/*

 * 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

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package java.lang.invoke;

import sun.misc.Unsafe;

import java.lang.reflect.Method;

import java.util.Arrays;

import sun.invoke.util.VerifyAccess;

import static java.lang.invoke.MethodHandleNatives.Constants.*;

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

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

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

import java.lang.ref.WeakReference;

import java.lang.reflect.Field;

import sun.invoke.util.ValueConversions;

import sun.invoke.util.VerifyType;

import sun.invoke.util.Wrapper;

/**

 * The flavor of method handle which implements a constant reference

 * to a class member.

 * @author jrose

 */

class DirectMethodHandle extends MethodHandle {

    final MemberName member;

    // Constructors and factory methods in this class *must* be package scoped or private.

    private DirectMethodHandle(MethodType mtype, LambdaForm form, MemberName member) {

        super(mtype, form);

        if (!member.isResolved())  throw new InternalError();

        this.member = member;

    }

    // Factory methods:

    static DirectMethodHandle make(Class<?> receiver, MemberName member) {

        MethodType mtype = member.getMethodOrFieldType();

        if (!member.isStatic()) {

            if (!member.getDeclaringClass().isAssignableFrom(receiver) || member.isConstructor())

                throw new InternalError(member.toString());

            mtype = mtype.insertParameterTypes(0, receiver);

        }

        if (!member.isField()) {

            LambdaForm lform = preparedLambdaForm(member);

            return new DirectMethodHandle(mtype, lform, member);

        } else {

            LambdaForm lform = preparedFieldLambdaForm(member);

            if (member.isStatic()) {

                long offset = MethodHandleNatives.staticFieldOffset(member);

                Object base = MethodHandleNatives.staticFieldBase(member);

                return new StaticAccessor(mtype, lform, member, base, offset);

            } else {

                long offset = MethodHandleNatives.objectFieldOffset(member);

                assert(offset == (int)offset);

                return new Accessor(mtype, lform, member, (int)offset);

            }

        }

    }

    static DirectMethodHandle make(MemberName member) {

        if (member.isConstructor())

            return makeAllocator(member);

        return make(member.getDeclaringClass(), member);

    }

    static DirectMethodHandle make(Method method) {

        return make(method.getDeclaringClass(), new MemberName(method));

    }

    static DirectMethodHandle make(Field field) {

        return make(field.getDeclaringClass(), new MemberName(field));

    }

    private static DirectMethodHandle makeAllocator(MemberName ctor) {

        assert(ctor.isConstructor() && ctor.getName().equals("<init>"));

        Class<?> instanceClass = ctor.getDeclaringClass();

        ctor = ctor.asConstructor();

        assert(ctor.isConstructor() && ctor.getReferenceKind() == REF_newInvokeSpecial) : ctor;

        MethodType mtype = ctor.getMethodType().changeReturnType(instanceClass);

        LambdaForm lform = preparedLambdaForm(ctor);

        MemberName init = ctor.asSpecial();

        assert(init.getMethodType().returnType() == void.class);

        return new Constructor(mtype, lform, ctor, init, instanceClass);

    }

    @Override

    MethodHandle copyWith(MethodType mt, LambdaForm lf) {

        return new DirectMethodHandle(mt, lf, member);

    }

    @Override

    String internalProperties() {

        return "/DMH="+member.toString();

    }

    //// Implementation methods.

    @Override

    @ForceInline

    MemberName internalMemberName() {

        return member;

    }

    @Override

    MethodHandle bindArgument(int pos, char basicType, Object value) {

        // If the member needs dispatching, do so.

        if (pos == 0 && basicType == 'L') {

            DirectMethodHandle concrete = maybeRebind(value);

            if (concrete != null)

                return concrete.bindReceiver(value);

        }

        return super.bindArgument(pos, basicType, value);

    }

    @Override

    MethodHandle bindReceiver(Object receiver) {

        // If the member needs dispatching, do so.

        DirectMethodHandle concrete = maybeRebind(receiver);

        if (concrete != null)

            return concrete.bindReceiver(receiver);

        return super.bindReceiver(receiver);

    }

    private static final MemberName.Factory IMPL_NAMES = MemberName.getFactory();

    private DirectMethodHandle maybeRebind(Object receiver) {

        if (receiver != null) {

            switch (member.getReferenceKind()) {

            case REF_invokeInterface:

            case REF_invokeVirtual:

                // Pre-dispatch the member.

                Class<?> concreteClass = receiver.getClass();

                MemberName concrete = new MemberName(concreteClass, member.getName(), member.getMethodType(), REF_invokeSpecial);

                concrete = IMPL_NAMES.resolveOrNull(REF_invokeSpecial, concrete, concreteClass);

                if (concrete != null)

                    return new DirectMethodHandle(type(), preparedLambdaForm(concrete), concrete);

                break;

            }

        }

        return null;

    }

    /**

     * Create a LF which can invoke the given method.

     * Cache and share this structure among all methods with

     * the same basicType and refKind.

     */

    private static LambdaForm preparedLambdaForm(MemberName m) {

        assert(m.isInvocable()) : m;  // call preparedFieldLambdaForm instead

        MethodType mtype = m.getInvocationType().basicType();

        assert(!m.isMethodHandleInvoke() || "invokeBasic".equals(m.getName())) : m;

        int which;

        switch (m.getReferenceKind()) {

        case REF_invokeVirtual:    which = LF_INVVIRTUAL;    break;

        case REF_invokeStatic:     which = LF_INVSTATIC;     break;

        case REF_invokeSpecial:    which = LF_INVSPECIAL;    break;

        case REF_invokeInterface:  which = LF_INVINTERFACE;  break;

        case REF_newInvokeSpecial: which = LF_NEWINVSPECIAL; break;

        default:  throw new InternalError(m.toString());

        }

        if (which == LF_INVSTATIC && shouldBeInitialized(m)) {

            // precompute the barrier-free version:

            preparedLambdaForm(mtype, which);

            which = LF_INVSTATIC_INIT;

        }

        LambdaForm lform = preparedLambdaForm(mtype, which);

        maybeCompile(lform, m);

        assert(lform.methodType().dropParameterTypes(0, 1)

                .equals(m.getInvocationType().basicType()))

                : Arrays.asList(m, m.getInvocationType().basicType(), lform, lform.methodType());

        return lform;

    }

    private static LambdaForm preparedLambdaForm(MethodType mtype, int which) {

        LambdaForm lform = mtype.form().cachedLambdaForm(which);

        if (lform != null)  return lform;

        lform = makePreparedLambdaForm(mtype, which);

        return mtype.form().setCachedLambdaForm(which, lform);

    }

    private static LambdaForm makePreparedLambdaForm(MethodType mtype, int which) {

        boolean needsInit = (which == LF_INVSTATIC_INIT);

        boolean doesAlloc = (which == LF_NEWINVSPECIAL);

        String linkerName, lambdaName;

        switch (which) {

        case LF_INVVIRTUAL:    linkerName = "linkToVirtual";    lambdaName = "DMH.invokeVirtual";    break;

        case LF_INVSTATIC:     linkerName = "linkToStatic";     lambdaName = "DMH.invokeStatic";     break;

        case LF_INVSTATIC_INIT:linkerName = "linkToStatic";     lambdaName = "DMH.invokeStaticInit"; break;

        case LF_INVSPECIAL:    linkerName = "linkToSpecial";    lambdaName = "DMH.invokeSpecial";    break;

        case LF_INVINTERFACE:  linkerName = "linkToInterface";  lambdaName = "DMH.invokeInterface";  break;

        case LF_NEWINVSPECIAL: linkerName = "linkToSpecial";    lambdaName = "DMH.newInvokeSpecial"; break;

        default:  throw new InternalError("which="+which);

        }

        MethodType mtypeWithArg = mtype.appendParameterTypes(MemberName.class);

        if (doesAlloc)

            mtypeWithArg = mtypeWithArg

                    .insertParameterTypes(0, Object.class)  // insert newly allocated obj

                    .changeReturnType(void.class);          // <init> returns void

        MemberName linker = new MemberName(MethodHandle.class, linkerName, mtypeWithArg, REF_invokeStatic);

        try {

            linker = IMPL_NAMES.resolveOrFail(REF_invokeStatic, linker, null, NoSuchMethodException.class);

        } catch (ReflectiveOperationException ex) {

            throw newInternalError(ex);

        }

        final int DMH_THIS    = 0;

        final int ARG_BASE    = 1;

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

        int nameCursor = ARG_LIMIT;

        final int NEW_OBJ     = (doesAlloc ? nameCursor++ : -1);

        final int GET_MEMBER  = nameCursor++;

        final int LINKER_CALL = nameCursor++;

        Name[] names = arguments(nameCursor - ARG_LIMIT, mtype.invokerType());

        assert(names.length == nameCursor);

        if (doesAlloc) {

            // names = { argx,y,z,... new C, init method }

            names[NEW_OBJ] = new Name(NF_allocateInstance, names[DMH_THIS]);

            names[GET_MEMBER] = new Name(NF_constructorMethod, names[DMH_THIS]);

        } else if (needsInit) {

            names[GET_MEMBER] = new Name(NF_internalMemberNameEnsureInit, names[DMH_THIS]);

        } else {

            names[GET_MEMBER] = new Name(NF_internalMemberName, names[DMH_THIS]);

        }

        Object[] outArgs = Arrays.copyOfRange(names, ARG_BASE, GET_MEMBER+1, Object[].class);

        assert(outArgs[outArgs.length-1] == names[GET_MEMBER]);  // look, shifted args!

        int result = LambdaForm.LAST_RESULT;

        if (doesAlloc) {

            assert(outArgs[outArgs.length-2] == names[NEW_OBJ]);  // got to move this one

            System.arraycopy(outArgs, 0, outArgs, 1, outArgs.length-2);

            outArgs[0] = names[NEW_OBJ];

            result = NEW_OBJ;

        }

        names[LINKER_CALL] = new Name(linker, outArgs);

        lambdaName += "_" + LambdaForm.basicTypeSignature(mtype);

        LambdaForm lform = new LambdaForm(lambdaName, ARG_LIMIT, names, result);

        // This is a tricky bit of code.  Don't send it through the LF interpreter.

        lform.compileToBytecode();

        return lform;

    }

    private static void maybeCompile(LambdaForm lform, MemberName m) {

        if (VerifyAccess.isSamePackage(m.getDeclaringClass(), MethodHandle.class))

            // Help along bootstrapping...

            lform.compileToBytecode();

    }

    /** Static wrapper for DirectMethodHandle.internalMemberName. */

    @ForceInline

    /*non-public*/ static Object internalMemberName(Object mh) {

        return ((DirectMethodHandle)mh).member;

    }

    /** Static wrapper for DirectMethodHandle.internalMemberName.

     * This one also forces initialization.

     */

    /*non-public*/ static Object internalMemberNameEnsureInit(Object mh) {

        DirectMethodHandle dmh = (DirectMethodHandle)mh;

        dmh.ensureInitialized();

        return dmh.member;

    }

    /*non-public*/ static

    boolean shouldBeInitialized(MemberName member) {

        switch (member.getReferenceKind()) {

        case REF_invokeStatic:

        case REF_getStatic:

        case REF_putStatic:

        case REF_newInvokeSpecial:

            break;

        default:

            // No need to initialize the class on this kind of member.

            return false;

        }

        Class<?> cls = member.getDeclaringClass();

        if (cls == ValueConversions.class ||

            cls == MethodHandleImpl.class ||

            cls == Invokers.class) {

            // These guys have lots of <clinit> DMH creation but we know

            // the MHs will not be used until the system is booted.

            return false;

        }

        if (VerifyAccess.isSamePackage(MethodHandle.class, cls) ||

            VerifyAccess.isSamePackage(ValueConversions.class, cls)) {

            // It is a system class.  It is probably in the process of

            // being initialized, but we will help it along just to be safe.

            if (UNSAFE.shouldBeInitialized(cls)) {

                UNSAFE.ensureClassInitialized(cls);

            }

            return false;

        }

        return UNSAFE.shouldBeInitialized(cls);

    }

    private static class EnsureInitialized extends ClassValue<WeakReference<Thread>> {

        @Override

        protected WeakReference<Thread> computeValue(Class<?> type) {

            UNSAFE.ensureClassInitialized(type);

            if (UNSAFE.shouldBeInitialized(type))

                // If the previous call didn't block, this can happen.

                // We are executing inside <clinit>.

                return new WeakReference<>(Thread.currentThread());

            return null;

        }

        static final EnsureInitialized INSTANCE = new EnsureInitialized();

    }

    private void ensureInitialized() {

        if (checkInitialized(member)) {

            // The coast is clear.  Delete the <clinit> barrier.

            if (member.isField())

                updateForm(preparedFieldLambdaForm(member));

            else

                updateForm(preparedLambdaForm(member));

        }

    }

    private static boolean checkInitialized(MemberName member) {

        Class<?> defc = member.getDeclaringClass();

        WeakReference<Thread> ref = EnsureInitialized.INSTANCE.get(defc);

        if (ref == null) {

            return true;  // the final state

        }

        Thread clinitThread = ref.get();

        // Somebody may still be running defc.<clinit>.

        if (clinitThread == Thread.currentThread()) {

            // If anybody is running defc.<clinit>, it is this thread.

            if (UNSAFE.shouldBeInitialized(defc))

                // Yes, we are running it; keep the barrier for now.

                return false;

        } else {

            // We are in a random thread.  Block.

            UNSAFE.ensureClassInitialized(defc);

        }

        assert(!UNSAFE.shouldBeInitialized(defc));

        // put it into the final state

        EnsureInitialized.INSTANCE.remove(defc);

        return true;

    }

    /*non-public*/ static void ensureInitialized(Object mh) {

        ((DirectMethodHandle)mh).ensureInitialized();

    }

    /** This subclass handles constructor references. */

    static class Constructor extends DirectMethodHandle {

        final MemberName initMethod;

        final Class<?>   instanceClass;

        private Constructor(MethodType mtype, LambdaForm form, MemberName constructor,

                            MemberName initMethod, Class<?> instanceClass) {

            super(mtype, form, constructor);

            this.initMethod = initMethod;

            this.instanceClass = instanceClass;

            assert(initMethod.isResolved());

        }

    }

    /*non-public*/ static Object constructorMethod(Object mh) {

        Constructor dmh = (Constructor)mh;

        return dmh.initMethod;

    }

    /*non-public*/ static Object allocateInstance(Object mh) throws InstantiationException {

        Constructor dmh = (Constructor)mh;

        return UNSAFE.allocateInstance(dmh.instanceClass);

    }

    /** This subclass handles non-static field references. */

    static class Accessor extends DirectMethodHandle {

        final Class<?> fieldType;

        final int      fieldOffset;

        private Accessor(MethodType mtype, LambdaForm form, MemberName member,

                         int fieldOffset) {

            super(mtype, form, member);

            this.fieldType   = member.getFieldType();

            this.fieldOffset = fieldOffset;

        }

        @Override Object checkCast(Object obj) {

            return fieldType.cast(obj);

        }

    }

    @ForceInline

    /*non-public*/ static long fieldOffset(Object accessorObj) {

        // Note: We return a long because that is what Unsafe.getObject likes.

        // We store a plain int because it is more compact.

        return ((Accessor)accessorObj).fieldOffset;

    }

    @ForceInline

    /*non-public*/ static Object checkBase(Object obj) {

        // Note that the object's class has already been verified,

        // since the parameter type of the Accessor method handle

        // is either member.getDeclaringClass or a subclass.

        // This was verified in DirectMethodHandle.make.

        // Therefore, the only remaining check is for null.

        // Since this check is *not* guaranteed by Unsafe.getInt

        // and its siblings, we need to make an explicit one here.

        obj.getClass();  // maybe throw NPE

        return obj;

    }

    /** This subclass handles static field references. */

    static class StaticAccessor extends DirectMethodHandle {

        final private Class<?> fieldType;

        final private Object   staticBase;

        final private long     staticOffset;

        private StaticAccessor(MethodType mtype, LambdaForm form, MemberName member,

                               Object staticBase, long staticOffset) {

            super(mtype, form, member);

            this.fieldType    = member.getFieldType();

            this.staticBase   = staticBase;

            this.staticOffset = staticOffset;

        }

        @Override Object checkCast(Object obj) {

            return fieldType.cast(obj);

        }

    }

    @ForceInline

    /*non-public*/ static Object nullCheck(Object obj) {

        obj.getClass();

        return obj;

    }

    @ForceInline

    /*non-public*/ static Object staticBase(Object accessorObj) {

        return ((StaticAccessor)accessorObj).staticBase;

    }

    @ForceInline

    /*non-public*/ static long staticOffset(Object accessorObj) {

        return ((StaticAccessor)accessorObj).staticOffset;

    }

    @ForceInline

    /*non-public*/ static Object checkCast(Object mh, Object obj) {

        return ((DirectMethodHandle) mh).checkCast(obj);

    }

    Object checkCast(Object obj) {

        return member.getReturnType().cast(obj);

    }

    // Caching machinery for field accessors:

    private static byte

            AF_GETFIELD        = 0,

            AF_PUTFIELD        = 1,

            AF_GETSTATIC       = 2,

            AF_PUTSTATIC       = 3,

            AF_GETSTATIC_INIT  = 4,

            AF_PUTSTATIC_INIT  = 5,

            AF_LIMIT           = 6;

    // Enumerate the different field kinds using Wrapper,

    // with an extra case added for checked references.

    private static int

            FT_LAST_WRAPPER    = Wrapper.values().length-1,

            FT_UNCHECKED_REF   = Wrapper.OBJECT.ordinal(),

            FT_CHECKED_REF     = FT_LAST_WRAPPER+1,

            FT_LIMIT           = FT_LAST_WRAPPER+2;

    private static int afIndex(byte formOp, boolean isVolatile, int ftypeKind) {

        return ((formOp * FT_LIMIT * 2)

                + (isVolatile ? FT_LIMIT : 0)

                + ftypeKind);

    }

    private static final LambdaForm[] ACCESSOR_FORMS

            = new LambdaForm[afIndex(AF_LIMIT, false, 0)];

    private static int ftypeKind(Class<?> ftype) {

        if (ftype.isPrimitive())

            return Wrapper.forPrimitiveType(ftype).ordinal();

        else if (VerifyType.isNullReferenceConversion(Object.class, ftype))

            return FT_UNCHECKED_REF;

        else

            return FT_CHECKED_REF;

    }