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76 lines
2.7 KiB
Java
76 lines
2.7 KiB
Java
// BOOTPMedium.java (C) K. J. Turner 08/03/06
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// Boot Protocol medium
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package protocol; // protocol package
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import java.util.*; // utility support
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import support.*; // protocol entity support
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/**
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This is the class for an IP medium.
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@author Iain A. Robin, Kenneth J. Turner
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@version 1.0 (1st September 1999, IAR): initial version <br/>
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<br/> 1.4 (9th March 2006, KJT): updated for JDK 1.5
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<br/> 1.5 (24th July 2010, KJT): minor tidying
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*/
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public class BOOTPMedium extends Medium { // protocol medium
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// protocol variables
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private static Vector<Float> randoms; // random number list
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private static int randomIndex; // random number index
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public BOOTPMedium() { // construct medium instance
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super(); // construct as generic medium
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randoms = new Vector<Float>(); // initialise list of randoms
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}
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protected PDU getMatchingPDU(String s) { // get matching PDU on channel
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PDU pdu; // PDU
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String sdu; // PDU contents
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int sourceStart = s.indexOf ('[') + 1; // get start of entity name
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int sourceEnd = s.indexOf (']'); // get end of entity name
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String sourceName = // get PDU source
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s.substring(sourceStart, sourceEnd);
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int typeStart = s.indexOf (' ') + 1; // get start of PDU type
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int typeEnd = s.indexOf ('('); // get end of PDU type
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String type = // get PDU type
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s.substring(typeStart, typeEnd);
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int parEnd = s.indexOf (')'); // get end of PDU parameters
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sdu = s.substring(typeEnd + 1, parEnd); // get PDU parameters
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for (Enumeration e = pdus.elements(); // go through PDUs on channel
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e.hasMoreElements(); ) {
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pdu = (PDU) e.nextElement(); // get next PDU on channel
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if (pdu != null && // valid PDU and ...
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pdu.type.equals(type) && // type matches and ...
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pdu.getSource().getName(). // source matches and ...
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equals(sourceName) &&
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sdu.equals(pdu.sdu)) // SDU matches
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return((pdu)); // return with this PDU
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}
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return((null)); // return no PDU as no match
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}
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public void initialise() { // initialise medium
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super.initialise(); // initialise generic medium
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randomIndex = 0; // initialise randoms index
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}
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protected static float random() { // random number (from list)
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Float rand; // random number
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if (randomIndex < randoms.size()) // get number from list?
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rand = (Float) randoms.elementAt(randomIndex++); // get number from list
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else { // make new random number
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rand = new Float(Math.random()); // get random number
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randoms.addElement(rand); // add to list
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randomIndex++; // increment list index
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}
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return((rand.floatValue())); // return random number
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}
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}
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