char destination) {
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ProtocolEntity entityDestination = // get protocol entity dest.
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MCAST.getEntity(destination);
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transmitPDU(sdu, entityDestination); // transmit PDU
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}
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/**
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Send an SDU to the given destination entity.
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@param sdu SDU
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@param destination destination entity
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*/
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public void transmitPDU(PDU sdu, ProtocolEntity destination) {
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destination = nextRouter(destination); // set next router destination
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sdu.setSource(this); // set source as this entity
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sdu.setDestination(destination); // set destination
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serviceEvents.addElement( // add send event
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new ProtocolEvent(ProtocolEvent.SEND, sdu));
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Vector<ProtocolEvent> receiveEvents = // receive SDU at destination
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destination.receivePDU(sdu);
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if (laterRouter(destination)) { // later router?
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serviceEvents.addElement( // add send event
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new ProtocolEvent(ProtocolEvent.TRAVERSE, sdu));
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}
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for (int i = 0; i < receiveEvents.size(); i++) // go through receive events
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serviceEvents.addElement( // append receive event
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receiveEvents.get(i));
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}
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}
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