org/rivoreo/net/Inet4AddressBlock.java

/*	Copyright 2015-2020 Rivoreo

	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 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 org.rivoreo.net;

import java.net.Inet4Address;
import java.util.Arrays;

public class Inet4AddressBlock {
	public Inet4AddressBlock(String s) {
		int slash_i = s.lastIndexOf('/');
		if(slash_i == 0) throw new IllegalArgumentException("malformed address string");
		String address_s = slash_i == -1 ? s : s.substring(0, slash_i);
		prefix_length = slash_i == -1 ? 32 : Integer.parseInt(s.substring(slash_i + 1));
		if(prefix_length < 0 || prefix_length > 32) throw new IllegalArgumentException("prefix length out of range");
		String[] splited_address = address_s.split("\\.");
		if(splited_address.length > 4) throw new IllegalArgumentException("malformed address string");
		raw_address = new byte[(prefix_length + 7) / 8];
		for(int i = 0; i < raw_address.length && i < splited_address.length; i++) {
			int n = Integer.parseInt(splited_address[i]);
			if(n < 0 || n > 255) throw new NumberFormatException("malformed address string");
			raw_address[i] = (byte)n;
		}
		truncate_host_bits();
	}
	public Inet4AddressBlock(Inet4Address address, int prefix_length) {
		if(prefix_length < 0 || prefix_length > 32) throw new IllegalArgumentException("prefix length out of range");
		raw_address = Arrays.copyOf(address.getAddress(), (prefix_length + 7) / 8);
		this.prefix_length = prefix_length;
		truncate_host_bits();
	}

	private byte[] raw_address;
	private int prefix_length;

	private void truncate_host_bits() {
		if(prefix_length % 8 == 0) return;
		int i = prefix_length / 8;
		int host_bit_len = 8 - (prefix_length - i * 8);
		raw_address[i] &= (byte)0xff << host_bit_len;
	}

	public boolean is_in_block(Inet4Address address) {
		if(prefix_length == 0) return true;
		byte[] ba = address.getAddress();
		int i = 0;
		while(i < raw_address.length - 1) {
			if(ba[i] != raw_address[i]) return false;
			i++;
		}
		int host_bit_len = 8 - (prefix_length - i * 8);
		return (ba[i] & ((byte)0xff << host_bit_len)) == raw_address[i];
	}

	private static int to_unsigned_byte(byte n) {
		return n < 0 ? n + 256 : n;
	}

	@Override
	public String toString() {
		StringBuilder s = new StringBuilder(18);
		switch(raw_address.length) {
			case 0:
				s.append("0.0.0.0");
				break;
			case 1:
				s.append(String.valueOf(to_unsigned_byte(raw_address[0])));
				s.append(".0.0.0");
				break;
			case 2:
				s.append(String.valueOf(to_unsigned_byte(raw_address[0])));
				s.append('.');
				s.append(String.valueOf(to_unsigned_byte(raw_address[1])));
				s.append(".0.0");
				break;
			case 3:
				s.append(String.valueOf(to_unsigned_byte(raw_address[0])));
				s.append('.');
				s.append(String.valueOf(to_unsigned_byte(raw_address[1])));
				s.append('.');
				s.append(String.valueOf(to_unsigned_byte(raw_address[2])));
				s.append(".0");
				break;
			case 4:
				s.append(String.format("%d.%d.%d.%d", to_unsigned_byte(raw_address[0]), to_unsigned_byte(raw_address[1]), to_unsigned_byte(raw_address[2]), to_unsigned_byte(raw_address[3])));
				break;
			default:
				throw new RuntimeException(String.format("Unexpected raw_address.length: %d", raw_address.length));
		}
		s.append('/').append(String.valueOf(prefix_length));
		return s.toString();
	}
}