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/*

 * This file is available under and governed by the GNU General Public

 * License version 2 only, as published by the Free Software Foundation.

 * However, the following notice accompanied the original version of this

 * file, and Oracle licenses the original version of this file under the BSD

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/*

   Copyright 2009-2013 Attila Szegedi

   Licensed under both the Apache License, Version 2.0 (the "Apache License")

   and the BSD License (the "BSD License"), with licensee being free to

   choose either of the two at their discretion.

   You may not use this file except in compliance with either the Apache

   License or the BSD License.

   If you choose to use this file in compliance with the Apache License, the

   following notice applies to you:

       You may obtain a copy of the Apache License at

           http://www.apache.org/licenses/LICENSE-2.0

       Unless required by applicable law or agreed to in writing, software

       distributed under the License is distributed on an "AS IS" BASIS,

       WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or

       implied. See the License for the specific language governing

       permissions and limitations under the License.

   If you choose to use this file in compliance with the BSD License, the

   following notice applies to you:

       Redistribution and use in source and binary forms, with or without

       modification, are permitted provided that the following conditions are

       met:

       * Redistributions of source code must retain the above copyright

         notice, this list of conditions and the following disclaimer.

       * Redistributions in binary form must reproduce the above copyright

         notice, this list of conditions and the following disclaimer in the

         documentation and/or other materials provided with the distribution.

       * Neither the name of the copyright holder nor the names of

         contributors may be used to endorse or promote products derived from

         this software without specific prior written permission.

       THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS

       IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED

       TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A

       PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL COPYRIGHT HOLDER

       BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR

       CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

       SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR

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       WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR

       OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF

       ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

*/

package jdk.internal.dynalink;

import java.lang.invoke.MutableCallSite;

import java.security.AccessController;

import java.security.PrivilegedAction;

import java.util.ArrayList;

import java.util.Arrays;

import java.util.Collections;

import java.util.HashSet;

import java.util.LinkedList;

import java.util.List;

import java.util.ServiceLoader;

import java.util.Set;

import jdk.internal.dynalink.beans.BeansLinker;

import jdk.internal.dynalink.linker.GuardedInvocation;

import jdk.internal.dynalink.linker.GuardingDynamicLinker;

import jdk.internal.dynalink.linker.GuardingTypeConverterFactory;

import jdk.internal.dynalink.linker.LinkRequest;

import jdk.internal.dynalink.linker.LinkerServices;

import jdk.internal.dynalink.linker.MethodHandleTransformer;

import jdk.internal.dynalink.linker.MethodTypeConversionStrategy;

/**

 * A factory class for creating {@link DynamicLinker} objects. The usual dynamic

 * linker is a linker composed of all {@link GuardingDynamicLinker} objects

 * known and pre-created by the caller as well as any guarding linkers

 * automatically discovered as declared in

 * {@code /META-INF/services/jdk.internal.dynalink.linker.GuardingDynamicLinker}

 * resources in the classpath (see {@link ServiceLoader} for the description of

 * this mechanism), and the standard fallback {@link BeansLinker}.

 * See {@link DynamicLinker} documentation for tips on how to use this class.

 */

public final class DynamicLinkerFactory {

    /**

     * Default value for {@link #setUnstableRelinkThreshold(int) unstable relink

     * threshold}.

     */

    public static final int DEFAULT_UNSTABLE_RELINK_THRESHOLD = 8;

    private boolean classLoaderExplicitlySet = false;

    private ClassLoader classLoader;

    private List<? extends GuardingDynamicLinker> prioritizedLinkers;

    private List<? extends GuardingDynamicLinker> fallbackLinkers;

    private boolean syncOnRelink = false;

    private int unstableRelinkThreshold = DEFAULT_UNSTABLE_RELINK_THRESHOLD;

    private MethodTypeConversionStrategy autoConversionStrategy;

    private MethodHandleTransformer internalObjectsFilter;

    /**

     * Creates a new dynamic linker factory with default configuration. Upon

     * creation, the factory can be configured using various {@code setXxx()}

     * methods and used to create one or more dynamic linkers according to its

     * current configuration using {@link #createLinker()}.

     */

    public DynamicLinkerFactory() {

    }

    /**

     * Sets the class loader for automatic discovery of available linkers. If

     * not set explicitly, then the thread context class loader of the thread

     * invoking {@link #createLinker()} invocation will be used.

     *

     * @param classLoader the class loader used for the automatic discovery of

     * available linkers.

     */

    public void setClassLoader(final ClassLoader classLoader) {

        this.classLoader = classLoader;

        classLoaderExplicitlySet = true;

    }

    /**

     * Sets the prioritized linkers. Language runtimes using this framework will usually precreate at least the linker

     * for their own language. These linkers will be consulted first in the resulting dynamic linker, before any

     * autodiscovered linkers. If the framework also autodiscovers a linker of the same class as one of the prioritized

     * linkers, it will be ignored and the explicit prioritized instance will be used.

     *

     * @param prioritizedLinkers the list of prioritized linkers. Null can be passed to indicate no prioritized linkers

     * (this is also the default value).

     */

    public void setPrioritizedLinkers(final List<? extends GuardingDynamicLinker> prioritizedLinkers) {

        this.prioritizedLinkers =

                prioritizedLinkers == null ? null : new ArrayList<>(prioritizedLinkers);

    }

    /**

     * Sets the prioritized linkers. Language runtimes using this framework will usually precreate at least the linker

     * for their own language. These linkers will be consulted first in the resulting dynamic linker, before any

     * autodiscovered linkers. If the framework also autodiscovers a linker of the same class as one of the prioritized

     * linkers, it will be ignored and the explicit prioritized instance will be used.

     *

     * @param prioritizedLinkers a list of prioritized linkers.

     */

    public void setPrioritizedLinkers(final GuardingDynamicLinker... prioritizedLinkers) {

        setPrioritizedLinkers(Arrays.asList(prioritizedLinkers));

    }

    /**

     * Sets a single prioritized linker. Identical to calling {@link #setPrioritizedLinkers(List)} with a single-element

     * list.

     *

     * @param prioritizedLinker the single prioritized linker. Must not be null.

     * @throws IllegalArgumentException if null is passed.

     */

    public void setPrioritizedLinker(final GuardingDynamicLinker prioritizedLinker) {

        if(prioritizedLinker == null) {

            throw new IllegalArgumentException("prioritizedLinker == null");

        }

        this.prioritizedLinkers = Collections.singletonList(prioritizedLinker);

    }

    /**

     * Sets the fallback linkers. These linkers will be consulted last in the resulting composite linker, after any

     * autodiscovered linkers. If the framework also autodiscovers a linker of the same class as one of the fallback

     * linkers, it will be ignored and the explicit fallback instance will be used.

     *

     * @param fallbackLinkers the list of fallback linkers. Can be empty to indicate the caller wishes to set no

     * fallback linkers.

     */

    public void setFallbackLinkers(final List<? extends GuardingDynamicLinker> fallbackLinkers) {

        this.fallbackLinkers = fallbackLinkers == null ? null : new ArrayList<>(fallbackLinkers);

    }

    /**

     * Sets the fallback linkers. These linkers will be consulted last in the resulting composite linker, after any

     * autodiscovered linkers. If the framework also autodiscovers a linker of the same class as one of the fallback

     * linkers, it will be ignored and the explicit fallback instance will be used.

     *

     * @param fallbackLinkers the list of fallback linkers. Can be empty to indicate the caller wishes to set no

     * fallback linkers. If it is left as null, the standard fallback {@link BeansLinker} will be used.

     */

    public void setFallbackLinkers(final GuardingDynamicLinker... fallbackLinkers) {

        setFallbackLinkers(Arrays.asList(fallbackLinkers));

    }

    /**

     * Sets whether the linker created by this factory will invoke {@link MutableCallSite#syncAll(MutableCallSite[])}

     * after a call site is relinked. Defaults to false. You probably want to set it to true if your runtime supports

     * multithreaded execution of dynamically linked code.

     * @param syncOnRelink true for invoking sync on relink, false otherwise.

     */

    public void setSyncOnRelink(final boolean syncOnRelink) {

        this.syncOnRelink = syncOnRelink;

    }

    /**

     * Sets the unstable relink threshold; the number of times a call site is relinked after which it will be

     * considered unstable, and subsequent link requests for it will indicate this.

     * @param unstableRelinkThreshold the new threshold. Must not be less than zero. The value of zero means that

     * call sites will never be considered unstable.

     * @see LinkRequest#isCallSiteUnstable()

     */

    public void setUnstableRelinkThreshold(final int unstableRelinkThreshold) {

        if(unstableRelinkThreshold < 0) {

            throw new IllegalArgumentException("unstableRelinkThreshold < 0");

        }

        this.unstableRelinkThreshold = unstableRelinkThreshold;

    }

    /**

     * guarded invocation after it has been created by a component linker and before the dynamic linker links it into

     * the call site. It is normally used to adapt the return value type of the invocation to the type of the call site.

     */

    }

    /**

     * Sets an object representing the conversion strategy for automatic type conversions. After

     * applied all custom conversions to a method handle, it still needs to effect

     * {@link TypeUtilities#isMethodInvocationConvertible(Class, Class) method invocation conversions} that

     * can usually be automatically applied as per

     * However, sometimes language runtimes will want to customize even those conversions for their own call

     * sites. A typical example is allowing unboxing of null return values, which is by default prohibited by

     * ordinary {@code MethodHandles.asType}. In this case, a language runtime can install its own custom

     * automatic conversion strategy, that can deal with null values. Note that when the strategy's

     * is invoked, the custom language conversions will already have been applied to the method handle, so by

     * design the difference between the handle's current method type and the desired final type will always

     * only be ones that can be subjected to method invocation conversions. The strategy also doesn't need to

     * invoke a final {@code MethodHandle.asType()} as the converter factory will do that as the final step.

     * @param autoConversionStrategy the strategy for applying method invocation conversions for the linker

     * created by this factory.

     */

    public void setAutoConversionStrategy(final MethodTypeConversionStrategy autoConversionStrategy) {

        this.autoConversionStrategy = autoConversionStrategy;

    }

    /**

     * Sets a method handle transformer that is supposed to act as the implementation of this linker factory's linkers'

     * services {@link LinkerServices#filterInternalObjects(java.lang.invoke.MethodHandle)} method.

     * @param internalObjectsFilter a method handle transformer filtering out internal objects, or null.

     */

    public void setInternalObjectsFilter(final MethodHandleTransformer internalObjectsFilter) {

        this.internalObjectsFilter = internalObjectsFilter;

    }

    /**

     * Creates a new dynamic linker consisting of all the prioritized, autodiscovered, and fallback linkers as well as

     *

     * @return the new dynamic Linker

     */

    public DynamicLinker createLinker() {

        // Treat nulls appropriately

        if(prioritizedLinkers == null) {

            prioritizedLinkers = Collections.emptyList();

        }

        if(fallbackLinkers == null) {

            fallbackLinkers = Collections.singletonList(new BeansLinker());

        }

        // Gather classes of all precreated (prioritized and fallback) linkers.

        // We'll filter out any discovered linkers of the same class.

        final Set<Class<? extends GuardingDynamicLinker>> knownLinkerClasses =

                new HashSet<>();

        addClasses(knownLinkerClasses, prioritizedLinkers);

        addClasses(knownLinkerClasses, fallbackLinkers);

        final ClassLoader effectiveClassLoader = classLoaderExplicitlySet ? classLoader : getThreadContextClassLoader();

        final List<GuardingDynamicLinker> discovered = new LinkedList<>();

        final ServiceLoader<GuardingDynamicLinker> linkerLoader = ServiceLoader.load(GuardingDynamicLinker.class, effectiveClassLoader);

        for(final GuardingDynamicLinker linker: linkerLoader) {

            discovered.add(linker);

        }

        // Now, concatenate ...

        final List<GuardingDynamicLinker> linkers =

                new ArrayList<>(prioritizedLinkers.size() + discovered.size()

                        + fallbackLinkers.size());

        // ... prioritized linkers, ...

        linkers.addAll(prioritizedLinkers);

        // ... filtered discovered linkers, ...

        for(final GuardingDynamicLinker linker: discovered) {

            if(!knownLinkerClasses.contains(linker.getClass())) {

                linkers.add(linker);

            }

        }

        // ... and finally fallback linkers.

        linkers.addAll(fallbackLinkers);

        final List<GuardingDynamicLinker> optimized = CompositeTypeBasedGuardingDynamicLinker.optimize(linkers);

        final GuardingDynamicLinker composite;

        switch(linkers.size()) {

            case 0: {

                composite = (r, s) -> null; // linker that can't link anything

                break;

            }

            case 1: {

                composite = optimized.get(0);

                break;

            }

            default: {

                composite = new CompositeGuardingDynamicLinker(optimized);

                break;

            }

        }

        final List<GuardingTypeConverterFactory> typeConverters = new LinkedList<>();

        for(final GuardingDynamicLinker linker: linkers) {

            if(linker instanceof GuardingTypeConverterFactory) {

                typeConverters.add((GuardingTypeConverterFactory)linker);

            }

        }

        }

        return new DynamicLinker(new LinkerServicesImpl(new TypeConverterFactory(typeConverters,

                syncOnRelink, unstableRelinkThreshold);

    }

    private static ClassLoader getThreadContextClassLoader() {

        return AccessController.doPrivileged(new PrivilegedAction<ClassLoader>() {

            @Override

            public ClassLoader run() {

                return Thread.currentThread().getContextClassLoader();

            }

        }, ClassLoaderGetterContextProvider.GET_CLASS_LOADER_CONTEXT);

    }

    private static void addClasses(final Set<Class<? extends GuardingDynamicLinker>> knownLinkerClasses,

            final List<? extends GuardingDynamicLinker> linkers) {

        for(final GuardingDynamicLinker linker: linkers) {

            knownLinkerClasses.add(linker.getClass());

        }

    }

}