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106 lines
3.1 KiB
Java
106 lines
3.1 KiB
Java
4 years ago
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// CSMAMedium.java
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package protocol; // protocol package
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import java.util.Enumeration; // import Java enumerations
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import java.util.HashSet; // import Java hash sets
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import java.util.StringTokenizer; // import Java string tokenisers
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import java.util.Vector; // import Java vectors
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import support.*; // import Jasper support classes
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/**
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This is the class that defines a CSMA/CD medium.
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@author Kenneth J. Turner
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@version 1.0 (24th July 2010): initial version
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*/
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public class CSMAMedium extends Medium {
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/** Medium deliver offer */
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private final static String DELIVER = "Deliver ";
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/** Medium name */
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private String mediumName;
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/**
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Constructor for a CSMA/CD medium.
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@param mediumName medium name
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*/
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public CSMAMedium(String mediumName) {
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this.mediumName = mediumName; // set protocol name
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}
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/**
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Return the PDU currently with the same destination and SDU, in a format such
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as "START(D1) to MAC 1".
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@param description service description
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@return corresponding PDU (or null if not found)
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*/
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protected PDU getMatchingPDU(String description) {
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description = // remove "Deliver "
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description.substring(DELIVER.length());
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for (Enumeration enumeration = pdus.elements();
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enumeration.hasMoreElements(); ) { // go through PDUs
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CSMAPdu pdu = // get next PDU
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(CSMAPdu) enumeration.nextElement();
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if (pdu.getDescription().equals(description)) // matching PDU found?
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return(pdu); // return matched PDU
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}
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return(null); // return no PDU
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}
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/**
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Get the medium name.
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@return medium name
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*/
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public String getName() {
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return(mediumName); // return protocol name
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}
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/**
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Return a list of strings describing actions (services) that can be carried
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out in the current state.
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@return service descriptions
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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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for (Enumeration enumeration = pdus.elements();
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enumeration.hasMoreElements(); ) { // go through PDUs in medium
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PDU pdu = (PDU) enumeration.nextElement();// get PDU
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if (pdu != null) { // non-null PDU?
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String description = pdu.getID(); // get PDU id
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String destination = // get PDU destination name
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pdu.getDestination().getName();
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if (!contains(destination, list)) // nothing for this destination?
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list.addElement(DELIVER + description + " to " + destination);
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}
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}
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return(list);
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}
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/**
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Check if the given string in contained in the given list.
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@param string string to search for
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@param list list to search
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@return true/false if the medium has no/has PDUs
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*/
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public boolean contains(String string, Vector<String> list) {
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for (int i = 0; i < list.size(); i++) { // go through list
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String text = (String) list.get(i); // get list text
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if (text.indexOf(string) >= 0) // text contains string?
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return(true); // return true immediately
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}
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return(false); // return false as no match
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}
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}
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