Converting CIDR address to subnet mask and network address

Question

Given a CIDR address, e.g. 192.168.10.0/24

• How to determine mask length? (24)
• How to determine mask address? (255.255.

Answer 1

this is my groovy's:)

//IP calculator by ku1gun

// input
String inputAddr = "12.34.56.78/20";

//magic
def(String ipAddrBin, String maskAddrBin, String invertedMaskBin, int hostsCount) = getIpAddrAndCidrMaskBin(inputAddr);

String broadcastAddr = retrieveBroadcastAddr(ipAddrBin, invertedMaskBin);
String ipAddr = getTenBaseAddrValueFromBin(ipAddrBin);
String maskAddr = getTenBaseAddrValueFromBin(maskAddrBin);
String invertedMask = getTenBaseAddrValueFromBin(invertedMaskBin);
String networkAddr = retrieveNetworkAddr(ipAddrBin, maskAddrBin);

def (String ipMinVal, String ipMaxVal) = getMinMaxIpRangeValues(networkAddr, broadcastAddr)

//Output "debug" results
System.out.println("Variables:");
System.out.println("ipInput: " + ipAddr);
System.out.println("MaskInput: " + maskAddr);
System.out.println("invertedMask: " + invertedMask);
System.out.println("-----------------------");
System.out.println("Binaries:");
System.out.println("ipBin: " + ipAddrBin);
System.out.println("MaskInBin: " + maskAddrBin);
System.out.println("InvertedMaskBin: " + invertedMaskBin);
System.out.println("-----------------------");
System.out.println("Results:");
System.out.println("maskAddr: " + maskAddr);
System.out.println("hostsCount: " + hostsCount);
System.out.println("networkAddr: " + networkAddr);
System.out.println("broadcastAddr: " + broadcastAddr);
System.out.println("ipMinVal: " + ipMinVal);
System.out.println("ipMaxVal: " + ipMaxVal);
System.out.println("-----------------------");
System.out.println("IP range list:");

long ipStart = host2long(ipMinVal);
long ipEnd = host2long(ipMaxVal);


for (long i=ipStart; i<=ipEnd; i++) 
{
    System.out.println(long2dotted(i));
}


//general methods
def getIpAddrAndCidrMaskBin(String inputAddrStr)
{
    def netMask = "";
    def invNetMask = "";

    def cidrAddressList = inputAddrStr.tokenize("\\/")
    def baseIPAddress = cidrAddressList.first()
    def cidrIPMask = cidrAddressList.last().toInteger()

    //retrieve binaryNetMask and binaryInvertedNetMask
    for(i=0; i<32; i++)
    {
        if(i=0 ? addr[i] : 0)) << 8*(3-i);
    }
    return ip;
}

public static int[] ip2intarray(String host) 
{
    Integer[] address = [-1,-1,-1,-1];
    int i=0;
    StringTokenizer tokens = new StringTokenizer(host,".");
    if (tokens.countTokens() > 4) return null;
    while (tokens.hasMoreTokens()) 
    {
        try 
        {
            address[i++] = Integer.parseInt(tokens.nextToken()) & 0xFF;
        } 
        catch(NumberFormatException nfe) 
        {
            return null;
        }
    }
    return address;
}

public static String long2dotted(long ip) 
{
    // if ip is bigger than 255.255.255.255 or smaller than 0.0.0.0
    if (ip > 4294967295l || ip < 0) 
    {
        throw new IllegalArgumentException("invalid ip");
    }
    StringBuilder ipAddress = new StringBuilder();
    for (int i = 3; i >= 0; i--) {
        int shift = i * 8;
        ipAddress.append((ip & (0xff << shift)) >> shift);
        if (i > 0) {
            ipAddress.append(".");
        }
    }
    return ipAddress.toString();
}