JDK-4262187 : add Subnet class
  • Type: Enhancement
  • Component: core-libs
  • Sub-Component: java.net
  • Affected Version: 1.2.2,1.4.0
  • Priority: P4
  • Status: Closed
  • Resolution: Duplicate
  • OS: generic
  • CPU: generic
  • Submitted: 1999-08-12
  • Updated: 2002-05-27
  • Resolved: 2002-05-27
Related Reports
Duplicate :  
JDK-4691932 - Programmatic access to network parameters
Duplicate :  
JDK-4509678 - obtaining IP netmask for a local network interface
Description

Name: skT88420			Date: 08/12/99


It would be very convenient if you would include a Subnet class
in the java.net package.  It should have a way to compare
an InetAddress to a Subnet to see if it is in the Subnet.
(Review ID: 93862) 
======================================================================
Comments
WORK AROUND Name: skT88420 Date: 08/12/99 I wrote my own, shown below. It does not yet have a way to create the subnet from its string representation, which it should have. It should also have some address/mask constructors as well as the address/bitlength constructors. import java.net.*; /***************************************************************************** * Objects that represent subnets (internet addresses and mask). * <P> * Subnets are represented as a string in the format "xxx.xxx.xxx.xxx/yy" * where "xxx.xxx.xxx.xxx" is the address and "yy" is the bitlength. * <P> * @author * Dan Lipofsky<BR> * Copyright &copy; 1999 Cycorp, Inc. All rights reserved. *****************************************************************************/ public class Subnet { private int address; // The 4 byte internet address private int bitlength; // The number of meaningful bits private int mask; // The mask used to select the meaningful bits /** * Constructs a Subnet with the given address and bitlength. * This is a private constructor. We want to hide how the integers * correspond to addresses. Only byte arrays or strings get passed in. */ private Subnet(int address, int bitlength) { if (bitlength < 0 || bitlength > 32) throw new IllegalArgumentException("Illegal bitlength " + bitlength); this.address = address; this.bitlength = bitlength; this.mask = makeMask(bitlength); } /** Constructs a Subnet with the given address and bitlength. */ public Subnet(byte addr[], int bitlength) { this(arrayToInt(addr), bitlength); } // Public Methods /** * Compares two Subnet objects. * @return true if address and bitlength are equal. */ public boolean equals(Object obj) { if (obj instanceof Subnet) { Subnet other = (Subnet)obj; return ((address == other.address) && (bitlength == other.bitlength)); } return false; } /** * Determines if an address is in a Subnet. * @return true if address is in the Subnet. */ public boolean compareAddressToSubnet(InetAddress a) { int tmp_address = arrayToInt(a.getAddress()); return ( (tmp_address & mask) == (address & mask) ); } /** Converts a Subnet to a string */ public String toString() { return (String) ( ((address >>> 24) & 0xFF) + "." + ((address >>> 16) & 0xFF) + "." + ((address >>> 8) & 0xFF) + "." + (address & 0xFF) + "/" + bitlength ) ; } // Private Methods /** Creates a mask from a bitlength. The most significant bitlength bits are 1, while the rest are 0. */ private static int makeMask(int bitlength) { int mask = 0; for (int i=0; i < bitlength; i++) { mask = (mask << 1) | 1; } mask = mask << (32 - bitlength); return mask; } /** Converts an array of 4 bytes to an int */ private static int arrayToInt(byte addr[]) { return (int)( addr[3] & 0xFF | ((addr[2] << 8) & 0xFF00) | ((addr[1] << 16) & 0xFF0000) | ((addr[0] << 24) & 0xFF000000) ); } /** Converts an int to an array of 4 bytes */ private static byte[] intToArray(int address) { byte[] addr = new byte[4]; addr[0] = (byte) ((address >>> 24) & 0xFF); addr[1] = (byte) ((address >>> 16) & 0xFF); addr[2] = (byte) ((address >>> 8) & 0xFF); addr[3] = (byte) (address & 0xFF); return addr; } static public void main(String argv[]) throws UnknownHostException { byte[] address = new byte[] { (byte)207, (byte)207, (byte)8, (byte)0 }; Subnet s = new Subnet(address, 30); InetAddress a1 = InetAddress.getByName("207.207.8.3"); InetAddress a2 = InetAddress.getByName("207.207.8.4"); System.out.println(s + " " + a1 + " " + s.compareAddressToSubnet(a1)); System.out.println(s + " " + a2 + " " + s.compareAddressToSubnet(a2)); } } ======================================================================
11-06-2004
EVALUATION We can't do this in Merlin time frame. Will reconsider it for Tiger. yingxian.wang@eng 2001-03-09 4691932 is collecting the bugs/rfes regarded to programmatic access to network parameters.
09-03-2001