GraphUtils.java revision 2990:70c852df047c 
1/*
2 * Copyright (c) 1999, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.  Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26package com.sun.tools.javac.util;
27
28import java.util.ArrayList;
29import java.util.Collection;
30import java.util.Properties;
31
32/** <p><b>This is NOT part of any supported API.
33 *  If you write code that depends on this, you do so at your own risk.
34 *  This code and its internal interfaces are subject to change or
35 *  deletion without notice.</b>
36 */
37public class GraphUtils {
38
39    /**
40     * Basic interface for defining various dependency kinds.
41     */
42    public interface DependencyKind { }
43
44    /**
45     * Common superinterfaces to all graph nodes.
46     */
47    public interface Node<D, N extends Node<D, N>> {
48        /**
49         * visitor method.
50         */
51        <A> void accept(NodeVisitor<D, N, A> visitor, A arg);
52    }
53
54    /**
55     * Visitor for graph nodes.
56     */
57    static abstract class NodeVisitor<D, N extends Node<D, N>, A> {
58        /**
59         * Visitor action for nodes.
60         */
61        public abstract void visitNode(N node, A arg);
62        /**
63         * Visitor action for a dependency between 'from' and 'to' with given kind.
64         */
65        public abstract void visitDependency(DependencyKind dk, N from, N to, A arg);
66
67        /**
68         * Visitor entry point.
69         */
70        public void visit(Collection<? extends N> nodes, A arg) {
71            for (N n : new ArrayList<>(nodes)) {
72                n.accept(this, arg);
73            }
74        }
75    }
76
77    /**
78     * Optional interface for nodes supporting dot-based representation.
79     */
80    public interface DottableNode<D, N extends DottableNode<D, N>> extends Node<D, N> {
81        /**
82         * Retrieves the set of dot attributes associated with the node.
83         */
84        Properties nodeAttributes();
85        /**
86         * Retrieves the set of dot attributes associated with a given dependency.
87         */
88        Properties dependencyAttributes(N to, DependencyKind dk);
89    }
90
91    /**
92     * This class is a basic abstract class for representing a node.
93     * A node is associated with a given data.
94     */
95    public static abstract class AbstractNode<D, N extends AbstractNode<D, N>> implements Node<D, N> {
96        public final D data;
97
98        public AbstractNode(D data) {
99            this.data = data;
100        }
101
102        /**
103         * Get an array of the dependency kinds supported by this node.
104         */
105        public abstract DependencyKind[] getSupportedDependencyKinds();
106
107        /**
108         * Get all dependencies of a given kind
109         */
110        public abstract Collection<? extends N> getDependenciesByKind(DependencyKind dk);
111
112        @Override
113        public String toString() {
114            return data.toString();
115        }
116
117        @SuppressWarnings("unchecked")
118        public <A> void accept(NodeVisitor<D, N, A> visitor, A arg) {
119            visitor.visitNode((N)this, arg);
120            for (DependencyKind dk : getSupportedDependencyKinds()) {
121                for (N dep : new ArrayList<>(getDependenciesByKind(dk))) {
122                    visitor.visitDependency(dk, (N)this, dep, arg);
123                }
124            }
125        }
126    }
127
128    /**
129     * This class specialized Node, by adding elements that are required in order
130     * to perform Tarjan computation of strongly connected components.
131     */
132    public static abstract class TarjanNode<D, N extends TarjanNode<D, N>> extends AbstractNode<D, N>
133            implements Comparable<N> {
134        int index = -1;
135        int lowlink;
136        boolean active;
137
138        public TarjanNode(D data) {
139            super(data);
140        }
141
142        public abstract Iterable<? extends N> getAllDependencies();
143
144        public int compareTo(N o) {
145            return (index < o.index) ? -1 : (index == o.index) ? 0 : 1;
146        }
147    }
148
149    /**
150     * Tarjan's algorithm to determine strongly connected components of a
151     * directed graph in linear time. Works on TarjanNode.
152     */
153    public static <D, N extends TarjanNode<D, N>> List<? extends List<? extends N>> tarjan(Iterable<? extends N> nodes) {
154        Tarjan<D, N> tarjan = new Tarjan<>();
155        return tarjan.findSCC(nodes);
156    }
157    //where
158    private static class Tarjan<D, N extends TarjanNode<D, N>> {
159
160        /** Unique node identifier. */
161        int index = 0;
162
163        /** List of SCCs found fso far. */
164        ListBuffer<List<N>> sccs = new ListBuffer<>();
165
166        /** Stack of all reacheable nodes from given root. */
167        ListBuffer<N> stack = new ListBuffer<>();
168
169        private List<? extends List<? extends N>> findSCC(Iterable<? extends N> nodes) {
170            for (N node : nodes) {
171                if (node.index == -1) {
172                    findSCC(node);
173                }
174            }
175            return sccs.toList();
176        }
177
178        private void findSCC(N v) {
179            visitNode(v);
180            for (N n: v.getAllDependencies()) {
181                if (n.index == -1) {
182                    //it's the first time we see this node
183                    findSCC(n);
184                    v.lowlink = Math.min(v.lowlink, n.lowlink);
185                } else if (stack.contains(n)) {
186                    //this node is already reachable from current root
187                    v.lowlink = Math.min(v.lowlink, n.index);
188                }
189            }
190            if (v.lowlink == v.index) {
191                //v is the root of a SCC
192                addSCC(v);
193            }
194        }
195
196        private void visitNode(N n) {
197            n.index = index;
198            n.lowlink = index;
199            index++;
200            stack.prepend(n);
201            n.active = true;
202        }
203
204        private void addSCC(N v) {
205            N n;
206            ListBuffer<N> cycle = new ListBuffer<>();
207            do {
208                n = stack.remove();
209                n.active = false;
210                cycle.add(n);
211            } while (n != v);
212            sccs.add(cycle.toList());
213        }
214    }
215
216    /**
217     * Debugging: dot representation of a set of connected nodes. The resulting
218     * dot representation will use {@code Node.toString} to display node labels
219     * and {@code Node.printDependency} to display edge labels. The resulting
220     * representation is also customizable with a graph name and a header.
221     */
222    public static <D, N extends DottableNode<D, N>> String toDot(Collection<? extends N> nodes, String name, String header) {
223        StringBuilder buf = new StringBuilder();
224        buf.append(String.format("digraph %s {\n", name));
225        buf.append(String.format("label = %s;\n", DotVisitor.wrap(header)));
226        DotVisitor<D, N> dotVisitor = new DotVisitor<>();
227        dotVisitor.visit(nodes, buf);
228        buf.append("}\n");
229        return buf.toString();
230    }
231
232    /**
233     * This visitor is used to dump the contents of a set of nodes of type {@link DottableNode}
234     * onto a string builder.
235     */
236    public static class DotVisitor<D, N extends DottableNode<D, N>> extends NodeVisitor<D, N, StringBuilder> {
237
238        @Override
239        public void visitDependency(DependencyKind dk, N from, N to, StringBuilder buf) {
240            buf.append(String.format("%s -> %s", from.hashCode(), to.hashCode()));
241            buf.append(formatProperties(from.dependencyAttributes(to, dk)));
242            buf.append('\n');
243        }
244
245        @Override
246        public void visitNode(N node, StringBuilder buf) {
247            buf.append(String.format("%s ", node.hashCode()));
248            buf.append(formatProperties(node.nodeAttributes()));
249            buf.append('\n');
250        }
251
252        protected String formatProperties(Properties p) {
253            return p.toString().replaceAll(",", " ")
254                .replaceAll("\\{", "[")
255                .replaceAll("\\}", "]");
256        }
257
258        protected static String wrap(String s) {
259            String res = "\"" + s + "\"";
260            return res.replaceAll("\n", "");
261        }
262    }
263}
264