Router.java

/*
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 * and open the template in the editor.
 */
package itcs3166_project;

/**
 *
 * @author Kyle1
 */
public class Router {
    /*
     * STATIC VARIABLES
     */
    private static final int NUM_ROUTES = 4;
    
    private static final String INTERFACE_0 = "135.46.56.0/22";
    private static final String INTERFACE_1 = "135.46.60.0/22";
    private static final String ROUTER_1 = "192.53.40.0/23";
    private static final String ROUTER_2 = "0.0.0.0/0";
    
    private static final class Route {
    	private String strIP;
    	private long ip; // must be long due to 2's complement and
                       // lack of unsigned integers in java
    	private int mask;
    	private String name;
    	
    	public Route(String ip, int mask, String name) {
    		this.strIP = ip;
    		this.mask = mask;
    		this.name = name;
    		this.ip = ipStringToBinary(ip);
    	}
    	
    	public long getIP() {
    		return this.ip;
    	}
    	
    	public String getStrIP() {
    		return this.strIP;
    	}
    	
    	public int getMask() {
    		return this.mask;
    	}
    	
    	public String getName() {
    		return this.name;
    	}
    	
    }
    
    /*
     * STATIC METHODS
     */
	private static long ipStringToBinary(String ipString) {
		String[] octets = ipString.split("\\.");
		long ip = 0;
		
		for(int i = 0; i < 4; i++) {
			ip = (ip << 8) + Integer.parseInt(octets[i]);
		}
		
		return ip;
	}
	
	
	private static String to32BitBinaryString(long ip) {
		return Long.toBinaryString(1L << 32 | ip).substring(1);
	}
	
	private static long intMaskToLong(int mask) {
		return ((Integer.MAX_VALUE << 1) + 1) << (32 - mask);
	}
	
	/*
	 * INSTANCE VARIABLES AND METHODS
	 */
    private Route[] routerTable;
    private long binaryIP;
    private Route matchedRoute;
    private String ipAddress;
    private String subnetMask;
    private String networkAddress;
    
    public Router() {
    	routerTable = new Route[NUM_ROUTES];
    	addRouteToTable(INTERFACE_0, "Interface 0");
    	addRouteToTable(INTERFACE_1, "Interface 1");
    	addRouteToTable(ROUTER_1, "Router 1");
    	addRouteToTable(ROUTER_2, "Router 2");
    }
    
    private void addRouteToTable(String addrMask, String name) {
    	String strIP = addrMask.split("/")[0];
    	int mask = Integer.parseInt(addrMask.split("/")[1]);
    	Route route = new Route(strIP, mask, name);

    	/*
    	 * The following for loop inserts routes in order of their mask, where
    	 * the route with the highest mask at index 0. This is analogous to the
    	 * way the router functioned in Exercise 33 from Chapter 5.
    	 */
    	for(int i = 0; i < NUM_ROUTES; i++) {
    		if(routerTable[i] == null) {
    			routerTable[i] = route;
    			break;
    		} else {
    			if(route.getMask() > routerTable[i].getMask()) {
    				Route swap = routerTable[i];
    				routerTable[i] = route;
    				route = swap;
    			}
    		}
    		
    	}
    	
    }
    
    public String getIPAddress() {
        return ipAddress;
    }
    
    private void setIPAddress(String s) {
        ipAddress = s;
    }
    
    public String getSubnetMask() {
        return subnetMask;
    }
    
    private void setSubnetMask(String s) {
        subnetMask = s;
    }
    
    public String getBinaryIPAddress() {
        return to32BitBinaryString(this.getBinaryIP());
    }
    
    public String getNetworkAddress() {
        return networkAddress;
    }
    
    private void setNetworkAddress(String s) {
        networkAddress = s;
    }
    
    private void setBinaryIP(long binaryIP) {
    	this.binaryIP = binaryIP;
    }
    
    private long getBinaryIP() {
    	return this.binaryIP;
    }
    
    private void setMatchedRoute(Route r) {
    	this.matchedRoute = r;
    }
    
    private Route getMatchedRoute() {
    	return this.matchedRoute;
    }
    
    public void setFields(String ip){
    	this.setIPAddress(ip);
        this.setBinaryIP(ipStringToBinary(ip));
        
        this.setMatchedRoute(this.calculateRoute(this.getBinaryIP()));
        
        this.setSubnetMask(this.calculateSubnetMask(this.getMatchedRoute().getMask()));
        
        this.setNetworkAddress(this.calculateNetworkAddress(this.getBinaryIP(), this.getMatchedRoute().getMask()));
    }
    
    private Route calculateRoute(long ip) {
    	Route cur = null;
    	
    	// traverse the router table, beginning with the entry that has the
    	// highest mask, and check the bitwise AND of the masked IP with
    	// the current entry
    	// NOTE: the last entry has a mask of 0, so it will match any IP
    	for(int i = 0; i < NUM_ROUTES; i++) {
    		cur = this.routerTable[i];
    		
    		if( (ip & intMaskToLong(cur.getMask())) == cur.getIP()) {
    			return cur;
    		}
    	}
    	
    	// need a catch all return statement to make the compiler happy
    	return cur;
    }
    
    private String calculateSubnetMask(int mask) {
    	// Integer.toBinaryString(...) trims leading 0's
    	if (mask == 0) {
    		return String.format("%032d", 0);
    	}
    	
    	/*
    	 * Start with -1, which is 32 1's in twos complement then bit shift
    	 * the 1's, 32 minus mask times, leaving you with the correct subnet mask.
    	 */
    	return Integer.toBinaryString(-1 << (32 - mask));
    }
    
    private String calculateNetworkAddress(long ip, int mask) {
        long longBitmask = intMaskToLong(mask);
        long maskedIP = longBitmask & ip;
        
        return to32BitBinaryString(maskedIP);
    }

    public String checkRouting() {
        return this.getMatchedRoute().getName();
    }
    
}