/*
 * Copyright 2002,2003,2004 The Apache Software Foundation
 *
 *  Licensed 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
 *
 *      https://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.springframework.cglib.proxy;

import java.lang.ref.WeakReference;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.security.ProtectionDomain;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;

import org.springframework.asm.ClassVisitor;
import org.springframework.asm.Label;
import org.springframework.asm.Type;
import org.springframework.cglib.core.AbstractClassGenerator;
import org.springframework.cglib.core.ClassEmitter;
import org.springframework.cglib.core.CodeEmitter;
import org.springframework.cglib.core.CodeGenerationException;
import org.springframework.cglib.core.CollectionUtils;
import org.springframework.cglib.core.Constants;
import org.springframework.cglib.core.DuplicatesPredicate;
import org.springframework.cglib.core.EmitUtils;
import org.springframework.cglib.core.KeyFactory;
import org.springframework.cglib.core.Local;
import org.springframework.cglib.core.MethodInfo;
import org.springframework.cglib.core.MethodInfoTransformer;
import org.springframework.cglib.core.MethodWrapper;
import org.springframework.cglib.core.ObjectSwitchCallback;
import org.springframework.cglib.core.ProcessSwitchCallback;
import org.springframework.cglib.core.ReflectUtils;
import org.springframework.cglib.core.RejectModifierPredicate;
import org.springframework.cglib.core.Signature;
import org.springframework.cglib.core.Transformer;
import org.springframework.cglib.core.TypeUtils;
import org.springframework.cglib.core.VisibilityPredicate;
import org.springframework.cglib.core.WeakCacheKey;

/**
 * Generates dynamic subclasses to enable method interception. This
 * class started as a substitute for the standard Dynamic Proxy support
 * included with JDK 1.3, but one that allowed the proxies to extend a
 * concrete base class, in addition to implementing interfaces. The dynamically
 * generated subclasses override the non-final methods of the superclass and
 * have hooks which callback to user-defined interceptor
 * implementations.
 * <p>
 * The original and most general callback type is the {@link MethodInterceptor}, which
 * in AOP terms enables "around advice"--that is, you can invoke custom code both before
 * and after the invocation of the "super" method. In addition you can modify the
 * arguments before calling the super method, or not call it at all.
 * <p>
 * Although <code>MethodInterceptor</code> is generic enough to meet any
 * interception need, it is often overkill. For simplicity and performance, additional
 * specialized callback types, such as {@link LazyLoader} are also available.
 * Often a single callback will be used per enhanced class, but you can control
 * which callback is used on a per-method basis with a {@link CallbackFilter}.
 * <p>
 * The most common uses of this class are embodied in the static helper methods. For
 * advanced needs, such as customizing the <code>ClassLoader</code> to use, you should create
 * a new instance of <code>Enhancer</code>. Other classes within CGLIB follow a similar pattern.
 * <p>
 * All enhanced objects implement the {@link Factory} interface, unless {@link #setUseFactory} is
 * used to explicitly disable this feature. The <code>Factory</code> interface provides an API
 * to change the callbacks of an existing object, as well as a faster and easier way to create
 * new instances of the same type.
 * <p>
 * For an almost drop-in replacement for
 * <code>java.lang.reflect.Proxy</code>, see the {@link Proxy} class.
 */
@SuppressWarnings({"rawtypes", "unchecked"})
public class Enhancer extends AbstractClassGenerator {

        private static final CallbackFilter ALL_ZERO = new CallbackFilter() {
                public int accept(Method method) {
                        return 0;
                }
        };

        private static final Source SOURCE = new Source(Enhancer.class.getName());

        private static final EnhancerKey KEY_FACTORY =
                        (EnhancerKey) KeyFactory.create(EnhancerKey.class, KeyFactory.HASH_ASM_TYPE, null);

        private static final String BOUND_FIELD = "CGLIB$BOUND";

        private static final String FACTORY_DATA_FIELD = "CGLIB$FACTORY_DATA";

        private static final String THREAD_CALLBACKS_FIELD = "CGLIB$THREAD_CALLBACKS";

        private static final String STATIC_CALLBACKS_FIELD = "CGLIB$STATIC_CALLBACKS";

        private static final String SET_THREAD_CALLBACKS_NAME = "CGLIB$SET_THREAD_CALLBACKS";

        private static final String SET_STATIC_CALLBACKS_NAME = "CGLIB$SET_STATIC_CALLBACKS";

        private static final String CONSTRUCTED_FIELD = "CGLIB$CONSTRUCTED";

        /**
         * {@link org.springframework.cglib.core.AbstractClassGenerator.ClassLoaderData#generatedClasses} requires to keep cache key
         * in a good shape (the keys should be up and running if the proxy class is alive), and one of the cache keys is
         * {@link CallbackFilter}. That is why the generated class contains static field that keeps strong reference to
         * the {@link #filter}.
         * <p>This dance achieves two goals: ensures generated class is reusable and available through generatedClasses
         * cache, and it enables to unload classloader and the related {@link CallbackFilter} in case user does not need
         * that</p>
         */
        private static final String CALLBACK_FILTER_FIELD = "CGLIB$CALLBACK_FILTER";

        private static final Type OBJECT_TYPE =
                        TypeUtils.parseType("Object");

        private static final Type FACTORY =
                        TypeUtils.parseType("org.springframework.cglib.proxy.Factory");

        private static final Type ILLEGAL_STATE_EXCEPTION =
                        TypeUtils.parseType("IllegalStateException");

        private static final Type ILLEGAL_ARGUMENT_EXCEPTION =
                        TypeUtils.parseType("IllegalArgumentException");

        private static final Type THREAD_LOCAL =
                        TypeUtils.parseType("ThreadLocal");

        private static final Type CALLBACK =
                        TypeUtils.parseType("org.springframework.cglib.proxy.Callback");

        private static final Type CALLBACK_ARRAY =
                        Type.getType(Callback[].class);

        private static final Signature CSTRUCT_NULL =
                        TypeUtils.parseConstructor("");

        private static final Signature SET_THREAD_CALLBACKS =
                        new Signature(SET_THREAD_CALLBACKS_NAME, Type.VOID_TYPE, new Type[]{CALLBACK_ARRAY});

        private static final Signature SET_STATIC_CALLBACKS =
                        new Signature(SET_STATIC_CALLBACKS_NAME, Type.VOID_TYPE, new Type[]{CALLBACK_ARRAY});

        private static final Signature NEW_INSTANCE =
                        new Signature("newInstance", Constants.TYPE_OBJECT, new Type[]{CALLBACK_ARRAY});

        private static final Signature MULTIARG_NEW_INSTANCE =
                        new Signature("newInstance", Constants.TYPE_OBJECT, new Type[]{
                                        Constants.TYPE_CLASS_ARRAY,
                                        Constants.TYPE_OBJECT_ARRAY,
                                        CALLBACK_ARRAY,
                        });

        private static final Signature SINGLE_NEW_INSTANCE =
                        new Signature("newInstance", Constants.TYPE_OBJECT, new Type[]{CALLBACK});

        private static final Signature SET_CALLBACK =
                        new Signature("setCallback", Type.VOID_TYPE, new Type[]{Type.INT_TYPE, CALLBACK});

        private static final Signature GET_CALLBACK =
                        new Signature("getCallback", CALLBACK, new Type[]{Type.INT_TYPE});

        private static final Signature SET_CALLBACKS =
                        new Signature("setCallbacks", Type.VOID_TYPE, new Type[]{CALLBACK_ARRAY});

        private static final Signature GET_CALLBACKS =
                        new Signature("getCallbacks", CALLBACK_ARRAY, new Type[0]);

        private static final Signature THREAD_LOCAL_GET =
                        TypeUtils.parseSignature("Object get()");

        private static final Signature THREAD_LOCAL_SET =
                        TypeUtils.parseSignature("void set(Object)");

        private static final Signature BIND_CALLBACKS =
                        TypeUtils.parseSignature("void CGLIB$BIND_CALLBACKS(Object)");

        private EnhancerFactoryData currentData;

        private Object currentKey;


        /**
         * Internal interface, only public due to ClassLoader issues.
         */
        public interface EnhancerKey {

                public Object newInstance(String type,
                                String[] interfaces,
                                WeakCacheKey<CallbackFilter> filter,
                                Type[] callbackTypes,
                                boolean useFactory,
                                boolean interceptDuringConstruction,
                                Long serialVersionUID);
        }


        private Class[] interfaces;

        private CallbackFilter filter;

        private Callback[] callbacks;

        private Type[] callbackTypes;

        private boolean validateCallbackTypes;

        private boolean classOnly;

        private Class superclass;

        private Class[] argumentTypes;

        private Object[] arguments;

        private boolean useFactory = true;

        private Long serialVersionUID;

        private boolean interceptDuringConstruction = true;

        /**
         * Create a new <code>Enhancer</code>. A new <code>Enhancer</code>
         * object should be used for each generated object, and should not
         * be shared across threads. To create additional instances of a
         * generated class, use the <code>Factory</code> interface.
         * @see Factory
         */
        public Enhancer() {
                super(SOURCE);
        }

        /**
         * Set the class which the generated class will extend. As a convenience,
         * if the supplied superclass is actually an interface, <code>setInterfaces</code>
         * will be called with the appropriate argument instead.
         * A non-interface argument must not be declared as final, and must have an
         * accessible constructor.
         * @param superclass class to extend or interface to implement
         * @see #setInterfaces(Class[])
         */
        public void setSuperclass(Class superclass) {
                if (superclass != null && superclass.isInterface()) {
                        setInterfaces(new Class[]{superclass});
                        // SPRING PATCH BEGIN
                        setContextClass(superclass);
                        // SPRING PATCH END
                }
                else if (superclass != null && superclass.equals(Object.class)) {
                        // affects choice of ClassLoader
                        this.superclass = null;
                }
                else {
                        this.superclass = superclass;
                        // SPRING PATCH BEGIN
                        setContextClass(superclass);
                        // SPRING PATCH END
                }
        }

        /**
         * Set the interfaces to implement. The <code>Factory</code> interface will
         * always be implemented regardless of what is specified here.
         * @param interfaces array of interfaces to implement, or null
         * @see Factory
         */
        public void setInterfaces(Class[] interfaces) {
                this.interfaces = interfaces;
        }

        /**
         * Set the {@link CallbackFilter} used to map the generated class' methods
         * to a particular callback index.
         * New object instances will always use the same mapping, but may use different
         * actual callback objects.
         * @param filter the callback filter to use when generating a new class
         * @see #setCallbacks
         */
        public void setCallbackFilter(CallbackFilter filter) {
                this.filter = filter;
        }


        /**
         * Set the single {@link Callback} to use.
         * Ignored if you use {@link #createClass}.
         * @param callback the callback to use for all methods
         * @see #setCallbacks
         */
        public void setCallback(final Callback callback) {
                setCallbacks(new Callback[]{callback});
        }

        /**
         * Set the array of callbacks to use.
         * Ignored if you use {@link #createClass}.
         * You must use a {@link CallbackFilter} to specify the index into this
         * array for each method in the proxied class.
         * @param callbacks the callback array
         * @see #setCallbackFilter
         * @see #setCallback
         */
        public void setCallbacks(Callback[] callbacks) {
                if (callbacks != null && callbacks.length == 0) {
                        throw new IllegalArgumentException("Array cannot be empty");
                }
                this.callbacks = callbacks;
        }

        /**
         * Set whether the enhanced object instances should implement
         * the {@link Factory} interface.
         * This was added for tools that need for proxies to be more
         * indistinguishable from their targets. Also, in some cases it may
         * be necessary to disable the <code>Factory</code> interface to
         * prevent code from changing the underlying callbacks.
         * @param useFactory whether to implement <code>Factory</code>; default is <code>true</code>
         */
        public void setUseFactory(boolean useFactory) {
                this.useFactory = useFactory;
        }

        /**
         * Set whether methods called from within the proxy's constructer
         * will be intercepted. The default value is true. Unintercepted methods
         * will call the method of the proxy's base class, if it exists.
         * @param interceptDuringConstruction whether to intercept methods called from the constructor
         */
        public void setInterceptDuringConstruction(boolean interceptDuringConstruction) {
                this.interceptDuringConstruction = interceptDuringConstruction;
        }

        /**
         * Set the single type of {@link Callback} to use.
         * This may be used instead of {@link #setCallback} when calling
         * {@link #createClass}, since it may not be possible to have
         * an array of actual callback instances.
         * @param callbackType the type of callback to use for all methods
         * @see #setCallbackTypes
         */
        public void setCallbackType(Class callbackType) {
                setCallbackTypes(new Class[]{callbackType});
        }

        /**
         * Set the array of callback types to use.
         * This may be used instead of {@link #setCallbacks} when calling
         * {@link #createClass}, since it may not be possible to have
         * an array of actual callback instances.
         * You must use a {@link CallbackFilter} to specify the index into this
         * array for each method in the proxied class.
         * @param callbackTypes the array of callback types
         */
        public void setCallbackTypes(Class[] callbackTypes) {
                if (callbackTypes != null && callbackTypes.length == 0) {
                        throw new IllegalArgumentException("Array cannot be empty");
                }
                this.callbackTypes = CallbackInfo.determineTypes(callbackTypes);
        }

        /**
         * Generate a new class if necessary and uses the specified
         * callbacks (if any) to create a new object instance.
         * Uses the no-arg constructor of the superclass.
         * @return a new instance
         */
        public Object create() {
                classOnly = false;
                argumentTypes = null;
                return createHelper();
        }

        /**
         * Generate a new class if necessary and uses the specified
         * callbacks (if any) to create a new object instance.
         * Uses the constructor of the superclass matching the <code>argumentTypes</code>
         * parameter, with the given arguments.
         * @param argumentTypes constructor signature
         * @param arguments compatible wrapped arguments to pass to constructor
         * @return a new instance
         */
        public Object create(Class[] argumentTypes, Object[] arguments) {
                classOnly = false;
                if (argumentTypes == null || arguments == null || argumentTypes.length != arguments.length) {
                        throw new IllegalArgumentException("Arguments must be non-null and of equal length");
                }
                this.argumentTypes = argumentTypes;
                this.arguments = arguments;
                return createHelper();
        }

        /**
         * Generate a new class if necessary and return it without creating a new instance.
         * This ignores any callbacks that have been set.
         * To create a new instance you will have to use reflection, and methods
         * called during the constructor will not be intercepted. To avoid this problem,
         * use the multi-arg <code>create</code> method.
         * @see #create(Class[], Object[])
         */
        public Class createClass() {
                classOnly = true;
                return (Class) createHelper();
        }

        /**
         * Insert a static serialVersionUID field into the generated class.
         * @param sUID the field value, or null to avoid generating field.
         */
        public void setSerialVersionUID(Long sUID) {
                serialVersionUID = sUID;
        }

        private void preValidate() {
                if (callbackTypes == null) {
                        callbackTypes = CallbackInfo.determineTypes(callbacks, false);
                        validateCallbackTypes = true;
                }
                if (filter == null) {
                        if (callbackTypes.length > 1) {
                                throw new IllegalStateException("Multiple callback types possible but no filter specified");
                        }
                        filter = ALL_ZERO;
                }
        }

        private void validate() {
                if (classOnly ^ (callbacks == null)) {
                        if (classOnly) {
                                throw new IllegalStateException("createClass does not accept callbacks");
                        }
                        else {
                                throw new IllegalStateException("Callbacks are required");
                        }
                }
                if (classOnly && (callbackTypes == null)) {
                        throw new IllegalStateException("Callback types are required");
                }
                if (validateCallbackTypes) {
                        callbackTypes = null;
                }
                if (callbacks != null && callbackTypes != null) {
                        if (callbacks.length != callbackTypes.length) {
                                throw new IllegalStateException("Lengths of callback and callback types array must be the same");
                        }
                        Type[] check = CallbackInfo.determineTypes(callbacks);
                        for (int i = 0; i < check.length; i++) {
                                if (!check[i].equals(callbackTypes[i])) {
                                        throw new IllegalStateException("Callback " + check[i] + " is not assignable to " + callbackTypes[i]);
                                }
                        }
                }
                else if (callbacks != null) {
                        callbackTypes = CallbackInfo.determineTypes(callbacks);
                }
                if (interfaces != null) {
                        for (int i = 0; i < interfaces.length; i++) {
                                if (interfaces[i] == null) {
                                        throw new IllegalStateException("Interfaces cannot be null");
                                }
                                if (!interfaces[i].isInterface()) {
                                        throw new IllegalStateException(interfaces[i] + " is not an interface");
                                }
                        }
                }
        }

        /**
         * The idea of the class is to cache relevant java.lang.reflect instances so
         * proxy-class can be instantiated faster that when using {@link ReflectUtils#newInstance(Class, Class[], Object[])}
         * and {@link Enhancer#setThreadCallbacks(Class, Callback[])}
         */
        static class EnhancerFactoryData {

                public final Class generatedClass;

                private final Method setThreadCallbacks;

                private final Class[] primaryConstructorArgTypes;

                private final Constructor primaryConstructor;

                public EnhancerFactoryData(Class generatedClass, Class[] primaryConstructorArgTypes, boolean classOnly) {
                        this.generatedClass = generatedClass;
                        try {
                                setThreadCallbacks = getCallbacksSetter(generatedClass, SET_THREAD_CALLBACKS_NAME);
                                if (classOnly) {
                                        this.primaryConstructorArgTypes = null;
                                        this.primaryConstructor = null;
                                }
                                else {
                                        this.primaryConstructorArgTypes = primaryConstructorArgTypes;
                                        this.primaryConstructor = ReflectUtils.getConstructor(generatedClass, primaryConstructorArgTypes);
                                }
                        }
                        catch (NoSuchMethodException e) {
                                throw new CodeGenerationException(e);
                        }
                }

                /**
                 * Creates proxy instance for given argument types, and assigns the callbacks.
                 * Ideally, for each proxy class, just one set of argument types should be used,
                 * otherwise it would have to spend time on constructor lookup.
                 * Technically, it is a re-implementation of {@link Enhancer#createUsingReflection(Class)},
                 * with "cache {@link #setThreadCallbacks} and {@link #primaryConstructor}"
                 * @param argumentTypes constructor argument types
                 * @param arguments constructor arguments
                 * @param callbacks callbacks to set for the new instance
                 * @return newly created proxy
                 * @see #createUsingReflection(Class)
                 */
                public Object newInstance(Class[] argumentTypes, Object[] arguments, Callback[] callbacks) {
                        setThreadCallbacks(callbacks);
                        try {
                                // Explicit reference equality is added here just in case Arrays.equals does not have one
                                if (primaryConstructorArgTypes == argumentTypes ||
                                                Arrays.equals(primaryConstructorArgTypes, argumentTypes)) {
                                        // If we have relevant Constructor instance at hand, just call it
                                        // This skips "get constructors" machinery
                                        return ReflectUtils.newInstance(primaryConstructor, arguments);
                                }
                                // Take a slow path if observing unexpected argument types
                                return ReflectUtils.newInstance(generatedClass, argumentTypes, arguments);
                        }
                        finally {
                                // clear thread callbacks to allow them to be gc'd
                                setThreadCallbacks(null);
                        }

                }

                private void setThreadCallbacks(Callback[] callbacks) {
                        try {
                                setThreadCallbacks.invoke(generatedClass, (Object) callbacks);
                        }
                        catch (IllegalAccessException e) {
                                throw new CodeGenerationException(e);
                        }
                        catch (InvocationTargetException e) {
                                throw new CodeGenerationException(e.getTargetException());
                        }
                }
        }

        private Object createHelper() {
                preValidate();
                Object key = KEY_FACTORY.newInstance((superclass != null) ? superclass.getName() : null,
                                ReflectUtils.getNames(interfaces),
                                filter == ALL_ZERO ? null : new WeakCacheKey<CallbackFilter>(filter),
                                callbackTypes,
                                useFactory,
                                interceptDuringConstruction,
                                serialVersionUID);
                this.currentKey = key;
                Object result = super.create(key);
                return result;
        }

        @Override
        protected Class generate(ClassLoaderData data) {
                validate();
                if (superclass != null) {
                        setNamePrefix(superclass.getName());
                }
                else if (interfaces != null) {
                        setNamePrefix(interfaces[ReflectUtils.findPackageProtected(interfaces)].getName());
                }
                return super.generate(data);
        }

        protected ClassLoader getDefaultClassLoader() {
                if (superclass != null) {
                        return superclass.getClassLoader();
                }
                else if (interfaces != null) {
                        return interfaces[0].getClassLoader();
                }
                else {
                        return null;
                }
        }

        protected ProtectionDomain getProtectionDomain() {
                if (superclass != null) {
                        return ReflectUtils.getProtectionDomain(superclass);
                }
                else if (interfaces != null) {
                        return ReflectUtils.getProtectionDomain(interfaces[0]);
                }
                else {
                        return null;
                }
        }

        private Signature rename(Signature sig, int index) {
                return new Signature("CGLIB$" + sig.getName() + "$" + index,
                                sig.getDescriptor());
        }

        /**
         * Finds all of the methods that will be extended by an
         * Enhancer-generated class using the specified superclass and
         * interfaces. This can be useful in building a list of Callback
         * objects. The methods are added to the end of the given list.  Due
         * to the subclassing nature of the classes generated by Enhancer,
         * the methods are guaranteed to be non-static, non-final, and
         * non-private. Each method signature will only occur once, even if
         * it occurs in multiple classes.
         * @param superclass the class that will be extended, or null
         * @param interfaces the list of interfaces that will be implemented, or null
         * @param methods the list into which to copy the applicable methods
         */
        public static void getMethods(Class superclass, Class[] interfaces, List methods) {
                getMethods(superclass, interfaces, methods, null, null);
        }

        private static void getMethods(Class superclass, Class[] interfaces, List methods, List interfaceMethods, Set forcePublic) {
                ReflectUtils.addAllMethods(superclass, methods);
                List target = (interfaceMethods != null) ? interfaceMethods : methods;
                if (interfaces != null) {
                        for (int i = 0; i < interfaces.length; i++) {
                                if (interfaces[i] != Factory.class) {
                                        ReflectUtils.addAllMethods(interfaces[i], target);
                                }
                        }
                }
                if (interfaceMethods != null) {
                        if (forcePublic != null) {
                                forcePublic.addAll(MethodWrapper.createSet(interfaceMethods));
                        }
                        methods.addAll(interfaceMethods);
                }
                CollectionUtils.filter(methods, new RejectModifierPredicate(Constants.ACC_STATIC));
                CollectionUtils.filter(methods, new VisibilityPredicate(superclass, true));
                CollectionUtils.filter(methods, new DuplicatesPredicate());
                CollectionUtils.filter(methods, new RejectModifierPredicate(Constants.ACC_FINAL));
        }

        public void generateClass(ClassVisitor v) throws Exception {
                Class sc = (superclass == null) ? Object.class : superclass;

                if (TypeUtils.isFinal(sc.getModifiers()))
                        throw new IllegalArgumentException("Cannot subclass final class " + sc.getName());
                List constructors = new ArrayList(Arrays.asList(sc.getDeclaredConstructors()));
                filterConstructors(sc, constructors);

                // Order is very important: must add superclass, then
                // its superclass chain, then each interface and
                // its superinterfaces.
                List actualMethods = new ArrayList();
                List interfaceMethods = new ArrayList();
                final Set forcePublic = new HashSet();
                getMethods(sc, interfaces, actualMethods, interfaceMethods, forcePublic);

                List methods = CollectionUtils.transform(actualMethods, new Transformer() {
                        public Object transform(Object value) {
                                Method method = (Method) value;
                                int modifiers = Constants.ACC_FINAL
                                                | (method.getModifiers()
                                                & ~Constants.ACC_ABSTRACT
                                                & ~Constants.ACC_NATIVE
                                                & ~Constants.ACC_SYNCHRONIZED);
                                if (forcePublic.contains(MethodWrapper.create(method))) {
                                        modifiers = (modifiers & ~Constants.ACC_PROTECTED) | Constants.ACC_PUBLIC;
                                }
                                return ReflectUtils.getMethodInfo(method, modifiers);
                        }
                });

                ClassEmitter e = new ClassEmitter(v);
                if (currentData == null) {
                        e.begin_class(Constants.V1_8,
                                        Constants.ACC_PUBLIC,
                                        getClassName(),
                                        Type.getType(sc),
                                        (useFactory ?
                                                        TypeUtils.add(TypeUtils.getTypes(interfaces), FACTORY) :
                                                        TypeUtils.getTypes(interfaces)),
                                        Constants.SOURCE_FILE);
                }
                else {
                        e.begin_class(Constants.V1_8,
                                        Constants.ACC_PUBLIC,
                                        getClassName(),
                                        null,
                                        new Type[]{FACTORY},
                                        Constants.SOURCE_FILE);
                }
                List constructorInfo = CollectionUtils.transform(constructors, MethodInfoTransformer.getInstance());

                e.declare_field(Constants.ACC_PRIVATE, BOUND_FIELD, Type.BOOLEAN_TYPE, null);
                e.declare_field(Constants.ACC_PUBLIC | Constants.ACC_STATIC, FACTORY_DATA_FIELD, OBJECT_TYPE, null);
                if (!interceptDuringConstruction) {
                        e.declare_field(Constants.ACC_PRIVATE, CONSTRUCTED_FIELD, Type.BOOLEAN_TYPE, null);
                }
                e.declare_field(Constants.PRIVATE_FINAL_STATIC, THREAD_CALLBACKS_FIELD, THREAD_LOCAL, null);
                e.declare_field(Constants.PRIVATE_FINAL_STATIC, STATIC_CALLBACKS_FIELD, CALLBACK_ARRAY, null);
                if (serialVersionUID != null) {
                        e.declare_field(Constants.PRIVATE_FINAL_STATIC, Constants.SUID_FIELD_NAME, Type.LONG_TYPE, serialVersionUID);
                }

                for (int i = 0; i < callbackTypes.length; i++) {
                        e.declare_field(Constants.ACC_PRIVATE, getCallbackField(i), callbackTypes[i], null);
                }
                // This is declared private to avoid "public field" pollution
                e.declare_field(Constants.ACC_PRIVATE | Constants.ACC_STATIC, CALLBACK_FILTER_FIELD, OBJECT_TYPE, null);

                if (currentData == null) {
                        emitMethods(e, methods, actualMethods);
                        emitConstructors(e, constructorInfo);
                }
                else {
                        emitDefaultConstructor(e);
                }
                emitSetThreadCallbacks(e);
                emitSetStaticCallbacks(e);
                emitBindCallbacks(e);

                if (useFactory || currentData != null) {
                        int[] keys = getCallbackKeys();
                        emitNewInstanceCallbacks(e);
                        emitNewInstanceCallback(e);
                        emitNewInstanceMultiarg(e, constructorInfo);
                        emitGetCallback(e, keys);
                        emitSetCallback(e, keys);
                        emitGetCallbacks(e);
                        emitSetCallbacks(e);
                }

                e.end_class();
        }

        /**
         * Filter the list of constructors from the superclass. The
         * constructors which remain will be included in the generated
         * class. The default implementation is to filter out all private
         * constructors, but subclasses may extend Enhancer to override this
         * behavior.
         * @param sc the superclass
         * @param constructors the list of all declared constructors from the superclass
         * @throws IllegalArgumentException if there are no non-private constructors
         */
        protected void filterConstructors(Class sc, List constructors) {
                CollectionUtils.filter(constructors, new VisibilityPredicate(sc, true));
                if (constructors.size() == 0)
                        throw new IllegalArgumentException("No visible constructors in " + sc);
        }

        /**
         * This method should not be called in regular flow.
         * Technically speaking {@link #wrapCachedClass(Class)} uses {@link Enhancer.EnhancerFactoryData} as a cache value,
         * and the latter enables faster instantiation than plain old reflection lookup and invoke.
         * This method is left intact for backward compatibility reasons: just in case it was ever used.
         * @param type class to instantiate
         * @return newly created proxy instance
         * @throws Exception if something goes wrong
         */
        protected Object firstInstance(Class type) throws Exception {
                if (classOnly) {
                        return type;
                }
                else {
                        return createUsingReflection(type);
                }
        }

        protected Object nextInstance(Object instance) {
                EnhancerFactoryData data = (EnhancerFactoryData) instance;

                if (classOnly) {
                        return data.generatedClass;
                }

                Class[] argumentTypes = this.argumentTypes;
                Object[] arguments = this.arguments;
                if (argumentTypes == null) {
                        argumentTypes = Constants.EMPTY_CLASS_ARRAY;
                        arguments = null;
                }
                return data.newInstance(argumentTypes, arguments, callbacks);
        }

        @Override
        protected Object wrapCachedClass(Class klass) {
                Class[] argumentTypes = this.argumentTypes;
                if (argumentTypes == null) {
                        argumentTypes = Constants.EMPTY_CLASS_ARRAY;
                }
                EnhancerFactoryData factoryData = new EnhancerFactoryData(klass, argumentTypes, classOnly);
                Field factoryDataField = null;
                try {
                        // The subsequent dance is performed just once for each class,
                        // so it does not matter much how fast it goes
                        factoryDataField = klass.getField(FACTORY_DATA_FIELD);
                        factoryDataField.set(null, factoryData);
                        Field callbackFilterField = klass.getDeclaredField(CALLBACK_FILTER_FIELD);
                        callbackFilterField.setAccessible(true);
                        callbackFilterField.set(null, this.filter);
                }
                catch (NoSuchFieldException e) {
                        throw new CodeGenerationException(e);
                }
                catch (IllegalAccessException e) {
                        throw new CodeGenerationException(e);
                }
                return new WeakReference<EnhancerFactoryData>(factoryData);
        }

        @Override
        protected Object unwrapCachedValue(Object cached) {
                if (currentKey instanceof EnhancerKey) {
                        EnhancerFactoryData data = ((WeakReference<EnhancerFactoryData>) cached).get();
                        return data;
                }
                return super.unwrapCachedValue(cached);
        }

        /**
         * Call this method to register the {@link Callback} array to use before
         * creating a new instance of the generated class via reflection. If you are using
         * an instance of <code>Enhancer</code> or the {@link Factory} interface to create
         * new instances, this method is unnecessary. Its primary use is for when you want to
         * cache and reuse a generated class yourself, and the generated class does
         * <i>not</i> implement the {@link Factory} interface.
         * <p>
         * Note that this method only registers the callbacks on the current thread.
         * If you want to register callbacks for instances created by multiple threads,
         * use {@link #registerStaticCallbacks}.
         * <p>
         * The registered callbacks are overwritten and subsequently cleared
         * when calling any of the <code>create</code> methods (such as
         * {@link #create}), or any {@link Factory} <code>newInstance</code> method.
         * Otherwise they are <i>not</i> cleared, and you should be careful to set them
         * back to <code>null</code> after creating new instances via reflection if
         * memory leakage is a concern.
         * @param generatedClass a class previously created by {@link Enhancer}
         * @param callbacks the array of callbacks to use when instances of the generated
         * class are created
         * @see #setUseFactory
         */
        public static void registerCallbacks(Class generatedClass, Callback[] callbacks) {
                setThreadCallbacks(generatedClass, callbacks);
        }

        /**
         * Similar to {@link #registerCallbacks}, but suitable for use
         * when multiple threads will be creating instances of the generated class.
         * The thread-level callbacks will always override the static callbacks.
         * Static callbacks are never cleared.
         * @param generatedClass a class previously created by {@link Enhancer}
         * @param callbacks the array of callbacks to use when instances of the generated
         * class are created
         */
        public static void registerStaticCallbacks(Class generatedClass, Callback[] callbacks) {
                setCallbacksHelper(generatedClass, callbacks, SET_STATIC_CALLBACKS_NAME);
        }

        /**
         * Determine if a class was generated using <code>Enhancer</code>.
         * @param type any class
         * @return whether the class was generated  using <code>Enhancer</code>
         */
        public static boolean isEnhanced(Class type) {
                try {
                        getCallbacksSetter(type, SET_THREAD_CALLBACKS_NAME);
                        return true;
                }
                catch (NoSuchMethodException e) {
                        return false;
                }
        }

        private static void setThreadCallbacks(Class type, Callback[] callbacks) {
                setCallbacksHelper(type, callbacks, SET_THREAD_CALLBACKS_NAME);
        }

        private static void setCallbacksHelper(Class type, Callback[] callbacks, String methodName) {
                // TODO: optimize
                try {
                        Method setter = getCallbacksSetter(type, methodName);
                        setter.invoke(null, new Object[]{callbacks});
                }
                catch (NoSuchMethodException e) {
                        throw new IllegalArgumentException(type + " is not an enhanced class");
                }
                catch (IllegalAccessException e) {
                        throw new CodeGenerationException(e);
                }
                catch (InvocationTargetException e) {
                        throw new CodeGenerationException(e);
                }
        }

        private static Method getCallbacksSetter(Class type, String methodName) throws NoSuchMethodException {
                return type.getDeclaredMethod(methodName, new Class[]{Callback[].class});
        }

        /**
         * Instantiates a proxy instance and assigns callback values.
         * Implementation detail: java.lang.reflect instances are not cached, so this method should not
         * be used on a hot path.
         * This method is used when {@link #setUseCache(boolean)} is set to {@code false}.
         * @param type class to instantiate
         * @return newly created instance
         */
        private Object createUsingReflection(Class type) {
                setThreadCallbacks(type, callbacks);
                try {

                        if (argumentTypes != null) {

                                return ReflectUtils.newInstance(type, argumentTypes, arguments);

                        }
                        else {

                                return ReflectUtils.newInstance(type);

                        }
                }
                finally {
                        // clear thread callbacks to allow them to be gc'd
                        setThreadCallbacks(type, null);
                }
        }

        /**
         * Helper method to create an intercepted object.
         * For finer control over the generated instance, use a new instance of <code>Enhancer</code>
         * instead of this static method.
         * @param type class to extend or interface to implement
         * @param callback the callback to use for all methods
         */
        public static Object create(Class type, Callback callback) {
                Enhancer e = new Enhancer();
                e.setSuperclass(type);
                e.setCallback(callback);
                return e.create();
        }

        /**
         * Helper method to create an intercepted object.
         * For finer control over the generated instance, use a new instance of <code>Enhancer</code>
         * instead of this static method.
         * @param superclass class to extend or interface to implement
         * @param interfaces array of interfaces to implement, or null
         * @param callback the callback to use for all methods
         */
        public static Object create(Class superclass, Class interfaces[], Callback callback) {
                Enhancer e = new Enhancer();
                e.setSuperclass(superclass);
                e.setInterfaces(interfaces);
                e.setCallback(callback);
                return e.create();
        }

        /**
         * Helper method to create an intercepted object.
         * For finer control over the generated instance, use a new instance of <code>Enhancer</code>
         * instead of this static method.
         * @param superclass class to extend or interface to implement
         * @param interfaces array of interfaces to implement, or null
         * @param filter the callback filter to use when generating a new class
         * @param callbacks callback implementations to use for the enhanced object
         */
        public static Object create(Class superclass, Class[] interfaces, CallbackFilter filter, Callback[] callbacks) {
                Enhancer e = new Enhancer();
                e.setSuperclass(superclass);
                e.setInterfaces(interfaces);
                e.setCallbackFilter(filter);
                e.setCallbacks(callbacks);
                return e.create();
        }

        private void emitDefaultConstructor(ClassEmitter ce) {
                Constructor<Object> declaredConstructor;
                try {
                        declaredConstructor = Object.class.getDeclaredConstructor();
                }
                catch (NoSuchMethodException e) {
                        throw new IllegalStateException("Object should have default constructor ", e);
                }
                MethodInfo constructor = (MethodInfo) MethodInfoTransformer.getInstance().transform(declaredConstructor);
                CodeEmitter e = EmitUtils.begin_method(ce, constructor, Constants.ACC_PUBLIC);
                e.load_this();
                e.dup();
                Signature sig = constructor.getSignature();
                e.super_invoke_constructor(sig);
                e.return_value();
                e.end_method();
        }

        private void emitConstructors(ClassEmitter ce, List constructors) {
                boolean seenNull = false;
                for (Iterator it = constructors.iterator(); it.hasNext(); ) {
                        MethodInfo constructor = (MethodInfo) it.next();
                        if (currentData != null && !"()V".equals(constructor.getSignature().getDescriptor())) {
                                continue;
                        }
                        CodeEmitter e = EmitUtils.begin_method(ce, constructor, Constants.ACC_PUBLIC);
                        e.load_this();
                        e.dup();
                        e.load_args();
                        Signature sig = constructor.getSignature();
                        seenNull = seenNull || sig.getDescriptor().equals("()V");
                        e.super_invoke_constructor(sig);
                        if (currentData == null) {
                                e.invoke_static_this(BIND_CALLBACKS);
                                if (!interceptDuringConstruction) {
                                        e.load_this();
                                        e.push(1);
                                        e.putfield(CONSTRUCTED_FIELD);
                                }
                        }
                        e.return_value();
                        e.end_method();
                }
                if (!classOnly && !seenNull && arguments == null)
                        throw new IllegalArgumentException("Superclass has no null constructors but no arguments were given");
        }

        private int[] getCallbackKeys() {
                int[] keys = new int[callbackTypes.length];
                for (int i = 0; i < callbackTypes.length; i++) {
                        keys[i] = i;
                }
                return keys;
        }

        private void emitGetCallback(ClassEmitter ce, int[] keys) {
                final CodeEmitter e = ce.begin_method(Constants.ACC_PUBLIC, GET_CALLBACK, null);
                e.load_this();
                e.invoke_static_this(BIND_CALLBACKS);
                e.load_this();
                e.load_arg(0);
                e.process_switch(keys, new ProcessSwitchCallback() {
                        public void processCase(int key, Label end) {
                                e.getfield(getCallbackField(key));
                                e.goTo(end);
                        }

                        public void processDefault() {
                                e.pop(); // stack height
                                e.aconst_null();
                        }
                });
                e.return_value();
                e.end_method();
        }

        private void emitSetCallback(ClassEmitter ce, int[] keys) {
                final CodeEmitter e = ce.begin_method(Constants.ACC_PUBLIC, SET_CALLBACK, null);
                e.load_arg(0);
                e.process_switch(keys, new ProcessSwitchCallback() {
                        public void processCase(int key, Label end) {
                                e.load_this();
                                e.load_arg(1);
                                e.checkcast(callbackTypes[key]);
                                e.putfield(getCallbackField(key));
                                e.goTo(end);
                        }

                        public void processDefault() {
                                // TODO: error?
                        }
                });
                e.return_value();
                e.end_method();
        }

        private void emitSetCallbacks(ClassEmitter ce) {
                CodeEmitter e = ce.begin_method(Constants.ACC_PUBLIC, SET_CALLBACKS, null);
                e.load_this();
                e.load_arg(0);
                for (int i = 0; i < callbackTypes.length; i++) {
                        e.dup2();
                        e.aaload(i);
                        e.checkcast(callbackTypes[i]);
                        e.putfield(getCallbackField(i));
                }
                e.return_value();
                e.end_method();
        }

        private void emitGetCallbacks(ClassEmitter ce) {
                CodeEmitter e = ce.begin_method(Constants.ACC_PUBLIC, GET_CALLBACKS, null);
                e.load_this();
                e.invoke_static_this(BIND_CALLBACKS);
                e.load_this();
                e.push(callbackTypes.length);
                e.newarray(CALLBACK);
                for (int i = 0; i < callbackTypes.length; i++) {
                        e.dup();
                        e.push(i);
                        e.load_this();
                        e.getfield(getCallbackField(i));
                        e.aastore();
                }
                e.return_value();
                e.end_method();
        }

        private void emitNewInstanceCallbacks(ClassEmitter ce) {
                CodeEmitter e = ce.begin_method(Constants.ACC_PUBLIC, NEW_INSTANCE, null);
                Type thisType = getThisType(e);
                e.load_arg(0);
                e.invoke_static(thisType, SET_THREAD_CALLBACKS, false);
                emitCommonNewInstance(e);
        }

        private Type getThisType(CodeEmitter e) {
                if (currentData == null) {
                        return e.getClassEmitter().getClassType();
                }
                else {
                        return Type.getType(currentData.generatedClass);
                }
        }

        private void emitCommonNewInstance(CodeEmitter e) {
                Type thisType = getThisType(e);
                e.new_instance(thisType);
                e.dup();
                e.invoke_constructor(thisType);
                e.aconst_null();
                e.invoke_static(thisType, SET_THREAD_CALLBACKS, false);
                e.return_value();
                e.end_method();
        }

        private void emitNewInstanceCallback(ClassEmitter ce) {
                CodeEmitter e = ce.begin_method(Constants.ACC_PUBLIC, SINGLE_NEW_INSTANCE, null);
                switch (callbackTypes.length) {
                        case 0:
                                // TODO: make sure Callback is null
                                break;
                        case 1:
                                // for now just make a new array; TODO: optimize
                                e.push(1);
                                e.newarray(CALLBACK);
                                e.dup();
                                e.push(0);
                                e.load_arg(0);
                                e.aastore();
                                e.invoke_static(getThisType(e), SET_THREAD_CALLBACKS, false);
                                break;
                        default:
                                e.throw_exception(ILLEGAL_STATE_EXCEPTION, "More than one callback object required");
                }
                emitCommonNewInstance(e);
        }

        private void emitNewInstanceMultiarg(ClassEmitter ce, List constructors) {
                final CodeEmitter e = ce.begin_method(Constants.ACC_PUBLIC, MULTIARG_NEW_INSTANCE, null);
                final Type thisType = getThisType(e);
                e.load_arg(2);
                e.invoke_static(thisType, SET_THREAD_CALLBACKS, false);
                e.new_instance(thisType);
                e.dup();
                e.load_arg(0);
                EmitUtils.constructor_switch(e, constructors, new ObjectSwitchCallback() {
                        public void processCase(Object key, Label end) {
                                MethodInfo constructor = (MethodInfo) key;
                                Type types[] = constructor.getSignature().getArgumentTypes();
                                for (int i = 0; i < types.length; i++) {
                                        e.load_arg(1);
                                        e.push(i);
                                        e.aaload();
                                        e.unbox(types[i]);
                                }
                                e.invoke_constructor(thisType, constructor.getSignature());
                                e.goTo(end);
                        }

                        public void processDefault() {
                                e.throw_exception(ILLEGAL_ARGUMENT_EXCEPTION, "Constructor not found");
                        }
                });
                e.aconst_null();
                e.invoke_static(thisType, SET_THREAD_CALLBACKS, false);
                e.return_value();
                e.end_method();
        }

        private void emitMethods(final ClassEmitter ce, List methods, List actualMethods) {
                CallbackGenerator[] generators = CallbackInfo.getGenerators(callbackTypes);

                Map groups = new HashMap();
                final Map indexes = new HashMap();
                final Map originalModifiers = new HashMap();
                final Map positions = CollectionUtils.getIndexMap(methods);
                final Map declToBridge = new HashMap();

                Iterator it1 = methods.iterator();
                Iterator it2 = (actualMethods != null) ? actualMethods.iterator() : null;

                while (it1.hasNext()) {
                        MethodInfo method = (MethodInfo) it1.next();
                        Method actualMethod = (it2 != null) ? (Method) it2.next() : null;
                        int index = filter.accept(actualMethod);
                        if (index >= callbackTypes.length) {
                                throw new IllegalArgumentException("Callback filter returned an index that is too large: " + index);
                        }
                        originalModifiers.put(method, (actualMethod != null ? actualMethod.getModifiers() : method.getModifiers()));
                        indexes.put(method, index);
                        List group = (List) groups.get(generators[index]);
                        if (group == null) {
                                groups.put(generators[index], group = new ArrayList(methods.size()));
                        }
                        group.add(method);

                        // Optimization: build up a map of Class -> bridge methods in class
                        // so that we can look up all the bridge methods in one pass for a class.
                        if (TypeUtils.isBridge(actualMethod.getModifiers())) {
                                Set bridges = (Set) declToBridge.get(actualMethod.getDeclaringClass());
                                if (bridges == null) {
                                        bridges = new HashSet();
                                        declToBridge.put(actualMethod.getDeclaringClass(), bridges);
                                }
                                bridges.add(method.getSignature());
                        }
                }

                final Map bridgeToTarget = new BridgeMethodResolver(declToBridge, getClassLoader()).resolveAll();

                Set seenGen = new HashSet();
                CodeEmitter se = ce.getStaticHook();
                se.new_instance(THREAD_LOCAL);
                se.dup();
                se.invoke_constructor(THREAD_LOCAL, CSTRUCT_NULL);
                se.putfield(THREAD_CALLBACKS_FIELD);

                final Object[] state = new Object[1];
                CallbackGenerator.Context context = new CallbackGenerator.Context() {
                        public ClassLoader getClassLoader() {
                                return Enhancer.this.getClassLoader();
                        }

                        public int getOriginalModifiers(MethodInfo method) {
                                return ((Integer) originalModifiers.get(method)).intValue();
                        }

                        public int getIndex(MethodInfo method) {
                                return ((Integer) indexes.get(method)).intValue();
                        }

                        public void emitCallback(CodeEmitter e, int index) {
                                emitCurrentCallback(e, index);
                        }

                        public Signature getImplSignature(MethodInfo method) {
                                return rename(method.getSignature(), ((Integer) positions.get(method)).intValue());
                        }

                        public void emitLoadArgsAndInvoke(CodeEmitter e, MethodInfo method) {
                                // If this is a bridge and we know the target was called from invokespecial,
                                // then we need to invoke_virtual w/ the bridge target instead of doing
                                // a super, because super may itself be using super, which would bypass
                                // any proxies on the target.
                                Signature bridgeTarget = (Signature) bridgeToTarget.get(method.getSignature());
                                if (bridgeTarget != null) {
                                        // checkcast each argument against the target's argument types
                                        for (int i = 0; i < bridgeTarget.getArgumentTypes().length; i++) {
                                                e.load_arg(i);
                                                Type target = bridgeTarget.getArgumentTypes()[i];
                                                if (!target.equals(method.getSignature().getArgumentTypes()[i])) {
                                                        e.checkcast(target);
                                                }
                                        }

                                        e.invoke_virtual_this(bridgeTarget);

                                        Type retType = method.getSignature().getReturnType();
                                        // Not necessary to cast if the target & bridge have
                                        // the same return type.
                                        // (This conveniently includes void and primitive types,
                                        // which would fail if casted.  It's not possible to
                                        // covariant from boxed to unbox (or vice versa), so no having
                                        // to box/unbox for bridges).
                                        // TODO: It also isn't necessary to checkcast if the return is
                                        // assignable from the target.  (This would happen if a subclass
                                        // used covariant returns to narrow the return type within a bridge
                                        // method.)
                                        if (!retType.equals(bridgeTarget.getReturnType())) {
                                                e.checkcast(retType);
                                        }
                                }
                                else {
                                        e.load_args();
                                        e.super_invoke(method.getSignature());
                                }
                        }

                        public CodeEmitter beginMethod(ClassEmitter ce, MethodInfo method) {
                                CodeEmitter e = EmitUtils.begin_method(ce, method);
                                if (!interceptDuringConstruction &&
                                                !TypeUtils.isAbstract(method.getModifiers())) {
                                        Label constructed = e.make_label();
                                        e.load_this();
                                        e.getfield(CONSTRUCTED_FIELD);
                                        e.if_jump(CodeEmitter.NE, constructed);
                                        e.load_this();
                                        e.load_args();
                                        e.super_invoke();
                                        e.return_value();
                                        e.mark(constructed);
                                }
                                return e;
                        }
                };
                for (int i = 0; i < callbackTypes.length; i++) {
                        CallbackGenerator gen = generators[i];
                        if (!seenGen.contains(gen)) {
                                seenGen.add(gen);
                                final List fmethods = (List) groups.get(gen);
                                if (fmethods != null) {
                                        try {
                                                gen.generate(ce, context, fmethods);
                                                gen.generateStatic(se, context, fmethods);
                                        }
                                        catch (RuntimeException x) {
                                                throw x;
                                        }
                                        catch (Exception x) {
                                                throw new CodeGenerationException(x);
                                        }
                                }
                        }
                }
                se.return_value();
                se.end_method();
        }

        private void emitSetThreadCallbacks(ClassEmitter ce) {
                CodeEmitter e = ce.begin_method(Constants.ACC_PUBLIC | Constants.ACC_STATIC,
                                SET_THREAD_CALLBACKS,
                                null);
                e.getfield(THREAD_CALLBACKS_FIELD);
                e.load_arg(0);
                e.invoke_virtual(THREAD_LOCAL, THREAD_LOCAL_SET);
                e.return_value();
                e.end_method();
        }

        private void emitSetStaticCallbacks(ClassEmitter ce) {
                CodeEmitter e = ce.begin_method(Constants.ACC_PUBLIC | Constants.ACC_STATIC,
                                SET_STATIC_CALLBACKS,
                                null);
                e.load_arg(0);
                e.putfield(STATIC_CALLBACKS_FIELD);
                e.return_value();
                e.end_method();
        }

        private void emitCurrentCallback(CodeEmitter e, int index) {
                e.load_this();
                e.getfield(getCallbackField(index));
                e.dup();
                Label end = e.make_label();
                e.ifnonnull(end);
                e.pop(); // stack height
                e.load_this();
                e.invoke_static_this(BIND_CALLBACKS);
                e.load_this();
                e.getfield(getCallbackField(index));
                e.mark(end);
        }

        private void emitBindCallbacks(ClassEmitter ce) {
                CodeEmitter e = ce.begin_method(Constants.PRIVATE_FINAL_STATIC,
                                BIND_CALLBACKS,
                                null);
                Local me = e.make_local();
                e.load_arg(0);
                e.checkcast_this();
                e.store_local(me);

                Label end = e.make_label();
                e.load_local(me);
                e.getfield(BOUND_FIELD);
                e.if_jump(CodeEmitter.NE, end);
                e.load_local(me);
                e.push(1);
                e.putfield(BOUND_FIELD);

                e.getfield(THREAD_CALLBACKS_FIELD);
                e.invoke_virtual(THREAD_LOCAL, THREAD_LOCAL_GET);
                e.dup();
                Label found_callback = e.make_label();
                e.ifnonnull(found_callback);
                e.pop();

                e.getfield(STATIC_CALLBACKS_FIELD);
                e.dup();
                e.ifnonnull(found_callback);
                e.pop();
                e.goTo(end);

                e.mark(found_callback);
                e.checkcast(CALLBACK_ARRAY);
                e.load_local(me);
                e.swap();
                for (int i = callbackTypes.length - 1; i >= 0; i--) {
                        if (i != 0) {
                                e.dup2();
                        }
                        e.aaload(i);
                        e.checkcast(callbackTypes[i]);
                        e.putfield(getCallbackField(i));
                }

                e.mark(end);
                e.return_value();
                e.end_method();
        }

        private static String getCallbackField(int index) {
                return "CGLIB$CALLBACK_" + index;
        }

}