Mercurial > jdk8-mips64-public > nashorn / file revision

 /*

  * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.  Oracle designates this

  * particular file as subject to the "Classpath" exception as provided

  * by Oracle in the LICENSE file that accompanied this code.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

  * or visit www.oracle.com if you need additional information or have any

  * questions.

  */

 package jdk.nashorn.internal.runtime.linker;

 import static jdk.internal.org.objectweb.asm.Opcodes.ACC_FINAL;

 import static jdk.internal.org.objectweb.asm.Opcodes.ACC_PRIVATE;

 import static jdk.internal.org.objectweb.asm.Opcodes.ACC_PUBLIC;

 import static jdk.internal.org.objectweb.asm.Opcodes.ACC_STATIC;

 import static jdk.internal.org.objectweb.asm.Opcodes.ACC_SUPER;

 import static jdk.internal.org.objectweb.asm.Opcodes.ACC_VARARGS;

 import static jdk.internal.org.objectweb.asm.Opcodes.ACONST_NULL;

 import static jdk.internal.org.objectweb.asm.Opcodes.ALOAD;

 import static jdk.internal.org.objectweb.asm.Opcodes.ASTORE;

 import static jdk.internal.org.objectweb.asm.Opcodes.DUP;

 import static jdk.internal.org.objectweb.asm.Opcodes.IFNONNULL;

 import static jdk.internal.org.objectweb.asm.Opcodes.ILOAD;

 import static jdk.internal.org.objectweb.asm.Opcodes.ISTORE;

 import static jdk.internal.org.objectweb.asm.Opcodes.POP;

 import static jdk.internal.org.objectweb.asm.Opcodes.RETURN;

 import static jdk.nashorn.internal.lookup.Lookup.MH;

 import static jdk.nashorn.internal.runtime.linker.AdaptationResult.Outcome.ERROR_NO_ACCESSIBLE_CONSTRUCTOR;

 import java.lang.invoke.MethodHandle;

 import java.lang.invoke.MethodType;

 import java.lang.reflect.AccessibleObject;

 import java.lang.reflect.Constructor;

 import java.lang.reflect.Method;

 import java.lang.reflect.Modifier;

 import java.security.AccessControlContext;

 import java.security.AccessController;

 import java.security.PrivilegedAction;

 import java.util.Arrays;

 import java.util.Collection;

 import java.util.HashSet;

 import java.util.Iterator;

 import java.util.LinkedHashMap;

 import java.util.List;

 import java.util.Map;

 import java.util.Set;

 import jdk.internal.org.objectweb.asm.ClassWriter;

 import jdk.internal.org.objectweb.asm.Handle;

 import jdk.internal.org.objectweb.asm.Label;

 import jdk.internal.org.objectweb.asm.Opcodes;

 import jdk.internal.org.objectweb.asm.Type;

 import jdk.internal.org.objectweb.asm.commons.InstructionAdapter;

 import jdk.nashorn.api.scripting.ScriptUtils;

 import jdk.nashorn.internal.runtime.Context;

 import jdk.nashorn.internal.runtime.JSType;

 import jdk.nashorn.internal.runtime.ScriptFunction;

 import jdk.nashorn.internal.runtime.ScriptObject;

 import jdk.nashorn.internal.runtime.linker.AdaptationResult.Outcome;

 import sun.reflect.CallerSensitive;

 /**

  * Generates bytecode for a Java adapter class. Used by the {@link JavaAdapterFactory}.

  * </p><p>

  * For every protected or public constructor in the extended class, the adapter class will have either one or two

  * public constructors (visibility of protected constructors in the extended class is promoted to public).

  * <li>

  * <li>For adapter classes with instance-level overrides, a constructor taking a trailing ScriptObject argument preceded

  * by original constructor arguments is always created on the adapter class. When such a constructor is invoked, the

  * passed ScriptObject's member functions are used to implement and/or override methods on the original class,

  * dispatched by name. A single JavaScript function will act as the implementation for all overloaded methods of the

  * same name. When methods on an adapter instance are invoked, the functions are invoked having the ScriptObject passed

  * in the instance constructor as their "this". Subsequent changes to the ScriptObject (reassignment or removal of its

  * functions) are not reflected in the adapter instance; the method implementations are bound to functions at

  * constructor invocation time.

  * {@code java.lang.Object} methods {@code equals}, {@code hashCode}, and {@code toString} can also be overridden. The

  * only restriction is that since every JavaScript object already has a {@code toString} function through the

  * {@code Object.prototype}, the {@code toString} in the adapter is only overridden if the passed ScriptObject has a

  * {@code toString} function as its own property, and not inherited from a prototype. All other adapter methods can be

  * implemented or overridden through a prototype-inherited function of the ScriptObject passed to the constructor too.

  * </li>

  * <li>

  * If the original types collectively have only one abstract method, or have several of them, but all share the

  * same name, an additional constructor for instance-level override adapter is provided for every original constructor;

  * this one takes a ScriptFunction as its last argument preceded by original constructor arguments. This constructor

  * will use the passed function as the implementation for all abstract methods. For consistency, any concrete methods

  * sharing the single abstract method name will also be overridden by the function. When methods on the adapter instance

  * are invoked, the ScriptFunction is invoked with UNDEFINED or Global as its "this" depending whether the function is

  * strict or not.

  * </li>

  * <li>

  * If the adapter being generated can have class-level overrides, constructors taking same arguments as the superclass

  * constructors are created. These constructors simply delegate to the superclass constructor. They are simply used to

  * create instances of the adapter class, with no instance-level overrides, as they don't have them. If the original

  * class' constructor was variable arity, the adapter constructor will also be variable arity. Protected constructors

  * are exposed as public.

  * </li>

  * </ul>

  * </p><p>

  * For adapter methods that return values, all the JavaScript-to-Java conversions supported by Nashorn will be in effect

  * to coerce the JavaScript function return value to the expected Java return type.

  * </p><p>

  * Since we are adding a trailing argument to the generated constructors in the adapter class, they will never be

  * declared as variable arity, even if the original constructor in the superclass was declared as variable arity. The

  * reason we are passing the additional argument at the end of the argument list instead at the front is that the

  * source-level script expression <code>new X(a, b) { ... }</code> (which is a proprietary syntax extension Nashorn uses

  * to resemble Java anonymous classes) is actually equivalent to <code>new X(a, b, { ... })</code>.

  * </p><p>

  * It is possible to create two different adapter classes: those that can have class-level overrides, and those that can

  * have instance-level overrides. When {@link JavaAdapterFactory#getAdapterClassFor(Class[], ScriptObject)} is invoked

  * with non-null {@code classOverrides} parameter, an adapter class is created that can have class-level overrides, and

  * the passed script object will be used as the implementations for its methods, just as in the above case of the

  * constructor taking a script object. Note that in the case of class-level overrides, a new adapter class is created on

  * every invocation, and the implementation object is bound to the class, not to any instance. All created instances

  * will share these functions. If it is required to have both class-level overrides and instance-level overrides, the

  * class-level override adapter class should be subclassed with an instance-override adapter. Since adapters delegate to

  * super class when an overriding method handle is not specified, this will behave as expected. It is not possible to

  * have both class-level and instance-level overrides in the same class for security reasons: adapter classes are

  * defined with a protection domain of their creator code, and an adapter class that has both class and instance level

  * overrides would need to have two potentially different protection domains: one for class-based behavior and one for

  * instance-based behavior; since Java classes can only belong to a single protection domain, this could not be

  * implemented securely.

  */

 final class JavaAdapterBytecodeGenerator {

     private static final Type SCRIPTUTILS_TYPE = Type.getType(ScriptUtils.class);

     private static final Type OBJECT_TYPE = Type.getType(Object.class);

     private static final Type CLASS_TYPE  = Type.getType(Class.class);

     static final String OBJECT_TYPE_NAME  = OBJECT_TYPE.getInternalName();

     static final String SCRIPTUTILS_TYPE_NAME  = SCRIPTUTILS_TYPE.getInternalName();

     static final String INIT = "<init>";

     static final String GLOBAL_FIELD_NAME = "global";

     // "global" is declared as Object instead of Global - avoid static references to internal Nashorn classes when possible.

     static final String GLOBAL_TYPE_DESCRIPTOR = OBJECT_TYPE.getDescriptor();

     static final String SET_GLOBAL_METHOD_DESCRIPTOR = Type.getMethodDescriptor(Type.VOID_TYPE, OBJECT_TYPE);

     static final String VOID_NOARG_METHOD_DESCRIPTOR = Type.getMethodDescriptor(Type.VOID_TYPE);

     private static final Type SCRIPT_OBJECT_TYPE = Type.getType(ScriptObject.class);

     private static final Type SCRIPT_FUNCTION_TYPE = Type.getType(ScriptFunction.class);

     private static final Type STRING_TYPE = Type.getType(String.class);

     private static final Type METHOD_TYPE_TYPE = Type.getType(MethodType.class);

     private static final Type METHOD_HANDLE_TYPE = Type.getType(MethodHandle.class);

     private static final String GET_HANDLE_OBJECT_DESCRIPTOR = Type.getMethodDescriptor(METHOD_HANDLE_TYPE,

             OBJECT_TYPE, STRING_TYPE, METHOD_TYPE_TYPE);

     private static final String GET_HANDLE_FUNCTION_DESCRIPTOR = Type.getMethodDescriptor(METHOD_HANDLE_TYPE,

             SCRIPT_FUNCTION_TYPE, METHOD_TYPE_TYPE);

     private static final String GET_CLASS_INITIALIZER_DESCRIPTOR = Type.getMethodDescriptor(OBJECT_TYPE);

     private static final Type RUNTIME_EXCEPTION_TYPE = Type.getType(RuntimeException.class);

     private static final Type THROWABLE_TYPE = Type.getType(Throwable.class);

     private static final Type UNSUPPORTED_OPERATION_TYPE = Type.getType(UnsupportedOperationException.class);

     private static final String SERVICES_CLASS_TYPE_NAME = Type.getInternalName(JavaAdapterServices.class);

     private static final String RUNTIME_EXCEPTION_TYPE_NAME = RUNTIME_EXCEPTION_TYPE.getInternalName();

     private static final String ERROR_TYPE_NAME = Type.getInternalName(Error.class);

     private static final String THROWABLE_TYPE_NAME = THROWABLE_TYPE.getInternalName();

     private static final String UNSUPPORTED_OPERATION_TYPE_NAME = UNSUPPORTED_OPERATION_TYPE.getInternalName();

     private static final String METHOD_HANDLE_TYPE_DESCRIPTOR = METHOD_HANDLE_TYPE.getDescriptor();

     private static final String GET_GLOBAL_METHOD_DESCRIPTOR = Type.getMethodDescriptor(OBJECT_TYPE);

     private static final String GET_CLASS_METHOD_DESCRIPTOR = Type.getMethodDescriptor(CLASS_TYPE);

     private static final String EXPORT_RETURN_VALUE_METHOD_DESCRIPTOR = Type.getMethodDescriptor(OBJECT_TYPE, OBJECT_TYPE);

     private static final String UNWRAP_METHOD_DESCRIPTOR = Type.getMethodDescriptor(OBJECT_TYPE, OBJECT_TYPE);

     private static final String GET_CONVERTER_METHOD_DESCRIPTOR = Type.getMethodDescriptor(METHOD_HANDLE_TYPE, CLASS_TYPE);

     private static final String TO_CHAR_PRIMITIVE_METHOD_DESCRIPTOR = Type.getMethodDescriptor(Type.CHAR_TYPE, OBJECT_TYPE);

     private static final String TO_STRING_METHOD_DESCRIPTOR = Type.getMethodDescriptor(STRING_TYPE, OBJECT_TYPE);

     // Package used when the adapter can't be defined in the adaptee's package (either because it's sealed, or because

     // it's a java.* package.

     private static final String ADAPTER_PACKAGE_PREFIX = "jdk/nashorn/javaadapters/";

     // Class name suffix used to append to the adaptee class name, when it can be defined in the adaptee's package.

     private static final String ADAPTER_CLASS_NAME_SUFFIX = "$$NashornJavaAdapter";

     private static final String JAVA_PACKAGE_PREFIX = "java/";

     private static final int MAX_GENERATED_TYPE_NAME_LENGTH = 255;

     private static final String CLASS_INIT = "<clinit>";

     // Method name prefix for invoking super-methods

     static final String SUPER_PREFIX = "super$";

     /**

      * Collection of methods we never override: Object.clone(), Object.finalize().

      */

     private static final Collection<MethodInfo> EXCLUDED = getExcludedMethods();

     // This is the superclass for our generated adapter.

     private final Class<?> superClass;

     // Interfaces implemented by our generated adapter.

     private final List<Class<?>> interfaces;

     // Class loader used as the parent for the class loader we'll create to load the generated class. It will be a class

     // loader that has the visibility of all original types (class to extend and interfaces to implement) and of the

     // Nashorn classes.

     private final ClassLoader commonLoader;

     // Is this a generator for the version of the class that can have overrides on the class level?

     private final boolean classOverride;

     // Binary name of the superClass

     private final String superClassName;

     // Binary name of the generated class.

     private final String generatedClassName;

     private final Set<String> usedFieldNames = new HashSet<>();

     private final Set<String> abstractMethodNames = new HashSet<>();

     private final String samName;

     private final Set<MethodInfo> finalMethods = new HashSet<>(EXCLUDED);

     private final Set<MethodInfo> methodInfos = new HashSet<>();

     private boolean autoConvertibleFromFunction = false;

     private boolean hasExplicitFinalizer = false;

     /**

      * Names of static fields holding type converter method handles for return value conversion. We are emitting code

      * for invoking these explicitly after the delegate handle is invoked, instead of doing an asType or

      * filterReturnValue on the delegate handle, as that would create a new converter handle wrapping the function's

      * handle for every instance of the adapter, causing the handle.invokeExact() call sites to become megamorphic.

      */

     private final Map<Class<?>, String> converterFields = new LinkedHashMap<>();

     /**

      * Subset of possible return types for all methods; namely, all possible return types of the SAM methods (we

      * identify SAM types by having all of their abstract methods share a single name, so there can be multiple

      * overloads with multiple return types. We use this set when emitting the constructor taking a ScriptFunction (the

      * SAM initializer) to avoid populating converter fields that will never be used by SAM methods.

      */

     private final Set<Class<?>> samReturnTypes = new HashSet<>();

     private final ClassWriter cw;

     /**

      * Creates a generator for the bytecode for the adapter for the specified superclass and interfaces.

      * @param superClass the superclass the adapter will extend.

      * @param interfaces the interfaces the adapter will implement.

      * @param commonLoader the class loader that can see all of superClass, interfaces, and Nashorn classes.

      * @param classOverride true to generate the bytecode for the adapter that has class-level overrides, false to

      * generate the bytecode for the adapter that has instance-level overrides.

      * @throws AdaptationException if the adapter can not be generated for some reason.

      */

     JavaAdapterBytecodeGenerator(final Class<?> superClass, final List<Class<?>> interfaces,

             final ClassLoader commonLoader, final boolean classOverride) throws AdaptationException {

         assert superClass != null && !superClass.isInterface();

         assert interfaces != null;

         this.superClass = superClass;

         this.interfaces = interfaces;

         this.classOverride = classOverride;

         this.commonLoader = commonLoader;

         cw = new ClassWriter(ClassWriter.COMPUTE_FRAMES | ClassWriter.COMPUTE_MAXS) {

             @Override

             protected String getCommonSuperClass(final String type1, final String type2) {

                 // We need to override ClassWriter.getCommonSuperClass to use this factory's commonLoader as a class

                 // loader to find the common superclass of two types when needed.

                 return JavaAdapterBytecodeGenerator.this.getCommonSuperClass(type1, type2);

             }

         };

         superClassName = Type.getInternalName(superClass);

         generatedClassName = getGeneratedClassName(superClass, interfaces);

         cw.visit(Opcodes.V1_7, ACC_PUBLIC | ACC_SUPER, generatedClassName, null, superClassName, getInternalTypeNames(interfaces));

         generateGlobalFields();

         gatherMethods(superClass);

         gatherMethods(interfaces);

         samName = abstractMethodNames.size() == 1 ? abstractMethodNames.iterator().next() : null;

         generateHandleFields();

         generateConverterFields();

         if(classOverride) {

             generateClassInit();

         }

         generateConstructors();

         generateMethods();

         generateSuperMethods();

         if (hasExplicitFinalizer) {

             generateFinalizerMethods();

         }

         // }

         cw.visitEnd();

     }

     private void generateGlobalFields() {

         cw.visitField(ACC_PRIVATE | ACC_FINAL | (classOverride ? ACC_STATIC : 0), GLOBAL_FIELD_NAME, GLOBAL_TYPE_DESCRIPTOR, null, null).visitEnd();

         usedFieldNames.add(GLOBAL_FIELD_NAME);

     }

     JavaAdapterClassLoader createAdapterClassLoader() {

         return new JavaAdapterClassLoader(generatedClassName, cw.toByteArray());

     }

     boolean isAutoConvertibleFromFunction() {

         return autoConvertibleFromFunction;

     }

     private static String getGeneratedClassName(final Class<?> superType, final List<Class<?>> interfaces) {

         // The class we use to primarily name our adapter is either the superclass, or if it is Object (meaning we're

         // just implementing interfaces or extending Object), then the first implemented interface or Object.

         final Class<?> namingType = superType == Object.class ? (interfaces.isEmpty()? Object.class : interfaces.get(0)) : superType;

         final Package pkg = namingType.getPackage();

         final String namingTypeName = Type.getInternalName(namingType);

         final StringBuilder buf = new StringBuilder();

         if (namingTypeName.startsWith(JAVA_PACKAGE_PREFIX) || pkg == null || pkg.isSealed()) {

             // Can't define new classes in java.* packages

             buf.append(ADAPTER_PACKAGE_PREFIX).append(namingTypeName);

         } else {

             buf.append(namingTypeName).append(ADAPTER_CLASS_NAME_SUFFIX);

         }

         final Iterator<Class<?>> it = interfaces.iterator();

         if(superType == Object.class && it.hasNext()) {

             it.next(); // Skip first interface, it was used to primarily name the adapter

         }

         // Append interface names to the adapter name

         while(it.hasNext()) {

             buf.append("$$").append(it.next().getSimpleName());

         }

         return buf.toString().substring(0, Math.min(MAX_GENERATED_TYPE_NAME_LENGTH, buf.length()));

     }

     /**

      * Given a list of class objects, return an array with their binary names. Used to generate the array of interface

      * names to implement.

      * @param classes the classes

      * @return an array of names

      */

     private static String[] getInternalTypeNames(final List<Class<?>> classes) {

         final int interfaceCount = classes.size();

         final String[] interfaceNames = new String[interfaceCount];

         for(int i = 0; i < interfaceCount; ++i) {

             interfaceNames[i] = Type.getInternalName(classes.get(i));

         }

         return interfaceNames;

     }

     private void generateHandleFields() {

         final int flags = ACC_PRIVATE | ACC_FINAL | (classOverride ? ACC_STATIC : 0);

         for (final MethodInfo mi: methodInfos) {

             cw.visitField(flags, mi.methodHandleFieldName, METHOD_HANDLE_TYPE_DESCRIPTOR, null, null).visitEnd();

         }

     }

     private void generateConverterFields() {

         final int flags = ACC_PRIVATE | ACC_FINAL | (classOverride ? ACC_STATIC : 0);

         for (final MethodInfo mi: methodInfos) {

             final Class<?> returnType = mi.type.returnType();

             // Handle primitive types, Object, and String specially

             if(!returnType.isPrimitive() && returnType != Object.class && returnType != String.class) {

                 if(!converterFields.containsKey(returnType)) {

                     final String name = nextName("convert");

                     converterFields.put(returnType, name);

                     if(mi.getName().equals(samName)) {

                         samReturnTypes.add(returnType);

                     }

                     cw.visitField(flags, name, METHOD_HANDLE_TYPE_DESCRIPTOR, null, null).visitEnd();

                 }

             }

         }

     }

     private void generateClassInit() {

         final InstructionAdapter mv = new InstructionAdapter(cw.visitMethod(ACC_STATIC, CLASS_INIT,

                 Type.getMethodDescriptor(Type.VOID_TYPE), null, null));

         mv.invokestatic(SERVICES_CLASS_TYPE_NAME, "getClassOverrides", GET_CLASS_INITIALIZER_DESCRIPTOR, false);

         final Label initGlobal;

         if(samName != null) {

             // If the class is a SAM, allow having a ScriptFunction passed as class overrides

             final Label notAFunction = new Label();

             mv.dup();

             mv.instanceOf(SCRIPT_FUNCTION_TYPE);

             mv.ifeq(notAFunction);

             mv.checkcast(SCRIPT_FUNCTION_TYPE);

             // Assign MethodHandle fields through invoking getHandle() for a ScriptFunction, only assigning the SAM

             // method(s).

             for (final MethodInfo mi : methodInfos) {

                 if(mi.getName().equals(samName)) {

                     mv.dup();

                     loadMethodTypeAndGetHandle(mv, mi, GET_HANDLE_FUNCTION_DESCRIPTOR);

                 } else {

                     mv.visitInsn(ACONST_NULL);

                 }

                 mv.putstatic(generatedClassName, mi.methodHandleFieldName, METHOD_HANDLE_TYPE_DESCRIPTOR);

             }

             initGlobal = new Label();

             mv.goTo(initGlobal);

             mv.visitLabel(notAFunction);

         } else {

             initGlobal = null;

         }

         // Assign MethodHandle fields through invoking getHandle() for a ScriptObject

         for (final MethodInfo mi : methodInfos) {

             mv.dup();

             mv.aconst(mi.getName());

             loadMethodTypeAndGetHandle(mv, mi, GET_HANDLE_OBJECT_DESCRIPTOR);

             mv.putstatic(generatedClassName, mi.methodHandleFieldName, METHOD_HANDLE_TYPE_DESCRIPTOR);

         }

         if(initGlobal != null) {

             mv.visitLabel(initGlobal);

         }

         // Assign "global = Context.getGlobal()"

         invokeGetGlobalWithNullCheck(mv);

         mv.putstatic(generatedClassName, GLOBAL_FIELD_NAME, GLOBAL_TYPE_DESCRIPTOR);

         generateConverterInit(mv, false);

         endInitMethod(mv);

     }

     private void generateConverterInit(final InstructionAdapter mv, final boolean samOnly) {

         assert !samOnly || !classOverride;

         for(final Map.Entry<Class<?>, String> converterField: converterFields.entrySet()) {

             final Class<?> returnType = converterField.getKey();

             if(!classOverride) {

                 mv.visitVarInsn(ALOAD, 0);

             }

             if(samOnly && !samReturnTypes.contains(returnType)) {

                 mv.visitInsn(ACONST_NULL);

             } else {

                 mv.aconst(Type.getType(converterField.getKey()));

                 mv.invokestatic(SERVICES_CLASS_TYPE_NAME, "getObjectConverter", GET_CONVERTER_METHOD_DESCRIPTOR, false);

             }

             if(classOverride) {

                 mv.putstatic(generatedClassName, converterField.getValue(), METHOD_HANDLE_TYPE_DESCRIPTOR);

             } else {

                 mv.putfield(generatedClassName, converterField.getValue(), METHOD_HANDLE_TYPE_DESCRIPTOR);

             }

         }

     }

     private static void loadMethodTypeAndGetHandle(final InstructionAdapter mv, final MethodInfo mi, final String getHandleDescriptor) {

         // NOTE: we're using generic() here because we'll be linking to the "generic" invoker version of

         // the functions anyway, so we cut down on megamorphism in the invokeExact() calls in adapter

         // bodies. Once we start linking to type-specializing invokers, this should be changed.

         mv.aconst(Type.getMethodType(mi.type.generic().toMethodDescriptorString()));

         mv.invokestatic(SERVICES_CLASS_TYPE_NAME, "getHandle", getHandleDescriptor, false);

     }

     private static void invokeGetGlobalWithNullCheck(final InstructionAdapter mv) {

         invokeGetGlobal(mv);

         mv.dup();

         mv.invokevirtual(OBJECT_TYPE_NAME, "getClass", GET_CLASS_METHOD_DESCRIPTOR, false); // check against null Context

         mv.pop();

     }

     private void generateConstructors() throws AdaptationException {

         boolean gotCtor = false;

         for (final Constructor<?> ctor: superClass.getDeclaredConstructors()) {

             final int modifier = ctor.getModifiers();

             if((modifier & (Modifier.PUBLIC | Modifier.PROTECTED)) != 0 && !isCallerSensitive(ctor)) {

                 generateConstructors(ctor);

                 gotCtor = true;

             }

         }

         if(!gotCtor) {

             throw new AdaptationException(ERROR_NO_ACCESSIBLE_CONSTRUCTOR, superClass.getCanonicalName());

         }

     }

     private void generateConstructors(final Constructor<?> ctor) {

         if(classOverride) {

             // Generate a constructor that just delegates to ctor. This is used with class-level overrides, when we want

             // to create instances without further per-instance overrides.

             generateDelegatingConstructor(ctor);

         } else {

             // Generate a constructor that delegates to ctor, but takes an additional ScriptObject parameter at the

             // beginning of its parameter list.

             generateOverridingConstructor(ctor, false);

             if (samName != null) {

                 if (!autoConvertibleFromFunction && ctor.getParameterTypes().length == 0) {

                     // If the original type only has a single abstract method name, as well as a default ctor, then it can

                     // be automatically converted from JS function.

                     autoConvertibleFromFunction = true;

                 }

                 // If all our abstract methods have a single name, generate an additional constructor, one that takes a

                 // ScriptFunction as its first parameter and assigns it as the implementation for all abstract methods.

                 generateOverridingConstructor(ctor, true);

             }

         }

     }

     private void generateDelegatingConstructor(final Constructor<?> ctor) {

         final Type originalCtorType = Type.getType(ctor);

         final Type[] argTypes = originalCtorType.getArgumentTypes();

         // All constructors must be public, even if in the superclass they were protected.

         final InstructionAdapter mv = new InstructionAdapter(cw.visitMethod(ACC_PUBLIC |

                 (ctor.isVarArgs() ? ACC_VARARGS : 0), INIT,

                 Type.getMethodDescriptor(originalCtorType.getReturnType(), argTypes), null, null));

         mv.visitCode();

         // Invoke super constructor with the same arguments.

         mv.visitVarInsn(ALOAD, 0);

         int offset = 1; // First arg is at position 1, after this.

         for (final Type argType: argTypes) {

             mv.load(offset, argType);

             offset += argType.getSize();

         }

         mv.invokespecial(superClassName, INIT, originalCtorType.getDescriptor(), false);

         endInitMethod(mv);

     }

     /**

      * Generates a constructor for the instance adapter class. This constructor will take the same arguments as the supertype

      * constructor passed as the argument here, and delegate to it. However, it will take an additional argument of

      * either ScriptObject or ScriptFunction type (based on the value of the "fromFunction" parameter), and initialize

      * all the method handle fields of the adapter instance with functions from the script object (or the script

      * function itself, if that's what's passed). There is one method handle field in the adapter class for every method

      * that can be implemented or overridden; the name of every field is same as the name of the method, with a number

      * suffix that makes it unique in case of overloaded methods. The generated constructor will invoke

      * {@link #getHandle(ScriptFunction, MethodType, boolean)} or {@link #getHandle(Object, String, MethodType,

      * boolean)} to obtain the method handles; these methods make sure to add the necessary conversions and arity

      * adjustments so that the resulting method handles can be invoked from generated methods using {@code invokeExact}.

      * The constructor that takes a script function will only initialize the methods with the same name as the single

      * abstract method. The constructor will also store the Nashorn global that was current at the constructor

      * invocation time in a field named "global". The generated constructor will be public, regardless of whether the

      * supertype constructor was public or protected. The generated constructor will not be variable arity, even if the

      * supertype constructor was.

      * @param ctor the supertype constructor that is serving as the base for the generated constructor.

      * @param fromFunction true if we're generating a constructor that initializes SAM types from a single

      * ScriptFunction passed to it, false if we're generating a constructor that initializes an arbitrary type from a

      * ScriptObject passed to it.

      */

     private void generateOverridingConstructor(final Constructor<?> ctor, final boolean fromFunction) {

         final Type originalCtorType = Type.getType(ctor);

         final Type[] originalArgTypes = originalCtorType.getArgumentTypes();

         final int argLen = originalArgTypes.length;

         final Type[] newArgTypes = new Type[argLen + 1];

         // Insert ScriptFunction|ScriptObject as the last argument to the constructor

         final Type extraArgumentType = fromFunction ? SCRIPT_FUNCTION_TYPE : SCRIPT_OBJECT_TYPE;

         newArgTypes[argLen] = extraArgumentType;

         System.arraycopy(originalArgTypes, 0, newArgTypes, 0, argLen);

         // All constructors must be public, even if in the superclass they were protected.

         // Existing super constructor <init>(this, args...) triggers generating <init>(this, args..., scriptObj).

         // Any variable arity constructors become fixed-arity with explicit array arguments.

         final InstructionAdapter mv = new InstructionAdapter(cw.visitMethod(ACC_PUBLIC, INIT,

                 Type.getMethodDescriptor(originalCtorType.getReturnType(), newArgTypes), null, null));

         mv.visitCode();

         // First, invoke super constructor with original arguments. If the form of the constructor we're generating is

         // <init>(this, args..., scriptFn), then we're invoking super.<init>(this, args...).

         mv.visitVarInsn(ALOAD, 0);

         final Class<?>[] argTypes = ctor.getParameterTypes();

         int offset = 1; // First arg is at position 1, after this.

         for (int i = 0; i < argLen; ++i) {

             final Type argType = Type.getType(argTypes[i]);

             mv.load(offset, argType);

             offset += argType.getSize();

         }

         mv.invokespecial(superClassName, INIT, originalCtorType.getDescriptor(), false);

         // Get a descriptor to the appropriate "JavaAdapterFactory.getHandle" method.

         final String getHandleDescriptor = fromFunction ? GET_HANDLE_FUNCTION_DESCRIPTOR : GET_HANDLE_OBJECT_DESCRIPTOR;

         // Assign MethodHandle fields through invoking getHandle()

         for (final MethodInfo mi : methodInfos) {

             mv.visitVarInsn(ALOAD, 0);

             if (fromFunction && !mi.getName().equals(samName)) {

                 // Constructors initializing from a ScriptFunction only initialize methods with the SAM name.

                 // NOTE: if there's a concrete overloaded method sharing the SAM name, it'll be overridden too. This

                 // is a deliberate design choice. All other method handles are initialized to null.

                 mv.visitInsn(ACONST_NULL);

             } else {

                 mv.visitVarInsn(ALOAD, offset);

                 if(!fromFunction) {

                     mv.aconst(mi.getName());

                 }

                 loadMethodTypeAndGetHandle(mv, mi, getHandleDescriptor);

             }

             mv.putfield(generatedClassName, mi.methodHandleFieldName, METHOD_HANDLE_TYPE_DESCRIPTOR);

         }

         // Assign "this.global = Context.getGlobal()"

         mv.visitVarInsn(ALOAD, 0);

         invokeGetGlobalWithNullCheck(mv);

         mv.putfield(generatedClassName, GLOBAL_FIELD_NAME, GLOBAL_TYPE_DESCRIPTOR);

         // Initialize converters

         generateConverterInit(mv, fromFunction);

         endInitMethod(mv);

         if (! fromFunction) {

             newArgTypes[argLen] = OBJECT_TYPE;

             final InstructionAdapter mv2 = new InstructionAdapter(cw.visitMethod(ACC_PUBLIC, INIT,

                     Type.getMethodDescriptor(originalCtorType.getReturnType(), newArgTypes), null, null));

             generateOverridingConstructorWithObjectParam(mv2, ctor, originalCtorType.getDescriptor());

         }

     }

     // Object additional param accepting constructor - generated to handle null and undefined value

     // for script adapters. This is effectively to throw TypeError on such script adapters. See

     // JavaAdapterServices.getHandle as well.

     private void generateOverridingConstructorWithObjectParam(final InstructionAdapter mv, final Constructor<?> ctor, final String ctorDescriptor) {

         mv.visitCode();

         mv.visitVarInsn(ALOAD, 0);

         final Class<?>[] argTypes = ctor.getParameterTypes();

         int offset = 1; // First arg is at position 1, after this.

         for (int i = 0; i < argTypes.length; ++i) {

             final Type argType = Type.getType(argTypes[i]);

             mv.load(offset, argType);

             offset += argType.getSize();

         }

         mv.invokespecial(superClassName, INIT, ctorDescriptor, false);

         mv.visitVarInsn(ALOAD, offset);

         mv.visitInsn(ACONST_NULL);

         mv.visitInsn(ACONST_NULL);

         mv.invokestatic(SERVICES_CLASS_TYPE_NAME, "getHandle", GET_HANDLE_OBJECT_DESCRIPTOR, false);

         endInitMethod(mv);

     }

     private static void endInitMethod(final InstructionAdapter mv) {

         mv.visitInsn(RETURN);

         endMethod(mv);

     }

     private static void endMethod(final InstructionAdapter mv) {

         mv.visitMaxs(0, 0);

         mv.visitEnd();

     }

     private static void invokeGetGlobal(final InstructionAdapter mv) {

         mv.invokestatic(SERVICES_CLASS_TYPE_NAME, "getGlobal", GET_GLOBAL_METHOD_DESCRIPTOR, false);

     }

     private static void invokeSetGlobal(final InstructionAdapter mv) {

         mv.invokestatic(SERVICES_CLASS_TYPE_NAME, "setGlobal", SET_GLOBAL_METHOD_DESCRIPTOR, false);

     }

     /**

      * Encapsulation of the information used to generate methods in the adapter classes. Basically, a wrapper around the

      * reflective Method object, a cached MethodType, and the name of the field in the adapter class that will hold the

      * method handle serving as the implementation of this method in adapter instances.

      *

      */

     private static class MethodInfo {

         private final Method method;

         private final MethodType type;

         private String methodHandleFieldName;

         private MethodInfo(final Class<?> clazz, final String name, final Class<?>... argTypes) throws NoSuchMethodException {

             this(clazz.getDeclaredMethod(name, argTypes));

         }

         private MethodInfo(final Method method) {

             this.method = method;

             this.type   = MH.type(method.getReturnType(), method.getParameterTypes());

         }

         @Override

         public boolean equals(final Object obj) {

             return obj instanceof MethodInfo && equals((MethodInfo)obj);

         }

         private boolean equals(final MethodInfo other) {

             // Only method name and type are used for comparison; method handle field name is not.

             return getName().equals(other.getName()) && type.equals(other.type);

         }

         String getName() {

             return method.getName();

         }

         @Override

         public int hashCode() {

             return getName().hashCode() ^ type.hashCode();

         }

         void setIsCanonical(final JavaAdapterBytecodeGenerator self) {

             methodHandleFieldName = self.nextName(getName());

         }

     }

     private String nextName(final String name) {

         int i = 0;

         String nextName = name;

         while (!usedFieldNames.add(nextName)) {

             final String ordinal = String.valueOf(i++);

             final int maxNameLen = 255 - ordinal.length();

             nextName = (name.length() <= maxNameLen ? name : name.substring(0, maxNameLen)).concat(ordinal);

         }

         return nextName;

     }

     private void generateMethods() {

         for(final MethodInfo mi: methodInfos) {

             generateMethod(mi);

         }

     }

     /**

      * Generates a method in the adapter class that adapts a method from the original class. The generated methods will

      * inspect the method handle field assigned to them. If it is null (the JS object doesn't provide an implementation

      * for the method) then it will either invoke its version in the supertype, or if it is abstract, throw an

      * {@link UnsupportedOperationException}. Otherwise, if the method handle field's value is not null, the handle is

      * invoked using invokeExact (signature polymorphic invocation as per JLS 15.12.3). Before the invocation, the

      * current Nashorn {@link Context} is checked, and if it is different than the global used to create the adapter

      * instance, the creating global is set to be the current global. In this case, the previously current global is

      * restored after the invocation. If invokeExact results in a Throwable that is not one of the method's declared

      * exceptions, and is not an unchecked throwable, then it is wrapped into a {@link RuntimeException} and the runtime

      * exception is thrown. The method handle retrieved from the field is guaranteed to exactly match the signature of

      * the method; this is guaranteed by the way constructors of the adapter class obtain them using

      * {@link #getHandle(Object, String, MethodType, boolean)}.

      * @param mi the method info describing the method to be generated.

      */

     private void generateMethod(final MethodInfo mi) {

         final Method method = mi.method;

         final Class<?>[] exceptions = method.getExceptionTypes();

         final String[] exceptionNames = getExceptionNames(exceptions);

         final MethodType type = mi.type;

         final String methodDesc = type.toMethodDescriptorString();

         final String name = mi.getName();

         final Type asmType = Type.getMethodType(methodDesc);

         final Type[] asmArgTypes = asmType.getArgumentTypes();

         final InstructionAdapter mv = new InstructionAdapter(cw.visitMethod(getAccessModifiers(method), name,

                 methodDesc, null, exceptionNames));

         mv.visitCode();

         final Label handleDefined = new Label();

         final Class<?> returnType = type.returnType();

         final Type asmReturnType = Type.getType(returnType);

         // See if we have overriding method handle defined

         if(classOverride) {

             mv.getstatic(generatedClassName, mi.methodHandleFieldName, METHOD_HANDLE_TYPE_DESCRIPTOR);

         } else {

             mv.visitVarInsn(ALOAD, 0);

             mv.getfield(generatedClassName, mi.methodHandleFieldName, METHOD_HANDLE_TYPE_DESCRIPTOR);

         }

         // stack: [handle]

         mv.visitInsn(DUP);

         mv.visitJumpInsn(IFNONNULL, handleDefined);

         // No handle is available, fall back to default behavior

         if(Modifier.isAbstract(method.getModifiers())) {

             // If the super method is abstract, throw an exception

             mv.anew(UNSUPPORTED_OPERATION_TYPE);

             mv.dup();

             mv.invokespecial(UNSUPPORTED_OPERATION_TYPE_NAME, INIT, VOID_NOARG_METHOD_DESCRIPTOR, false);

             mv.athrow();

         } else {

             mv.visitInsn(POP);

             // If the super method is not abstract, delegate to it.

             emitSuperCall(mv, method.getDeclaringClass(), name, methodDesc);

         }

         mv.visitLabel(handleDefined);

         // Load the creatingGlobal object

         if(classOverride) {

             // If class handle is defined, load the static defining global

             mv.getstatic(generatedClassName, GLOBAL_FIELD_NAME, GLOBAL_TYPE_DESCRIPTOR);

         } else {

             mv.visitVarInsn(ALOAD, 0);

             mv.getfield(generatedClassName, GLOBAL_FIELD_NAME, GLOBAL_TYPE_DESCRIPTOR);

         }

         // stack: [creatingGlobal, handle]

         final Label setupGlobal = new Label();

         mv.visitLabel(setupGlobal);

         // Determine the first index for a local variable

         int nextLocalVar = 1; // "this" is at 0

         for(final Type t: asmArgTypes) {

             nextLocalVar += t.getSize();

         }

         // Set our local variable indices

         final int currentGlobalVar  = nextLocalVar++;

         final int globalsDifferVar  = nextLocalVar++;

         mv.dup();

         // stack: [creatingGlobal, creatingGlobal, handle]

         // Emit code for switching to the creating global

         // Global currentGlobal = Context.getGlobal();

         invokeGetGlobal(mv);

         mv.dup();

         mv.visitVarInsn(ASTORE, currentGlobalVar);

         // stack: [currentGlobal, creatingGlobal, creatingGlobal, handle]

         // if(definingGlobal == currentGlobal) {

         final Label globalsDiffer = new Label();

         mv.ifacmpne(globalsDiffer);

         // stack: [creatingGlobal, handle]

         //     globalsDiffer = false

         mv.pop();

         // stack: [handle]

         mv.iconst(0); // false

         // stack: [false, handle]

         final Label invokeHandle = new Label();

         mv.goTo(invokeHandle);

         mv.visitLabel(globalsDiffer);

         // } else {

         //     Context.setGlobal(definingGlobal);

         // stack: [creatingGlobal, handle]

         invokeSetGlobal(mv);

         // stack: [handle]

         //     globalsDiffer = true

         mv.iconst(1);

         // stack: [true, handle]

         mv.visitLabel(invokeHandle);

         mv.visitVarInsn(ISTORE, globalsDifferVar);

         // stack: [handle]

         // Load all parameters back on stack for dynamic invocation. NOTE: since we're using a generic

         // Object(Object, Object, ...) type signature for the method, we must box all arguments here.

         int varOffset = 1;

         for (final Type t : asmArgTypes) {

             mv.load(varOffset, t);

             boxStackTop(mv, t);

             varOffset += t.getSize();

         }

         // Invoke the target method handle

         final Label tryBlockStart = new Label();

         mv.visitLabel(tryBlockStart);

         emitInvokeExact(mv, type.generic());

         convertReturnValue(mv, returnType, asmReturnType);

         final Label tryBlockEnd = new Label();

         mv.visitLabel(tryBlockEnd);

         emitFinally(mv, currentGlobalVar, globalsDifferVar);

         mv.areturn(asmReturnType);

         // If Throwable is not declared, we need an adapter from Throwable to RuntimeException

         final boolean throwableDeclared = isThrowableDeclared(exceptions);

         final Label throwableHandler;

         if (!throwableDeclared) {

             // Add "throw new RuntimeException(Throwable)" handler for Throwable

             throwableHandler = new Label();

             mv.visitLabel(throwableHandler);

             mv.anew(RUNTIME_EXCEPTION_TYPE);

             mv.dupX1();

             mv.swap();

             mv.invokespecial(RUNTIME_EXCEPTION_TYPE_NAME, INIT, Type.getMethodDescriptor(Type.VOID_TYPE, THROWABLE_TYPE), false);

             // Fall through to rethrow handler

         } else {

             throwableHandler = null;

         }

         final Label rethrowHandler = new Label();

         mv.visitLabel(rethrowHandler);

         // Rethrow handler for RuntimeException, Error, and all declared exception types

         emitFinally(mv, currentGlobalVar, globalsDifferVar);

         mv.athrow();

         final Label methodEnd = new Label();

         mv.visitLabel(methodEnd);

         mv.visitLocalVariable("currentGlobal", GLOBAL_TYPE_DESCRIPTOR, null, setupGlobal, methodEnd, currentGlobalVar);

         mv.visitLocalVariable("globalsDiffer", Type.BOOLEAN_TYPE.getDescriptor(), null, setupGlobal, methodEnd, globalsDifferVar);

         if(throwableDeclared) {

             mv.visitTryCatchBlock(tryBlockStart, tryBlockEnd, rethrowHandler, THROWABLE_TYPE_NAME);

             assert throwableHandler == null;

         } else {

             mv.visitTryCatchBlock(tryBlockStart, tryBlockEnd, rethrowHandler, RUNTIME_EXCEPTION_TYPE_NAME);

             mv.visitTryCatchBlock(tryBlockStart, tryBlockEnd, rethrowHandler, ERROR_TYPE_NAME);

             for(final String excName: exceptionNames) {

                 mv.visitTryCatchBlock(tryBlockStart, tryBlockEnd, rethrowHandler, excName);

             }

             mv.visitTryCatchBlock(tryBlockStart, tryBlockEnd, throwableHandler, THROWABLE_TYPE_NAME);

         }

         endMethod(mv);

     }

     private void convertReturnValue(final InstructionAdapter mv, final Class<?> returnType, final Type asmReturnType) {

         switch(asmReturnType.getSort()) {

         case Type.VOID:

             mv.pop();

             break;

         case Type.BOOLEAN:

             JSType.TO_BOOLEAN.invoke(mv);

             break;

         case Type.BYTE:

             JSType.TO_INT32.invoke(mv);

             mv.visitInsn(Opcodes.I2B);

             break;

         case Type.SHORT:

             JSType.TO_INT32.invoke(mv);

             mv.visitInsn(Opcodes.I2S);

             break;

         case Type.CHAR:

             // JSType doesn't have a TO_CHAR, so we have services supply us one.

             mv.invokestatic(SERVICES_CLASS_TYPE_NAME, "toCharPrimitive", TO_CHAR_PRIMITIVE_METHOD_DESCRIPTOR, false);

             break;

         case Type.INT:

             JSType.TO_INT32.invoke(mv);

             break;

         case Type.LONG:

             JSType.TO_LONG.invoke(mv);

             break;

         case Type.FLOAT:

             JSType.TO_NUMBER.invoke(mv);

             mv.visitInsn(Opcodes.D2F);

             break;

         case Type.DOUBLE:

             JSType.TO_NUMBER.invoke(mv);

             break;

         default:

             if(asmReturnType.equals(OBJECT_TYPE)) {

                 // Must hide ConsString (and potentially other internal Nashorn types) from callers

                 mv.invokestatic(SERVICES_CLASS_TYPE_NAME, "exportReturnValue", EXPORT_RETURN_VALUE_METHOD_DESCRIPTOR, false);

             } else if(asmReturnType.equals(STRING_TYPE)){

                 // Well-known conversion to String. Not using the JSType one as we want to preserve null as null instead

                 // of the string "n,u,l,l".

                 mv.invokestatic(SERVICES_CLASS_TYPE_NAME, "toString", TO_STRING_METHOD_DESCRIPTOR, false);

             } else {

                 // Invoke converter method handle for everything else. Note that we could have just added an asType or

                 // filterReturnValue to the invoked handle instead, but then every instance would have the function

                 // method handle wrapped in a separate converter method handle, making handle.invokeExact() megamorphic.

                 if(classOverride) {

                     mv.getstatic(generatedClassName, converterFields.get(returnType), METHOD_HANDLE_TYPE_DESCRIPTOR);

                 } else {

                     mv.visitVarInsn(ALOAD, 0);

                     mv.getfield(generatedClassName, converterFields.get(returnType), METHOD_HANDLE_TYPE_DESCRIPTOR);

                 }

                 mv.swap();

                 emitInvokeExact(mv, MethodType.methodType(returnType, Object.class));

             }

         }

     }

     private static void emitInvokeExact(final InstructionAdapter mv, final MethodType type) {

         mv.invokevirtual(METHOD_HANDLE_TYPE.getInternalName(), "invokeExact", type.toMethodDescriptorString(), false);

     }

     private static void boxStackTop(final InstructionAdapter mv, final Type t) {

         switch(t.getSort()) {

         case Type.BOOLEAN:

             invokeValueOf(mv, "Boolean", 'Z');

             break;

         case Type.BYTE:

         case Type.SHORT:

         case Type.INT:

             // bytes and shorts get boxed as integers

             invokeValueOf(mv, "Integer", 'I');

             break;

         case Type.CHAR:

             invokeValueOf(mv, "Character", 'C');

             break;

         case Type.FLOAT:

             // floats get boxed as doubles

             mv.visitInsn(Opcodes.F2D);

             invokeValueOf(mv, "Double", 'D');

             break;

         case Type.LONG:

             invokeValueOf(mv, "Long", 'J');

             break;

         case Type.DOUBLE:

             invokeValueOf(mv, "Double", 'D');

             break;

         case Type.ARRAY:

         case Type.METHOD:

             // Already boxed

             break;

         case Type.OBJECT:

             if(t.equals(OBJECT_TYPE)) {

                 mv.invokestatic(SCRIPTUTILS_TYPE_NAME, "unwrap", UNWRAP_METHOD_DESCRIPTOR, false);

             }

             break;

         default:

             // Not expecting anything else (e.g. VOID)

             assert false;

             break;

         }

     }

     private static void invokeValueOf(final InstructionAdapter mv, final String boxedType, final char unboxedType) {

         mv.invokestatic("java/lang/" + boxedType, "valueOf", "(" + unboxedType + ")Ljava/lang/" + boxedType + ";", false);

     }

     /**

      * Emit code to restore the previous Nashorn Context when needed.

      * @param mv the instruction adapter

      * @param currentGlobalVar index of the local variable holding the reference to the current global at method

      * entry.

      * @param globalsDifferVar index of the boolean local variable that is true if the global needs to be restored.

      */

     private static void emitFinally(final InstructionAdapter mv, final int currentGlobalVar, final int globalsDifferVar) {

         // Emit code to restore the previous Nashorn global if needed

         mv.visitVarInsn(ILOAD, globalsDifferVar);

         final Label skip = new Label();

         mv.ifeq(skip);

         mv.visitVarInsn(ALOAD, currentGlobalVar);

         invokeSetGlobal(mv);

         mv.visitLabel(skip);

     }

     private static boolean isThrowableDeclared(final Class<?>[] exceptions) {

         for (final Class<?> exception : exceptions) {

             if (exception == Throwable.class) {

                 return true;

             }

         }

         return false;

     }

     private void generateSuperMethods() {

         for(final MethodInfo mi: methodInfos) {

             if(!Modifier.isAbstract(mi.method.getModifiers())) {

                 generateSuperMethod(mi);

             }

         }

     }

     private void generateSuperMethod(final MethodInfo mi) {

         final Method method = mi.method;

         final String methodDesc = mi.type.toMethodDescriptorString();

         final String name = mi.getName();

         final InstructionAdapter mv = new InstructionAdapter(cw.visitMethod(getAccessModifiers(method),

                 SUPER_PREFIX + name, methodDesc, null, getExceptionNames(method.getExceptionTypes())));

         mv.visitCode();

         emitSuperCall(mv, method.getDeclaringClass(), name, methodDesc);

         endMethod(mv);

     }

     // find the appropriate super type to use for invokespecial on the given interface

     private Class<?> findInvokespecialOwnerFor(final Class<?> cl) {

         assert Modifier.isInterface(cl.getModifiers()) : cl + " is not an interface";

         if (cl.isAssignableFrom(superClass)) {

             return superClass;

         }

         for (final Class<?> iface : interfaces) {

              if (cl.isAssignableFrom(iface)) {

                  return iface;

              }

         }

         // we better that interface that extends the given interface!

         throw new AssertionError("can't find the class/interface that extends " + cl);

     }

     private void emitSuperCall(final InstructionAdapter mv, final Class<?> owner, final String name, final String methodDesc) {

         mv.visitVarInsn(ALOAD, 0);

         int nextParam = 1;

         final Type methodType = Type.getMethodType(methodDesc);

         for(final Type t: methodType.getArgumentTypes()) {

             mv.load(nextParam, t);

             nextParam += t.getSize();

         }

         // default method - non-abstract, interface method

         if (Modifier.isInterface(owner.getModifiers())) {

             // we should call default method on the immediate "super" type - not on (possibly)

             // the indirectly inherited interface class!

             mv.invokespecial(Type.getInternalName(findInvokespecialOwnerFor(owner)), name, methodDesc, false);

         } else {

             mv.invokespecial(superClassName, name, methodDesc, false);

         }

         mv.areturn(methodType.getReturnType());

     }

     private void generateFinalizerMethods() {

         final String finalizerDelegateName = nextName("access$");

         generateFinalizerDelegate(finalizerDelegateName);

         generateFinalizerOverride(finalizerDelegateName);

     }

     private void generateFinalizerDelegate(final String finalizerDelegateName) {

         // Generate a delegate that will be invoked from the no-permission trampoline. Note it can be private, as we'll

         // refer to it with a MethodHandle constant pool entry in the overridden finalize() method (see

         // generateFinalizerOverride()).

         final InstructionAdapter mv = new InstructionAdapter(cw.visitMethod(ACC_PRIVATE | ACC_STATIC,

                 finalizerDelegateName, Type.getMethodDescriptor(Type.VOID_TYPE, OBJECT_TYPE), null, null));

         // Simply invoke super.finalize()

         mv.visitVarInsn(ALOAD, 0);

         mv.checkcast(Type.getType(generatedClassName));

         mv.invokespecial(superClassName, "finalize", Type.getMethodDescriptor(Type.VOID_TYPE), false);

         mv.visitInsn(RETURN);

         endMethod(mv);

     }

     private void generateFinalizerOverride(final String finalizerDelegateName) {

         final InstructionAdapter mv = new InstructionAdapter(cw.visitMethod(ACC_PUBLIC, "finalize",

                 VOID_NOARG_METHOD_DESCRIPTOR, null, null));

         // Overridden finalizer will take a MethodHandle to the finalizer delegating method, ...

         mv.aconst(new Handle(Opcodes.H_INVOKESTATIC, generatedClassName, finalizerDelegateName,

                 Type.getMethodDescriptor(Type.VOID_TYPE, OBJECT_TYPE)));

         mv.visitVarInsn(ALOAD, 0);

         // ...and invoke it through JavaAdapterServices.invokeNoPermissions

         mv.invokestatic(SERVICES_CLASS_TYPE_NAME, "invokeNoPermissions",

                 Type.getMethodDescriptor(METHOD_HANDLE_TYPE, OBJECT_TYPE), false);

         mv.visitInsn(RETURN);

         endMethod(mv);

     }

     private static String[] getExceptionNames(final Class<?>[] exceptions) {

         final String[] exceptionNames = new String[exceptions.length];

         for (int i = 0; i < exceptions.length; ++i) {

             exceptionNames[i] = Type.getInternalName(exceptions[i]);

         }

         return exceptionNames;

     }

     private static int getAccessModifiers(final Method method) {

         return ACC_PUBLIC | (method.isVarArgs() ? ACC_VARARGS : 0);

     }

     /**

      * Gathers methods that can be implemented or overridden from the specified type into this factory's

      * {@link #methodInfos} set. It will add all non-final, non-static methods that are either public or protected from

      * the type if the type itself is public. If the type is a class, the method will recursively invoke itself for its

      * superclass and the interfaces it implements, and add further methods that were not directly declared on the

      * class.

      * @param type the type defining the methods.

      */

     private void gatherMethods(final Class<?> type) throws AdaptationException {

         if (Modifier.isPublic(type.getModifiers())) {

             final Method[] typeMethods = type.isInterface() ? type.getMethods() : type.getDeclaredMethods();

             for (final Method typeMethod: typeMethods) {

                 final String name = typeMethod.getName();

                 if(name.startsWith(SUPER_PREFIX)) {

                     continue;

                 }

                 final int m = typeMethod.getModifiers();

                 if (Modifier.isStatic(m)) {

                     continue;

                 }

                 if (Modifier.isPublic(m) || Modifier.isProtected(m)) {

                     // Is it a "finalize()"?

                     if(name.equals("finalize") && typeMethod.getParameterCount() == 0) {

                         if(type != Object.class) {

                             hasExplicitFinalizer = true;

                             if(Modifier.isFinal(m)) {

                                 // Must be able to override an explicit finalizer

                                 throw new AdaptationException(Outcome.ERROR_FINAL_FINALIZER, type.getCanonicalName());

                             }

                         }

                         continue;

                     }

                     final MethodInfo mi = new MethodInfo(typeMethod);

                     if (Modifier.isFinal(m) || isCallerSensitive(typeMethod)) {

                         finalMethods.add(mi);

                     } else if (!finalMethods.contains(mi) && methodInfos.add(mi)) {

                         if (Modifier.isAbstract(m)) {

                             abstractMethodNames.add(mi.getName());

                         }

                         mi.setIsCanonical(this);

                     }

                 }

             }

         }

         // If the type is a class, visit its superclasses and declared interfaces. If it's an interface, we're done.

         // Needing to invoke the method recursively for a non-interface Class object is the consequence of needing to

         // see all declared protected methods, and Class.getDeclaredMethods() doesn't provide those declared in a

         // superclass. For interfaces, we used Class.getMethods(), as we're only interested in public ones there, and

         // getMethods() does provide those declared in a superinterface.

         if (!type.isInterface()) {

             final Class<?> superType = type.getSuperclass();

             if (superType != null) {

                 gatherMethods(superType);

             }

             for (final Class<?> itf: type.getInterfaces()) {

                 gatherMethods(itf);

             }

         }

     }

     private void gatherMethods(final List<Class<?>> classes) throws AdaptationException {

         for(final Class<?> c: classes) {

             gatherMethods(c);

         }

     }

     private static final AccessControlContext GET_DECLARED_MEMBERS_ACC_CTXT = ClassAndLoader.createPermAccCtxt("accessDeclaredMembers");

     /**

      * Creates a collection of methods that are not final, but we still never allow them to be overridden in adapters,

      * as explicitly declaring them automatically is a bad idea. Currently, this means {@code Object.finalize()} and

      * {@code Object.clone()}.

      * @return a collection of method infos representing those methods that we never override in adapter classes.

      */

     private static Collection<MethodInfo> getExcludedMethods() {

         return AccessController.doPrivileged(new PrivilegedAction<Collection<MethodInfo>>() {

             @Override

             public Collection<MethodInfo> run() {

                 try {

                     return Arrays.asList(

                             new MethodInfo(Object.class, "finalize"),

                             new MethodInfo(Object.class, "clone"));

                 } catch (final NoSuchMethodException e) {

                     throw new AssertionError(e);

                 }

             }

         }, GET_DECLARED_MEMBERS_ACC_CTXT);

     }

     private String getCommonSuperClass(final String type1, final String type2) {

         try {

             final Class<?> c1 = Class.forName(type1.replace('/', '.'), false, commonLoader);

             final Class<?> c2 = Class.forName(type2.replace('/', '.'), false, commonLoader);

             if (c1.isAssignableFrom(c2)) {

                 return type1;

             }

             if (c2.isAssignableFrom(c1)) {

                 return type2;

             }

             if (c1.isInterface() || c2.isInterface()) {

                 return OBJECT_TYPE_NAME;

             }

             return assignableSuperClass(c1, c2).getName().replace('.', '/');

         } catch(final ClassNotFoundException e) {

             throw new RuntimeException(e);

         }

     }

     private static Class<?> assignableSuperClass(final Class<?> c1, final Class<?> c2) {

         final Class<?> superClass = c1.getSuperclass();

         return superClass.isAssignableFrom(c2) ? superClass : assignableSuperClass(superClass, c2);

     }

     private static boolean isCallerSensitive(final AccessibleObject e) {

         return e.isAnnotationPresent(CallerSensitive.class);

     }

 }