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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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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 The Java™
Language Specification , for example, "java.lang". /**
 * 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.
/**
     * 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.
/**
     * 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.
/**
     * 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
/**
     * 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.
/**
     * 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.
/**
     * 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.
/**
     * 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.
/**
     * 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
/**
     * 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.
/**
     * 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.
/**
     * 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.
/**
     * 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;

}