/*

 * Copyright (c) 2008, 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 java.lang.invoke;

import java.security.AccessController;

import java.security.PrivilegedAction;

import java.util.ArrayList;

import java.util.Arrays;

import java.util.Collections;

import java.util.function.Function;

import sun.invoke.empty.Empty;

import sun.invoke.util.ValueConversions;

import sun.invoke.util.VerifyType;

import sun.invoke.util.Wrapper;

import sun.reflect.CallerSensitive;

import sun.reflect.Reflection;

import static java.lang.invoke.LambdaForm.*;

import static java.lang.invoke.MethodHandleStatics.*;

import static java.lang.invoke.MethodHandles.Lookup.IMPL_LOOKUP;

/**

 * Trusted implementation code for MethodHandle.

 * @author jrose

 */

/*non-public*/ abstract class MethodHandleImpl {

    // Do not adjust this except for special platforms:

    private static final int MAX_ARITY;

    static {

        final Object[] values = { 255 };

        AccessController.doPrivileged(new PrivilegedAction<Void>() {

            @Override

            public Void run() {

                values[0] = Integer.getInteger(MethodHandleImpl.class.getName()+".MAX_ARITY", 255);

                return null;

            }

        });

        MAX_ARITY = (Integer) values[0];

    }

    /// Factory methods to create method handles:

    static void initStatics() {

        // Trigger selected static initializations.

        MemberName.Factory.INSTANCE.getClass();

    }

    static MethodHandle makeArrayElementAccessor(Class<?> arrayClass, boolean isSetter) {

        if (arrayClass == Object[].class)

            return (isSetter ? ArrayAccessor.OBJECT_ARRAY_SETTER : ArrayAccessor.OBJECT_ARRAY_GETTER);

        if (!arrayClass.isArray())

            throw newIllegalArgumentException("not an array: "+arrayClass);

        MethodHandle[] cache = ArrayAccessor.TYPED_ACCESSORS.get(arrayClass);

        int cacheIndex = (isSetter ? ArrayAccessor.SETTER_INDEX : ArrayAccessor.GETTER_INDEX);

        MethodHandle mh = cache[cacheIndex];

        if (mh != null)  return mh;

        mh = ArrayAccessor.getAccessor(arrayClass, isSetter);

        MethodType correctType = ArrayAccessor.correctType(arrayClass, isSetter);

        if (mh.type() != correctType) {

            assert(mh.type().parameterType(0) == Object[].class);

            assert((isSetter ? mh.type().parameterType(2) : mh.type().returnType()) == Object.class);

            assert(isSetter || correctType.parameterType(0).getComponentType() == correctType.returnType());

            // safe to view non-strictly, because element type follows from array type

            mh = mh.viewAsType(correctType, false);

        }

        mh = makeIntrinsic(mh, (isSetter ? Intrinsic.ARRAY_STORE : Intrinsic.ARRAY_LOAD));

        // Atomically update accessor cache.

        synchronized(cache) {

            if (cache[cacheIndex] == null) {

                cache[cacheIndex] = mh;

            } else {

                // Throw away newly constructed accessor and use cached version.

                mh = cache[cacheIndex];

            }

        }

        return mh;

    }

    static final class ArrayAccessor {

        /// Support for array element access

        static final int GETTER_INDEX = 0, SETTER_INDEX = 1, INDEX_LIMIT = 2;

        static final ClassValue<MethodHandle[]> TYPED_ACCESSORS

                = new ClassValue<MethodHandle[]>() {

                    @Override

                    protected MethodHandle[] computeValue(Class<?> type) {

                        return new MethodHandle[INDEX_LIMIT];

                    }

                };

        static final MethodHandle OBJECT_ARRAY_GETTER, OBJECT_ARRAY_SETTER;

        static {

            MethodHandle[] cache = TYPED_ACCESSORS.get(Object[].class);

            cache[GETTER_INDEX] = OBJECT_ARRAY_GETTER = makeIntrinsic(getAccessor(Object[].class, false), Intrinsic.ARRAY_LOAD);

            cache[SETTER_INDEX] = OBJECT_ARRAY_SETTER = makeIntrinsic(getAccessor(Object[].class, true),  Intrinsic.ARRAY_STORE);

            assert(InvokerBytecodeGenerator.isStaticallyInvocable(ArrayAccessor.OBJECT_ARRAY_GETTER.internalMemberName()));

            assert(InvokerBytecodeGenerator.isStaticallyInvocable(ArrayAccessor.OBJECT_ARRAY_SETTER.internalMemberName()));

        }

        static int     getElementI(int[]     a, int i)            { return              a[i]; }

        static long    getElementJ(long[]    a, int i)            { return              a[i]; }

        static float   getElementF(float[]   a, int i)            { return              a[i]; }

        static double  getElementD(double[]  a, int i)            { return              a[i]; }

        static boolean getElementZ(boolean[] a, int i)            { return              a[i]; }

        static byte    getElementB(byte[]    a, int i)            { return              a[i]; }

        static short   getElementS(short[]   a, int i)            { return              a[i]; }

        static char    getElementC(char[]    a, int i)            { return              a[i]; }

        static Object  getElementL(Object[]  a, int i)            { return              a[i]; }

        static void    setElementI(int[]     a, int i, int     x) {              a[i] = x; }

        static void    setElementJ(long[]    a, int i, long    x) {              a[i] = x; }

        static void    setElementF(float[]   a, int i, float   x) {              a[i] = x; }

        static void    setElementD(double[]  a, int i, double  x) {              a[i] = x; }

        static void    setElementZ(boolean[] a, int i, boolean x) {              a[i] = x; }

        static void    setElementB(byte[]    a, int i, byte    x) {              a[i] = x; }

        static void    setElementS(short[]   a, int i, short   x) {              a[i] = x; }

        static void    setElementC(char[]    a, int i, char    x) {              a[i] = x; }

        static void    setElementL(Object[]  a, int i, Object  x) {              a[i] = x; }

        static String name(Class<?> arrayClass, boolean isSetter) {

            Class<?> elemClass = arrayClass.getComponentType();

            if (elemClass == null)  throw newIllegalArgumentException("not an array", arrayClass);

            return (!isSetter ? "getElement" : "setElement") + Wrapper.basicTypeChar(elemClass);

        }

        static MethodType type(Class<?> arrayClass, boolean isSetter) {

            Class<?> elemClass = arrayClass.getComponentType();

            Class<?> arrayArgClass = arrayClass;

            if (!elemClass.isPrimitive()) {

                arrayArgClass = Object[].class;

                elemClass = Object.class;

            }

            return !isSetter ?

                    MethodType.methodType(elemClass,  arrayArgClass, int.class) :

                    MethodType.methodType(void.class, arrayArgClass, int.class, elemClass);

        }

        static MethodType correctType(Class<?> arrayClass, boolean isSetter) {

            Class<?> elemClass = arrayClass.getComponentType();

            return !isSetter ?

                    MethodType.methodType(elemClass,  arrayClass, int.class) :

                    MethodType.methodType(void.class, arrayClass, int.class, elemClass);

        }

        static MethodHandle getAccessor(Class<?> arrayClass, boolean isSetter) {

            String     name = name(arrayClass, isSetter);

            MethodType type = type(arrayClass, isSetter);

            try {

                return IMPL_LOOKUP.findStatic(ArrayAccessor.class, name, type);

            } catch (ReflectiveOperationException ex) {

                throw uncaughtException(ex);

            }

        }

    }

    /**

     * Create a JVM-level adapter method handle to conform the given method

     * handle to the similar newType, using only pairwise argument conversions.

     * For each argument, convert incoming argument to the exact type needed.

     * The argument conversions allowed are casting, boxing and unboxing,

     * integral widening or narrowing, and floating point widening or narrowing.

     * @param srcType required call type

     * @param target original method handle

     * @param strict if true, only asType conversions are allowed; if false, explicitCastArguments conversions allowed

     * @param monobox if true, unboxing conversions are assumed to be exactly typed (Integer to int only, not long or double)

     * @return an adapter to the original handle with the desired new type,

     *          or the original target if the types are already identical

     *          or null if the adaptation cannot be made

     */

    static MethodHandle makePairwiseConvert(MethodHandle target, MethodType srcType,

                                            boolean strict, boolean monobox) {

        MethodType dstType = target.type();

        if (srcType == dstType)

            return target;

        return makePairwiseConvertByEditor(target, srcType, strict, monobox);

    }

    private static int countNonNull(Object[] array) {

        int count = 0;

        for (Object x : array) {

            if (x != null)  ++count;

        }

        return count;

    }

    static MethodHandle makePairwiseConvertByEditor(MethodHandle target, MethodType srcType,

                                                    boolean strict, boolean monobox) {

        Object[] convSpecs = computeValueConversions(srcType, target.type(), strict, monobox);

        int convCount = countNonNull(convSpecs);

        if (convCount == 0)

            return target.viewAsType(srcType, strict);

        MethodType basicSrcType = srcType.basicType();

        MethodType midType = target.type().basicType();

        BoundMethodHandle mh = target.rebind();

        // FIXME: Reduce number of bindings when there is more than one Class conversion.

        // FIXME: Reduce number of bindings when there are repeated conversions.

        for (int i = 0; i < convSpecs.length-1; i++) {

            Object convSpec = convSpecs[i];

            if (convSpec == null)  continue;

            MethodHandle fn;

            if (convSpec instanceof Class) {

                fn = Lazy.MH_castReference.bindTo(convSpec);

            } else {

                fn = (MethodHandle) convSpec;

            }

            Class<?> newType = basicSrcType.parameterType(i);

            if (--convCount == 0)

                midType = srcType;

            else

                midType = midType.changeParameterType(i, newType);

            LambdaForm form2 = mh.editor().filterArgumentForm(1+i, BasicType.basicType(newType));

            mh = mh.copyWithExtendL(midType, form2, fn);

            mh = mh.rebind();

        }

        Object convSpec = convSpecs[convSpecs.length-1];

        if (convSpec != null) {

            MethodHandle fn;

            if (convSpec instanceof Class) {

                if (convSpec == void.class)

                    fn = null;

                else

                    fn = Lazy.MH_castReference.bindTo(convSpec);

            } else {

                fn = (MethodHandle) convSpec;

            }

            Class<?> newType = basicSrcType.returnType();

            assert(--convCount == 0);

            midType = srcType;

            if (fn != null) {

                mh = mh.rebind();  // rebind if too complex

                LambdaForm form2 = mh.editor().filterReturnForm(BasicType.basicType(newType), false);

                mh = mh.copyWithExtendL(midType, form2, fn);

            } else {

                LambdaForm form2 = mh.editor().filterReturnForm(BasicType.basicType(newType), true);

                mh = mh.copyWith(midType, form2);

            }

        }

        assert(convCount == 0);

        assert(mh.type().equals(srcType));

        return mh;

    }

    static MethodHandle makePairwiseConvertIndirect(MethodHandle target, MethodType srcType,

                                                    boolean strict, boolean monobox) {

        assert(target.type().parameterCount() == srcType.parameterCount());

        // Calculate extra arguments (temporaries) required in the names array.

        Object[] convSpecs = computeValueConversions(srcType, target.type(), strict, monobox);

        final int INARG_COUNT = srcType.parameterCount();

        int convCount = countNonNull(convSpecs);

        boolean retConv = (convSpecs[INARG_COUNT] != null);

        boolean retVoid = srcType.returnType() == void.class;

        if (retConv && retVoid) {

            convCount -= 1;

            retConv = false;

        }

        final int IN_MH         = 0;

        final int INARG_BASE    = 1;

        final int INARG_LIMIT   = INARG_BASE + INARG_COUNT;

        final int NAME_LIMIT    = INARG_LIMIT + convCount + 1;

        final int RETURN_CONV   = (!retConv ? -1         : NAME_LIMIT - 1);

        final int OUT_CALL      = (!retConv ? NAME_LIMIT : RETURN_CONV) - 1;

        final int RESULT        = (retVoid ? -1 : NAME_LIMIT - 1);

        // Now build a LambdaForm.

        MethodType lambdaType = srcType.basicType().invokerType();

        Name[] names = arguments(NAME_LIMIT - INARG_LIMIT, lambdaType);

        // Collect the arguments to the outgoing call, maybe with conversions:

        final int OUTARG_BASE = 0;  // target MH is Name.function, name Name.arguments[0]

        Object[] outArgs = new Object[OUTARG_BASE + INARG_COUNT];

        int nameCursor = INARG_LIMIT;

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

            Object convSpec = convSpecs[i];

            if (convSpec == null) {

                // do nothing: difference is trivial

                outArgs[OUTARG_BASE + i] = names[INARG_BASE + i];

                continue;

            }

            Name conv;

            if (convSpec instanceof Class) {

                Class<?> convClass = (Class<?>) convSpec;

                conv = new Name(Lazy.MH_castReference, convClass, names[INARG_BASE + i]);

            } else {

                MethodHandle fn = (MethodHandle) convSpec;

                conv = new Name(fn, names[INARG_BASE + i]);

            }

            assert(names[nameCursor] == null);

            names[nameCursor++] = conv;

            assert(outArgs[OUTARG_BASE + i] == null);

            outArgs[OUTARG_BASE + i] = conv;

        }

        // Build argument array for the call.

        assert(nameCursor == OUT_CALL);

        names[OUT_CALL] = new Name(target, outArgs);

        Object convSpec = convSpecs[INARG_COUNT];

        if (!retConv) {

            assert(OUT_CALL == names.length-1);

        } else {

            Name conv;

            if (convSpec == void.class) {

                conv = new Name(LambdaForm.constantZero(BasicType.basicType(srcType.returnType())));

            } else if (convSpec instanceof Class) {

                Class<?> convClass = (Class<?>) convSpec;

                conv = new Name(Lazy.MH_castReference, convClass, names[OUT_CALL]);

            } else {

                MethodHandle fn = (MethodHandle) convSpec;

                if (fn.type().parameterCount() == 0)

                    conv = new Name(fn);  // don't pass retval to void conversion

                else

                    conv = new Name(fn, names[OUT_CALL]);

            }

            assert(names[RETURN_CONV] == null);

            names[RETURN_CONV] = conv;

            assert(RETURN_CONV == names.length-1);

        }

        LambdaForm form = new LambdaForm("convert", lambdaType.parameterCount(), names, RESULT);

        return SimpleMethodHandle.make(srcType, form);

    }

    /**

     * Identity function, with reference cast.

     * @param t an arbitrary reference type

     * @param x an arbitrary reference value

     * @return the same value x

     */

    @ForceInline

    @SuppressWarnings("unchecked")

    static <T,U> T castReference(Class<? extends T> t, U x) {

        // inlined Class.cast because we can't ForceInline it

        if (x != null && !t.isInstance(x))

            throw newClassCastException(t, x);

        return (T) x;

    }

    private static ClassCastException newClassCastException(Class<?> t, Object obj) {

        return new ClassCastException("Cannot cast " + obj.getClass().getName() + " to " + t.getName());

    }

    static Object[] computeValueConversions(MethodType srcType, MethodType dstType,

                                            boolean strict, boolean monobox) {

        final int INARG_COUNT = srcType.parameterCount();

        Object[] convSpecs = new Object[INARG_COUNT+1];

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

            boolean isRet = (i == INARG_COUNT);

            Class<?> src = isRet ? dstType.returnType() : srcType.parameterType(i);

            Class<?> dst = isRet ? srcType.returnType() : dstType.parameterType(i);

            if (!VerifyType.isNullConversion(src, dst, /*keepInterfaces=*/ strict)) {

                convSpecs[i] = valueConversion(src, dst, strict, monobox);

            }

        }

        return convSpecs;

    }

    static MethodHandle makePairwiseConvert(MethodHandle target, MethodType srcType,

                                            boolean strict) {

        return makePairwiseConvert(target, srcType, strict, /*monobox=*/ false);

    }

    /**

     * Find a conversion function from the given source to the given destination.

     * This conversion function will be used as a LF NamedFunction.

     * Return a Class object if a simple cast is needed.

     * Return void.class if void is involved.

     */

    static Object valueConversion(Class<?> src, Class<?> dst, boolean strict, boolean monobox) {

        assert(!VerifyType.isNullConversion(src, dst, /*keepInterfaces=*/ strict));  // caller responsibility

        if (dst == void.class)

            return dst;

        MethodHandle fn;

        if (src.isPrimitive()) {

            if (src == void.class) {

                return void.class;  // caller must recognize this specially

            } else if (dst.isPrimitive()) {

                // Examples: int->byte, byte->int, boolean->int (!strict)

                fn = ValueConversions.convertPrimitive(src, dst);

            } else {

                // Examples: int->Integer, boolean->Object, float->Number

                Wrapper wsrc = Wrapper.forPrimitiveType(src);

                fn = ValueConversions.boxExact(wsrc);

                assert(fn.type().parameterType(0) == wsrc.primitiveType());

                assert(fn.type().returnType() == wsrc.wrapperType());

                if (!VerifyType.isNullConversion(wsrc.wrapperType(), dst, strict)) {

                    // Corner case, such as int->Long, which will probably fail.

                    MethodType mt = MethodType.methodType(dst, src);

                    if (strict)

                        fn = fn.asType(mt);

                    else

                        fn = MethodHandleImpl.makePairwiseConvert(fn, mt, /*strict=*/ false);

                }

            }

        } else if (dst.isPrimitive()) {

            Wrapper wdst = Wrapper.forPrimitiveType(dst);

            if (monobox || src == wdst.wrapperType()) {

                // Use a strongly-typed unboxer, if possible.

                fn = ValueConversions.unboxExact(wdst, strict);

            } else {

                // Examples:  Object->int, Number->int, Comparable->int, Byte->int

                // must include additional conversions

                // src must be examined at runtime, to detect Byte, Character, etc.

                fn = (strict

                        ? ValueConversions.unboxWiden(wdst)

                        : ValueConversions.unboxCast(wdst));

            }

        } else {

            // Simple reference conversion.

            // Note:  Do not check for a class hierarchy relation

            // between src and dst.  In all cases a 'null' argument

            // will pass the cast conversion.

            return dst;

        }

        assert(fn.type().parameterCount() <= 1) : "pc"+Arrays.asList(src.getSimpleName(), dst.getSimpleName(), fn);

        return fn;

    }

    static MethodHandle makeVarargsCollector(MethodHandle target, Class<?> arrayType) {

        MethodType type = target.type();

        int last = type.parameterCount() - 1;

        if (type.parameterType(last) != arrayType)

            target = target.asType(type.changeParameterType(last, arrayType));

        target = target.asFixedArity();  // make sure this attribute is turned off

        return new AsVarargsCollector(target, arrayType);

    }

    private static final class AsVarargsCollector extends DelegatingMethodHandle {

        private final MethodHandle target;

        private final Class<?> arrayType;

        private @Stable MethodHandle asCollectorCache;

        AsVarargsCollector(MethodHandle target, Class<?> arrayType) {

            this(target.type(), target, arrayType);

        }

        AsVarargsCollector(MethodType type, MethodHandle target, Class<?> arrayType) {

            super(type, target);

            this.target = target;

            this.arrayType = arrayType;

            this.asCollectorCache = target.asCollector(arrayType, 0);

        }

        @Override

        public boolean isVarargsCollector() {

            return true;

        }

        @Override

        protected MethodHandle getTarget() {

            return target;

        }

        @Override

        public MethodHandle asFixedArity() {

            return target;

        }

        @Override

        MethodHandle setVarargs(MemberName member) {

            if (member.isVarargs())  return this;

            return asFixedArity();

        }

        @Override

        public MethodHandle asTypeUncached(MethodType newType) {

            MethodType type = this.type();

            int collectArg = type.parameterCount() - 1;

            int newArity = newType.parameterCount();

            if (newArity == collectArg+1 &&

                type.parameterType(collectArg).isAssignableFrom(newType.parameterType(collectArg))) {

                // if arity and trailing parameter are compatible, do normal thing

                return asTypeCache = asFixedArity().asType(newType);

            }

            // check cache

            MethodHandle acc = asCollectorCache;

            if (acc != null && acc.type().parameterCount() == newArity)

                return asTypeCache = acc.asType(newType);

            // build and cache a collector

            int arrayLength = newArity - collectArg;

            MethodHandle collector;

            try {

                collector = asFixedArity().asCollector(arrayType, arrayLength);

                assert(collector.type().parameterCount() == newArity) : "newArity="+newArity+" but collector="+collector;

            } catch (IllegalArgumentException ex) {

                throw new WrongMethodTypeException("cannot build collector", ex);

            }

            asCollectorCache = collector;

            return asTypeCache = collector.asType(newType);

        }

        @Override

        boolean viewAsTypeChecks(MethodType newType, boolean strict) {

            super.viewAsTypeChecks(newType, true);

            if (strict) return true;

            // extra assertion for non-strict checks:

            assert (type().lastParameterType().getComponentType()

                    .isAssignableFrom(

                            newType.lastParameterType().getComponentType()))

                    : Arrays.asList(this, newType);

            return true;

        }

    }

    /** Factory method:  Spread selected argument. */

    static MethodHandle makeSpreadArguments(MethodHandle target,

                                            Class<?> spreadArgType, int spreadArgPos, int spreadArgCount) {

        MethodType targetType = target.type();

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

            Class<?> arg = VerifyType.spreadArgElementType(spreadArgType, i);

            if (arg == null)  arg = Object.class;

            targetType = targetType.changeParameterType(spreadArgPos + i, arg);

        }

        target = target.asType(targetType);

        MethodType srcType = targetType

                .replaceParameterTypes(spreadArgPos, spreadArgPos + spreadArgCount, spreadArgType);

        // Now build a LambdaForm.

        MethodType lambdaType = srcType.invokerType();

        Name[] names = arguments(spreadArgCount + 2, lambdaType);

        int nameCursor = lambdaType.parameterCount();

        int[] indexes = new int[targetType.parameterCount()];

        for (int i = 0, argIndex = 1; i < targetType.parameterCount() + 1; i++, argIndex++) {

            Class<?> src = lambdaType.parameterType(i);

            if (i == spreadArgPos) {

                // Spread the array.

                MethodHandle aload = MethodHandles.arrayElementGetter(spreadArgType);

                Name array = names[argIndex];

                names[nameCursor++] = new Name(Lazy.NF_checkSpreadArgument, array, spreadArgCount);

                for (int j = 0; j < spreadArgCount; i++, j++) {

                    indexes[i] = nameCursor;

                    names[nameCursor++] = new Name(aload, array, j);

                }

            } else if (i < indexes.length) {

                indexes[i] = argIndex;

            }

        }

        assert(nameCursor == names.length-1);  // leave room for the final call

        // Build argument array for the call.

        Name[] targetArgs = new Name[targetType.parameterCount()];

        for (int i = 0; i < targetType.parameterCount(); i++) {

            int idx = indexes[i];

            targetArgs[i] = names[idx];

        }

        names[names.length - 1] = new Name(target, (Object[]) targetArgs);

        LambdaForm form = new LambdaForm("spread", lambdaType.parameterCount(), names);

        return SimpleMethodHandle.make(srcType, form);

    }

    static void checkSpreadArgument(Object av, int n) {

        if (av == null) {

            if (n == 0)  return;

        } else if (av instanceof Object[]) {

            int len = ((Object[])av).length;

            if (len == n)  return;

        } else {

            int len = java.lang.reflect.Array.getLength(av);

            if (len == n)  return;

        }

        // fall through to error:

        throw newIllegalArgumentException("array is not of length "+n);

    }

    /**

     * Pre-initialized NamedFunctions for bootstrapping purposes.

     * Factored in an inner class to delay initialization until first usage.

     */

    static class Lazy {

        private static final Class<?> MHI = MethodHandleImpl.class;

        private static final MethodHandle[] ARRAYS;

        private static final MethodHandle[] FILL_ARRAYS;

        static final NamedFunction NF_checkSpreadArgument;

        static final NamedFunction NF_guardWithCatch;

        static final NamedFunction NF_throwException;

        static final NamedFunction NF_profileBoolean;

        static final MethodHandle MH_castReference;

        static final MethodHandle MH_selectAlternative;

        static final MethodHandle MH_copyAsPrimitiveArray;

        static final MethodHandle MH_fillNewTypedArray;

        static final MethodHandle MH_fillNewArray;

        static final MethodHandle MH_arrayIdentity;

        static {

            ARRAYS      = makeArrays();

            FILL_ARRAYS = makeFillArrays();

            try {

                NF_checkSpreadArgument = new NamedFunction(MHI.getDeclaredMethod("checkSpreadArgument", Object.class, int.class));

                NF_guardWithCatch      = new NamedFunction(MHI.getDeclaredMethod("guardWithCatch", MethodHandle.class, Class.class,

                                                                                 MethodHandle.class, Object[].class));

                NF_throwException      = new NamedFunction(MHI.getDeclaredMethod("throwException", Throwable.class));

                NF_profileBoolean      = new NamedFunction(MHI.getDeclaredMethod("profileBoolean", boolean.class, int[].class));

                NF_checkSpreadArgument.resolve();

                NF_guardWithCatch.resolve();

                NF_throwException.resolve();

                NF_profileBoolean.resolve();

                MH_castReference        = IMPL_LOOKUP.findStatic(MHI, "castReference",

                                            MethodType.methodType(Object.class, Class.class, Object.class));

                MH_copyAsPrimitiveArray = IMPL_LOOKUP.findStatic(MHI, "copyAsPrimitiveArray",

                                            MethodType.methodType(Object.class, Wrapper.class, Object[].class));

                MH_arrayIdentity        = IMPL_LOOKUP.findStatic(MHI, "identity",

                                            MethodType.methodType(Object[].class, Object[].class));

                MH_fillNewArray         = IMPL_LOOKUP.findStatic(MHI, "fillNewArray",

                                            MethodType.methodType(Object[].class, Integer.class, Object[].class));

                MH_fillNewTypedArray    = IMPL_LOOKUP.findStatic(MHI, "fillNewTypedArray",

                                            MethodType.methodType(Object[].class, Object[].class, Integer.class, Object[].class));

                MH_selectAlternative    = makeIntrinsic(

                        IMPL_LOOKUP.findStatic(MHI, "selectAlternative",

                                MethodType.methodType(MethodHandle.class, boolean.class, MethodHandle.class, MethodHandle.class)),

                        Intrinsic.SELECT_ALTERNATIVE);

            } catch (ReflectiveOperationException ex) {

                throw newInternalError(ex);

            }

        }

    }

    /** Factory method:  Collect or filter selected argument(s). */

    static MethodHandle makeCollectArguments(MethodHandle target,

                MethodHandle collector, int collectArgPos, boolean retainOriginalArgs) {

        MethodType targetType = target.type();          // (a..., c, [b...])=>r

        MethodType collectorType = collector.type();    // (b...)=>c

        int collectArgCount = collectorType.parameterCount();

        Class<?> collectValType = collectorType.returnType();

        int collectValCount = (collectValType == void.class ? 0 : 1);

        MethodType srcType = targetType                 // (a..., [b...])=>r

                .dropParameterTypes(collectArgPos, collectArgPos+collectValCount);

        if (!retainOriginalArgs) {                      // (a..., b...)=>r

            srcType = srcType.insertParameterTypes(collectArgPos, collectorType.parameterList());

        }

        // in  arglist: [0: ...keep1 | cpos: collect...  | cpos+cacount: keep2... ]

        // out arglist: [0: ...keep1 | cpos: collectVal? | cpos+cvcount: keep2... ]

        // out(retain): [0: ...keep1 | cpos: cV? coll... | cpos+cvc+cac: keep2... ]

        // Now build a LambdaForm.

        MethodType lambdaType = srcType.invokerType();

        Name[] names = arguments(2, lambdaType);

        final int collectNamePos = names.length - 2;

        final int targetNamePos  = names.length - 1;

        Name[] collectorArgs = Arrays.copyOfRange(names, 1 + collectArgPos, 1 + collectArgPos + collectArgCount);

        names[collectNamePos] = new Name(collector, (Object[]) collectorArgs);

        // Build argument array for the target.

        // Incoming LF args to copy are: [ (mh) headArgs collectArgs tailArgs ].

        // Output argument array is [ headArgs (collectVal)? (collectArgs)? tailArgs ].

        Name[] targetArgs = new Name[targetType.parameterCount()];

        int inputArgPos  = 1;  // incoming LF args to copy to target

        int targetArgPos = 0;  // fill pointer for targetArgs

        int chunk = collectArgPos;  // |headArgs|

        System.arraycopy(names, inputArgPos, targetArgs, targetArgPos, chunk);

        inputArgPos  += chunk;

        targetArgPos += chunk;

        if (collectValType != void.class) {

            targetArgs[targetArgPos++] = names[collectNamePos];

        }

        chunk = collectArgCount;

        if (retainOriginalArgs) {

            System.arraycopy(names, inputArgPos, targetArgs, targetArgPos, chunk);

            targetArgPos += chunk;   // optionally pass on the collected chunk

        }

        inputArgPos += chunk;

        chunk = targetArgs.length - targetArgPos;  // all the rest

        System.arraycopy(names, inputArgPos, targetArgs, targetArgPos, chunk);

        assert(inputArgPos + chunk == collectNamePos);  // use of rest of input args also

        names[targetNamePos] = new Name(target, (Object[]) targetArgs);

        LambdaForm form = new LambdaForm("collect", lambdaType.parameterCount(), names);

        return SimpleMethodHandle.make(srcType, form);

    }

    @LambdaForm.Hidden

    static

    MethodHandle selectAlternative(boolean testResult, MethodHandle target, MethodHandle fallback) {

        if (testResult) {

            return target;

        } else {

            return fallback;

        }

    }

    // Intrinsified by C2. Counters are used during parsing to calculate branch frequencies.

    @LambdaForm.Hidden

    static

    boolean profileBoolean(boolean result, int[] counters) {

        // Profile is int[2] where [0] and [1] correspond to false and true occurrences respectively.

        int idx = result ? 1 : 0;

        try {

            counters[idx] = Math.addExact(counters[idx], 1);

        } catch (ArithmeticException e) {

            // Avoid continuous overflow by halving the problematic count.

            counters[idx] = counters[idx] / 2;

        }

        return result;

    }

    static

    MethodHandle makeGuardWithTest(MethodHandle test,

                                   MethodHandle target,

                                   MethodHandle fallback) {

        MethodType type = target.type();

        assert(test.type().equals(type.changeReturnType(boolean.class)) && fallback.type().equals(type));

        MethodType basicType = type.basicType();

        LambdaForm form = makeGuardWithTestForm(basicType);

        BoundMethodHandle mh;

        try {

            if (PROFILE_GWT) {

                int[] counts = new int[2];

                mh = (BoundMethodHandle)

                        BoundMethodHandle.speciesData_LLLL().constructor().invokeBasic(type, form,

                                (Object) test, (Object) profile(target), (Object) profile(fallback), counts);

            } else {

                mh = (BoundMethodHandle)

                        BoundMethodHandle.speciesData_LLL().constructor().invokeBasic(type, form,

                                (Object) test, (Object) profile(target), (Object) profile(fallback));

            }

        } catch (Throwable ex) {

            throw uncaughtException(ex);

        }

        assert(mh.type() == type);

        return mh;

    }

    static

    MethodHandle profile(MethodHandle target) {

        if (DONT_INLINE_THRESHOLD >= 0) {

            return makeBlockInlningWrapper(target);

        } else {

            return target;

        }

    }

    /**

     * Block inlining during JIT-compilation of a target method handle if it hasn't been invoked enough times.

     * Corresponding LambdaForm has @DontInline when compiled into bytecode.

     */

    static

    MethodHandle makeBlockInlningWrapper(MethodHandle target) {

        LambdaForm lform = PRODUCE_BLOCK_INLINING_FORM.apply(target);

        return new CountingWrapper(target, lform,

                PRODUCE_BLOCK_INLINING_FORM, PRODUCE_REINVOKER_FORM,

                                   DONT_INLINE_THRESHOLD);

    }

    /** Constructs reinvoker lambda form which block inlining during JIT-compilation for a particular method handle */

    private static final Function<MethodHandle, LambdaForm> PRODUCE_BLOCK_INLINING_FORM = new Function<MethodHandle, LambdaForm>() {

        @Override

        public LambdaForm apply(MethodHandle target) {

            return DelegatingMethodHandle.makeReinvokerForm(target,

                               MethodTypeForm.LF_DELEGATE_BLOCK_INLINING, CountingWrapper.class, "reinvoker.dontInline", false,

                               DelegatingMethodHandle.NF_getTarget, CountingWrapper.NF_maybeStopCounting);

        }

    };

    /** Constructs simple reinvoker lambda form for a particular method handle */

    private static final Function<MethodHandle, LambdaForm> PRODUCE_REINVOKER_FORM = new Function<MethodHandle, LambdaForm>() {

        @Override

        public LambdaForm apply(MethodHandle target) {

            return DelegatingMethodHandle.makeReinvokerForm(target,

                    MethodTypeForm.LF_DELEGATE, DelegatingMethodHandle.class, DelegatingMethodHandle.NF_getTarget);

        }

    };

    /**

     * Counting method handle. It has 2 states: counting and non-counting.

     * It is in counting state for the first n invocations and then transitions to non-counting state.

     * Behavior in counting and non-counting states is determined by lambda forms produced by

     * countingFormProducer & nonCountingFormProducer respectively.

     */

    static class CountingWrapper extends DelegatingMethodHandle {

        private final MethodHandle target;

        private int count;

        private Function<MethodHandle, LambdaForm> countingFormProducer;

        private Function<MethodHandle, LambdaForm> nonCountingFormProducer;

        private volatile boolean isCounting;

        private CountingWrapper(MethodHandle target, LambdaForm lform,

                                Function<MethodHandle, LambdaForm> countingFromProducer,

                                Function<MethodHandle, LambdaForm> nonCountingFormProducer,

                                int count) {

            super(target.type(), lform);

            this.target = target;

            this.count = count;

            this.countingFormProducer = countingFromProducer;

            this.nonCountingFormProducer = nonCountingFormProducer;

            this.isCounting = (count > 0);

        }

        @Hidden

        @Override

        protected MethodHandle getTarget() {

            return target;

        }

        @Override

        public MethodHandle asTypeUncached(MethodType newType) {

            MethodHandle newTarget = target.asType(newType);

            MethodHandle wrapper;

            if (isCounting) {

                LambdaForm lform;

                lform = countingFormProducer.apply(newTarget);

                wrapper = new CountingWrapper(newTarget, lform, countingFormProducer, nonCountingFormProducer, DONT_INLINE_THRESHOLD);

            } else {

                wrapper = newTarget; // no need for a counting wrapper anymore

            }

            return (asTypeCache = wrapper);

        }

        boolean countDown() {

            if (count <= 0) {

                // Try to limit number of updates. MethodHandle.updateForm() doesn't guarantee LF update visibility.

                if (isCounting) {

                    isCounting = false;

                    return true;

                } else {

                    return false;

                }

            } else {

                --count;

                return false;

            }

        }

        @Hidden

        static void maybeStopCounting(Object o1) {

             CountingWrapper wrapper = (CountingWrapper) o1;

             if (wrapper.countDown()) {

                 // Reached invocation threshold. Replace counting behavior with a non-counting one.

                 LambdaForm lform = wrapper.nonCountingFormProducer.apply(wrapper.target);

                 lform.compileToBytecode(); // speed up warmup by avoiding LF interpretation again after transition

                 wrapper.updateForm(lform);

             }

        }

        static final NamedFunction NF_maybeStopCounting;

        static {

            Class<?> THIS_CLASS = CountingWrapper.class;

            try {

                NF_maybeStopCounting = new NamedFunction(THIS_CLASS.getDeclaredMethod("maybeStopCounting", Object.class));

            } catch (ReflectiveOperationException ex) {

                throw newInternalError(ex);

            }

        }

    }

    static

    LambdaForm makeGuardWithTestForm(MethodType basicType) {

        LambdaForm lform = basicType.form().cachedLambdaForm(MethodTypeForm.LF_GWT);

        if (lform != null)  return lform;

        final int THIS_MH      = 0;  // the BMH_LLL

        final int ARG_BASE     = 1;  // start of incoming arguments

        final int ARG_LIMIT    = ARG_BASE + basicType.parameterCount();

        int nameCursor = ARG_LIMIT;

        final int GET_TEST     = nameCursor++;

        final int GET_TARGET   = nameCursor++;

        final int GET_FALLBACK = nameCursor++;

        final int GET_COUNTERS = PROFILE_GWT ? nameCursor++ : -1;

        final int CALL_TEST    = nameCursor++;

        final int PROFILE      = (GET_COUNTERS != -1) ? nameCursor++ : -1;

        final int TEST         = nameCursor-1; // previous statement: either PROFILE or CALL_TEST

        final int SELECT_ALT   = nameCursor++;

        final int CALL_TARGET  = nameCursor++;

        assert(CALL_TARGET == SELECT_ALT+1);  // must be true to trigger IBG.emitSelectAlternative

        MethodType lambdaType = basicType.invokerType();

        Name[] names = arguments(nameCursor - ARG_LIMIT, lambdaType);

        BoundMethodHandle.SpeciesData data =

                (GET_COUNTERS != -1) ? BoundMethodHandle.speciesData_LLLL()

                                     : BoundMethodHandle.speciesData_LLL();

        names[THIS_MH] = names[THIS_MH].withConstraint(data);

        names[GET_TEST]     = new Name(data.getterFunction(0), names[THIS_MH]);

        names[GET_TARGET]   = new Name(data.getterFunction(1), names[THIS_MH]);

        names[GET_FALLBACK] = new Name(data.getterFunction(2), names[THIS_MH]);

        if (GET_COUNTERS != -1) {

            names[GET_COUNTERS] = new Name(data.getterFunction(3), names[THIS_MH]);

        }

        Object[] invokeArgs = Arrays.copyOfRange(names, 0, ARG_LIMIT, Object[].class);

        // call test

        MethodType testType = basicType.changeReturnType(boolean.class).basicType();

        invokeArgs[0] = names[GET_TEST];

        names[CALL_TEST] = new Name(testType, invokeArgs);

        // profile branch

        if (PROFILE != -1) {

            names[PROFILE] = new Name(Lazy.NF_profileBoolean, names[CALL_TEST], names[GET_COUNTERS]);

        }

        // call selectAlternative

        names[SELECT_ALT] = new Name(Lazy.MH_selectAlternative, names[TEST], names[GET_TARGET], names[GET_FALLBACK]);

        // call target or fallback

        invokeArgs[0] = names[SELECT_ALT];

        names[CALL_TARGET] = new Name(basicType, invokeArgs);

        lform = new LambdaForm("guard", lambdaType.parameterCount(), names, /*forceInline=*/true);

        return basicType.form().setCachedLambdaForm(MethodTypeForm.LF_GWT, lform);

    }

    /**

     * The LambaForm shape for catchException combinator is the following:

     * <blockquote><pre>{@code

     *  guardWithCatch=Lambda(a0:L,a1:L,a2:L)=>{

     *    t3:L=BoundMethodHandle$Species_LLLLL.argL0(a0:L);

     *    t4:L=BoundMethodHandle$Species_LLLLL.argL1(a0:L);

     *    t5:L=BoundMethodHandle$Species_LLLLL.argL2(a0:L);

     *    t6:L=BoundMethodHandle$Species_LLLLL.argL3(a0:L);

     *    t7:L=BoundMethodHandle$Species_LLLLL.argL4(a0:L);

     *    t8:L=MethodHandle.invokeBasic(t6:L,a1:L,a2:L);

     *    t9:L=MethodHandleImpl.guardWithCatch(t3:L,t4:L,t5:L,t8:L);

     *   t10:I=MethodHandle.invokeBasic(t7:L,t9:L);t10:I}

     * }</pre></blockquote>

     *

     * argL0 and argL2 are target and catcher method handles. argL1 is exception class.

     * argL3 and argL4 are auxiliary method handles: argL3 boxes arguments and wraps them into Object[]

     * (ValueConversions.array()) and argL4 unboxes result if necessary (ValueConversions.unbox()).

     *

     * Having t8 and t10 passed outside and not hardcoded into a lambda form allows to share lambda forms

     * among catchException combinators with the same basic type.

     */

    private static LambdaForm makeGuardWithCatchForm(MethodType basicType) {

        MethodType lambdaType = basicType.invokerType();

        LambdaForm lform = basicType.form().cachedLambdaForm(MethodTypeForm.LF_GWC);

        if (lform != null) {

            return lform;

        }

        final int THIS_MH      = 0;  // the BMH_LLLLL

        final int ARG_BASE     = 1;  // start of incoming arguments

        final int ARG_LIMIT    = ARG_BASE + basicType.parameterCount();

        int nameCursor = ARG_LIMIT;

        final int GET_TARGET       = nameCursor++;

        final int GET_CLASS        = nameCursor++;

        final int GET_CATCHER      = nameCursor++;

        final int GET_COLLECT_ARGS = nameCursor++;

        final int GET_UNBOX_RESULT = nameCursor++;

        final int BOXED_ARGS       = nameCursor++;

        final int TRY_CATCH        = nameCursor++;

        final int UNBOX_RESULT     = nameCursor++;

        Name[] names = arguments(nameCursor - ARG_LIMIT, lambdaType);

        BoundMethodHandle.SpeciesData data = BoundMethodHandle.speciesData_LLLLL();

        names[THIS_MH]          = names[THIS_MH].withConstraint(data);

        names[GET_TARGET]       = new Name(data.getterFunction(0), names[THIS_MH]);

        names[GET_CLASS]        = new Name(data.getterFunction(1), names[THIS_MH]);

        names[GET_CATCHER]      = new Name(data.getterFunction(2), names[THIS_MH]);

        names[GET_COLLECT_ARGS] = new Name(data.getterFunction(3), names[THIS_MH]);

        names[GET_UNBOX_RESULT] = new Name(data.getterFunction(4), names[THIS_MH]);

        // FIXME: rework argument boxing/result unboxing logic for LF interpretation

        // t_{i}:L=MethodHandle.invokeBasic(collectArgs:L,a1:L,...);

        MethodType collectArgsType = basicType.changeReturnType(Object.class);

        MethodHandle invokeBasic = MethodHandles.basicInvoker(collectArgsType);

        Object[] args = new Object[invokeBasic.type().parameterCount()];

        args[0] = names[GET_COLLECT_ARGS];

        System.arraycopy(names, ARG_BASE, args, 1, ARG_LIMIT-ARG_BASE);

        names[BOXED_ARGS] = new Name(makeIntrinsic(invokeBasic, Intrinsic.GUARD_WITH_CATCH), args);

        // t_{i+1}:L=MethodHandleImpl.guardWithCatch(target:L,exType:L,catcher:L,t_{i}:L);

        Object[] gwcArgs = new Object[] {names[GET_TARGET], names[GET_CLASS], names[GET_CATCHER], names[BOXED_ARGS]};

        names[TRY_CATCH] = new Name(Lazy.NF_guardWithCatch, gwcArgs);

        // t_{i+2}:I=MethodHandle.invokeBasic(unbox:L,t_{i+1}:L);

        MethodHandle invokeBasicUnbox = MethodHandles.basicInvoker(MethodType.methodType(basicType.rtype(), Object.class));

        Object[] unboxArgs  = new Object[] {names[GET_UNBOX_RESULT], names[TRY_CATCH]};

        names[UNBOX_RESULT] = new Name(invokeBasicUnbox, unboxArgs);

        lform = new LambdaForm("guardWithCatch", lambdaType.parameterCount(), names);

        return basicType.form().setCachedLambdaForm(MethodTypeForm.LF_GWC, lform);

    }

    static

    MethodHandle makeGuardWithCatch(MethodHandle target,

                                    Class<? extends Throwable> exType,

                                    MethodHandle catcher) {

        MethodType type = target.type();

        LambdaForm form = makeGuardWithCatchForm(type.basicType());

        // Prepare auxiliary method handles used during LambdaForm interpreation.

        // Box arguments and wrap them into Object[]: ValueConversions.array().

        MethodType varargsType = type.changeReturnType(Object[].class);

        MethodHandle collectArgs = varargsArray(type.parameterCount()).asType(varargsType);

        // Result unboxing: ValueConversions.unbox() OR ValueConversions.identity() OR ValueConversions.ignore().

        MethodHandle unboxResult;

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

        if (rtype.isPrimitive()) {

            if (rtype == void.class) {

                unboxResult = ValueConversions.ignore();

            } else {

                Wrapper w = Wrapper.forPrimitiveType(type.returnType());

                unboxResult = ValueConversions.unboxExact(w);

            }

        } else {

            unboxResult = MethodHandles.identity(Object.class);

        }

        BoundMethodHandle.SpeciesData data = BoundMethodHandle.speciesData_LLLLL();

        BoundMethodHandle mh;

        try {

            mh = (BoundMethodHandle)

                    data.constructor().invokeBasic(type, form, (Object) target, (Object) exType, (Object) catcher,

                                                   (Object) collectArgs, (Object) unboxResult);

        } catch (Throwable ex) {

            throw uncaughtException(ex);

        }

        assert(mh.type() == type);

        return mh;

    }

    /**

     * Intrinsified during LambdaForm compilation

     * (see {@link InvokerBytecodeGenerator#emitGuardWithCatch emitGuardWithCatch}).

     */

    @LambdaForm.Hidden

    static Object guardWithCatch(MethodHandle target, Class<? extends Throwable> exType, MethodHandle catcher,

                                 Object... av) throws Throwable {

        // Use asFixedArity() to avoid unnecessary boxing of last argument for VarargsCollector case.

        try {

            return target.asFixedArity().invokeWithArguments(av);

        } catch (Throwable t) {

            if (!exType.isInstance(t)) throw t;

            return catcher.asFixedArity().invokeWithArguments(prepend(t, av));

        }

    }

    /** Prepend an element {@code elem} to an {@code array}. */

    @LambdaForm.Hidden

    private static Object[] prepend(Object elem, Object[] array) {

        Object[] newArray = new Object[array.length+1];

        newArray[0] = elem;

        System.arraycopy(array, 0, newArray, 1, array.length);

        return newArray;

    }

    static

    MethodHandle throwException(MethodType type) {

        assert(Throwable.class.isAssignableFrom(type.parameterType(0)));

        int arity = type.parameterCount();

        if (arity > 1) {

            MethodHandle mh = throwException(type.dropParameterTypes(1, arity));

            mh = MethodHandles.dropArguments(mh, 1, type.parameterList().subList(1, arity));

            return mh;

        }

        return makePairwiseConvert(Lazy.NF_throwException.resolvedHandle(), type, false, true);

    }

    static <T extends Throwable> Empty throwException(T t) throws T { throw t; }

    static MethodHandle[] FAKE_METHOD_HANDLE_INVOKE = new MethodHandle[2];

    static MethodHandle fakeMethodHandleInvoke(MemberName method) {

        int idx;

        assert(method.isMethodHandleInvoke());

        switch (method.getName()) {

        case "invoke":       idx = 0; break;

        case "invokeExact":  idx = 1; break;

        default:             throw new InternalError(method.getName());

        }

        MethodHandle mh = FAKE_METHOD_HANDLE_INVOKE[idx];

        if (mh != null)  return mh;

        MethodType type = MethodType.methodType(Object.class, UnsupportedOperationException.class,

                                                MethodHandle.class, Object[].class);

        mh = throwException(type);

        mh = mh.bindTo(new UnsupportedOperationException("cannot reflectively invoke MethodHandle"));

        if (!method.getInvocationType().equals(mh.type()))

            throw new InternalError(method.toString());

        mh = mh.withInternalMemberName(method, false);

        mh = mh.asVarargsCollector(Object[].class);

        assert(method.isVarargs());

        FAKE_METHOD_HANDLE_INVOKE[idx] = mh;

        return mh;

    }

    /**

     * Create an alias for the method handle which, when called,

     * appears to be called from the same class loader and protection domain

     * as hostClass.

     * This is an expensive no-op unless the method which is called

     * is sensitive to its caller.  A small number of system methods

     * are in this category, including Class.forName and Method.invoke.

     */

    static

    MethodHandle bindCaller(MethodHandle mh, Class<?> hostClass) {

        return BindCaller.bindCaller(mh, hostClass);

    }

    // Put the whole mess into its own nested class.

    // That way we can lazily load the code and set up the constants.

    private static class BindCaller {

        static

        MethodHandle bindCaller(MethodHandle mh, Class<?> hostClass) {

            // Do not use this function to inject calls into system classes.

            if (hostClass == null

                ||    (hostClass.isArray() ||

                       hostClass.isPrimitive() ||

                       hostClass.getName().startsWith("java.") ||

                       hostClass.getName().startsWith("sun."))) {

                throw new InternalError();  // does not happen, and should not anyway

            }

            // For simplicity, convert mh to a varargs-like method.

            MethodHandle vamh = prepareForInvoker(mh);

            // Cache the result of makeInjectedInvoker once per argument class.

            MethodHandle bccInvoker = CV_makeInjectedInvoker.get(hostClass);

            return restoreToType(bccInvoker.bindTo(vamh), mh, hostClass);

        }

        private static MethodHandle makeInjectedInvoker(Class<?> hostClass) {

            Class<?> bcc = UNSAFE.defineAnonymousClass(hostClass, T_BYTES, null);

            if (hostClass.getClassLoader() != bcc.getClassLoader())

                throw new InternalError(hostClass.getName()+" (CL)");

            try {

                if (hostClass.getProtectionDomain() != bcc.getProtectionDomain())

                    throw new InternalError(hostClass.getName()+" (PD)");

            } catch (SecurityException ex) {

                // Self-check was blocked by security manager.  This is OK.

                // In fact the whole try body could be turned into an assertion.

            }

            try {

                MethodHandle init = IMPL_LOOKUP.findStatic(bcc, "init", MethodType.methodType(void.class));

                init.invokeExact();  // force initialization of the class

            } catch (Throwable ex) {

                throw uncaughtException(ex);

            }

            MethodHandle bccInvoker;

            try {

                MethodType invokerMT = MethodType.methodType(Object.class, MethodHandle.class, Object[].class);

                bccInvoker = IMPL_LOOKUP.findStatic(bcc, "invoke_V", invokerMT);

            } catch (ReflectiveOperationException ex) {

                throw uncaughtException(ex);

            }

            // Test the invoker, to ensure that it really injects into the right place.

            try {

                MethodHandle vamh = prepareForInvoker(MH_checkCallerClass);

                Object ok = bccInvoker.invokeExact(vamh, new Object[]{hostClass, bcc});

            } catch (Throwable ex) {

                throw new InternalError(ex);

            }

            return bccInvoker;

        }

        private static ClassValue<MethodHandle> CV_makeInjectedInvoker = new ClassValue<MethodHandle>() {

            @Override protected MethodHandle computeValue(Class<?> hostClass) {

                return makeInjectedInvoker(hostClass);

            }

        };

        // Adapt mh so that it can be called directly from an injected invoker:

        private static MethodHandle prepareForInvoker(MethodHandle mh) {

            mh = mh.asFixedArity();

            MethodType mt = mh.type();

            int arity = mt.parameterCount();

            MethodHandle vamh = mh.asType(mt.generic());

            vamh.internalForm().compileToBytecode();  // eliminate LFI stack frames

            vamh = vamh.asSpreader(Object[].class, arity);

            vamh.internalForm().compileToBytecode();  // eliminate LFI stack frames

            return vamh;

        }

        // Undo the adapter effect of prepareForInvoker:

        private static MethodHandle restoreToType(MethodHandle vamh,