subnet.java

mina是以Java实现的一个开源的网络程序框架

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 *  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.
 *
 */

package org.apache.mina.filter.firewall;

import java.net.Inet4Address;
import java.net.InetAddress;

/**
 * A IP subnet using the CIDR notation. Currently, only IP version 4
 * address are supported.
 *
 * @author The Apache MINA Project ([e-mail])
 * @version $Rev: 636538 $, $Date: 2008-03-12 22:19:27 +0000 (Wed, 12 Mar 2008) $
 */
public class Subnet {

	private static final int IP_MASK = 0x80000000;
	private static final int BYTE_MASK = 0xFF;

	private InetAddress subnet;
	private int subnetInt;
	private int subnetMask;
	private int suffix;

	/**
	 * Creates a subnet from CIDR notation. For example, the subnet
	 * 192.168.0.0/24 would be created using the {@link InetAddress}  
	 * 192.168.0.0 and the mask 24.
	 * @param subnet The {@link InetAddress} of the subnet
	 * @param mask The mask
	 */
	public Subnet(InetAddress subnet, int mask) {
		if(subnet == null) {
			throw new NullPointerException("Subnet address can not be null");
		}
		if(!(subnet instanceof Inet4Address)) {
			throw new IllegalArgumentException("Only IPv4 supported");
		}

		if(mask < 0 || mask > 32) {
			throw new IllegalArgumentException("Mask has to be an integer between 0 and 32");
		}
		
		this.subnet = subnet;
		this.subnetInt = toInt(subnet);
		this.suffix = mask;
		
		// binary mask for this subnet
		this.subnetMask = IP_MASK >> (mask - 1);
	}

	/** 
	 * Converts an IP address into an integer
	 */ 
	private int toInt(InetAddress inetAddress) {
		byte[] address = inetAddress.getAddress();
		int result = 0;
		for (int i = 0; i < address.length; i++) {
			result <<= 8;
			result |= address[i] & BYTE_MASK;
		}
		return result;
	}

	/**
	 * Converts an IP address to a subnet using the provided 
	 * mask
	 * @param address The address to convert into a subnet
	 * @return The subnet as an integer
	 */
	private int toSubnet(InetAddress address) {
		return toInt(address) & subnetMask;
	}
	
	/**
	 * Checks if the {@link InetAddress} is within this subnet
	 * @param address The {@link InetAddress} to check
	 * @return True if the address is within this subnet, false otherwise
	 */
	public boolean inSubnet(InetAddress address) {
		return toSubnet(address) == subnetInt;
	}

	/**
	 * @see Object#toString()
	 */
	@Override
	public String toString() {
		return subnet.getHostAddress() + "/" + suffix;
	}

	@Override
	public boolean equals(Object obj) {
		if(!(obj instanceof Subnet)) {
			return false;
		}
		
		Subnet other = (Subnet) obj;
		
		return other.subnetInt == subnetInt && other.suffix == suffix;
	}

	
}