1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/src/share/classes/com/sun/tools/javac/util/GraphUtils.java Tue Feb 12 19:25:09 2013 +0000
1.3 @@ -0,0 +1,145 @@
1.4 +/*
1.5 + * Copyright (c) 1999, 2013, Oracle and/or its affiliates. All rights reserved.
1.6 + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
1.7 + *
1.8 + * This code is free software; you can redistribute it and/or modify it
1.9 + * under the terms of the GNU General Public License version 2 only, as
1.10 + * published by the Free Software Foundation. Oracle designates this
1.11 + * particular file as subject to the "Classpath" exception as provided
1.12 + * by Oracle in the LICENSE file that accompanied this code.
1.13 + *
1.14 + * This code is distributed in the hope that it will be useful, but WITHOUT
1.15 + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
1.16 + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
1.17 + * version 2 for more details (a copy is included in the LICENSE file that
1.18 + * accompanied this code).
1.19 + *
1.20 + * You should have received a copy of the GNU General Public License version
1.21 + * 2 along with this work; if not, write to the Free Software Foundation,
1.22 + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
1.23 + *
1.24 + * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
1.25 + * or visit www.oracle.com if you need additional information or have any
1.26 + * questions.
1.27 + */
1.28 +
1.29 +package com.sun.tools.javac.util;
1.30 +
1.31 +/** <p><b>This is NOT part of any supported API.
1.32 + * If you write code that depends on this, you do so at your own risk.
1.33 + * This code and its internal interfaces are subject to change or
1.34 + * deletion without notice.</b>
1.35 + */
1.36 +public class GraphUtils {
1.37 +
1.38 + /**
1.39 + * This class is a basic abstract class for representing a node.
1.40 + * A node is associated with a given data.
1.41 + */
1.42 + public static abstract class Node<D> {
1.43 + public final D data;
1.44 +
1.45 + public Node(D data) {
1.46 + this.data = data;
1.47 + }
1.48 +
1.49 + public abstract Iterable<? extends Node<D>> getDependencies();
1.50 +
1.51 + public abstract String printDependency(Node<D> to);
1.52 +
1.53 + @Override
1.54 + public String toString() {
1.55 + return data.toString();
1.56 + }
1.57 + }
1.58 +
1.59 + /**
1.60 + * This class specialized Node, by adding elements that are required in order
1.61 + * to perform Tarjan computation of strongly connected components.
1.62 + */
1.63 + public static abstract class TarjanNode<D> extends Node<D> implements Comparable<TarjanNode<D>> {
1.64 + int index = -1;
1.65 + int lowlink;
1.66 + boolean active;
1.67 +
1.68 + public TarjanNode(D data) {
1.69 + super(data);
1.70 + }
1.71 +
1.72 + public abstract Iterable<? extends TarjanNode<D>> getDependencies();
1.73 +
1.74 + public int compareTo(TarjanNode<D> o) {
1.75 + return (index < o.index) ? -1 : (index == o.index) ? 0 : 1;
1.76 + }
1.77 + }
1.78 +
1.79 + /**
1.80 + * Tarjan's algorithm to determine strongly connected components of a
1.81 + * directed graph in linear time. Works on TarjanNode.
1.82 + */
1.83 + public static <D, N extends TarjanNode<D>> List<? extends List<? extends N>> tarjan(Iterable<? extends N> nodes) {
1.84 + ListBuffer<List<N>> cycles = ListBuffer.lb();
1.85 + ListBuffer<N> stack = ListBuffer.lb();
1.86 + int index = 0;
1.87 + for (N node: nodes) {
1.88 + if (node.index == -1) {
1.89 + index += tarjan(node, index, stack, cycles);
1.90 + }
1.91 + }
1.92 + return cycles.toList();
1.93 + }
1.94 +
1.95 + private static <D, N extends TarjanNode<D>> int tarjan(N v, int index, ListBuffer<N> stack, ListBuffer<List<N>> cycles) {
1.96 + v.index = index;
1.97 + v.lowlink = index;
1.98 + index++;
1.99 + stack.prepend(v);
1.100 + v.active = true;
1.101 + for (TarjanNode<D> nd: v.getDependencies()) {
1.102 + @SuppressWarnings("unchecked")
1.103 + N n = (N)nd;
1.104 + if (n.index == -1) {
1.105 + tarjan(n, index, stack, cycles);
1.106 + v.lowlink = Math.min(v.lowlink, n.lowlink);
1.107 + } else if (stack.contains(n)) {
1.108 + v.lowlink = Math.min(v.lowlink, n.index);
1.109 + }
1.110 + }
1.111 + if (v.lowlink == v.index) {
1.112 + N n;
1.113 + ListBuffer<N> cycle = ListBuffer.lb();
1.114 + do {
1.115 + n = stack.remove();
1.116 + n.active = false;
1.117 + cycle.add(n);
1.118 + } while (n != v);
1.119 + cycles.add(cycle.toList());
1.120 + }
1.121 + return index;
1.122 + }
1.123 +
1.124 + /**
1.125 + * Debugging: dot representation of a set of connected nodes. The resulting
1.126 + * dot representation will use {@code Node.toString} to display node labels
1.127 + * and {@code Node.printDependency} to display edge labels. The resulting
1.128 + * representation is also customizable with a graph name and a header.
1.129 + */
1.130 + public static <D> String toDot(Iterable<? extends TarjanNode<D>> nodes, String name, String header) {
1.131 + StringBuilder buf = new StringBuilder();
1.132 + buf.append(String.format("digraph %s {\n", name));
1.133 + buf.append(String.format("label = \"%s\";\n", header));
1.134 + //dump nodes
1.135 + for (TarjanNode<D> n : nodes) {
1.136 + buf.append(String.format("%s [label = \"%s\"];\n", n.hashCode(), n.toString()));
1.137 + }
1.138 + //dump arcs
1.139 + for (TarjanNode<D> from : nodes) {
1.140 + for (TarjanNode<D> to : from.getDependencies()) {
1.141 + buf.append(String.format("%s -> %s [label = \" %s \"];\n",
1.142 + from.hashCode(), to.hashCode(), from.printDependency(to)));
1.143 + }
1.144 + }
1.145 + buf.append("}\n");
1.146 + return buf.toString();
1.147 + }
1.148 +}
