Umesh Krishnaswamy | 345ee99 | 2012-12-13 20:29:48 -0800 | [diff] [blame] | 1 | /** |
| 2 | * Copyright 2011, Big Switch Networks, Inc. |
| 3 | * Originally created by David Erickson, Stanford University |
| 4 | * |
| 5 | * Licensed under the Apache License, Version 2.0 (the "License"); you may |
| 6 | * not use this file except in compliance with the License. You may obtain |
| 7 | * a copy of the License at |
| 8 | * |
| 9 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 10 | * |
| 11 | * Unless required by applicable law or agreed to in writing, software |
| 12 | * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT |
| 13 | * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the |
| 14 | * License for the specific language governing permissions and limitations |
| 15 | * under the License. |
| 16 | **/ |
| 17 | |
| 18 | package net.floodlightcontroller.core.util; |
| 19 | |
| 20 | import java.util.ArrayList; |
| 21 | import java.util.HashSet; |
| 22 | import java.util.List; |
| 23 | |
| 24 | import org.slf4j.Logger; |
| 25 | import org.slf4j.LoggerFactory; |
| 26 | |
| 27 | import net.floodlightcontroller.core.IListener; |
| 28 | import net.floodlightcontroller.core.annotations.LogMessageDoc; |
| 29 | |
| 30 | /** |
| 31 | * Maintain lists of listeners ordered by dependency. |
| 32 | * |
| 33 | * @author readams |
| 34 | * |
| 35 | */ |
| 36 | public class ListenerDispatcher<U, T extends IListener<U>> { |
| 37 | protected static Logger logger = LoggerFactory.getLogger(ListenerDispatcher.class); |
| 38 | List<T> listeners = null; |
| 39 | |
| 40 | private void visit(List<T> newlisteners, U type, HashSet<T> visited, |
| 41 | List<T> ordering, T listener) { |
| 42 | if (!visited.contains(listener)) { |
| 43 | visited.add(listener); |
| 44 | |
| 45 | for (T i : newlisteners) { |
| 46 | if (ispre(type, i, listener)) { |
| 47 | visit(newlisteners, type, visited, ordering, i); |
| 48 | } |
| 49 | } |
| 50 | ordering.add(listener); |
| 51 | } |
| 52 | } |
| 53 | |
| 54 | private boolean ispre(U type, T l1, T l2) { |
| 55 | return (l2.isCallbackOrderingPrereq(type, l1.getName()) || |
| 56 | l1.isCallbackOrderingPostreq(type, l2.getName())); |
| 57 | } |
| 58 | |
| 59 | /** |
| 60 | * Add a listener to the list of listeners |
| 61 | * @param listener |
| 62 | */ |
| 63 | @LogMessageDoc(level="ERROR", |
| 64 | message="No listener dependency solution: " + |
| 65 | "No listeners without incoming dependencies", |
| 66 | explanation="The set of listeners installed " + |
| 67 | "have dependencies with no solution", |
| 68 | recommendation="Install a different set of listeners " + |
| 69 | "or install all dependencies. This is a defect in " + |
| 70 | "the controller installation.") |
| 71 | public void addListener(U type, T listener) { |
| 72 | List<T> newlisteners = new ArrayList<T>(); |
| 73 | if (listeners != null) |
| 74 | newlisteners.addAll(listeners); |
| 75 | |
| 76 | newlisteners.add(listener); |
| 77 | // Find nodes without outgoing edges |
| 78 | List<T> terminals = new ArrayList<T>(); |
| 79 | for (T i : newlisteners) { |
| 80 | boolean isterm = true; |
| 81 | for (T j : newlisteners) { |
| 82 | if (ispre(type, i, j)) { |
| 83 | isterm = false; |
| 84 | break; |
| 85 | } |
| 86 | } |
| 87 | if (isterm) { |
| 88 | terminals.add(i); |
| 89 | } |
| 90 | } |
| 91 | |
| 92 | if (terminals.size() == 0) { |
| 93 | logger.error("No listener dependency solution: " + |
| 94 | "No listeners without incoming dependencies"); |
| 95 | listeners = newlisteners; |
| 96 | return; |
| 97 | } |
| 98 | |
| 99 | // visit depth-first traversing in the opposite order from |
| 100 | // the dependencies. Note we will not generally detect cycles |
| 101 | HashSet<T> visited = new HashSet<T>(); |
| 102 | List<T> ordering = new ArrayList<T>(); |
| 103 | for (T term : terminals) { |
| 104 | visit(newlisteners, type, visited, ordering, term); |
| 105 | } |
| 106 | listeners = ordering; |
| 107 | } |
| 108 | |
| 109 | /** |
| 110 | * Remove the given listener |
| 111 | * @param listener the listener to remove |
| 112 | */ |
| 113 | public void removeListener(T listener) { |
| 114 | if (listeners != null) { |
| 115 | List<T> newlisteners = new ArrayList<T>(); |
| 116 | newlisteners.addAll(listeners); |
| 117 | newlisteners.remove(listener); |
| 118 | listeners = newlisteners; |
| 119 | } |
| 120 | } |
| 121 | |
| 122 | /** |
| 123 | * Clear all listeners |
| 124 | */ |
| 125 | public void clearListeners() { |
| 126 | listeners = new ArrayList<T>(); |
| 127 | } |
| 128 | |
| 129 | /** |
| 130 | * Get the ordered list of listeners ordered by dependencies |
| 131 | * @return |
| 132 | */ |
| 133 | public List<T> getOrderedListeners() { |
| 134 | return listeners; |
| 135 | } |
| 136 | } |