| // Copyright (c) 2003-2004 Brian Wellington (bwelling@xbill.org) |
| |
| package org.xbill.DNS; |
| |
| /** |
| * Helper functions for doing serial arithmetic. These should be used when |
| * setting/checking SOA serial numbers. SOA serial number arithmetic is |
| * defined in RFC 1982. |
| * |
| * @author Brian Wellington |
| */ |
| |
| public final class Serial { |
| |
| private static final long MAX32 = 0xFFFFFFFFL; |
| |
| private |
| Serial() { |
| } |
| |
| /** |
| * Compares two numbers using serial arithmetic. The numbers are assumed |
| * to be 32 bit unsigned integers stored in longs. |
| * @param serial1 The first integer |
| * @param serial2 The second integer |
| * @return 0 if the 2 numbers are equal, a positive number if serial1 is greater |
| * than serial2, and a negative number if serial2 is greater than serial1. |
| * @throws IllegalArgumentException serial1 or serial2 is out of range |
| */ |
| public static int |
| compare(long serial1, long serial2) { |
| if (serial1 < 0 || serial1 > MAX32) |
| throw new IllegalArgumentException(serial1 + " out of range"); |
| if (serial2 < 0 || serial2 > MAX32) |
| throw new IllegalArgumentException(serial2 + " out of range"); |
| long diff = serial1 - serial2; |
| if (diff >= MAX32) |
| diff -= (MAX32 + 1); |
| else if (diff < -MAX32) |
| diff += (MAX32 + 1); |
| return (int)diff; |
| } |
| |
| /** |
| * Increments a serial number. The number is assumed to be a 32 bit unsigned |
| * integer stored in a long. This basically adds 1 and resets the value to |
| * 0 if it is 2^32. |
| * @param serial The serial number |
| * @return The incremented serial number |
| * @throws IllegalArgumentException serial is out of range |
| */ |
| public static long |
| increment(long serial) { |
| if (serial < 0 || serial > MAX32) |
| throw new IllegalArgumentException(serial + " out of range"); |
| if (serial == MAX32) |
| return 0; |
| return serial + 1; |
| } |
| |
| } |