com.sun.tools.javac.util.GraphUtils Maven / Gradle / Ivy
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/*
* 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
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*/
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 {
/**
* 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 {
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> getAllDependencies();
/**
* Get a name for the dependency (of given kind) linking this node to a given node
*/
public abstract String getDependencyName(Node 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 extends Node implements Comparable> {
int index = -1;
int lowlink;
boolean active;
public TarjanNode(D data) {
super(data);
}
public abstract Iterable> getAllDependencies();
public abstract Iterable> getDependenciesByKind(DependencyKind dk);
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> tarjan(Iterable nodes) {
ListBuffer> cycles = new ListBuffer<>();
ListBuffer stack = new ListBuffer<>();
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.getAllDependencies()) {
@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 = new ListBuffer<>();
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> 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 (DependencyKind dk : from.getSupportedDependencyKinds()) {
for (TarjanNode 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();
}
}