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 * 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
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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_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.ALOAD;
import static jdk.internal.org.objectweb.asm.Opcodes.RETURN;
import static jdk.nashorn.internal.runtime.ECMAErrors.typeError;

import java.lang.invoke.CallSite;
import java.lang.invoke.ConstantCallSite;
import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodHandles.Lookup;
import java.lang.invoke.MethodType;
import java.lang.reflect.Field;
import java.security.AccessController;
import java.security.CodeSigner;
import java.security.CodeSource;
import java.security.Permissions;
import java.security.PrivilegedAction;
import java.security.ProtectionDomain;
import java.security.SecureClassLoader;
import java.util.Objects;
import jdk.internal.org.objectweb.asm.ClassWriter;
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.ScriptObjectMirror;
import jdk.nashorn.internal.objects.Global;
import jdk.nashorn.internal.runtime.Context;
import jdk.nashorn.internal.runtime.ECMAException;
import jdk.nashorn.internal.runtime.JSType;
import jdk.nashorn.internal.runtime.ScriptFunction;
import jdk.nashorn.internal.runtime.ScriptObject;
import jdk.nashorn.internal.runtime.ScriptRuntime;

Provides static utility services to generated Java adapter classes.
/**
 * Provides static utility services to generated Java adapter classes.
 */
public final class JavaAdapterServices {
    private static final ThreadLocal<ScriptObject> classOverrides = new ThreadLocal<>();
    private static final MethodHandle NO_PERMISSIONS_INVOKER = createNoPermissionsInvoker();

    private JavaAdapterServices() {
    }

    
Given a script function used as a delegate for a SAM adapter, figure out
the right object to use as its "this" when called.
Params:
delegate – the delegate function
global – the current global of the adapter
Returns:
either the passed global, or UNDEFINED if the function is strict./**
     * Given a script function used as a delegate for a SAM adapter, figure out
     * the right object to use as its "this" when called.
     * @param delegate the delegate function
     * @param global the current global of the adapter
     * @return either the passed global, or UNDEFINED if the function is strict.
     */
    public static Object getCallThis(final ScriptFunction delegate, final Object global) {
        return delegate.isStrict() ? ScriptRuntime.UNDEFINED : global;
    }

    
Throws a "not.an.object" type error. Used when the delegate passed to the
adapter constructor is not a script object.
Params:
obj – the object that is not a script object./**
     * Throws a "not.an.object" type error. Used when the delegate passed to the
     * adapter constructor is not a script object.
     * @param obj the object that is not a script object.
     */
    public static void notAnObject(final Object obj) {
        throw typeError("not.an.object", ScriptRuntime.safeToString(obj));
    }

    
Checks if the passed object, which is supposed to be a callee retrieved
through applying the GET_METHOD_PROPERTY operation on the delegate, is
a ScriptFunction, or null or undefined. These are the only allowed values
for adapter method implementations, so in case it is neither, it throws
a type error. Note that this restriction is somewhat artificial; as the
CALL dynamic operation could invoke any Nashorn callable. We are
restricting adapters to actual ScriptFunction objects for now though.
Params:
callee – the callee to check
name – the name of the function
Throws:
ECMAException – representing a JS TypeError with "not.a.function"
message if the passed callee is neither a script function, nor null, nor
undefined.
Returns:
the callee cast to a ScriptFunction, or null if it was null or undefined./**
     * Checks if the passed object, which is supposed to be a callee retrieved
     * through applying the GET_METHOD_PROPERTY operation on the delegate, is
     * a ScriptFunction, or null or undefined. These are the only allowed values
     * for adapter method implementations, so in case it is neither, it throws
     * a type error. Note that this restriction is somewhat artificial; as the
     * CALL dynamic operation could invoke any Nashorn callable. We are
     * restricting adapters to actual ScriptFunction objects for now though.
     * @param callee the callee to check
     * @param name the name of the function
     * @return the callee cast to a ScriptFunction, or null if it was null or undefined.
     * @throws ECMAException representing a JS TypeError with "not.a.function"
     * message if the passed callee is neither a script function, nor null, nor
     * undefined.
     */
    public static ScriptFunction checkFunction(final Object callee, final String name) {
        if (callee instanceof ScriptFunction) {
            return (ScriptFunction)callee;
        } else if (JSType.nullOrUndefined(callee)) {
            return null;
        }
        throw typeError("not.a.function.value", name, ScriptRuntime.safeToString(callee));
    }

    
Returns a thread-local JS object used to define methods for the adapter class being initialized on the current
thread. This method is public solely for implementation reasons, so the adapter classes can invoke it from their
static initializers.
Returns:
the thread-local JS object used to define methods for the class being initialized./**
     * Returns a thread-local JS object used to define methods for the adapter class being initialized on the current
     * thread. This method is public solely for implementation reasons, so the adapter classes can invoke it from their
     * static initializers.
     * @return the thread-local JS object used to define methods for the class being initialized.
     */
    public static ScriptObject getClassOverrides() {
        final ScriptObject overrides = classOverrides.get();
        assert overrides != null;
        return overrides;
    }

    
Takes a method handle and an argument to it, and invokes the method handle passing it the argument. Basically equivalent to method.invokeExact(arg), except that the method handle will be invoked in a protection domain with absolutely no permissions. 
Params:
method – the method handle to invoke. The handle must have the exact type of void(Object).
arg – the argument to pass to the handle.
Throws:
Throwable – if anything goes wrong./**
     * Takes a method handle and an argument to it, and invokes the method handle passing it the argument. Basically
     * equivalent to {@code method.invokeExact(arg)}, except that the method handle will be invoked in a protection
     * domain with absolutely no permissions.
     * @param method the method handle to invoke. The handle must have the exact type of {@code void(Object)}.
     * @param arg the argument to pass to the handle.
     * @throws Throwable if anything goes wrong.
     */
    public static void invokeNoPermissions(final MethodHandle method, final Object arg) throws Throwable {
        NO_PERMISSIONS_INVOKER.invokeExact(method, arg);
    }

    
Set the current global scope to that of the adapter global
Params:
adapterGlobal – the adapter's global scope
Returns:
a Runnable that when invoked restores the previous global/**
     * Set the current global scope to that of the adapter global
     * @param adapterGlobal the adapter's global scope
     * @return a Runnable that when invoked restores the previous global
     */
    public static Runnable setGlobal(final ScriptObject adapterGlobal) {
        final Global currentGlobal = Context.getGlobal();
        if (adapterGlobal != currentGlobal) {
            Context.setGlobal(adapterGlobal);
            return ()->Context.setGlobal(currentGlobal);
        }
        return ()->{};
    }

    
Get the current non-null global scope
Throws:
NullPointerException – if the current global scope is null.
Returns:
the current global scope/**
     * Get the current non-null global scope
     * @return the current global scope
     * @throws NullPointerException if the current global scope is null.
     */
    public static ScriptObject getNonNullGlobal() {
        return Objects.requireNonNull(Context.getGlobal(), "Current global is null");
    }

    
Returns true if the object has its own toString function. Used
when implementing toString for adapters. Since every JS Object has a
toString function, we only override "String toString()" in adapters if
it is explicitly specified and not inherited from a prototype.
Params:
sobj – the object
Returns:
true if the object has its own toString function./**
     * Returns true if the object has its own toString function. Used
     * when implementing toString for adapters. Since every JS Object has a
     * toString function, we only override "String toString()" in adapters if
     * it is explicitly specified and not inherited from a prototype.
     * @param sobj the object
     * @return true if the object has its own toString function.
     */
    public static boolean hasOwnToString(final ScriptObject sobj) {
        // NOTE: we could just use ScriptObject.hasOwnProperty("toString"), but
        // its logic is more complex and this is what it boils down to with a
        // fixed "toString" argument.
        return sobj.getMap().findProperty("toString") != null;
    }

    
Returns the ScriptObject or Global field value from a ScriptObjectMirror using reflection.
Params:
mirror – the mirror object
getGlobal – true if we want the global object, false to return the script object
Returns:
the script object or global object/**
     * Returns the ScriptObject or Global field value from a ScriptObjectMirror using reflection.
     *
     * @param mirror the mirror object
     * @param getGlobal true if we want the global object, false to return the script object
     * @return the script object or global object
     */
    public static ScriptObject unwrapMirror(final Object mirror, final boolean getGlobal) {
        assert mirror instanceof ScriptObjectMirror;
        try {
            final Field field = getGlobal ? MirrorFieldHolder.GLOBAL_FIELD : MirrorFieldHolder.SOBJ_FIELD;
            return (ScriptObject) field.get(mirror);
        } catch (final IllegalAccessException x) {
            throw new RuntimeException(x);
        }
    }

    
Delegate to Bootstrap.bootstrap(Lookup, String, MethodType, int). 
Params:
lookup – MethodHandle lookup.
opDesc – Dynalink dynamic operation descriptor.
type –   Method type.
flags –  flags for call type, trace/profile etc.
Returns:
CallSite with MethodHandle to appropriate method or null if not found./**
     * Delegate to {@link Bootstrap#bootstrap(Lookup, String, MethodType, int)}.
     * @param lookup MethodHandle lookup.
     * @param opDesc Dynalink dynamic operation descriptor.
     * @param type   Method type.
     * @param flags  flags for call type, trace/profile etc.
     * @return CallSite with MethodHandle to appropriate method or null if not found.
     */
    public static CallSite bootstrap(final Lookup lookup, final String opDesc, final MethodType type, final int flags) {
        return Bootstrap.bootstrap(lookup, opDesc, type, flags);
    }

    static void setClassOverrides(final ScriptObject overrides) {
        classOverrides.set(overrides);
    }

    private static MethodHandle createNoPermissionsInvoker() {
        final String className = "NoPermissionsInvoker";

        final ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_FRAMES | ClassWriter.COMPUTE_MAXS);
        cw.visit(Opcodes.V1_7, ACC_PUBLIC | ACC_SUPER | ACC_FINAL, className, null, "java/lang/Object", null);
        final Type objectType = Type.getType(Object.class);
        final Type methodHandleType = Type.getType(MethodHandle.class);
        final InstructionAdapter mv = new InstructionAdapter(cw.visitMethod(ACC_PUBLIC | ACC_STATIC, "invoke",
                Type.getMethodDescriptor(Type.VOID_TYPE, methodHandleType, objectType), null, null));
        mv.visitCode();
        mv.visitVarInsn(ALOAD, 0);
        mv.visitVarInsn(ALOAD, 1);
        mv.invokevirtual(methodHandleType.getInternalName(), "invokeExact", Type.getMethodDescriptor(
                Type.VOID_TYPE, objectType), false);
        mv.visitInsn(RETURN);
        mv.visitMaxs(0, 0);
        mv.visitEnd();
        cw.visitEnd();
        final byte[] bytes = cw.toByteArray();

        final ClassLoader loader = AccessController.doPrivileged(new PrivilegedAction<ClassLoader>() {
            @Override
            public ClassLoader run() {
                return new SecureClassLoader(null) {
                    @Override
                    protected Class<?> findClass(final String name) throws ClassNotFoundException {
                        if(name.equals(className)) {
                            return defineClass(name, bytes, 0, bytes.length, new ProtectionDomain(
                                    new CodeSource(null, (CodeSigner[])null), new Permissions()));
                        }
                        throw new ClassNotFoundException(name);
                    }
                };
            }
        });

        try {
            return MethodHandles.publicLookup().findStatic(Class.forName(className, true, loader), "invoke",
                    MethodType.methodType(void.class, MethodHandle.class, Object.class));
        } catch(final ReflectiveOperationException e) {
            throw new AssertionError(e.getMessage(), e);
        }
    }

    
Invoked when returning Object from an adapted method to filter out internal Nashorn objects that must not be seen by the callers. Currently only transforms ConsString into String and transforms ScriptObject into ScriptObjectMirror. 
Params:
obj – the return value
Returns:
the filtered return value./**
     * Invoked when returning Object from an adapted method to filter out internal Nashorn objects that must not be seen
     * by the callers. Currently only transforms {@code ConsString} into {@code String} and transforms {@code ScriptObject} into {@code ScriptObjectMirror}.
     * @param obj the return value
     * @return the filtered return value.
     */
    public static Object exportReturnValue(final Object obj) {
        return NashornBeansLinker.exportArgument(obj, true);
    }

    
Invoked to convert a return value of a delegate function to primitive char. There's no suitable conversion in JSType, so we provide our own to adapters. 
Params:
obj – the return value.
Returns:
the character value of the return value/**
     * Invoked to convert a return value of a delegate function to primitive char. There's no suitable conversion in
     * {@code JSType}, so we provide our own to adapters.
     * @param obj the return value.
     * @return the character value of the return value
     */
    public static char toCharPrimitive(final Object obj) {
        return JavaArgumentConverters.toCharPrimitive(obj);
    }

    
Returns a new RuntimeException wrapping the passed throwable. Makes generated bytecode smaller by doing an INVOKESTATIC to this method rather than the NEW/DUP_X1/SWAP/INVOKESPECIAL <init> sequence. 
Params:
t – the original throwable to wrap
Returns:
a newly created runtime exception wrapping the passed throwable./**
     * Returns a new {@link RuntimeException} wrapping the passed throwable.
     * Makes generated bytecode smaller by doing an INVOKESTATIC to this method
     * rather than the NEW/DUP_X1/SWAP/INVOKESPECIAL &lt;init&gt; sequence.
     * @param t the original throwable to wrap
     * @return a newly created runtime exception wrapping the passed throwable.
     */
    public static RuntimeException wrapThrowable(final Throwable t) {
        return new RuntimeException(t);
    }

    
Creates and returns a new UnsupportedOperationException. Makes generated bytecode smaller by doing INVOKESTATIC to this method rather than the NEW/DUP/INVOKESPECIAL <init> sequence. 
Returns:
a newly created UnsupportedOperationException./**
     * Creates and returns a new {@link UnsupportedOperationException}. Makes
     * generated bytecode smaller by doing INVOKESTATIC to this method rather
     * than the NEW/DUP/INVOKESPECIAL &lt;init&gt; sequence.
     * @return a newly created {@link UnsupportedOperationException}.
     */
    public static UnsupportedOperationException unsupported() {
        return new UnsupportedOperationException();
    }

    
A bootstrap method used to collect invocation arguments into an Object array.
for variable arity invocation.
Params:
lookup – the adapter's lookup (not used).
name – the call site name (not used).
type – the method type
Returns:
a method that takes the input parameters and packs them into a
newly allocated Object array./**
     * A bootstrap method used to collect invocation arguments into an Object array.
     * for variable arity invocation.
     * @param lookup the adapter's lookup (not used).
     * @param name the call site name (not used).
     * @param type the method type
     * @return a method that takes the input parameters and packs them into a
     * newly allocated Object array.
     */
    public static CallSite createArrayBootstrap(final MethodHandles.Lookup lookup, final String name, final MethodType type) {
        return new ConstantCallSite(
                MethodHandles.identity(Object[].class)
                .asCollector(Object[].class, type.parameterCount())
                .asType(type));
    }

    // Initialization on demand holder for accessible ScriptObjectMirror fields
    private static class MirrorFieldHolder {

        private static final Field SOBJ_FIELD   = getMirrorField("sobj");
        private static final Field GLOBAL_FIELD = getMirrorField("global");

        private static Field getMirrorField(final String fieldName) {
            try {
                final Field field = ScriptObjectMirror.class.getDeclaredField(fieldName);
                AccessController.doPrivileged((PrivilegedAction<Void>) () -> {
                    field.setAccessible(true);
                    return null;
                });
                return field;
            } catch (final NoSuchFieldException e) {
                throw new RuntimeException(e);
            }
        }
    }
}