检查ip是否在指定范围（子网）内

转自：https://github.com/edazdarevic/CIDRUtils.git
该方法同时支持ipv4和ipv6，检查ip是否在指定的cidr内。
实现代码为java。

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 final String cidr;

     private InetAddress inetAddress;
     private InetAddress startAddress;
     private InetAddress endAddress;
     private final int prefixLength;

     public CIDRUtils(String cidr) throws UnknownHostException {

          this.cidr = cidr;

          /* split CIDR to address and prefix part */
          if (this.cidr.contains("/")) {
               int index = this.cidr.indexOf("/");
               String addressPart = this.cidr.substring(0, index);
               String networkPart = this.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);

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

     }

     private byte[] toBytes(byte[] array, int targetSize) {
          int counter = 0;
          List<Byte> newArr = new ArrayList<Byte>();
          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 String getNetworkAddress() {

          return this.startAddress.getHostAddress();
     }

     public String getBroadcastAddress() {
          return this.endAddress.getHostAddress();
     }

     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);
     }
    
     public static void main(String[] args){
          CIDRUtils cidr = null;
          try {
               cidr = new CIDRUtils("107.0.0.0/8");
               System.out.println(cidr.isInRange("107.1.1.1"));
          } catch (UnknownHostException e) {
               e.printStackTrace();
          }
         
     }
    
}
# end