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87 lines
2.4 KiB
Java
87 lines
2.4 KiB
Java
4 years ago
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// ABPReceiver.java (C) I. A. Robin, K. J. Turner 08/03/06
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package protocol;
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import java.util.Enumeration; // enumeration
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import java.util.Vector; // vector (list)
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import support.*; // protocol entity support
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public class ABPReceiver implements ProtocolEntity {
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private int seqExpected;
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private PDU pduReceived;
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private PDU ackPDU;
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private ProtocolEntity peer;
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private Medium medium;
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private String name;
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private Vector<ProtocolEvent> entityEvents; // events from entity
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public ABPReceiver(Medium m, String name) {
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this.name = name;
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medium = m;
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initialise();
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}
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public String getName() {
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return(name);
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}
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public Vector<String> getServices() {
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Vector<String> list = new Vector<String>();
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if (pduReceived != null && pduReceived.type.equals("DATA")) {
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if (pduReceived.seq == seqExpected) seqExpected = inc(seqExpected);
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list.addElement(
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"Send ACK(" + seqExpected +
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") - with sequence number of next message");
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}
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return(list);
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}
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/** Increment PDU sequence number (0 or 1 only in ABP protocol) */
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private int inc(int seq) {
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return(1 - seq);
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}
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public void initialise() {
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seqExpected = 0;
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pduReceived = null;
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entityEvents = new Vector<ProtocolEvent>(); // empty entity events
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}
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public Vector<ProtocolEvent> performService(String s) {
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Vector<ProtocolEvent> events = new Vector<ProtocolEvent>();
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if (s.startsWith("Send ACK")) {
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int startIndex = s.indexOf( '(' ) + 1;
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int endIndex = s.indexOf( ')' );
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int seq = Integer.parseInt(s.substring(startIndex, endIndex));
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transmitPDU(new PDU("ACK", seq), peer);
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events.addElement(
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new ProtocolEvent(ProtocolEvent.TRANSMIT, ackPDU));
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}
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for (Enumeration e = entityEvents.elements(); // get medium events
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e.hasMoreElements(); )
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events.addElement( // add medium event
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(ProtocolEvent) e.nextElement());
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return(events);
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}
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public Vector<ProtocolEvent> receivePDU(PDU pdu) {
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pduReceived = pdu;
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return(new Vector<ProtocolEvent>());
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}
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public void setPeer(ProtocolEntity peer) {
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this.peer = peer;
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}
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public void transmitPDU(PDU pdu, ProtocolEntity dest) {
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pdu.setSource(this);
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pdu.setDestination(dest);
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ackPDU = pdu;
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entityEvents = medium.receivePDU(pdu);
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pduReceived = null;
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}
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}
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