java/11 : jdk.scripting.nashorn/jdk/nashorn/internal/runtime/linker/Bootstrap.java

Bootstrap
https://openjdk.java.net/
GPLv2 + Classpath Exception
/*
 * Copyright (c) 2010, 2016, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package jdk.nashorn.internal.runtime.linker;

import static jdk.nashorn.internal.codegen.CompilerConstants.staticCallNoLookup;
import static jdk.nashorn.internal.runtime.ECMAErrors.typeError;

import java.lang.invoke.CallSite;
import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodHandles.Lookup;
import java.lang.invoke.MethodType;
import java.util.Collections;
import java.util.List;
import jdk.dynalink.CallSiteDescriptor;
import jdk.dynalink.DynamicLinker;
import jdk.dynalink.DynamicLinkerFactory;
import jdk.dynalink.beans.BeansLinker;
import jdk.dynalink.beans.StaticClass;
import jdk.dynalink.linker.GuardedInvocation;
import jdk.dynalink.linker.GuardingDynamicLinker;
import jdk.dynalink.linker.LinkRequest;
import jdk.dynalink.linker.LinkerServices;
import jdk.dynalink.linker.MethodTypeConversionStrategy;
import jdk.dynalink.linker.TypeBasedGuardingDynamicLinker;
import jdk.dynalink.linker.support.TypeUtilities;
import jdk.nashorn.api.scripting.JSObject;
import jdk.nashorn.internal.codegen.CompilerConstants.Call;
import jdk.nashorn.internal.lookup.MethodHandleFactory;
import jdk.nashorn.internal.lookup.MethodHandleFunctionality;
import jdk.nashorn.internal.runtime.Context;
import jdk.nashorn.internal.runtime.ECMAException;
import jdk.nashorn.internal.runtime.JSType;
import jdk.nashorn.internal.runtime.OptimisticReturnFilters;
import jdk.nashorn.internal.runtime.ScriptFunction;
import jdk.nashorn.internal.runtime.ScriptRuntime;

This class houses bootstrap method for invokedynamic instructions generated by compiler.
/**
 * This class houses bootstrap method for invokedynamic instructions generated by compiler.
 */
public final class Bootstrap {
    Reference to the seed boostrap function /** Reference to the seed boostrap function */
    public static final Call BOOTSTRAP = staticCallNoLookup(Bootstrap.class, "bootstrap", CallSite.class, Lookup.class, String.class, MethodType.class, int.class);

    private static final MethodHandleFunctionality MH = MethodHandleFactory.getFunctionality();

    private static final MethodHandle VOID_TO_OBJECT = MH.constant(Object.class, ScriptRuntime.UNDEFINED);

    private static final BeansLinker beansLinker = new BeansLinker(Bootstrap::createMissingMemberHandler);
    private static final GuardingDynamicLinker[] prioritizedLinkers;
    private static final GuardingDynamicLinker[] fallbackLinkers;

    static {
        final NashornBeansLinker nashornBeansLinker = new NashornBeansLinker(beansLinker);
        prioritizedLinkers = new GuardingDynamicLinker[] {
            new NashornLinker(),
            new NashornPrimitiveLinker(),
            new BoundCallableLinker(),
            new JavaSuperAdapterLinker(beansLinker),
            new JSObjectLinker(nashornBeansLinker),
            new BrowserJSObjectLinker(nashornBeansLinker),
            new ReflectionCheckLinker()
        };
        fallbackLinkers = new GuardingDynamicLinker[] {
            new NashornStaticClassLinker(beansLinker),
            nashornBeansLinker,
            new NashornBottomLinker()
        };
    }

    // do not create me!!
    private Bootstrap() {
    }

    Returns a list of exposed nashorn dynalink linkers.
Returns: a list of exposed nashorn dynalink linkers./**
     * Returns a list of exposed nashorn dynalink linkers.
     *
     * @return a list of exposed nashorn dynalink linkers.
     */
    public static List<GuardingDynamicLinker> getExposedLinkers() {
        // we have to create BeansLinker without nashorn specific missing member handler!
        // Or else, we'd return values such as 'undefined' to the external world!
        final NashornBeansLinker nbl = new NashornBeansLinker(new BeansLinker());
        final JSObjectLinker linker = new JSObjectLinker(nbl);
        return Collections.singletonList(linker);
    }

    Creates a Nashorn dynamic linker with the given app class loader.
Params: appLoader – the app class loader. It will be used to discover
additional language runtime linkers (if any).
unstableRelinkThreshold – the unstable relink threshold
Returns: a newly created dynamic linker./**
     * Creates a Nashorn dynamic linker with the given app class loader.
     * @param appLoader the app class loader. It will be used to discover
     * additional language runtime linkers (if any).
     * @param unstableRelinkThreshold the unstable relink threshold
     * @return a newly created dynamic linker.
     */
    public static DynamicLinker createDynamicLinker(final ClassLoader appLoader,
            final int unstableRelinkThreshold) {
        final DynamicLinkerFactory factory = new DynamicLinkerFactory();
        factory.setPrioritizedLinkers(prioritizedLinkers);
        factory.setFallbackLinkers(fallbackLinkers);
        factory.setSyncOnRelink(true);
        factory.setPrelinkTransformer((inv, request, linkerServices) -> {
            final CallSiteDescriptor desc = request.getCallSiteDescriptor();
            return OptimisticReturnFilters.filterOptimisticReturnValue(inv, desc).asType(linkerServices, desc.getMethodType());
        });
        factory.setAutoConversionStrategy(Bootstrap::unboxReturnType);
        factory.setInternalObjectsFilter(NashornBeansLinker.createHiddenObjectFilter());
        factory.setUnstableRelinkThreshold(unstableRelinkThreshold);

        // Linkers for any additional language runtimes deployed alongside Nashorn will be picked up by the factory.
        factory.setClassLoader(appLoader);
        return factory.createLinker();
    }

    Returns a dynamic linker for the specific Java class using beans semantics.
Params: clazz – the Java class
Returns: a dynamic linker for the specific Java class using beans semantics./**
     * Returns a dynamic linker for the specific Java class using beans semantics.
     * @param clazz the Java class
     * @return a dynamic linker for the specific Java class using beans semantics.
     */
    public static TypeBasedGuardingDynamicLinker getBeanLinkerForClass(final Class<?> clazz) {
        return beansLinker.getLinkerForClass(clazz);
    }

    Returns if the given object is a "callable"
Params: obj – object to be checked for callability
Returns: true if the obj is callable/**
     * Returns if the given object is a "callable"
     * @param obj object to be checked for callability
     * @return true if the obj is callable
     */
    public static boolean isCallable(final Object obj) {
        if (obj == ScriptRuntime.UNDEFINED || obj == null) {
            return false;
        }

        return obj instanceof ScriptFunction ||
            isJSObjectFunction(obj) ||
            BeansLinker.isDynamicMethod(obj) ||
            obj instanceof BoundCallable ||
            isFunctionalInterfaceObject(obj) ||
            obj instanceof StaticClass;
    }

    Returns true if the given object is a strict callable
Params: callable – the callable object to be checked for strictness
Throws: ECMAException – with TypeError if the object is not a callable.
Returns: true if the obj is a strict callable, false if it is a non-strict callable./**
     * Returns true if the given object is a strict callable
     * @param callable the callable object to be checked for strictness
     * @return true if the obj is a strict callable, false if it is a non-strict callable.
     * @throws ECMAException with {@code TypeError} if the object is not a callable.
     */
    public static boolean isStrictCallable(final Object callable) {
        if (callable instanceof ScriptFunction) {
            return ((ScriptFunction)callable).isStrict();
        } else if (isJSObjectFunction(callable)) {
            return ((JSObject)callable).isStrictFunction();
        } else if (callable instanceof BoundCallable) {
            return isStrictCallable(((BoundCallable)callable).getCallable());
        } else if (BeansLinker.isDynamicMethod(callable) ||
                callable instanceof StaticClass ||
                isFunctionalInterfaceObject(callable)) {
            return false;
        }
        throw notFunction(callable);
    }

    private static ECMAException notFunction(final Object obj) {
        return typeError("not.a.function", ScriptRuntime.safeToString(obj));
    }

    private static boolean isJSObjectFunction(final Object obj) {
        return obj instanceof JSObject && ((JSObject)obj).isFunction();
    }

    Returns if the given object is a dynalink Dynamic method
Params: obj – object to be checked
Returns: true if the obj is a dynamic method/**
     * Returns if the given object is a dynalink Dynamic method
     * @param obj object to be checked
     * @return true if the obj is a dynamic method
     */
    public static boolean isDynamicMethod(final Object obj) {
        return BeansLinker.isDynamicMethod(obj instanceof BoundCallable ? ((BoundCallable)obj).getCallable() : obj);
    }

    Returns if the given object is an instance of an interface annotated with
java.lang.FunctionalInterface
Params: obj – object to be checked
Returns: true if the obj is an instance of @FunctionalInterface interface/**
     * Returns if the given object is an instance of an interface annotated with
     * java.lang.FunctionalInterface
     * @param obj object to be checked
     * @return true if the obj is an instance of @FunctionalInterface interface
     */
    public static boolean isFunctionalInterfaceObject(final Object obj) {
        return !JSType.isPrimitive(obj) && (NashornBeansLinker.getFunctionalInterfaceMethodName(obj.getClass()) != null);
    }

    Create a call site and link it for Nashorn. This version of the method conforms to the invokedynamic bootstrap
method expected signature and is referenced from Nashorn generated bytecode as the bootstrap method for all
invokedynamic instructions.
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./**
     * Create a call site and link it for Nashorn. This version of the method conforms to the invokedynamic bootstrap
     * method expected signature and is referenced from Nashorn generated bytecode as the bootstrap method for all
     * invokedynamic instructions.
     * @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 Context.getDynamicLinker(lookup.lookupClass()).link(LinkerCallSite.newLinkerCallSite(lookup, opDesc, type, flags));
    }

    Returns a dynamic invoker for a specified dynamic operation using the public lookup. You can use this method to create a method handle that when invoked acts completely as if it were a Nashorn-linked call site. Note that the available operations are encoded in the flags, see NashornCallSiteDescriptor operation constants. If the operation takes a name, it should be set otherwise empty name (not null) should be used. All names (including the empty one) should be encoded using NameCodec.encode(String). Few examples: 
  Get a named property with fixed name:
    MethodHandle getColor = Boostrap.createDynamicInvoker(
    "color",
    NashornCallSiteDescriptor.GET_PROPERTY,
    Object.class, Object.class);
Object obj = ...; // somehow obtain the object
Object color = getColor.invokeExact(obj);
    
  
  Get a named property with variable name:
    MethodHandle getProperty = Boostrap.createDynamicInvoker(
    NameCodec.encode(""),
    NashornCallSiteDescriptor.GET_PROPERTY,
    Object.class, Object.class, String.class);
Object obj = ...; // somehow obtain the object
Object color = getProperty.invokeExact(obj, "color");
Object shape = getProperty.invokeExact(obj, "shape");
MethodHandle getNumProperty = Boostrap.createDynamicInvoker(
    NameCodec.encode(""),
    NashornCallSiteDescriptor.GET_ELEMENT,
    Object.class, Object.class, int.class);
Object elem42 = getNumProperty.invokeExact(obj, 42);
    
  
  Set a named property with fixed name:
    MethodHandle setColor = Boostrap.createDynamicInvoker(
    "color",
    NashornCallSiteDescriptor.SET_PROPERTY,
    void.class, Object.class, Object.class);
Object obj = ...; // somehow obtain the object
setColor.invokeExact(obj, Color.BLUE);
    
  
  Set a property with variable name:
    MethodHandle setProperty = Boostrap.createDynamicInvoker(
    NameCodec.encode(""),
    NashornCallSiteDescriptor.SET_PROPERTY,
    void.class, Object.class, String.class, Object.class);
Object obj = ...; // somehow obtain the object
setProperty.invokeExact(obj, "color", Color.BLUE);
setProperty.invokeExact(obj, "shape", Shape.CIRCLE);
    
  
  Call a function on an object; note it's a two-step process: get the
  method, then invoke the method. This is the actual:
    MethodHandle findFooFunction = Boostrap.createDynamicInvoker(
    "foo",
    NashornCallSiteDescriptor.GET_METHOD,
    Object.class, Object.class);
Object obj = ...; // somehow obtain the object
Object foo_fn = findFooFunction.invokeExact(obj);
MethodHandle callFunctionWithTwoArgs = Boostrap.createDynamicCallInvoker(
    Object.class, Object.class, Object.class, Object.class, Object.class);
// Note: "call" operation takes a function, then a "this" value, then the arguments:
Object foo_retval = callFunctionWithTwoArgs.invokeExact(foo_fn, obj, arg1, arg2);
    
  

Few additional remarks:

Just as Nashorn works with any Java object, the invokers returned
from this method can also be applied to arbitrary Java objects in
addition to Nashorn JavaScript objects.
For invoking a named function on an object, you can also use the InvokeByName convenience class.
There's no rule that the variable property identifier has to be a String for GET_PROPERTY/SET_PROPERTY and int for GET_ELEMENT/SET_ELEMENT. You can declare their type to be int, double, Object, and so on regardless of the kind of the operation.
You can be as specific in parameter types as you want. E.g. if you know that the receiver of the operation will always be ScriptObject, you can pass ScriptObject.class as its parameter type. If you happen to link to a method that expects different types, (you can use these invokers on POJOs too, after all, and end up linking with their methods that have strongly-typed signatures), all necessary conversions allowed by either Java or JavaScript will be applied: if invoked methods specify either primitive or wrapped Java numeric types, or String or boolean/Boolean, then the parameters might be subjected to standard ECMAScript ToNumber, ToString, and ToBoolean conversion, respectively. Less obviously, if the expected parameter type is a SAM type, and you pass a JavaScript function, a proxy object implementing the SAM type and delegating to the function will be passed. Linkage can often be optimized when linkers have more specific type information than "everything can be an object".
You can also be as specific in return types as you want. For return types any necessary type conversion available in either Java or JavaScript will be automatically applied, similar to the process described for parameters, only in reverse direction: if you specify any either primitive or wrapped Java numeric type, or String or boolean/Boolean, then the return values will be subjected to standard ECMAScript ToNumber, ToString, and ToBoolean conversion, respectively. Less obviously, if the return type is a SAM type, and the return value is a JavaScript function, a proxy object implementing the SAM type and delegating to the function will be returned.

Params: name – name at the call site. Must not be null. Must be encoded using NameCodec.encode(String). If the operation does not take a name, use empty string (also has to be encoded).
flags – the call site flags for the operation; see NashornCallSiteDescriptor for available flags. The most important part of the flags are the ones encoding the actual operation.
rtype – the return type for the operation
ptypes – the parameter types for the operation
Returns: MethodHandle for invoking the operation./**
     * Returns a dynamic invoker for a specified dynamic operation using the
     * public lookup. You can use this method to create a method handle that
     * when invoked acts completely as if it were a Nashorn-linked call site.
     * Note that the available operations are encoded in the flags, see
     * {@link NashornCallSiteDescriptor} operation constants. If the operation
     * takes a name, it should be set otherwise empty name (not null) should be
     * used. All names (including the empty one) should be encoded using
     * {@link NameCodec#encode(String)}. Few examples:
     * <ul>
     *   <li>Get a named property with fixed name:
     *     <pre>
     * MethodHandle getColor = Boostrap.createDynamicInvoker(
     *     "color",
     *     NashornCallSiteDescriptor.GET_PROPERTY,
     *     Object.class, Object.class);
     * Object obj = ...; // somehow obtain the object
     * Object color = getColor.invokeExact(obj);
     *     </pre>
     *   </li>
     *   <li>Get a named property with variable name:
     *     <pre>
     * MethodHandle getProperty = Boostrap.createDynamicInvoker(
     *     NameCodec.encode(""),
     *     NashornCallSiteDescriptor.GET_PROPERTY,
     *     Object.class, Object.class, String.class);
     * Object obj = ...; // somehow obtain the object
     * Object color = getProperty.invokeExact(obj, "color");
     * Object shape = getProperty.invokeExact(obj, "shape");
     *
     * MethodHandle getNumProperty = Boostrap.createDynamicInvoker(
     *     NameCodec.encode(""),
     *     NashornCallSiteDescriptor.GET_ELEMENT,
     *     Object.class, Object.class, int.class);
     * Object elem42 = getNumProperty.invokeExact(obj, 42);
     *     </pre>
     *   </li>
     *   <li>Set a named property with fixed name:
     *     <pre>
     * MethodHandle setColor = Boostrap.createDynamicInvoker(
     *     "color",
     *     NashornCallSiteDescriptor.SET_PROPERTY,
     *     void.class, Object.class, Object.class);
     * Object obj = ...; // somehow obtain the object
     * setColor.invokeExact(obj, Color.BLUE);
     *     </pre>
     *   </li>
     *   <li>Set a property with variable name:
     *     <pre>
     * MethodHandle setProperty = Boostrap.createDynamicInvoker(
     *     NameCodec.encode(""),
     *     NashornCallSiteDescriptor.SET_PROPERTY,
     *     void.class, Object.class, String.class, Object.class);
     * Object obj = ...; // somehow obtain the object
     * setProperty.invokeExact(obj, "color", Color.BLUE);
     * setProperty.invokeExact(obj, "shape", Shape.CIRCLE);
     *     </pre>
     *   </li>
     *   <li>Call a function on an object; note it's a two-step process: get the
     *   method, then invoke the method. This is the actual:
     *     <pre>
     * MethodHandle findFooFunction = Boostrap.createDynamicInvoker(
     *     "foo",
     *     NashornCallSiteDescriptor.GET_METHOD,
     *     Object.class, Object.class);
     * Object obj = ...; // somehow obtain the object
     * Object foo_fn = findFooFunction.invokeExact(obj);
     * MethodHandle callFunctionWithTwoArgs = Boostrap.createDynamicCallInvoker(
     *     Object.class, Object.class, Object.class, Object.class, Object.class);
     * // Note: "call" operation takes a function, then a "this" value, then the arguments:
     * Object foo_retval = callFunctionWithTwoArgs.invokeExact(foo_fn, obj, arg1, arg2);
     *     </pre>
     *   </li>
     * </ul>
     * Few additional remarks:
     * <ul>
     * <li>Just as Nashorn works with any Java object, the invokers returned
     * from this method can also be applied to arbitrary Java objects in
     * addition to Nashorn JavaScript objects.</li>
     * <li>For invoking a named function on an object, you can also use the
     * {@link InvokeByName} convenience class.</li>
     * <li>There's no rule that the variable property identifier has to be a
     * {@code String} for {@code GET_PROPERTY/SET_PROPERTY} and {@code int} for
     * {@code GET_ELEMENT/SET_ELEMENT}. You can declare their type to be
     * {@code int}, {@code double}, {@code Object}, and so on regardless of the
     * kind of the operation.</li>
     * <li>You can be as specific in parameter types as you want. E.g. if you
     * know that the receiver of the operation will always be
     * {@code ScriptObject}, you can pass {@code ScriptObject.class} as its
     * parameter type. If you happen to link to a method that expects different
     * types, (you can use these invokers on POJOs too, after all, and end up
     * linking with their methods that have strongly-typed signatures), all
     * necessary conversions allowed by either Java or JavaScript will be
     * applied: if invoked methods specify either primitive or wrapped Java
     * numeric types, or {@code String} or {@code boolean/Boolean}, then the
     * parameters might be subjected to standard ECMAScript {@code ToNumber},
     * {@code ToString}, and {@code ToBoolean} conversion, respectively. Less
     * obviously, if the expected parameter type is a SAM type, and you pass a
     * JavaScript function, a proxy object implementing the SAM type and
     * delegating to the function will be passed. Linkage can often be optimized
     * when linkers have more specific type information than "everything can be
     * an object".</li>
     * <li>You can also be as specific in return types as you want. For return
     * types any necessary type conversion available in either Java or
     * JavaScript will be automatically applied, similar to the process
     * described for parameters, only in reverse direction: if you specify any
     * either primitive or wrapped Java numeric type, or {@code String} or
     * {@code boolean/Boolean}, then the return values will be subjected to
     * standard ECMAScript {@code ToNumber}, {@code ToString}, and
     * {@code ToBoolean} conversion, respectively. Less obviously, if the return
     * type is a SAM type, and the return value is a JavaScript function, a
     * proxy object implementing the SAM type and delegating to the function
     * will be returned.</li>
     * </ul>
     * @param name name at the call site. Must not be null. Must be encoded
     * using {@link NameCodec#encode(String)}. If the operation does not take a
     * name, use empty string (also has to be encoded).
     * @param flags the call site flags for the operation; see
     * {@link NashornCallSiteDescriptor} for available flags. The most important
     * part of the flags are the ones encoding the actual operation.
     * @param rtype the return type for the operation
     * @param ptypes the parameter types for the operation
     * @return MethodHandle for invoking the operation.
     */
    public static MethodHandle createDynamicInvoker(final String name, final int flags, final Class<?> rtype, final Class<?>... ptypes) {
        return bootstrap(MethodHandles.publicLookup(), name, MethodType.methodType(rtype, ptypes), flags).dynamicInvoker();
    }

    Returns a dynamic invoker for the NashornCallSiteDescriptor.CALL operation using the public lookup. 
Params: rtype – the return type for the operation
ptypes – the parameter types for the operation
Returns: a dynamic invoker for the CALL operation./**
     * Returns a dynamic invoker for the {@link NashornCallSiteDescriptor#CALL}
     * operation using the public lookup.
     * @param rtype the return type for the operation
     * @param ptypes the parameter types for the operation
     * @return a dynamic invoker for the {@code CALL} operation.
     */
    public static MethodHandle createDynamicCallInvoker(final Class<?> rtype, final Class<?>... ptypes) {
        return createDynamicInvoker("", NashornCallSiteDescriptor.CALL, rtype, ptypes);
    }

    Returns a dynamic invoker for a specified dynamic operation using the public lookup. Similar to createDynamicInvoker(String, int, Class<?>, Class<?>...) but with already precomposed method type. 
Params: name – name at the call site.
flags – flags at the call site
type – the method type for the operation
Returns: MethodHandle for invoking the operation./**
     * Returns a dynamic invoker for a specified dynamic operation using the
     * public lookup. Similar to
     * {@link #createDynamicInvoker(String, int, Class, Class...)} but with
     * already precomposed method type.
     * @param name name at the call site.
     * @param flags flags at the call site
     * @param type the method type for the operation
     * @return MethodHandle for invoking the operation.
     */
    public static MethodHandle createDynamicInvoker(final String name, final int flags, final MethodType type) {
        return bootstrap(MethodHandles.publicLookup(), name, type, flags).dynamicInvoker();
    }

    Binds any object Nashorn can use as a [[Callable]] to a receiver and optionally arguments.
Params: callable – the callable to bind
boundThis – the bound "this" value.
boundArgs – the bound arguments. Can be either null or empty array to signify no arguments are bound.
Throws: ECMAException – with TypeError if the object is not a callable.
Returns: a bound callable./**
     * Binds any object Nashorn can use as a [[Callable]] to a receiver and optionally arguments.
     * @param callable the callable to bind
     * @param boundThis the bound "this" value.
     * @param boundArgs the bound arguments. Can be either null or empty array to signify no arguments are bound.
     * @return a bound callable.
     * @throws ECMAException with {@code TypeError} if the object is not a callable.
     */
    public static Object bindCallable(final Object callable, final Object boundThis, final Object[] boundArgs) {
        if (callable instanceof ScriptFunction) {
            return ((ScriptFunction)callable).createBound(boundThis, boundArgs);
        } else if (callable instanceof BoundCallable) {
            return ((BoundCallable)callable).bind(boundArgs);
        } else if (isCallable(callable)) {
            return new BoundCallable(callable, boundThis, boundArgs);
        }
        throw notFunction(callable);
    }

    Creates a super-adapter for an adapter, that is, an adapter to the adapter that allows invocation of superclass
methods on it.
Params: adapter – the original adapter
Returns: a new adapter that can be used to invoke super methods on the original adapter./**
     * Creates a super-adapter for an adapter, that is, an adapter to the adapter that allows invocation of superclass
     * methods on it.
     * @param adapter the original adapter
     * @return a new adapter that can be used to invoke super methods on the original adapter.
     */
    public static Object createSuperAdapter(final Object adapter) {
        return new JavaSuperAdapter(adapter);
    }

    If the given class is a reflection-specific class (anything in java.lang.reflect and java.lang.invoke package, as well a Class and any subclass of ClassLoader) and there is a security manager in the system, then it checks the nashorn.JavaReflection RuntimePermission. 
Params: clazz – the class being tested
isStatic – is access checked for static members (or instance members)/**
     * If the given class is a reflection-specific class (anything in {@code java.lang.reflect} and
     * {@code java.lang.invoke} package, as well a {@link Class} and any subclass of {@link ClassLoader}) and there is
     * a security manager in the system, then it checks the {@code nashorn.JavaReflection} {@code RuntimePermission}.
     * @param clazz the class being tested
     * @param isStatic is access checked for static members (or instance members)
     */
    public static void checkReflectionAccess(final Class<?> clazz, final boolean isStatic) {
        ReflectionCheckLinker.checkReflectionAccess(clazz, isStatic);
    }

    Returns the Nashorn's internally used dynamic linker's services object. Note that in code that is processing a linking request, you will normally use the LinkerServices object passed by whatever top-level linker invoked the linking (if the call site is in Nashorn-generated code, you'll get this object anyway). You should only resort to retrieving a linker services object using this method when you need some linker services (e.g. type converter method handles) outside of a code path that is linking a call site. 
Returns: Nashorn's internal dynamic linker's services object./**
     * Returns the Nashorn's internally used dynamic linker's services object. Note that in code that is processing a
     * linking request, you will normally use the {@code LinkerServices} object passed by whatever top-level linker
     * invoked the linking (if the call site is in Nashorn-generated code, you'll get this object anyway). You should
     * only resort to retrieving a linker services object using this method when you need some linker services (e.g.
     * type converter method handles) outside of a code path that is linking a call site.
     * @return Nashorn's internal dynamic linker's services object.
     */
    public static LinkerServices getLinkerServices() {
        return Context.getDynamicLinker().getLinkerServices();
    }

    Takes a guarded invocation, and ensures its method and guard conform to the type of the call descriptor, using
all type conversions allowed by the linker's services. This method is used by Nashorn's linkers as a last step
before returning guarded invocations. Most of the code used to produce the guarded invocations does not make an
effort to coordinate types of the methods, and so a final type adjustment before a guarded invocation is returned
to the aggregating linker is the responsibility of the linkers themselves.
Params: inv – the guarded invocation that needs to be type-converted. Can be null.
linkerServices – the linker services object providing the type conversions.
desc – the call site descriptor to whose method type the invocation needs to conform.
Returns: the type-converted guarded invocation. If input is null, null is returned. If the input invocation
already conforms to the requested type, it is returned unchanged./**
     * Takes a guarded invocation, and ensures its method and guard conform to the type of the call descriptor, using
     * all type conversions allowed by the linker's services. This method is used by Nashorn's linkers as a last step
     * before returning guarded invocations. Most of the code used to produce the guarded invocations does not make an
     * effort to coordinate types of the methods, and so a final type adjustment before a guarded invocation is returned
     * to the aggregating linker is the responsibility of the linkers themselves.
     * @param inv the guarded invocation that needs to be type-converted. Can be null.
     * @param linkerServices the linker services object providing the type conversions.
     * @param desc the call site descriptor to whose method type the invocation needs to conform.
     * @return the type-converted guarded invocation. If input is null, null is returned. If the input invocation
     * already conforms to the requested type, it is returned unchanged.
     */
    static GuardedInvocation asTypeSafeReturn(final GuardedInvocation inv, final LinkerServices linkerServices, final CallSiteDescriptor desc) {
        return inv == null ? null : inv.asTypeSafeReturn(linkerServices, desc.getMethodType());
    }

    Adapts the return type of the method handle with explicitCastArguments when it is an unboxing conversion. This will ensure that nulls are unwrapped to false or 0. 
Params: target – the target method handle
newType – the desired new type. Note that this method does not adapt the method handle completely to the new type, it only adapts the return type; this is allowed as per DynamicLinkerFactory.setAutoConversionStrategy(MethodTypeConversionStrategy), which is what this method is used for.
Returns: the method handle with adapted return type, if it required an unboxing conversion./**
     * Adapts the return type of the method handle with {@code explicitCastArguments} when it is an unboxing
     * conversion. This will ensure that nulls are unwrapped to false or 0.
     * @param target the target method handle
     * @param newType the desired new type. Note that this method does not adapt the method handle completely to the
     * new type, it only adapts the return type; this is allowed as per
     * {@link DynamicLinkerFactory#setAutoConversionStrategy(MethodTypeConversionStrategy)}, which is what this method
     * is used for.
     * @return the method handle with adapted return type, if it required an unboxing conversion.
     */
    private static MethodHandle unboxReturnType(final MethodHandle target, final MethodType newType) {
        final MethodType targetType = target.type();
        final Class<?> oldReturnType = targetType.returnType();
        final Class<?> newReturnType = newType.returnType();
        if (TypeUtilities.isWrapperType(oldReturnType)) {
            if (newReturnType.isPrimitive()) {
                // The contract of setAutoConversionStrategy is such that the difference between newType and targetType
                // can only be JLS method invocation conversions.
                assert TypeUtilities.isMethodInvocationConvertible(oldReturnType, newReturnType);
                return MethodHandles.explicitCastArguments(target, targetType.changeReturnType(newReturnType));
            }
        } else if (oldReturnType == void.class && newReturnType == Object.class) {
            return MethodHandles.filterReturnValue(target, VOID_TO_OBJECT);
        }
        return target;
    }

    private static MethodHandle createMissingMemberHandler(
            final LinkRequest linkRequest, final LinkerServices linkerServices) throws Exception {
        if (BrowserJSObjectLinker.canLinkTypeStatic(linkRequest.getReceiver().getClass())) {
            // Don't create missing member handlers for the browser JS objects as they
            // have their own logic.
            return null;
        }
        return NashornBottomLinker.linkMissingBeanMember(linkRequest, linkerServices);
    }
}
Params:	appLoader – the app class loader. It will be used to discover additional language runtime linkers (if any). unstableRelinkThreshold – the unstable relink threshold
Returns:	a newly created dynamic linker.
Params:	clazz – the Java class
Returns:	a dynamic linker for the specific Java class using beans semantics.
Params:	obj – object to be checked for callability
Returns:	true if the obj is callable
Params:	callable – the callable object to be checked for strictness
Throws:	ECMAException – with `TypeError` if the object is not a callable.
Returns:	true if the obj is a strict callable, false if it is a non-strict callable.
Params:	obj – object to be checked
Returns:	true if the obj is a dynamic method
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.
Params:	rtype – the return type for the operation ptypes – the parameter types for the operation
Returns:	a dynamic invoker for the `CALL` operation.
Params:	name – name at the call site. flags – flags at the call site type – the method type for the operation
Returns:	MethodHandle for invoking the operation.
Params:	callable – the callable to bind boundThis – the bound "this" value. boundArgs – the bound arguments. Can be either null or empty array to signify no arguments are bound.
Throws:	ECMAException – with `TypeError` if the object is not a callable.
Returns:	a bound callable.
Params:	adapter – the original adapter
Returns:	a new adapter that can be used to invoke super methods on the original adapter.
Params:	inv – the guarded invocation that needs to be type-converted. Can be null. linkerServices – the linker services object providing the type conversions. desc – the call site descriptor to whose method type the invocation needs to conform.
Returns:	the type-converted guarded invocation. If input is null, null is returned. If the input invocation already conforms to the requested type, it is returned unchanged.
Params:	target – the target method handle newType – the desired new type. Note that this method does not adapt the method handle completely to the new type, it only adapts the return type; this is allowed as per `DynamicLinkerFactory.setAutoConversionStrategy(MethodTypeConversionStrategy)`, which is what this method is used for.
Returns:	the method handle with adapted return type, if it required an unboxing conversion.
/

java/ 11/ jdk.scripting.nashorn/jdk/nashorn/internal/runtime/linker/Bootstrap.java
