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

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 * 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,

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 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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package jdk.internal.module;

import java.lang.module.Configuration;

import java.lang.module.ModuleDescriptor;

import java.lang.module.ModuleFinder;

import java.lang.module.ModuleReference;

import java.lang.module.ResolvedModule;

import java.net.URI;

import java.security.AccessController;

import java.security.PrivilegedAction;

import java.util.List;

import java.util.Map;

import java.util.Optional;

import java.util.Set;

import java.util.function.Function;

import java.util.stream.Collectors;

import jdk.internal.loader.BootLoader;

import jdk.internal.loader.BuiltinClassLoader;

import jdk.internal.loader.ClassLoaders;

import jdk.internal.access.JavaLangAccess;

import jdk.internal.access.SharedSecrets;

/**

 * A helper class for creating and updating modules. This class is intended to

 * support command-line options, tests, and the instrumentation API. It is also

 * used by the VM to load modules or add read edges when agents are instrumenting

 * code that need to link to supporting classes.

 *

 * The parameters that are package names in this API are the fully-qualified

 * names of the packages as defined in section 6.5.3 of <cite>The Java&trade;

 * Language Specification </cite>, for example, {@code "java.lang"}.

 */

public class Modules {

    private Modules() { }

    private static final JavaLangAccess JLA = SharedSecrets.getJavaLangAccess();

    /**

     * Creates a new Module. The module has the given ModuleDescriptor and

     * is defined to the given class loader.

     *

     * The resulting Module is in a larval state in that it does not read

     * any other module and does not have any exports.

     *

     * The URI is for information purposes only.

     */

    public static Module defineModule(ClassLoader loader,

                                      ModuleDescriptor descriptor,

                                      URI uri)

    {

        return JLA.defineModule(loader, descriptor, uri);

    }

    /**

     * Updates m1 to read m2.

     * Same as m1.addReads(m2) but without a caller check.

     */

    public static void addReads(Module m1, Module m2) {

        JLA.addReads(m1, m2);

    }

    /**

     * Update module m to read all unnamed modules.

     */

    public static void addReadsAllUnnamed(Module m) {

        JLA.addReadsAllUnnamed(m);

    }

    /**

     * Updates module m1 to export a package to module m2.

     * Same as m1.addExports(pn, m2) but without a caller check

     */

    public static void addExports(Module m1, String pn, Module m2) {

        JLA.addExports(m1, pn, m2);

    }

    /**

     * Updates module m to export a package to all unnamed modules.

     */

    public static void addExportsToAllUnnamed(Module m, String pn) {

        JLA.addExportsToAllUnnamed(m, pn);

    }

    /**

     * Updates module m1 to open a package to module m2.

     * Same as m1.addOpens(pn, m2) but without a caller check.

     */

    public static void addOpens(Module m1, String pn, Module m2) {

        JLA.addOpens(m1, pn, m2);

    }

    /**

     * Updates module m to open a package to all unnamed modules.

     */

    public static void addOpensToAllUnnamed(Module m, String pn) {

        JLA.addOpensToAllUnnamed(m, pn);

    }

    /**

     * Updates module m to use a service.

     * Same as m2.addUses(service) but without a caller check.

     */

    public static void addUses(Module m, Class<?> service) {

        JLA.addUses(m, service);

    }

    /**

     * Updates module m to provide a service

     */

    public static void addProvides(Module m, Class<?> service, Class<?> impl) {

        ModuleLayer layer = m.getLayer();

        PrivilegedAction<ClassLoader> pa = m::getClassLoader;

        ClassLoader loader = AccessController.doPrivileged(pa);

        ClassLoader platformClassLoader = ClassLoaders.platformClassLoader();

        if (layer == null || loader == null || loader == platformClassLoader) {

            // update ClassLoader catalog

            ServicesCatalog catalog;

            if (loader == null) {

                catalog = BootLoader.getServicesCatalog();

            } else {

                catalog = ServicesCatalog.getServicesCatalog(loader);

            }

            catalog.addProvider(m, service, impl);

        }

        if (layer != null) {

            // update Layer catalog

            JLA.getServicesCatalog(layer).addProvider(m, service, impl);

        }

    }

    /**

     * Called by the VM when code in the given Module has been transformed by

     * an agent and so may have been instrumented to call into supporting

     * classes on the boot class path or application class path.

     */

    public static void transformedByAgent(Module m) {

        addReads(m, BootLoader.getUnnamedModule());

        addReads(m, ClassLoaders.appClassLoader().getUnnamedModule());

    }

    /**

     * Called by the VM to load a system module, typically "java.instrument" or

     * "jdk.management.agent". If the module is not loaded then it is resolved

     * and loaded (along with any dependences that weren't previously loaded)

     * into a child layer.

     */

    public static synchronized Module loadModule(String name) {

        ModuleLayer top = topLayer;

        if (top == null)

            top = ModuleLayer.boot();

        Module module = top.findModule(name).orElse(null);

        if (module != null) {

            // module already loaded

            return module;

        }

        // resolve the module with the top-most layer as the parent

        ModuleFinder empty = ModuleFinder.of();

        ModuleFinder finder = ModuleBootstrap.unlimitedFinder();

        Set<String> roots = Set.of(name);

        Configuration cf = top.configuration().resolveAndBind(empty, finder, roots);

        // create the child layer

        Function<String, ClassLoader> clf = ModuleLoaderMap.mappingFunction(cf);

        ModuleLayer newLayer = top.defineModules(cf, clf);

        // add qualified exports/opens to give access to modules in child layer

        Map<String, Module> map = newLayer.modules().stream()

                                          .collect(Collectors.toMap(Module::getName,

                                                  Function.identity()));

        ModuleLayer layer = top;

        while (layer != null) {

            for (Module m : layer.modules()) {

                // qualified exports

                m.getDescriptor().exports().stream()

                    .filter(ModuleDescriptor.Exports::isQualified)

                    .forEach(e -> e.targets().forEach(target -> {

                        Module other = map.get(target);

                        if (other != null) {

                            addExports(m, e.source(), other);

                        }}));

                // qualified opens

                m.getDescriptor().opens().stream()

                    .filter(ModuleDescriptor.Opens::isQualified)

                    .forEach(o -> o.targets().forEach(target -> {

                        Module other = map.get(target);

                        if (other != null) {

                            addOpens(m, o.source(), other);

                        }}));

            }

            List<ModuleLayer> parents = layer.parents();

            assert parents.size() <= 1;

            layer = parents.isEmpty() ? null : parents.get(0);

        }

        // update security manager before making types visible

        JLA.addNonExportedPackages(newLayer);

        // update the built-in class loaders to make the types visible

        for (ResolvedModule resolvedModule : cf.modules()) {

            ModuleReference mref = resolvedModule.reference();

            String mn = mref.descriptor().name();

            ClassLoader cl = clf.apply(mn);

            if (cl == null) {

                BootLoader.loadModule(mref);

            } else {

                ((BuiltinClassLoader) cl).loadModule(mref);

            }

        }

        // new top layer

        topLayer = newLayer;

        // return module

        return newLayer.findModule(name)

                       .orElseThrow(() -> new InternalError("module not loaded"));

    }

    /**

     * Finds the module with the given name in the boot layer or any child

     * layers created to load the "java.instrument" or "jdk.management.agent"

     * modules into a running VM.

     */

    public static Optional<Module> findLoadedModule(String name) {

        ModuleLayer top = topLayer;

        if (top == null)

            top = ModuleLayer.boot();

        return top.findModule(name);

    }

    // the top-most layer

    private static volatile ModuleLayer topLayer;

}