path: root/src/main/java/org/apache/bcel/classfile/JavaClass.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License. 
 *
 */
package org.apache.bcel.classfile;

import java.io.ByteArrayOutputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.List;
import java.util.Set;
import java.util.StringTokenizer;
import java.util.TreeSet;
import org.apache.bcel.Constants;
import org.apache.bcel.generic.Type;
import org.apache.bcel.util.BCELComparator;
import org.apache.bcel.util.ClassQueue;
import org.apache.bcel.util.SyntheticRepository;

/**
 * Represents a Java class, i.e., the data structures, constant pool,
 * fields, methods and commands contained in a Java .class file.
 * See <a href="ftp://java.sun.com/docs/specs/">JVM specification</a> for details.
 * The intent of this class is to represent a parsed or otherwise existing
 * class file.  Those interested in programatically generating classes
 * should see the <a href="../generic/ClassGen.html">ClassGen</a> class.

 * @version $Id$
 * @see org.apache.bcel.generic.ClassGen
 * @author  <A HREF="mailto:m.dahm@gmx.de">M. Dahm</A>
 */
public class JavaClass extends AccessFlags implements Cloneable, Node, Comparable<JavaClass> {

    private static final long serialVersionUID = 2179314813560563755L;
    private String file_name;
    private String package_name;
    private String source_file_name = "<Unknown>";
    private int class_name_index;
    private int superclass_name_index;
    private String class_name;
    private String superclass_name;
    private int major, minor; // Compiler version
    private ConstantPool constant_pool; // Constant pool
    private int[] interfaces; // implemented interfaces
    private String[] interface_names;
    private Field[] fields; // Fields, i.e., variables of class
    private Method[] methods; // methods defined in the class
    private Attribute[] attributes; // attributes defined in the class
    private AnnotationEntry[] annotations;   // annotations defined on the class
    private byte source = HEAP; // Generated in memory
    private boolean isAnonymous = false;
    private boolean isNested = false;
    private boolean computedNestedTypeStatus = false;
    public static final byte HEAP = 1;
    public static final byte FILE = 2;
    public static final byte ZIP = 3;
    static boolean debug = false; // Debugging on/off
    static char sep = '/'; // directory separator
    
    //  Annotations are collected from certain attributes, don't do it more than necessary!
    private boolean annotationsOutOfDate = true;
    
    private static BCELComparator _cmp = new BCELComparator() {

        public boolean equals( Object o1, Object o2 ) {
            JavaClass THIS = (JavaClass) o1;
            JavaClass THAT = (JavaClass) o2;
            return THIS.getClassName().equals(THAT.getClassName());
        }


        public int hashCode( Object o ) {
            JavaClass THIS = (JavaClass) o;
            return THIS.getClassName().hashCode();
        }
    };
    /**
     * In cases where we go ahead and create something,
     * use the default SyntheticRepository, because we
     * don't know any better.
     */
    private transient org.apache.bcel.util.Repository repository = SyntheticRepository
            .getInstance();


    /**
     * Constructor gets all contents as arguments.
     *
     * @param class_name_index Index into constant pool referencing a
     * ConstantClass that represents this class.
     * @param superclass_name_index Index into constant pool referencing a
     * ConstantClass that represents this class's superclass.
     * @param file_name File name
     * @param major Major compiler version
     * @param minor Minor compiler version
     * @param access_flags Access rights defined by bit flags
     * @param constant_pool Array of constants
     * @param interfaces Implemented interfaces
     * @param fields Class fields
     * @param methods Class methods
     * @param attributes Class attributes
     * @param source Read from file or generated in memory?
     */
    public JavaClass(int class_name_index, int superclass_name_index, String file_name, int major,
            int minor, int access_flags, ConstantPool constant_pool, int[] interfaces,
            Field[] fields, Method[] methods, Attribute[] attributes, byte source) {
        if (interfaces == null) {
            interfaces = new int[0];
        }
        if (attributes == null) {
            attributes = new Attribute[0];
        }
        if (fields == null) {
            fields = new Field[0];
        }
        if (methods == null) {
            methods = new Method[0];
        }
        this.class_name_index = class_name_index;
        this.superclass_name_index = superclass_name_index;
        this.file_name = file_name;
        this.major = major;
        this.minor = minor;
        this.access_flags = access_flags;
        this.constant_pool = constant_pool;
        this.interfaces = interfaces;
        this.fields = fields;
        this.methods = methods;
        this.attributes = attributes;
        annotationsOutOfDate = true;
        this.source = source;
        // Get source file name if available
        for (Attribute attribute : attributes) {
            if (attribute instanceof SourceFile) {
                source_file_name = ((SourceFile) attribute).getSourceFileName();
                break;
            }
        }
        /* According to the specification the following entries must be of type
         * `ConstantClass' but we check that anyway via the 
         * `ConstPool.getConstant' method.
         */
        class_name = constant_pool.getConstantString(class_name_index, Constants.CONSTANT_Class);
        class_name = Utility.compactClassName(class_name, false);
        int index = class_name.lastIndexOf('.');
        if (index < 0) {
            package_name = "";
        } else {
            package_name = class_name.substring(0, index);
        }
        if (superclass_name_index > 0) {
            // May be zero -> class is java.lang.Object
            superclass_name = constant_pool.getConstantString(superclass_name_index,
                    Constants.CONSTANT_Class);
            superclass_name = Utility.compactClassName(superclass_name, false);
        } else {
            superclass_name = "java.lang.Object";
        }
        interface_names = new String[interfaces.length];
        for (int i = 0; i < interfaces.length; i++) {
            String str = constant_pool.getConstantString(interfaces[i], Constants.CONSTANT_Class);
            interface_names[i] = Utility.compactClassName(str, false);
        }
    }


    /**
     * Constructor gets all contents as arguments.
     *
     * @param class_name_index Class name
     * @param superclass_name_index Superclass name
     * @param file_name File name
     * @param major Major compiler version
     * @param minor Minor compiler version
     * @param access_flags Access rights defined by bit flags
     * @param constant_pool Array of constants
     * @param interfaces Implemented interfaces
     * @param fields Class fields
     * @param methods Class methods
     * @param attributes Class attributes
     */
    public JavaClass(int class_name_index, int superclass_name_index, String file_name, int major,
            int minor, int access_flags, ConstantPool constant_pool, int[] interfaces,
            Field[] fields, Method[] methods, Attribute[] attributes) {
        this(class_name_index, superclass_name_index, file_name, major, minor, access_flags,
                constant_pool, interfaces, fields, methods, attributes, HEAP);
    }


    /**
     * Called by objects that are traversing the nodes of the tree implicitely
     * defined by the contents of a Java class. I.e., the hierarchy of methods,
     * fields, attributes, etc. spawns a tree of objects.
     *
     * @param v Visitor object
     */
    public void accept( Visitor v ) {
        v.visitJavaClass(this);
    }


    /* Print debug information depending on `JavaClass.debug'
     */
    static final void Debug( String str ) {
        if (debug) {
            System.out.println(str);
        }
    }


    /** 
     * Dump class to a file.
     *
     * @param file Output file
     * @throws IOException
     */
    public void dump( File file ) throws IOException {
        String parent = file.getParent();
        if (parent != null) {
            File dir = new File(parent);
            dir.mkdirs();
        }
        DataOutputStream dos = null;
        try {
            dos = new DataOutputStream(new FileOutputStream(file));
            dump(dos);
        } finally {
            if (dos != null) {
                dos.close();
            }
        }
    }


    /** 
     * Dump class to a file named file_name.
     *
     * @param _file_name Output file name
     * @exception IOException
     */
    public void dump( String _file_name ) throws IOException {
        dump(new File(_file_name));
    }


    /**
     * @return class in binary format
     */
    public byte[] getBytes() {
        ByteArrayOutputStream s = new ByteArrayOutputStream();
        DataOutputStream ds = new DataOutputStream(s);
        try {
            dump(ds);
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                ds.close();
            } catch (IOException e2) {
                e2.printStackTrace();
            }
        }
        return s.toByteArray();
    }


    /**
     * Dump Java class to output stream in binary format.
     *
     * @param file Output stream
     * @exception IOException
     */
    public void dump( OutputStream file ) throws IOException {
        dump(new DataOutputStream(file));
    }


    /**
     * Dump Java class to output stream in binary format.
     *
     * @param file Output stream
     * @exception IOException
     */
    public void dump( DataOutputStream file ) throws IOException {
        file.writeInt(0xcafebabe);
        file.writeShort(minor);
        file.writeShort(major);
        constant_pool.dump(file);
        file.writeShort(access_flags);
        file.writeShort(class_name_index);
        file.writeShort(superclass_name_index);
        file.writeShort(interfaces.length);
        for (int interface1 : interfaces) {
            file.writeShort(interface1);
        }
        file.writeShort(fields.length);
        for (Field field : fields) {
            field.dump(file);
        }
        file.writeShort(methods.length);
        for (Method method : methods) {
            method.dump(file);
        }
        if (attributes != null) {
            file.writeShort(attributes.length);
            for (Attribute attribute : attributes) {
                attribute.dump(file);
            }
        } else {
            file.writeShort(0);
        }
        file.flush();
    }


    /**
     * @return Attributes of the class.
     */
    public Attribute[] getAttributes() {
        return attributes;
    }
    
    public AnnotationEntry[] getAnnotationEntries() {
      	if (annotationsOutOfDate) { 
      		// Find attributes that contain annotation data
      		Attribute[] attrs = getAttributes();
      		List<AnnotationEntry> accumulatedAnnotations = new ArrayList<AnnotationEntry>();
      		for (Attribute attribute : attrs) {
    			if (attribute instanceof Annotations) {				
    				Annotations runtimeAnnotations = (Annotations)attribute;
    				for(int j = 0; j < runtimeAnnotations.getAnnotationEntries().length; j++) {
                        accumulatedAnnotations.add(runtimeAnnotations.getAnnotationEntries()[j]);
                    }
    			}
    		}
      		annotations = accumulatedAnnotations.toArray(new AnnotationEntry[accumulatedAnnotations.size()]);
      		annotationsOutOfDate = false;
      	}
      	return annotations;
      }
    /**
     * @return Class name.
     */
    public String getClassName() {
        return class_name;
    }


    /**
     * @return Package name.
     */
    public String getPackageName() {
        return package_name;
    }


    /**
     * @return Class name index.
     */
    public int getClassNameIndex() {
        return class_name_index;
    }


    /**
     * @return Constant pool.
     */
    public ConstantPool getConstantPool() {
        return constant_pool;
    }


    /**
     * @return Fields, i.e., variables of the class. Like the JVM spec
     * mandates for the classfile format, these fields are those specific to
     * this class, and not those of the superclass or superinterfaces.
     */
    public Field[] getFields() {
        return fields;
    }


    /**
     * @return File name of class, aka SourceFile attribute value
     */
    public String getFileName() {
        return file_name;
    }


    /**
     * @return Names of implemented interfaces.
     */
    public String[] getInterfaceNames() {
        return interface_names;
    }


    /**
     * @return Indices in constant pool of implemented interfaces.
     */
    public int[] getInterfaceIndices() {
        return interfaces;
    }


    /**
     * @return Major number of class file version.
     */
    public int getMajor() {
        return major;
    }


    /**
     * @return Methods of the class.
     */
    public Method[] getMethods() {
        return methods;
    }


    /**
     * @return A org.apache.bcel.classfile.Method corresponding to
     * java.lang.reflect.Method if any
     */
    public Method getMethod( java.lang.reflect.Method m ) {
        for (Method method : methods) {
            if (m.getName().equals(method.getName()) && (m.getModifiers() == method.getModifiers())
                    && Type.getSignature(m).equals(method.getSignature())) {
                return method;
            }
        }
        return null;
    }


    /**
     * @return Minor number of class file version.
     */
    public int getMinor() {
        return minor;
    }


    /**
     * @return sbsolute path to file where this class was read from
     */
    public String getSourceFileName() {
        return source_file_name;
    }


    /**
     * returns the super class name of this class. In the case that this class is
     * java.lang.Object, it will return itself (java.lang.Object). This is probably incorrect
     * but isn't fixed at this time to not break existing clients.
     *
     * @return Superclass name.
     */
    public String getSuperclassName() {
        return superclass_name;
    }


    /**
     * @return Class name index.
     */
    public int getSuperclassNameIndex() {
        return superclass_name_index;
    }

    static {
        // Debugging ... on/off
        debug = Boolean.getBoolean("JavaClass.debug");
        // Get path separator either / or \ usually
        String _sep = System.getProperty("file.separator");
        if (_sep != null) {
            try {
                JavaClass.sep = _sep.charAt(0);
            } catch (StringIndexOutOfBoundsException e) {
            } // Never reached
        }
    }


    /**
     * @param attributes .
     */
    public void setAttributes( Attribute[] attributes ) {
        this.attributes = attributes;
    }


    /**
     * @param class_name .
     */
    public void setClassName( String class_name ) {
        this.class_name = class_name;
    }


    /**
     * @param class_name_index .
     */
    public void setClassNameIndex( int class_name_index ) {
        this.class_name_index = class_name_index;
    }


    /**
     * @param constant_pool .
     */
    public void setConstantPool( ConstantPool constant_pool ) {
        this.constant_pool = constant_pool;
    }


    /**
     * @param fields .
     */
    public void setFields( Field[] fields ) {
        this.fields = fields;
    }


    /**
     * Set File name of class, aka SourceFile attribute value
     */
    public void setFileName( String file_name ) {
        this.file_name = file_name;
    }


    /**
     * @param interface_names .
     */
    public void setInterfaceNames( String[] interface_names ) {
        this.interface_names = interface_names;
    }


    /**
     * @param interfaces .
     */
    public void setInterfaces( int[] interfaces ) {
        this.interfaces = interfaces;
    }


    /**
     * @param major .
     */
    public void setMajor( int major ) {
        this.major = major;
    }


    /**
     * @param methods .
     */
    public void setMethods( Method[] methods ) {
        this.methods = methods;
    }


    /**
     * @param minor .
     */
    public void setMinor( int minor ) {
        this.minor = minor;
    }


    /**
     * Set absolute path to file this class was read from.
     */
    public void setSourceFileName( String source_file_name ) {
        this.source_file_name = source_file_name;
    }


    /**
     * @param superclass_name .
     */
    public void setSuperclassName( String superclass_name ) {
        this.superclass_name = superclass_name;
    }


    /**
     * @param superclass_name_index .
     */
    public void setSuperclassNameIndex( int superclass_name_index ) {
        this.superclass_name_index = superclass_name_index;
    }


    /**
     * @return String representing class contents.
     */
    @Override
    public String toString() {
        String access = Utility.accessToString(access_flags, true);
        access = access.equals("") ? "" : (access + " ");
        StringBuilder buf = new StringBuilder(128);
        buf.append(access).append(Utility.classOrInterface(access_flags)).append(" ").append(
                class_name).append(" extends ").append(
                Utility.compactClassName(superclass_name, false)).append('\n');
        int size = interfaces.length;
        if (size > 0) {
            buf.append("implements\t\t");
            for (int i = 0; i < size; i++) {
                buf.append(interface_names[i]);
                if (i < size - 1) {
                    buf.append(", ");
                }
            }
            buf.append('\n');
        }
        buf.append("filename\t\t").append(file_name).append('\n');
        buf.append("compiled from\t\t").append(source_file_name).append('\n');
        buf.append("compiler version\t").append(major).append(".").append(minor).append('\n');
        buf.append("access flags\t\t").append(access_flags).append('\n');
        buf.append("constant pool\t\t").append(constant_pool.getLength()).append(" entries\n");
        buf.append("ACC_SUPER flag\t\t").append(isSuper()).append("\n");
        if (attributes.length > 0) {
            buf.append("\nAttribute(s):\n");
            for (Attribute attribute : attributes) {
                buf.append(indent(attribute));
            }
        }
        AnnotationEntry[] annotations = getAnnotationEntries();
        if (annotations!=null && annotations.length>0) {
        	buf.append("\nAnnotation(s):\n");
        	for (AnnotationEntry annotation : annotations) {
                buf.append(indent(annotation));
            }
        }
        if (fields.length > 0) {
            buf.append("\n").append(fields.length).append(" fields:\n");
            for (Field field : fields) {
                buf.append("\t").append(field).append('\n');
            }
        }
        if (methods.length > 0) {
            buf.append("\n").append(methods.length).append(" methods:\n");
            for (Method method : methods) {
                buf.append("\t").append(method).append('\n');
            }
        }
        return buf.toString();
    }


    private static String indent( Object obj ) {
        StringTokenizer tok = new StringTokenizer(obj.toString(), "\n");
        StringBuilder buf = new StringBuilder();
        while (tok.hasMoreTokens()) {
            buf.append("\t").append(tok.nextToken()).append("\n");
        }
        return buf.toString();
    }


    /**
     * @return deep copy of this class
     */
    public JavaClass copy() {
        JavaClass c = null;
        try {
            c = (JavaClass) clone();
            c.constant_pool = constant_pool.copy();
            c.interfaces = interfaces.clone();
            c.interface_names = interface_names.clone();
            c.fields = new Field[fields.length];
            for (int i = 0; i < fields.length; i++) {
                c.fields[i] = fields[i].copy(c.constant_pool);
            }
            c.methods = new Method[methods.length];
            for (int i = 0; i < methods.length; i++) {
                c.methods[i] = methods[i].copy(c.constant_pool);
            }
            c.attributes = new Attribute[attributes.length];
            for (int i = 0; i < attributes.length; i++) {
                c.attributes[i] = attributes[i].copy(c.constant_pool);
            }
        } catch (CloneNotSupportedException e) {
        }
        return c;
    }


    public final boolean isSuper() {
        return (access_flags & Constants.ACC_SUPER) != 0;
    }


    public final boolean isClass() {
        return (access_flags & Constants.ACC_INTERFACE) == 0;
    }
    
    public final boolean isAnonymous() {
  	  computeNestedTypeStatus();
  	  return this.isAnonymous;
    }
    
    public final boolean isNested() {
  	  computeNestedTypeStatus();
  	  return this.isNested;
    }
    
    private void computeNestedTypeStatus() {
  	  if (computedNestedTypeStatus) {
        return;
    }
  	  for (Attribute attribute : this.attributes) {
  			if (attribute instanceof InnerClasses) {
  				InnerClass[] innerClasses = ((InnerClasses) attribute).getInnerClasses();
  				for (InnerClass innerClasse : innerClasses) {
  					boolean innerClassAttributeRefersToMe = false;
  					String inner_class_name = constant_pool.getConstantString(innerClasse.getInnerClassIndex(),
  						       Constants.CONSTANT_Class);
  					inner_class_name = Utility.compactClassName(inner_class_name);
  					if (inner_class_name.equals(getClassName())) {
  						innerClassAttributeRefersToMe = true;
  					}
  					if (innerClassAttributeRefersToMe) {
  						this.isNested = true;
  						if (innerClasse.getInnerNameIndex() == 0) {
  							this.isAnonymous = true;
  						}
  					}
  				}
  			}
  	  }
  	  this.computedNestedTypeStatus = true;
    }


    /** @return returns either HEAP (generated), FILE, or ZIP
     */
    public final byte getSource() {
        return source;
    }


    /********************* New repository functionality *********************/
    /**
     * Gets the ClassRepository which holds its definition. By default
     * this is the same as SyntheticRepository.getInstance();
     */
    public org.apache.bcel.util.Repository getRepository() {
        return repository;
    }


    /**
     * Sets the ClassRepository which loaded the JavaClass.
     * Should be called immediately after parsing is done.
     */
    public void setRepository( org.apache.bcel.util.Repository repository ) {
        this.repository = repository;
    }


    /** Equivalent to runtime "instanceof" operator.
     *
     * @return true if this JavaClass is derived from the super class
     * @throws ClassNotFoundException if superclasses or superinterfaces
     *   of this object can't be found
     */
    public final boolean instanceOf( JavaClass super_class ) throws ClassNotFoundException {
        if (this.equals(super_class)) {
            return true;
        }
        JavaClass[] super_classes = getSuperClasses();
        for (JavaClass super_classe : super_classes) {
            if (super_classe.equals(super_class)) {
                return true;
            }
        }
        if (super_class.isInterface()) {
            return implementationOf(super_class);
        }
        return false;
    }


    /**
     * @return true, if this class is an implementation of interface inter
     * @throws ClassNotFoundException if superclasses or superinterfaces
     *   of this class can't be found
     */
    public boolean implementationOf( JavaClass inter ) throws ClassNotFoundException {
        if (!inter.isInterface()) {
            throw new IllegalArgumentException(inter.getClassName() + " is no interface");
        }
        if (this.equals(inter)) {
            return true;
        }
        JavaClass[] super_interfaces = getAllInterfaces();
        for (JavaClass super_interface : super_interfaces) {
            if (super_interface.equals(inter)) {
                return true;
            }
        }
        return false;
    }


    /**
     * @return the superclass for this JavaClass object, or null if this
     * is java.lang.Object
     * @throws ClassNotFoundException if the superclass can't be found
     */
    public JavaClass getSuperClass() throws ClassNotFoundException {
        if ("java.lang.Object".equals(getClassName())) {
            return null;
        }
        return repository.loadClass(getSuperclassName());
    }


    /**
     * @return list of super classes of this class in ascending order, i.e.,
     * java.lang.Object is always the last element
     * @throws ClassNotFoundException if any of the superclasses can't be found
     */
    public JavaClass[] getSuperClasses() throws ClassNotFoundException {
        JavaClass clazz = this;
        List<JavaClass> allSuperClasses = new ArrayList<JavaClass>();
        for (clazz = clazz.getSuperClass(); clazz != null; clazz = clazz.getSuperClass()) {
            allSuperClasses.add(clazz);
        }
        return allSuperClasses.toArray(new JavaClass[allSuperClasses.size()]);
    }


    /**
     * Get interfaces directly implemented by this JavaClass.
     */
    public JavaClass[] getInterfaces() throws ClassNotFoundException {
        String[] _interfaces = getInterfaceNames();
        JavaClass[] classes = new JavaClass[_interfaces.length];
        for (int i = 0; i < _interfaces.length; i++) {
            classes[i] = repository.loadClass(_interfaces[i]);
        }
        return classes;
    }


    /**
     * Get all interfaces implemented by this JavaClass (transitively).
     */
    public JavaClass[] getAllInterfaces() throws ClassNotFoundException {
        ClassQueue queue = new ClassQueue();
        Set<JavaClass> allInterfaces = new TreeSet<JavaClass>();
        queue.enqueue(this);
        while (!queue.empty()) {
            JavaClass clazz = queue.dequeue();
            JavaClass souper = clazz.getSuperClass();
            JavaClass[] _interfaces = clazz.getInterfaces();
            if (clazz.isInterface()) {
                allInterfaces.add(clazz);
            } else {
                if (souper != null) {
                    queue.enqueue(souper);
                }
            }
            for (JavaClass _interface : _interfaces) {
                queue.enqueue(_interface);
            }
        }
        return allInterfaces.toArray(new JavaClass[allInterfaces.size()]);
    }


    /**
     * @return Comparison strategy object
     */
    public static BCELComparator getComparator() {
        return _cmp;
    }


    /**
     * @param comparator Comparison strategy object
     */
    public static void setComparator( BCELComparator comparator ) {
        _cmp = comparator;
    }


    /**
     * Return value as defined by given BCELComparator strategy.
     * By default two JavaClass objects are said to be equal when
     * their class names are equal.
     * 
     * @see java.lang.Object#equals(java.lang.Object)
     */
    @Override
    public boolean equals( Object obj ) {
        return _cmp.equals(this, obj);
    }


    /**
     * Return the natural ordering of two JavaClasses.
     * This ordering is based on the class name
     */
    public int compareTo( JavaClass obj ) {
        return getClassName().compareTo(obj.getClassName());
    }


    /**
     * Return value as defined by given BCELComparator strategy.
     * By default return the hashcode of the class name.
     * 
     * @see java.lang.Object#hashCode()
     */
    @Override
    public int hashCode() {
        return _cmp.hashCode(this);
    }
}