|
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 |
|
26 package com.sun.tools.javac.util; |
|
27 |
|
28 /** <p><b>This is NOT part of any supported API. |
|
29 * If you write code that depends on this, you do so at your own risk. |
|
30 * This code and its internal interfaces are subject to change or |
|
31 * deletion without notice.</b> |
|
32 */ |
|
33 public class GraphUtils { |
|
34 |
|
35 /** |
|
36 * This class is a basic abstract class for representing a node. |
|
37 * A node is associated with a given data. |
|
38 */ |
|
39 public static abstract class Node<D> { |
|
40 public final D data; |
|
41 |
|
42 public Node(D data) { |
|
43 this.data = data; |
|
44 } |
|
45 |
|
46 public abstract Iterable<? extends Node<D>> getDependencies(); |
|
47 |
|
48 public abstract String printDependency(Node<D> to); |
|
49 |
|
50 @Override |
|
51 public String toString() { |
|
52 return data.toString(); |
|
53 } |
|
54 } |
|
55 |
|
56 /** |
|
57 * This class specialized Node, by adding elements that are required in order |
|
58 * to perform Tarjan computation of strongly connected components. |
|
59 */ |
|
60 public static abstract class TarjanNode<D> extends Node<D> implements Comparable<TarjanNode<D>> { |
|
61 int index = -1; |
|
62 int lowlink; |
|
63 boolean active; |
|
64 |
|
65 public TarjanNode(D data) { |
|
66 super(data); |
|
67 } |
|
68 |
|
69 public abstract Iterable<? extends TarjanNode<D>> getDependencies(); |
|
70 |
|
71 public int compareTo(TarjanNode<D> o) { |
|
72 return (index < o.index) ? -1 : (index == o.index) ? 0 : 1; |
|
73 } |
|
74 } |
|
75 |
|
76 /** |
|
77 * Tarjan's algorithm to determine strongly connected components of a |
|
78 * directed graph in linear time. Works on TarjanNode. |
|
79 */ |
|
80 public static <D, N extends TarjanNode<D>> List<? extends List<? extends N>> tarjan(Iterable<? extends N> nodes) { |
|
81 ListBuffer<List<N>> cycles = ListBuffer.lb(); |
|
82 ListBuffer<N> stack = ListBuffer.lb(); |
|
83 int index = 0; |
|
84 for (N node: nodes) { |
|
85 if (node.index == -1) { |
|
86 index += tarjan(node, index, stack, cycles); |
|
87 } |
|
88 } |
|
89 return cycles.toList(); |
|
90 } |
|
91 |
|
92 private static <D, N extends TarjanNode<D>> int tarjan(N v, int index, ListBuffer<N> stack, ListBuffer<List<N>> cycles) { |
|
93 v.index = index; |
|
94 v.lowlink = index; |
|
95 index++; |
|
96 stack.prepend(v); |
|
97 v.active = true; |
|
98 for (TarjanNode<D> nd: v.getDependencies()) { |
|
99 @SuppressWarnings("unchecked") |
|
100 N n = (N)nd; |
|
101 if (n.index == -1) { |
|
102 tarjan(n, index, stack, cycles); |
|
103 v.lowlink = Math.min(v.lowlink, n.lowlink); |
|
104 } else if (stack.contains(n)) { |
|
105 v.lowlink = Math.min(v.lowlink, n.index); |
|
106 } |
|
107 } |
|
108 if (v.lowlink == v.index) { |
|
109 N n; |
|
110 ListBuffer<N> cycle = ListBuffer.lb(); |
|
111 do { |
|
112 n = stack.remove(); |
|
113 n.active = false; |
|
114 cycle.add(n); |
|
115 } while (n != v); |
|
116 cycles.add(cycle.toList()); |
|
117 } |
|
118 return index; |
|
119 } |
|
120 |
|
121 /** |
|
122 * Debugging: dot representation of a set of connected nodes. The resulting |
|
123 * dot representation will use {@code Node.toString} to display node labels |
|
124 * and {@code Node.printDependency} to display edge labels. The resulting |
|
125 * representation is also customizable with a graph name and a header. |
|
126 */ |
|
127 public static <D> String toDot(Iterable<? extends TarjanNode<D>> nodes, String name, String header) { |
|
128 StringBuilder buf = new StringBuilder(); |
|
129 buf.append(String.format("digraph %s {\n", name)); |
|
130 buf.append(String.format("label = \"%s\";\n", header)); |
|
131 //dump nodes |
|
132 for (TarjanNode<D> n : nodes) { |
|
133 buf.append(String.format("%s [label = \"%s\"];\n", n.hashCode(), n.toString())); |
|
134 } |
|
135 //dump arcs |
|
136 for (TarjanNode<D> from : nodes) { |
|
137 for (TarjanNode<D> to : from.getDependencies()) { |
|
138 buf.append(String.format("%s -> %s [label = \" %s \"];\n", |
|
139 from.hashCode(), to.hashCode(), from.printDependency(to))); |
|
140 } |
|
141 } |
|
142 buf.append("}\n"); |
|
143 return buf.toString(); |
|
144 } |
|
145 } |