diff -r 073696f59241 -r 2154ed9ff6c8 src/share/classes/com/sun/tools/javac/util/GraphUtils.java
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/src/share/classes/com/sun/tools/javac/util/GraphUtils.java Tue Feb 12 19:25:09 2013 +0000
@@ -0,0 +1,145 @@
+/*
+ * Copyright (c) 1999, 2013, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation. Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package com.sun.tools.javac.util;
+
+/**
This is NOT part of any supported API.
+ * If you write code that depends on this, you do so at your own risk.
+ * This code and its internal interfaces are subject to change or
+ * deletion without notice.
+ */
+public class GraphUtils {
+
+ /**
+ * This class is a basic abstract class for representing a node.
+ * A node is associated with a given data.
+ */
+ public static abstract class Node {
+ public final D data;
+
+ public Node(D data) {
+ this.data = data;
+ }
+
+ public abstract Iterable extends Node> getDependencies();
+
+ public abstract String printDependency(Node to);
+
+ @Override
+ public String toString() {
+ return data.toString();
+ }
+ }
+
+ /**
+ * This class specialized Node, by adding elements that are required in order
+ * to perform Tarjan computation of strongly connected components.
+ */
+ public static abstract class TarjanNode extends Node implements Comparable> {
+ int index = -1;
+ int lowlink;
+ boolean active;
+
+ public TarjanNode(D data) {
+ super(data);
+ }
+
+ public abstract Iterable extends TarjanNode> getDependencies();
+
+ public int compareTo(TarjanNode o) {
+ return (index < o.index) ? -1 : (index == o.index) ? 0 : 1;
+ }
+ }
+
+ /**
+ * Tarjan's algorithm to determine strongly connected components of a
+ * directed graph in linear time. Works on TarjanNode.
+ */
+ public static > List extends List extends N>> tarjan(Iterable extends N> nodes) {
+ ListBuffer> cycles = ListBuffer.lb();
+ ListBuffer stack = ListBuffer.lb();
+ int index = 0;
+ for (N node: nodes) {
+ if (node.index == -1) {
+ index += tarjan(node, index, stack, cycles);
+ }
+ }
+ return cycles.toList();
+ }
+
+ private static > int tarjan(N v, int index, ListBuffer stack, ListBuffer> cycles) {
+ v.index = index;
+ v.lowlink = index;
+ index++;
+ stack.prepend(v);
+ v.active = true;
+ for (TarjanNode nd: v.getDependencies()) {
+ @SuppressWarnings("unchecked")
+ N n = (N)nd;
+ if (n.index == -1) {
+ tarjan(n, index, stack, cycles);
+ v.lowlink = Math.min(v.lowlink, n.lowlink);
+ } else if (stack.contains(n)) {
+ v.lowlink = Math.min(v.lowlink, n.index);
+ }
+ }
+ if (v.lowlink == v.index) {
+ N n;
+ ListBuffer cycle = ListBuffer.lb();
+ do {
+ n = stack.remove();
+ n.active = false;
+ cycle.add(n);
+ } while (n != v);
+ cycles.add(cycle.toList());
+ }
+ return index;
+ }
+
+ /**
+ * Debugging: dot representation of a set of connected nodes. The resulting
+ * dot representation will use {@code Node.toString} to display node labels
+ * and {@code Node.printDependency} to display edge labels. The resulting
+ * representation is also customizable with a graph name and a header.
+ */
+ public static String toDot(Iterable extends TarjanNode> nodes, String name, String header) {
+ StringBuilder buf = new StringBuilder();
+ buf.append(String.format("digraph %s {\n", name));
+ buf.append(String.format("label = \"%s\";\n", header));
+ //dump nodes
+ for (TarjanNode n : nodes) {
+ buf.append(String.format("%s [label = \"%s\"];\n", n.hashCode(), n.toString()));
+ }
+ //dump arcs
+ for (TarjanNode from : nodes) {
+ for (TarjanNode to : from.getDependencies()) {
+ buf.append(String.format("%s -> %s [label = \" %s \"];\n",
+ from.hashCode(), to.hashCode(), from.printDependency(to)));
+ }
+ }
+ buf.append("}\n");
+ return buf.toString();
+ }
+}