hotspot/agent/src/share/classes/sun/jvm/hotspot/utilities/HeapGXLWriter.java - edge/openjdk - Git at Google

 /*
  * Copyright (c) 2004, 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.
  *
  * 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 sun.jvm.hotspot.utilities;

 import java.io.*;
 import java.util.*;
 import sun.jvm.hotspot.oops.*;
 import sun.jvm.hotspot.runtime.*;

 /**
  * <p>This class writes Java heap in Graph eXchange Language (GXL)
  * format. GXL is an open standard for serializing arbitrary graphs in
  * XML syntax.</p>
  *
  * <p>A GXL document contains one or more graphs. A graph contains
  * nodes and edges. Both nodes and edges can have attributes. graphs,
  * nodes, edges and attributes are represented by XML elements graph,
  * node, edge and attr respectively. Attributes can be typed. GXL
  * supports locator, bool, int, float, bool, string, enum as well as
  * set, seq, bag, tup types. Nodes must have a XML attribute 'id' that
  * is unique id of the node in the GXL document. Edges must have
  * 'from' and 'to' XML attributes that are ids of from and to nodes.</p>
  *
  * <p>Java heap to GXL document mapping:</p>
  * <ul>
  * <li>Java object - GXL node.
  * <li>Java primitive field - GXL attribute (type mapping below).
  * <li>Java reference field - GXL edge from referee to referent node.
  * <li>Java primitive array - GXL node with seq type attribute.
  * <li>Java char array - GXL node with one attribute of string type.
  * <li>Java object array - GXL node and 'length' edges.
  * </ul>
  *
  * <p>Java primitive to GXL type mapping:</p>
  * <ul>
  * <li>Java byte, int, short, long - GXL int attribute
  * <li>Java float, double - GXL float attribute
  * <li>Java boolean - GXL bool atttribute
  * <li>Java char - GXL string attribute
  * </ul>
  *
  * Exact Java primitive type code is written in 'kind' attribute of
  * 'attr' element.  Type code is specified in JVM spec. second edition
  * section 4.3.2 (Field Descriptor).
  *
  * @see <a href="http://www.gupro.de/GXL/">GXL</a>
  * @see <a href="http://www.gupro.de/GXL/dtd/dtd.html">GXL DTD</a>
  */

 public class HeapGXLWriter extends AbstractHeapGraphWriter {
     public void write(String fileName) throws IOException {
         out = new PrintWriter(new BufferedWriter(new FileWriter(fileName)));
         super.write();
         if (out.checkError()) {
             throw new IOException();
         }
         out.flush();
     }

     protected void writeHeapHeader() throws IOException {
         // XML processing instruction
         out.print("<?xml version='1.0' encoding='");
         out.print(ENCODING);
         out.println("'?>");

         out.println("<gxl>");
         out.println("<graph id='JavaHeap'>");

         // document properties
         writeAttribute("creation-date", "string", new Date().toString());

         // write VM info
         writeVMInfo();

         // emit a node for null
         out.print("<node id='");
         out.print(getID(null));
         out.println("'/>");
     }

     protected void writeObjectHeader(Oop oop) throws IOException  {
         refFields = new ArrayList();
         isArray = oop.isArray();

         // generate an edge for instanceof relation
         // between object node and it's class node.
         writeEdge(oop, oop.getKlass().getJavaMirror(), "instanceof");

         out.print("<node id='");
         out.print(getID(oop));
         out.println("'>");
     }

     protected void writeObjectFooter(Oop oop) throws IOException  {
         out.println("</node>");

         // write the reference fields as edges
         for (Iterator itr = refFields.iterator(); itr.hasNext();) {
             OopField field = (OopField) itr.next();
             Oop ref = field.getValue(oop);

             String name = field.getID().getName();
             if (isArray) {
                 // for arrays elements we use element<index> pattern
                 name = "element" + name;
             } else {
                 name = identifierToXMLName(name);
             }
             writeEdge(oop, ref, name);
         }
         refFields = null;
     }

     protected void writeObjectArray(ObjArray array) throws IOException {
         writeObjectHeader(array);
         writeArrayLength(array);
         writeObjectFields(array);
         writeObjectFooter(array);
     }

     protected void writePrimitiveArray(TypeArray array)
         throws IOException  {
         writeObjectHeader(array);
         // write array length
         writeArrayLength(array);
         // write array elements
         out.println("\t<attr name='elements'>");
         TypeArrayKlass klass = (TypeArrayKlass) array.getKlass();
         if (klass.getElementType() == TypeArrayKlass.T_CHAR) {
             // char[] special treatment -- write it as string
             out.print("\t<string>");
             out.print(escapeXMLChars(OopUtilities.charArrayToString(array)));
             out.println("</string>");
         } else {
             out.println("\t<seq>");
             writeObjectFields(array);
             out.println("\t</seq>");
         }
         out.println("\t</attr>");
         writeObjectFooter(array);
     }

     protected void writeClass(Instance instance) throws IOException  {
         writeObjectHeader(instance);
         Klass reflectedType = java_lang_Class.asKlass(instance);
         boolean isInstanceKlass = (reflectedType instanceof InstanceKlass);
         // reflectedType is null for primitive types (int.class etc).
         if (reflectedType != null) {
             Symbol name = reflectedType.getName();
             if (name != null) {
                 // write class name as an attribute
                 writeAttribute("class-name", "string", name.asString());
             }
             if (isInstanceKlass) {
                 // write object-size as an attribute
                 long sizeInBytes = reflectedType.getLayoutHelper();
                 writeAttribute("object-size", "int",
                                Long.toString(sizeInBytes));
                 // write static fields of this class.
                 writeObjectFields((InstanceKlass)reflectedType);
             }
         }
         out.println("</node>");

         // write edges for super class and direct interfaces
         if (reflectedType != null) {
             Klass superType = reflectedType.getSuper();
             Oop superMirror = (superType == null)?
                               null : superType.getJavaMirror();
             writeEdge(instance, superMirror, "extends");
             if (isInstanceKlass) {
                 // write edges for directly implemented interfaces
                 InstanceKlass ik = (InstanceKlass) reflectedType;
                 KlassArray interfaces = ik.getLocalInterfaces();
                 final int len = interfaces.length();
                 for (int i = 0; i < len; i++) {
                     Klass k = interfaces.getAt(i);
                     writeEdge(instance, k.getJavaMirror(), "implements");
                 }

                 // write loader
                 Oop loader = ik.getClassLoader();
                 writeEdge(instance, loader, "loaded-by");

                 // write signers NYI
                 // Oop signers = ik.getJavaMirror().getSigners();
                 writeEdge(instance, null, "signed-by");

                 // write protection domain NYI
                 // Oop protectionDomain = ik.getJavaMirror().getProtectionDomain();
                 writeEdge(instance, null, "protection-domain");

                 // write edges for static reference fields from this class
                 for (Iterator itr = refFields.iterator(); itr.hasNext();) {
                     OopField field = (OopField) itr.next();
                     Oop ref = field.getValue(reflectedType);
                     String name = field.getID().getName();
                     writeEdge(instance, ref, identifierToXMLName(name));
                 }
             }
         }
         refFields = null;
     }

     protected void writeReferenceField(Oop oop, OopField field)
         throws IOException {
         refFields.add(field);
     }

     protected void writeByteField(Oop oop, ByteField field)
         throws IOException {
         writeField(field, "int", "B", Byte.toString(field.getValue(oop)));
     }

     protected void writeCharField(Oop oop, CharField field)
         throws IOException {
         writeField(field, "string", "C",
                    escapeXMLChars(Character.toString(field.getValue(oop))));
     }

     protected void writeBooleanField(Oop oop, BooleanField field)
         throws IOException {
         writeField(field, "bool", "Z", Boolean.toString(field.getValue(oop)));
     }

     protected void writeShortField(Oop oop, ShortField field)
         throws IOException {
         writeField(field, "int", "S", Short.toString(field.getValue(oop)));
     }

     protected void writeIntField(Oop oop, IntField field)
         throws IOException {
         writeField(field, "int", "I", Integer.toString(field.getValue(oop)));
     }

     protected void writeLongField(Oop oop, LongField field)
         throws IOException {
         writeField(field, "int", "J", Long.toString(field.getValue(oop)));
     }

     protected void writeFloatField(Oop oop, FloatField field)
         throws IOException {
         writeField(field, "float", "F", Float.toString(field.getValue(oop)));
     }

     protected void writeDoubleField(Oop oop, DoubleField field)
         throws IOException {
         writeField(field, "float", "D", Double.toString(field.getValue(oop)));
     }

     protected void writeHeapFooter() throws IOException  {
         out.println("</graph>");
         out.println("</gxl>");
     }

     //-- Internals only below this point

     // Java identifier to XML NMTOKEN type string
     private static String identifierToXMLName(String name) {
         // for now, just replace '$' with '_'
         return name.replace('$', '_');
     }

     // escapes XML meta-characters and illegal characters
     private static String escapeXMLChars(String s) {
         // FIXME: is there a better way or API?
         StringBuffer result = null;
         for(int i = 0, max = s.length(), delta = 0; i < max; i++) {
             char c = s.charAt(i);
             String replacement = null;
             if (c == '&') {
                 replacement = "&amp;";
             } else if (c == '<') {
                 replacement = "&lt;";
             } else if (c == '>') {
                 replacement = "&gt;";
             } else if (c == '"') {
                 replacement = "&quot;";
             } else if (c == '\'') {
                 replacement = "&apos;";
             } else if (c <  '\u0020' || (c > '\ud7ff' && c < '\ue000') ||
                        c == '\ufffe' || c == '\uffff') {
                 // These are illegal in XML -- put these in a CDATA section.
                 // Refer to section 2.2 Characters in XML specification at
                 // http://www.w3.org/TR/2004/REC-xml-20040204/
                 replacement = "<![CDATA[&#x" +
                     Integer.toHexString((int)c) + ";]]>";
             }

             if (replacement != null) {
                 if (result == null) {
                     result = new StringBuffer(s);
                 }
                 result.replace(i + delta, i + delta + 1, replacement);
                 delta += (replacement.length() - 1);
             }
         }
         if (result == null) {
             return s;
         }
         return result.toString();
     }

     private static String getID(Oop oop) {
         // address as unique id for node -- prefixed by "ID_".
         if (oop == null) {
             return "ID_NULL";
         } else {
             return "ID_" + oop.getHandle().toString();
         }
     }

     private void writeArrayLength(Array array) throws IOException {
         writeAttribute("length", "int",
                        Integer.toString((int) array.getLength()));
     }

     private void writeAttribute(String name, String type, String value) {
         out.print("\t<attr name='");
         out.print(name);
         out.print("'><");
         out.print(type);
         out.print('>');
         out.print(value);
         out.print("</");
         out.print(type);
         out.println("></attr>");
     }

     private void writeEdge(Oop from, Oop to, String name) throws IOException {
         out.print("<edge from='");
         out.print(getID(from));
         out.print("' to='");
         out.print(getID(to));
         out.println("'>");
         writeAttribute("name", "string", name);
         out.println("</edge>");
     }

     private void writeField(Field field, String type, String kind,
                             String value) throws IOException  {
         // 'type' is GXL type of the attribute
         // 'kind' is Java type code ("B", "C", "Z", "S", "I", "J", "F", "D")
         if (isArray) {
             out.print('\t');
         } else {
             out.print("\t<attr name='");
             String name = field.getID().getName();
             out.print(identifierToXMLName(name));
             out.print("' kind='");
             out.print(kind);
             out.print("'>");
         }
         out.print('<');
         out.print(type);
         out.print('>');
         out.print(value);
         out.print("</");
         out.print(type);
         out.print('>');
         if (isArray) {
             out.println();
         } else {
             out.println("</attr>");
         }
     }

     private void writeVMInfo() throws IOException {
         VM vm = VM.getVM();
         writeAttribute("vm-version", "string", vm.getVMRelease());
         writeAttribute("vm-type", "string",
                        (vm.isClientCompiler())? "client" :
                        ((vm.isServerCompiler())? "server" : "core"));
         writeAttribute("os", "string", vm.getOS());
         writeAttribute("cpu", "string", vm.getCPU());
         writeAttribute("pointer-size", "string",
                        Integer.toString((int)vm.getOopSize() * 8));
     }

     // XML encoding that we'll use
     private static final String ENCODING = "UTF-8";

     // reference fields of currently visited object
     private List/*<OopField>*/ refFields;
     // are we writing an array now?
     private boolean isArray;
     private PrintWriter out;
 }
	/*
	* Copyright (c) 2004, 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.
	*
	* 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 sun.jvm.hotspot.utilities;

	import java.io.*;
	import java.util.*;
	import sun.jvm.hotspot.oops.*;
	import sun.jvm.hotspot.runtime.*;

	/**
	* <p>This class writes Java heap in Graph eXchange Language (GXL)
	* format. GXL is an open standard for serializing arbitrary graphs in
	* XML syntax.</p>
	*
	* <p>A GXL document contains one or more graphs. A graph contains
	* nodes and edges. Both nodes and edges can have attributes. graphs,
	* nodes, edges and attributes are represented by XML elements graph,
	* node, edge and attr respectively. Attributes can be typed. GXL
	* supports locator, bool, int, float, bool, string, enum as well as
	* set, seq, bag, tup types. Nodes must have a XML attribute 'id' that
	* is unique id of the node in the GXL document. Edges must have
	* 'from' and 'to' XML attributes that are ids of from and to nodes.</p>
	*
	* <p>Java heap to GXL document mapping:</p>
	* <ul>
	* <li>Java object - GXL node.
	* <li>Java primitive field - GXL attribute (type mapping below).
	* <li>Java reference field - GXL edge from referee to referent node.
	* <li>Java primitive array - GXL node with seq type attribute.
	* <li>Java char array - GXL node with one attribute of string type.
	* <li>Java object array - GXL node and 'length' edges.
	* </ul>
	*
	* <p>Java primitive to GXL type mapping:</p>
	* <ul>
	* <li>Java byte, int, short, long - GXL int attribute
	* <li>Java float, double - GXL float attribute
	* <li>Java boolean - GXL bool atttribute
	* <li>Java char - GXL string attribute
	* </ul>
	*
	* Exact Java primitive type code is written in 'kind' attribute of
	* 'attr' element. Type code is specified in JVM spec. second edition
	* section 4.3.2 (Field Descriptor).
	*
	* @see <a href="http://www.gupro.de/GXL/">GXL</a>
	* @see <a href="http://www.gupro.de/GXL/dtd/dtd.html">GXL DTD</a>
	*/

	public class HeapGXLWriter extends AbstractHeapGraphWriter {
	public void write(String fileName) throws IOException {
	out = new PrintWriter(new BufferedWriter(new FileWriter(fileName)));
	super.write();
	if (out.checkError()) {
	throw new IOException();
	}
	out.flush();
	}

	protected void writeHeapHeader() throws IOException {
	// XML processing instruction
	out.print("<?xml version='1.0' encoding='");
	out.print(ENCODING);
	out.println("'?>");

	out.println("<gxl>");
	out.println("<graph id='JavaHeap'>");

	// document properties
	writeAttribute("creation-date", "string", new Date().toString());

	// write VM info
	writeVMInfo();

	// emit a node for null
	out.print("<node id='");
	out.print(getID(null));
	out.println("'/>");
	}

	protected void writeObjectHeader(Oop oop) throws IOException {
	refFields = new ArrayList();
	isArray = oop.isArray();

	// generate an edge for instanceof relation
	// between object node and it's class node.
	writeEdge(oop, oop.getKlass().getJavaMirror(), "instanceof");

	out.print("<node id='");
	out.print(getID(oop));
	out.println("'>");
	}

	protected void writeObjectFooter(Oop oop) throws IOException {
	out.println("</node>");

	// write the reference fields as edges
	for (Iterator itr = refFields.iterator(); itr.hasNext();) {
	OopField field = (OopField) itr.next();
	Oop ref = field.getValue(oop);

	String name = field.getID().getName();
	if (isArray) {
	// for arrays elements we use element<index> pattern
	name = "element" + name;
	} else {
	name = identifierToXMLName(name);
	}
	writeEdge(oop, ref, name);
	}
	refFields = null;
	}

	protected void writeObjectArray(ObjArray array) throws IOException {
	writeObjectHeader(array);
	writeArrayLength(array);
	writeObjectFields(array);
	writeObjectFooter(array);
	}

	protected void writePrimitiveArray(TypeArray array)
	throws IOException {
	writeObjectHeader(array);
	// write array length
	writeArrayLength(array);
	// write array elements
	out.println("\t<attr name='elements'>");
	TypeArrayKlass klass = (TypeArrayKlass) array.getKlass();
	if (klass.getElementType() == TypeArrayKlass.T_CHAR) {
	// char[] special treatment -- write it as string
	out.print("\t<string>");
	out.print(escapeXMLChars(OopUtilities.charArrayToString(array)));
	out.println("</string>");
	} else {
	out.println("\t<seq>");
	writeObjectFields(array);
	out.println("\t</seq>");
	}
	out.println("\t</attr>");
	writeObjectFooter(array);
	}

	protected void writeClass(Instance instance) throws IOException {
	writeObjectHeader(instance);
	Klass reflectedType = java_lang_Class.asKlass(instance);
	boolean isInstanceKlass = (reflectedType instanceof InstanceKlass);
	// reflectedType is null for primitive types (int.class etc).
	if (reflectedType != null) {
	Symbol name = reflectedType.getName();
	if (name != null) {
	// write class name as an attribute
	writeAttribute("class-name", "string", name.asString());
	}
	if (isInstanceKlass) {
	// write object-size as an attribute
	long sizeInBytes = reflectedType.getLayoutHelper();
	writeAttribute("object-size", "int",
	Long.toString(sizeInBytes));
	// write static fields of this class.
	writeObjectFields((InstanceKlass)reflectedType);
	}
	}
	out.println("</node>");

	// write edges for super class and direct interfaces
	if (reflectedType != null) {
	Klass superType = reflectedType.getSuper();
	Oop superMirror = (superType == null)?
	null : superType.getJavaMirror();
	writeEdge(instance, superMirror, "extends");
	if (isInstanceKlass) {
	// write edges for directly implemented interfaces
	InstanceKlass ik = (InstanceKlass) reflectedType;
	KlassArray interfaces = ik.getLocalInterfaces();
	final int len = interfaces.length();
	for (int i = 0; i < len; i++) {
	Klass k = interfaces.getAt(i);
	writeEdge(instance, k.getJavaMirror(), "implements");
	}

	// write loader
	Oop loader = ik.getClassLoader();
	writeEdge(instance, loader, "loaded-by");

	// write signers NYI
	// Oop signers = ik.getJavaMirror().getSigners();
	writeEdge(instance, null, "signed-by");

	// write protection domain NYI
	// Oop protectionDomain = ik.getJavaMirror().getProtectionDomain();
	writeEdge(instance, null, "protection-domain");

	// write edges for static reference fields from this class
	for (Iterator itr = refFields.iterator(); itr.hasNext();) {
	OopField field = (OopField) itr.next();
	Oop ref = field.getValue(reflectedType);
	String name = field.getID().getName();
	writeEdge(instance, ref, identifierToXMLName(name));
	}
	}
	}
	refFields = null;
	}

	protected void writeReferenceField(Oop oop, OopField field)
	throws IOException {
	refFields.add(field);
	}

	protected void writeByteField(Oop oop, ByteField field)
	throws IOException {
	writeField(field, "int", "B", Byte.toString(field.getValue(oop)));
	}

	protected void writeCharField(Oop oop, CharField field)
	throws IOException {
	writeField(field, "string", "C",
	escapeXMLChars(Character.toString(field.getValue(oop))));
	}

	protected void writeBooleanField(Oop oop, BooleanField field)
	throws IOException {
	writeField(field, "bool", "Z", Boolean.toString(field.getValue(oop)));
	}

	protected void writeShortField(Oop oop, ShortField field)
	throws IOException {
	writeField(field, "int", "S", Short.toString(field.getValue(oop)));
	}

	protected void writeIntField(Oop oop, IntField field)
	throws IOException {
	writeField(field, "int", "I", Integer.toString(field.getValue(oop)));
	}

	protected void writeLongField(Oop oop, LongField field)
	throws IOException {
	writeField(field, "int", "J", Long.toString(field.getValue(oop)));
	}

	protected void writeFloatField(Oop oop, FloatField field)
	throws IOException {
	writeField(field, "float", "F", Float.toString(field.getValue(oop)));
	}

	protected void writeDoubleField(Oop oop, DoubleField field)
	throws IOException {
	writeField(field, "float", "D", Double.toString(field.getValue(oop)));
	}

	protected void writeHeapFooter() throws IOException {
	out.println("</graph>");
	out.println("</gxl>");
	}

	//-- Internals only below this point

	// Java identifier to XML NMTOKEN type string
	private static String identifierToXMLName(String name) {
	// for now, just replace '$' with '_'
	return name.replace('$', '_');
	}

	// escapes XML meta-characters and illegal characters
	private static String escapeXMLChars(String s) {
	// FIXME: is there a better way or API?
	StringBuffer result = null;
	for(int i = 0, max = s.length(), delta = 0; i < max; i++) {
	char c = s.charAt(i);
	String replacement = null;
	if (c == '&') {
	replacement = "&";
	} else if (c == '<') {
	replacement = "<";
	} else if (c == '>') {
	replacement = ">";
	} else if (c == '"') {
	replacement = """;
	} else if (c == '\'') {
	replacement = "'";
	} else if (c < '\u0020' \|\| (c > '\ud7ff' && c < '\ue000') \|\|
	c == '\ufffe' \|\| c == '\uffff') {
	// These are illegal in XML -- put these in a CDATA section.
	// Refer to section 2.2 Characters in XML specification at
	// http://www.w3.org/TR/2004/REC-xml-20040204/
	replacement = "<![CDATA[&#x" +
	Integer.toHexString((int)c) + ";]]>";
	}

	if (replacement != null) {
	if (result == null) {
	result = new StringBuffer(s);
	}
	result.replace(i + delta, i + delta + 1, replacement);
	delta += (replacement.length() - 1);
	}
	}
	if (result == null) {
	return s;
	}
	return result.toString();
	}

	private static String getID(Oop oop) {
	// address as unique id for node -- prefixed by "ID_".
	if (oop == null) {
	return "ID_NULL";
	} else {
	return "ID_" + oop.getHandle().toString();
	}
	}

	private void writeArrayLength(Array array) throws IOException {
	writeAttribute("length", "int",
	Integer.toString((int) array.getLength()));
	}

	private void writeAttribute(String name, String type, String value) {
	out.print("\t<attr name='");
	out.print(name);
	out.print("'><");
	out.print(type);
	out.print('>');
	out.print(value);
	out.print("</");
	out.print(type);
	out.println("></attr>");
	}

	private void writeEdge(Oop from, Oop to, String name) throws IOException {
	out.print("<edge from='");
	out.print(getID(from));
	out.print("' to='");
	out.print(getID(to));
	out.println("'>");
	writeAttribute("name", "string", name);
	out.println("</edge>");
	}

	private void writeField(Field field, String type, String kind,
	String value) throws IOException {
	// 'type' is GXL type of the attribute
	// 'kind' is Java type code ("B", "C", "Z", "S", "I", "J", "F", "D")
	if (isArray) {
	out.print('\t');
	} else {
	out.print("\t<attr name='");
	String name = field.getID().getName();
	out.print(identifierToXMLName(name));
	out.print("' kind='");
	out.print(kind);
	out.print("'>");
	}
	out.print('<');
	out.print(type);
	out.print('>');
	out.print(value);
	out.print("</");
	out.print(type);
	out.print('>');
	if (isArray) {
	out.println();
	} else {
	out.println("</attr>");
	}
	}

	private void writeVMInfo() throws IOException {
	VM vm = VM.getVM();
	writeAttribute("vm-version", "string", vm.getVMRelease());
	writeAttribute("vm-type", "string",
	(vm.isClientCompiler())? "client" :
	((vm.isServerCompiler())? "server" : "core"));
	writeAttribute("os", "string", vm.getOS());
	writeAttribute("cpu", "string", vm.getCPU());
	writeAttribute("pointer-size", "string",
	Integer.toString((int)vm.getOopSize() * 8));
	}

	// XML encoding that we'll use
	private static final String ENCODING = "UTF-8";

	// reference fields of currently visited object
	private List/<OopField>/ refFields;
	// are we writing an array now?
	private boolean isArray;
	private PrintWriter out;
	}