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* 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
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*/
package com.sun.tools.javac.util;
/** <p><b>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.</b>
*/
public class GraphUtils {
/**
* Basic interface for defining various dependency kinds. All dependency kinds
* must at least support basic capabilities to tell the DOT engine how to render them.
*/
public interface DependencyKind {
/**
* Returns the DOT representation (to be used in a {@code style} attribute
* that's most suited for this dependency kind.
*/
String getDotStyle();
}
/**
* This class is a basic abstract class for representing a node.
* A node is associated with a given data.
*/
public static abstract class Node<D> {
public final D data;
public Node(D data) {
this.data = data;
}
/**
* Get an array of the dependency kinds supported by this node.
*/
public abstract DependencyKind[] getSupportedDependencyKinds();
/**
* Get all dependencies, regardless of their kind.
*/
public abstract Iterable<? extends Node<D>> getAllDependencies();
/**
* Get a name for the dependency (of given kind) linking this node to a given node
*/
public abstract String getDependencyName(Node<D> to, DependencyKind dk);
@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<D> extends Node<D> implements Comparable<TarjanNode<D>> {
int index = -1;
int lowlink;
boolean active;
public TarjanNode(D data) {
super(data);
}
public abstract Iterable<? extends TarjanNode<D>> getAllDependencies();
public abstract Iterable<? extends TarjanNode<D>> getDependenciesByKind(DependencyKind dk);
public int compareTo(TarjanNode<D> 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 <D, N extends TarjanNode<D>> List<? extends List<? extends N>> tarjan(Iterable<? extends N> nodes) {
Tarjan<D, N> tarjan = new Tarjan<>();
return tarjan.findSCC(nodes);
}
//where
private static class Tarjan<D, N extends TarjanNode<D>> {
/** Unique node identifier. */
int index = 0;
/** List of SCCs found so far. */
ListBuffer<List<N>> sccs = new ListBuffer<>();
/** Stack of all reacheable nodes from given root. */
ListBuffer<N> stack = new ListBuffer<>();
private List<? extends List<? extends N>> findSCC(Iterable<? extends N> nodes) {
for (N node : nodes) {
if (node.index == -1) {
findSCC(node);
}
}
return sccs.toList();
}
private void findSCC(N v) {
visitNode(v);
for (TarjanNode<D> tn : v.getAllDependencies()) {
@SuppressWarnings("unchecked")
N n = (N)tn;
if (n.index == -1) {
//it's the first time we see this node
findSCC(n);
v.lowlink = Math.min(v.lowlink, n.lowlink);
} else if (stack.contains(n)) {
//this node is already reachable from current root
v.lowlink = Math.min(v.lowlink, n.index);
}
}
if (v.lowlink == v.index) {
//v is the root of a SCC
addSCC(v);
}
}
private void visitNode(N n) {
n.index = index;
n.lowlink = index;
index++;
stack.prepend(n);
n.active = true;
}
private void addSCC(N v) {
N n;
ListBuffer<N> cycle = new ListBuffer<>();
do {
n = stack.remove();
n.active = false;
cycle.add(n);
} while (n != v);
sccs.add(cycle.toList());
}
}
/**
* 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 <D> String toDot(Iterable<? extends TarjanNode<D>> 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<D> n : nodes) {
buf.append(String.format("%s [label = \"%s\"];\n", n.hashCode(), n.toString()));
}
//dump arcs
for (TarjanNode<D> from : nodes) {
for (DependencyKind dk : from.getSupportedDependencyKinds()) {
for (TarjanNode<D> to : from.getDependenciesByKind(dk)) {
buf.append(String.format("%s -> %s [label = \" %s \" style = %s ];\n",
from.hashCode(), to.hashCode(), from.getDependencyName(to, dk), dk.getDotStyle()));
}
}
}
buf.append("}\n");
return buf.toString();
}
}