A class that performs some subnet calculations given a network address and a subnet mask.
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import java.util.regex.Matcher;
import java.util.regex.Pattern;
/**
* A class that performs some subnet calculations given a network address and a subnet mask.
* @see http://www.faqs.org/rfcs/rfc1519.html
* @author <rwinston@apache.org>
* @since 2.0
*/
public class SubnetUtils {
private static final String IP_ADDRESS = "(\\d{1,3})\\.(\\d{1,3})\\.(\\d{1,3})\\.(\\d{1,3})";
private static final String SLASH_FORMAT = IP_ADDRESS + "/(\\d{1,3})";
private static final Pattern addressPattern = Pattern.compile(IP_ADDRESS);
private static final Pattern cidrPattern = Pattern.compile(SLASH_FORMAT);
private static final int NBITS = 32;
private int netmask = 0;
private int address = 0;
private int network = 0;
private int broadcast = 0;
/**
* Constructor that takes a CIDR-notation string, e.g. "192.168.0.1/16"
* @param cidrNotation A CIDR-notation string, e.g. "192.168.0.1/16"
*/
public SubnetUtils(String cidrNotation) {
calculate(cidrNotation);
}
/**
* Constructor that takes two dotted decimal addresses.
* @param address An IP address, e.g. "192.168.0.1"
* @param mask A dotted decimal netmask e.g. "255.255.0.0"
*/
public SubnetUtils(String address, String mask) {
calculate(toCidrNotation(address, mask));
}
/**
* Convenience container for subnet summary information.
*
*/
public final class SubnetInfo {
private SubnetInfo() {}
private int netmask() { return netmask; }
private int network() { return network; }
private int address() { return address; }
private int broadcast() { return broadcast; }
private int low() { return network() + 1; }
private int high() { return broadcast() - 1; }
public boolean isInRange(String address) { return isInRange(toInteger(address)); }
private boolean isInRange(int address) { return ((address-low()) <= (high()-low())); }
public String getBroadcastAddress() { return format(toArray(broadcast())); }
public String getNetworkAddress() { return format(toArray(network())); }
public String getNetmask() { return format(toArray(netmask())); }
public String getAddress() { return format(toArray(address())); }
public String getLowAddress() { return format(toArray(low())); }
public String getHighAddress() { return format(toArray(high())); }
public int getAddressCount() { return (broadcast() - low()); }
public int asInteger(String address) { return toInteger(address); }
public String getCidrSignature() {
return toCidrNotation(
format(toArray(address())),
format(toArray(netmask()))
);
}
public String[] getAllAddresses() {
String[] addresses = new String[getAddressCount()];
for (int add = low(), j=0; add <= high(); ++add, ++j) {
addresses[j] = format(toArray(add));
}
return addresses;
}
}
/**
* Return a {@link SubnetInfo} instance that contains subnet-specific statistics
* @return
*/
public final SubnetInfo getInfo() { return new SubnetInfo(); }
/*
* Initialize the internal fields from the supplied CIDR mask
*/
private void calculate(String mask) {
Matcher matcher = cidrPattern.matcher(mask);
if (matcher.matches()) {
address = matchAddress(matcher);
/* Create a binary netmask from the number of bits specification /x */
int cidrPart = rangeCheck(Integer.parseInt(matcher.group(5)), 0, NBITS-1);
for (int j = 0; j < cidrPart; ++j) {
netmask |= (1 << 31-j);
}
/* Calculate base network address */
network = (address & netmask);
/* Calculate broadcast address */
broadcast = network | ~(netmask);
}
else
throw new IllegalArgumentException("Could not parse [" + mask + "]");
}
/*
* Convert a dotted decimal format address to a packed integer format
*/
private int toInteger(String address) {
Matcher matcher = addressPattern.matcher(address);
if (matcher.matches()) {
return matchAddress(matcher);
}
else
throw new IllegalArgumentException("Could not parse [" + address + "]");
}
/*
* Convenience method to extract the components of a dotted decimal address and
* pack into an integer using a regex match
*/
private int matchAddress(Matcher matcher) {
int addr = 0;
for (int i = 1; i <= 4; ++i) {
int n = (rangeCheck(Integer.parseInt(matcher.group(i)), 0, 255));
addr |= ((n & 0xff) << 8*(4-i));
}
return addr;
}
/*
* Convert a packed integer address into a 4-element array
*/
private int[] toArray(int val) {
int ret[] = new int[4];
for (int j = 3; j >= 0; --j)
ret[j] |= ((val >>> 8*(3-j)) & (0xff));
return ret;
}
/*
* Convert a 4-element array into dotted decimal format
*/
private String format(int[] octets) {
StringBuilder str = new StringBuilder();
for (int i =0; i < octets.length; ++i){
str.append(octets[i]);
if (i != octets.length - 1) {
str.append(".");
}
}
return str.toString();
}
/*
* Convenience function to check integer boundaries
*/
private int rangeCheck(int value, int begin, int end) {
if (value >= begin && value <= end)
return value;
throw new IllegalArgumentException("Value out of range: [" + value + "]");
}
/*
* Count the number of 1-bits in a 32-bit integer using a divide-and-conquer strategy
* see Hacker's Delight section 5.1
*/
int pop(int x) {
x = x - ((x >>> 1) & 0x55555555);
x = (x & 0x33333333) + ((x >>> 2) & 0x33333333);
x = (x + (x >>> 4)) & 0x0F0F0F0F;
x = x + (x >>> 8);
x = x + (x >>> 16);
return x & 0x0000003F;
}
/* Convert two dotted decimal addresses to a single xxx.xxx.xxx.xxx/yy format
* by counting the 1-bit population in the mask address. (It may be better to count
* NBITS-#trailing zeroes for this case)
*/
private String toCidrNotation(String addr, String mask) {
return addr + "/" + pop(toInteger(mask));
}
}
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