CIDRUtils.java

/*
* The MIT License
*
* Copyright (c) 2013 Edin Dazdarevic (edin.dazdarevic@gmail.com)

* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:

* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.

* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*
*/

package com.ruesga.android.wallpapers.photophase.cast;

import java.math.BigInteger;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.List;

/**
 * A class that enables to get an IP range from CIDR specification. It supports
 * both IPv4 and IPv6.
 */
public class CIDRUtils {
    private InetAddress inetAddress;
    private InetAddress startAddress;
    private InetAddress endAddress;
    private final int prefixLength;

    public CIDRUtils(final String cidr) throws UnknownHostException {
        /* split CIDR to address and prefix part */
        if (cidr.contains("/")) {
            int index = cidr.indexOf("/");
            String addressPart = cidr.substring(0, index);
            String networkPart = cidr.substring(index + 1);

            inetAddress = InetAddress.getByName(addressPart);
            prefixLength = Integer.parseInt(networkPart);

            calculate();
        } else {
            throw new IllegalArgumentException("not an valid CIDR format!");
        }
    }


    private void calculate() throws UnknownHostException {
        ByteBuffer maskBuffer;
        int targetSize;
        if (inetAddress.getAddress().length == 4) {
            maskBuffer =
                    ByteBuffer
                            .allocate(4)
                            .putInt(-1);
            targetSize = 4;
        } else {
            maskBuffer = ByteBuffer.allocate(16)
                    .putLong(-1L)
                    .putLong(-1L);
            targetSize = 16;
        }

        BigInteger mask = (new BigInteger(1, maskBuffer.array())).not().shiftRight(prefixLength);

        ByteBuffer buffer = ByteBuffer.wrap(inetAddress.getAddress());
        BigInteger ipVal = new BigInteger(1, buffer.array());

        BigInteger startIp = ipVal.and(mask);
        BigInteger endIp = startIp.add(mask.not());

        byte[] startIpArr = toBytes(startIp.toByteArray(), targetSize);
        byte[] endIpArr = toBytes(endIp.toByteArray(), targetSize);

        startAddress = InetAddress.getByAddress(startIpArr);
        endAddress = InetAddress.getByAddress(endIpArr);
    }

    private static byte[] toBytes(byte[] array, int targetSize) {
        int counter = 0;
        List<Byte> newArr = new ArrayList<>();
        while (counter < targetSize && (array.length - 1 - counter >= 0)) {
            newArr.add(0, array[array.length - 1 - counter]);
            counter++;
        }

        int size = newArr.size();
        for (int i = 0; i < (targetSize - size); i++) {

            newArr.add(0, (byte) 0);
        }

        byte[] ret = new byte[newArr.size()];
        for (int i = 0; i < newArr.size(); i++) {
            ret[i] = newArr.get(i);
        }
        return ret;
    }

    public boolean isInRange(String ipAddress) throws UnknownHostException {
        InetAddress address = InetAddress.getByName(ipAddress);
        BigInteger start = new BigInteger(1, this.startAddress.getAddress());
        BigInteger end = new BigInteger(1, this.endAddress.getAddress());
        BigInteger target = new BigInteger(1, address.getAddress());

        int st = start.compareTo(target);
        int te = target.compareTo(end);

        return (st == -1 || st == 0) && (te == -1 || te == 0);
    }
}