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

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

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 * published by the Free Software Foundation.  Oracle designates this

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

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 *

 * 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,

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 *

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package jdk.nashorn.internal.runtime.linker;

import static jdk.nashorn.internal.codegen.CompilerConstants.staticCallNoLookup;

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 jdk.internal.dynalink.CallSiteDescriptor;

import jdk.internal.dynalink.DynamicLinker;

import jdk.internal.dynalink.DynamicLinkerFactory;

import jdk.internal.dynalink.beans.BeansLinker;

import jdk.internal.dynalink.linker.GuardedInvocation;

import jdk.internal.dynalink.linker.LinkerServices;

import jdk.nashorn.internal.codegen.CompilerConstants.Call;

import jdk.nashorn.internal.codegen.RuntimeCallSite;

import jdk.nashorn.internal.runtime.options.Options;

/**

 * This class houses bootstrap method for invokedynamic instructions generated by compiler.

 */

public final class Bootstrap {

    /** 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);

    // do not create me!!

    private Bootstrap() {

    }

    private static final DynamicLinker dynamicLinker;

    static {

        final DynamicLinkerFactory factory = new DynamicLinkerFactory();

        factory.setPrioritizedLinkers(new NashornLinker(), new NashornPrimitiveLinker(), new NashornStaticClassLinker(),

        factory.setFallbackLinkers(new BeansLinker(), new NashornBottomLinker());

        factory.setSyncOnRelink(true);

        final int relinkThreshold = Options.getIntProperty("nashorn.unstable.relink.threshold", -1);

        if (relinkThreshold > -1) {

            factory.setUnstableRelinkThreshold(relinkThreshold);

        }

        dynamicLinker = factory.createLinker();

    }

    /**

     * 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. Ignored as Nashorn only uses public 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 dynamicLinker.link(LinkerCallSite.newLinkerCallSite(opDesc, type, flags));

    }

    /**

     * Bootstrapper for a specialized Runtime call

     *

     * @param lookup       lookup

     * @param initialName  initial name for callsite

     * @param type         method type for call site

     *

     * @return callsite for a runtime node

     */

    public static CallSite runtimeBootstrap(final MethodHandles.Lookup lookup, final String initialName, final MethodType type) {

        return new RuntimeCallSite(type, initialName);

    }

    /**

     * Returns a dynamic invoker for a specified dynamic operation. You can use this method to create a method handle

     * that when invoked acts completely as if it were a Nashorn-linked call site. An overview of available dynamic

     * operations can be found in the <a href="https://github.com/szegedi/dynalink/wiki/User-Guide-0.4">Dynalink User Guide</a>,

     * but we'll show few examples here:

     * <ul>

     *   <li>Get a named property with fixed name:

     *     <pre>

     * MethodHandle getColor = Boostrap.createDynamicInvoker("dyn:getProp:color", 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("dyn:getElem", 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("dyn:getElem", 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("dyn:setProp:color", 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("dyn:setElem", 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; two-step variant. This is the actual variant used by Nashorn-generated code:

     *     <pre>

     * MethodHandle findFooFunction = Boostrap.createDynamicInvoker("dyn:getMethod:foo", Object.class, Object.class);

     * Object obj = ...; // somehow obtain the object

     * Object foo_fn = findFooFunction.invokeExact(obj);

     * MethodHandle callFunctionWithTwoArgs = Boostrap.createDynamicInvoker("dyn:call", 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>

     *   <li>Call a function on an object; single-step variant. Although Nashorn doesn't use this variant and never

     *   emits any INVOKEDYNAMIC instructions with {@code dyn:getMethod}, it still supports this standard Dynalink

     *   operation:

     *     <pre>

     * MethodHandle callFunctionFooWithTwoArgs = Boostrap.createDynamicInvoker("dyn:callMethod:foo", Object.class, Object.class, Object.class, Object.class);

     * Object obj = ...; // somehow obtain the object

     * Object foo_retval = callFunctionFooWithTwoArgs.invokeExact(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>For Nashorn objects {@code getElem}, {@code getProp}, and {@code getMethod} are handled almost identically,

     * since JavaScript doesn't distinguish between different kinds of properties on an object. Either can be used with

     * fixed property name or a variable property name. The only significant difference is handling of missing

     * properties: {@code getMethod} for a missing member will link to a potential invocation of

     * {@code __noSuchMethod__} on the object, {@code getProp} for a missing member will link to a potential invocation

     * of {@code __noSuchProperty__}, while {@code getElem} for a missing member will link to an empty getter.</li>

     * <li>In similar vein, {@code setElem} and {@code setProp} are handled identically on Nashorn objects.</li>

     * <li>There's no rule that the variable property identifier has to be a {@code String} for {@code getProp/setProp}

     * and {@code int} for {@code getElem/setElem}. 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 opDesc Dynalink dynamic operation descriptor.

     * @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 opDesc, final Class<?> rtype, final Class<?>... ptypes) {

        return createDynamicInvoker(opDesc, MethodType.methodType(rtype, ptypes));

    }

    /**

     * Returns a dynamic invoker for a specified dynamic operation. Similar to

     * {@link #createDynamicInvoker(String, Class, Class...)} but with return and parameter types composed into a

     * method type in the signature. See the discussion of that method for details.

     * @param opDesc Dynalink dynamic operation descriptor.

     * @param type the method type for the operation

     * @return MethodHandle for invoking the operation.

     */

    public static MethodHandle createDynamicInvoker(final String opDesc, final MethodType type) {

        return bootstrap(null, opDesc, type, 0).dynamicInvoker();

    }

    /**

     * 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 dynamicLinker.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 to the callers. 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 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 asType(final GuardedInvocation inv, final LinkerServices linkerServices, final CallSiteDescriptor desc) {

        return inv == null ? null : inv.asType(linkerServices, desc.getMethodType());

    }

}