1/* 2 * [The "BSD license"] 3 * Copyright (c) 2010 Terence Parr 4 * All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 3. The name of the author may not be used to endorse or promote products 15 * derived from this software without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 */ 28package org.antlr.misc; 29 30import java.util.*; 31 32/** A generic graph with edges; Each node as a single Object payload. 33 * This is only used to topologically sort a list of file dependencies 34 * at the moment. 35 */ 36public class Graph { 37 38 public static class Node { 39 Object payload; 40 List<Node> edges; // points at which nodes? 41 42 public Node(Object payload) { this.payload = payload; } 43 44 public void addEdge(Node n) { 45 if ( edges==null ) edges = new ArrayList<Node>(); 46 if ( !edges.contains(n) ) edges.add(n); 47 } 48 49 public String toString() { return payload.toString(); } 50 } 51 52 /** Map from node payload to node containing it */ 53 protected Map<Object,Node> nodes = new HashMap<Object,Node>(); 54 55 public void addEdge(Object a, Object b) { 56 //System.out.println("add edge "+a+" to "+b); 57 Node a_node = getNode(a); 58 Node b_node = getNode(b); 59 a_node.addEdge(b_node); 60 } 61 62 protected Node getNode(Object a) { 63 Node existing = nodes.get(a); 64 if ( existing!=null ) return existing; 65 Node n = new Node(a); 66 nodes.put(a, n); 67 return n; 68 } 69 70 /** DFS-based topological sort. A valid sort is the reverse of 71 * the post-order DFA traversal. Amazingly simple but true. 72 * For sorting, I'm not following convention here since ANTLR 73 * needs the opposite. Here's what I assume for sorting: 74 * 75 * If there exists an edge u -> v then u depends on v and v 76 * must happen before u. 77 * 78 * So if this gives nonreversed postorder traversal, I get the order 79 * I want. 80 */ 81 public List<Object> sort() { 82 Set<Node> visited = new OrderedHashSet<Node>(); 83 ArrayList<Object> sorted = new ArrayList<Object>(); 84 while ( visited.size() < nodes.size() ) { 85 // pick any unvisited node, n 86 Node n = null; 87 for (Iterator it = nodes.values().iterator(); it.hasNext();) { 88 n = (Node)it.next(); 89 if ( !visited.contains(n) ) break; 90 } 91 DFS(n, visited, sorted); 92 } 93 return sorted; 94 } 95 96 public void DFS(Node n, Set<Node> visited, ArrayList<Object> sorted) { 97 if ( visited.contains(n) ) return; 98 visited.add(n); 99 if ( n.edges!=null ) { 100 for (Iterator it = n.edges.iterator(); it.hasNext();) { 101 Node target = (Node) it.next(); 102 DFS(target, visited, sorted); 103 } 104 } 105 sorted.add(n.payload); 106 } 107}