75 lines
2.1 KiB
Java
Executable File
75 lines
2.1 KiB
Java
Executable File
// Copyright (c) 2003-2004 Brian Wellington (bwelling@xbill.org)
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package org.xbill.DNS2.clients;
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/**
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* Helper functions for doing serial arithmetic. These should be used when
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* setting/checking SOA serial numbers. SOA serial number arithmetic is
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* defined in RFC 1982.
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*
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* @author Brian Wellington
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*/
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public final
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class Serial {
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private static final long MAX32 = 0xFFFFFFFFL;
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private
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Serial() {
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}
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/**
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* Compares two numbers using serial arithmetic. The numbers are assumed
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* to be 32 bit unsigned integers stored in longs.
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*
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* @param serial1 The first integer
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* @param serial2 The second integer
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*
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* @return 0 if the 2 numbers are equal, a positive number if serial1 is greater
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* than serial2, and a negative number if serial2 is greater than serial1.
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*
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* @throws IllegalArgumentException serial1 or serial2 is out of range
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*/
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public static
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int compare(long serial1, long serial2) {
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if (serial1 < 0 || serial1 > MAX32) {
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throw new IllegalArgumentException(serial1 + " out of range");
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}
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if (serial2 < 0 || serial2 > MAX32) {
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throw new IllegalArgumentException(serial2 + " out of range");
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}
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long diff = serial1 - serial2;
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if (diff >= MAX32) {
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diff -= (MAX32 + 1);
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}
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else if (diff < -MAX32) {
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diff += (MAX32 + 1);
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}
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return (int) diff;
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}
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/**
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* Increments a serial number. The number is assumed to be a 32 bit unsigned
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* integer stored in a long. This basically adds 1 and resets the value to
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* 0 if it is 2^32.
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*
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* @param serial The serial number
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*
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* @return The incremented serial number
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*
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* @throws IllegalArgumentException serial is out of range
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*/
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public static
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long increment(long serial) {
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if (serial < 0 || serial > MAX32) {
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throw new IllegalArgumentException(serial + " out of range");
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}
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if (serial == MAX32) {
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return 0;
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}
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return serial + 1;
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}
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}
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