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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.catalina.tribes.group;
import java.io.Serializable;
import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
import org.apache.catalina.tribes.Member;
/**
* <p>
* Title: Membership - Absolute Order
* </p>
* <p>
* Description: A simple, yet agreeable and efficient way of ordering members
* </p>
* <p>
* Ordering members can serve as a basis for electing a leader or coordinating efforts.<br>
* This is stinky simple, it works on the basis of the <code>Member</code> interface and orders members in the following
* format:
* </p>
* <ol>
* <li>IP comparison - byte by byte, lower byte higher rank</li>
* <li>IPv4 addresses rank higher than IPv6, ie the lesser number of bytes, the higher rank</li>
* <li>Port comparison - lower port, higher rank</li>
* <li>UniqueId comparison- byte by byte, lower byte higher rank</li>
* </ol>
*
* @see org.apache.catalina.tribes.Member
*/
public class AbsoluteOrder {
public static final AbsoluteComparator comp = new AbsoluteComparator();
protected AbsoluteOrder() {
super();
}
public static void absoluteOrder(Member[] members) {
if (members == null || members.length <= 1) {
return;
}
Arrays.sort(members, comp);
}
public static void absoluteOrder(List<Member> members) {
if (members == null || members.size() <= 1) {
return;
}
members.sort(comp);
}
public static class AbsoluteComparator implements Comparator<Member>, Serializable {
private static final long serialVersionUID = 1L;
@Override
public int compare(Member m1, Member m2) {
int result = compareIps(m1, m2);
if (result == 0) {
result = comparePorts(m1, m2);
}
if (result == 0) {
result = compareIds(m1, m2);
}
return result;
}
public int compareIps(Member m1, Member m2) {
return compareBytes(m1.getHost(), m2.getHost());
}
public int comparePorts(Member m1, Member m2) {
return compareInts(m1.getPort(), m2.getPort());
}
public int compareIds(Member m1, Member m2) {
return compareBytes(m1.getUniqueId(), m2.getUniqueId());
}
protected int compareBytes(byte[] d1, byte[] d2) {
int result = 0;
if (d1.length == d2.length) {
for (int i = 0; (result == 0) && (i < d1.length); i++) {
result = compareBytes(d1[i], d2[i]);
}
} else if (d1.length < d2.length) {
result = -1;
} else {
result = 1;
}
return result;
}
protected int compareBytes(byte b1, byte b2) {
return compareInts(b1, b2);
}
protected int compareInts(int b1, int b2) {
return Integer.compare(b1, b2);
}
}
}
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