/*
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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;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Properties;
/** <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.
*/
public interface DependencyKind { }
/**
* Common superinterfaces to all graph nodes.
*/
public interface Node<D, N extends Node<D, N>> {
/**
* visitor method.
*/
<A> void accept(NodeVisitor<D, N, A> visitor, A arg);
}
/**
* Visitor for graph nodes.
*/
static abstract class NodeVisitor<D, N extends Node<D, N>, A> {
/**
* Visitor action for nodes.
*/
public abstract void visitNode(N node, A arg);
/**
* Visitor action for a dependency between 'from' and 'to' with given kind.
*/
public abstract void visitDependency(DependencyKind dk, N from, N to, A arg);
/**
* Visitor entry point.
*/
public void visit(Collection<? extends N> nodes, A arg) {
for (N n : new ArrayList<>(nodes)) {
n.accept(this, arg);
}
}
}
/**
* Optional interface for nodes supporting dot-based representation.
*/
public interface DottableNode<D, N extends DottableNode<D, N>> extends Node<D, N> {
/**
* Retrieves the set of dot attributes associated with the node.
*/
Properties nodeAttributes();
/**
* Retrieves the set of dot attributes associated with a given dependency.
*/
Properties dependencyAttributes(N to, DependencyKind dk);
}
/**
* This class is a basic abstract class for representing a node.
* A node is associated with a given data.
*/
public static abstract class AbstractNode<D, N extends AbstractNode<D, N>> implements Node<D, N> {
public final D data;
public AbstractNode(D data) {
this.data = data;
}
/**
* Get an array of the dependency kinds supported by this node.
*/
public abstract DependencyKind[] getSupportedDependencyKinds();
/**
* Get all dependencies of a given kind
*/
public abstract Collection<? extends N> getDependenciesByKind(DependencyKind dk);
@Override
public String toString() {
return data.toString();
}
@SuppressWarnings("unchecked")
public <A> void accept(NodeVisitor<D, N, A> visitor, A arg) {
visitor.visitNode((N)this, arg);
for (DependencyKind dk : getSupportedDependencyKinds()) {
for (N dep : new ArrayList<>(getDependenciesByKind(dk))) {
visitor.visitDependency(dk, (N)this, dep, arg);
}
}
}
}
/**
* 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, N extends TarjanNode<D, N>> extends AbstractNode<D, N>
implements Comparable<N> {
int index = -1;
int lowlink;
boolean active;
public TarjanNode(D data) {
super(data);
}
public abstract Iterable<? extends N> getAllDependencies();
public int compareTo(N 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, N>> 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, N>> {
/** Unique node identifier. */
int index = 0;
/** List of SCCs found fso 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 (N n: v.getAllDependencies()) {
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, N extends DottableNode<D, N>> String toDot(Collection<? extends N> nodes, String name, String header) {
StringBuilder buf = new StringBuilder();
buf.append(String.format("digraph %s {\n", name));
buf.append(String.format("label = %s;\n", DotVisitor.wrap(header)));
DotVisitor<D, N> dotVisitor = new DotVisitor<>();
dotVisitor.visit(nodes, buf);
buf.append("}\n");
return buf.toString();
}
/**
* This visitor is used to dump the contents of a set of nodes of type {@link DottableNode}
* onto a string builder.
*/
public static class DotVisitor<D, N extends DottableNode<D, N>> extends NodeVisitor<D, N, StringBuilder> {
@Override
public void visitDependency(DependencyKind dk, N from, N to, StringBuilder buf) {
buf.append(String.format("%s -> %s", from.hashCode(), to.hashCode()));
buf.append(formatProperties(from.dependencyAttributes(to, dk)));
buf.append('\n');
}
@Override
public void visitNode(N node, StringBuilder buf) {
buf.append(String.format("%s ", node.hashCode()));
buf.append(formatProperties(node.nodeAttributes()));
buf.append('\n');
}
protected String formatProperties(Properties p) {
return p.toString().replaceAll(",", " ")
.replaceAll("\\{", "[")
.replaceAll("\\}", "]");
}
protected static String wrap(String s) {
String res = "\"" + s + "\"";
return res.replaceAll("\n", "");
}
}
}