/*

 * Copyright (c) 2015, 2019, 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.internal.loader;

import java.io.IOException;

import java.io.InputStream;

import java.lang.module.ModuleDescriptor;

import java.lang.module.ModuleReference;

import java.lang.module.ModuleReader;

import java.lang.ref.SoftReference;

import java.net.MalformedURLException;

import java.net.URI;

import java.net.URL;

import java.nio.ByteBuffer;

import java.security.AccessController;

import java.security.CodeSigner;

import java.security.CodeSource;

import java.security.PermissionCollection;

import java.security.PrivilegedAction;

import java.security.PrivilegedActionException;

import java.security.PrivilegedExceptionAction;

import java.security.SecureClassLoader;

import java.util.ArrayList;

import java.util.Collections;

import java.util.Enumeration;

import java.util.Iterator;

import java.util.List;

import java.util.Map;

import java.util.NoSuchElementException;

import java.util.Optional;

import java.util.concurrent.ConcurrentHashMap;

import java.util.function.Function;

import java.util.jar.Attributes;

import java.util.jar.Manifest;

import java.util.stream.Stream;

import jdk.internal.access.SharedSecrets;

import jdk.internal.misc.VM;

import jdk.internal.module.ModulePatcher.PatchedModuleReader;

import jdk.internal.module.Resources;

import jdk.internal.vm.annotation.Stable;

import sun.security.util.LazyCodeSourcePermissionCollection;

/**

 * The platform or application class loader. Resources loaded from modules

 * defined to the boot class loader are also loaded via an instance of this

 * ClassLoader type.

 *

 * <p> This ClassLoader supports loading of classes and resources from modules.

 * Modules are defined to the ClassLoader by invoking the {@link #loadModule}

 * method. Defining a module to this ClassLoader has the effect of making the

 * types in the module visible. </p>

 *

 * <p> This ClassLoader also supports loading of classes and resources from a

 * class path of URLs that are specified to the ClassLoader at construction

 * time. The class path may expand at runtime (the Class-Path attribute in JAR

 * files or via instrumentation agents). </p>

 *

 * <p> The delegation model used by this ClassLoader differs to the regular

 * delegation model. When requested to load a class then this ClassLoader first

 * maps the class name to its package name. If there is a module defined to a

 * BuiltinClassLoader containing this package then the class loader delegates

 * directly to that class loader. If there isn't a module containing the

 * package then it delegates the search to the parent class loader and if not

 * found in the parent then it searches the class path. The main difference

 * between this and the usual delegation model is that it allows the platform

 * class loader to delegate to the application class loader, important with

 * upgraded modules defined to the platform class loader.

 */

public class BuiltinClassLoader

    extends SecureClassLoader

{

    static {

        if (!ClassLoader.registerAsParallelCapable())

            throw new InternalError("Unable to register as parallel capable");

    }

    // parent ClassLoader

    private final BuiltinClassLoader parent;

    // the URL class path, or null if there is no class path

    private final URLClassPath ucp;

    /**

     * A module defined/loaded by a built-in class loader.

     *

     * A LoadedModule encapsulates a ModuleReference along with its CodeSource

     * URL to avoid needing to create this URL when defining classes.

     */

    private static class LoadedModule {

        private final BuiltinClassLoader loader;

        private final ModuleReference mref;

        private final URI uri;                      // may be null

        private @Stable URL codeSourceURL;          // may be null

        LoadedModule(BuiltinClassLoader loader, ModuleReference mref) {

            URL url = null;

            this.uri = mref.location().orElse(null);

            // for non-jrt schemes we need to resolve the codeSourceURL

            // eagerly during bootstrap since the handler might be

            // overridden

            if (uri != null && !"jrt".equals(uri.getScheme())) {

                url = createURL(uri);

            }

            this.loader = loader;

            this.mref = mref;

            this.codeSourceURL = url;

        }

        BuiltinClassLoader loader() { return loader; }

        ModuleReference mref() { return mref; }

        String name() { return mref.descriptor().name(); }

        URL codeSourceURL() {

            URL url = codeSourceURL;

            if (url == null && uri != null) {

                codeSourceURL = url = createURL(uri);

            }

            return url;

        }

        private URL createURL(URI uri) {

            URL url = null;

            try {

                url = uri.toURL();

            } catch (MalformedURLException | IllegalArgumentException e) {

            }

            return url;

        }

    }

    // maps package name to loaded module for modules in the boot layer

    private static final Map<String, LoadedModule> packageToModule

        = new ConcurrentHashMap<>(1024);

    // maps a module name to a module reference

    private final Map<String, ModuleReference> nameToModule;

    // maps a module reference to a module reader

    private final Map<ModuleReference, ModuleReader> moduleToReader;

    // cache of resource name -> list of URLs.

    // used only for resources that are not in module packages

    private volatile SoftReference<Map<String, List<URL>>> resourceCache;

    /**

     * Create a new instance.

     */

    BuiltinClassLoader(String name, BuiltinClassLoader parent, URLClassPath ucp) {

        // ensure getParent() returns null when the parent is the boot loader

        super(name, parent == null || parent == ClassLoaders.bootLoader() ? null : parent);

        this.parent = parent;

        this.ucp = ucp;

        this.nameToModule = new ConcurrentHashMap<>(32);

        this.moduleToReader = new ConcurrentHashMap<>();

    }

    /**

     * Returns {@code true} if there is a class path associated with this

     * class loader.

     */

    boolean hasClassPath() {

        return ucp != null;

    }

    /**

     * Register a module this class loader. This has the effect of making the

     * types in the module visible.

     */

    public void loadModule(ModuleReference mref) {

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

        if (nameToModule.putIfAbsent(mn, mref) != null) {

            throw new InternalError(mn + " already defined to this loader");

        }

        LoadedModule loadedModule = new LoadedModule(this, mref);

        for (String pn : mref.descriptor().packages()) {

            LoadedModule other = packageToModule.putIfAbsent(pn, loadedModule);

            if (other != null) {

                throw new InternalError(pn + " in modules " + mn + " and "

                                        + other.mref().descriptor().name());

            }

        }

        // clear resources cache if VM is already initialized

        if (VM.isModuleSystemInited() && resourceCache != null) {

            resourceCache = null;

        }

    }

    /**

     * Returns the {@code ModuleReference} for the named module defined to

     * this class loader; or {@code null} if not defined.

     *

     * @param name The name of the module to find

     */

    protected ModuleReference findModule(String name) {

        return nameToModule.get(name);

    }

    // -- finding resources

    /**

     * Returns a URL to a resource of the given name in a module defined to

     * this class loader.

     */

    @Override

    public URL findResource(String mn, String name) throws IOException {

        URL url = null;

        if (mn != null) {

            // find in module

            ModuleReference mref = nameToModule.get(mn);

            if (mref != null) {

                url = findResource(mref, name);

            }

        } else {

            // find on class path

            url = findResourceOnClassPath(name);

        }

        return checkURL(url);  // check access before returning

    }

    /**

     * Returns an input stream to a resource of the given name in a module

     * defined to this class loader.

     */

    public InputStream findResourceAsStream(String mn, String name)

        throws IOException

    {

        // Need URL to resource when running with a security manager so that

        // the right permission check is done.

        if (System.getSecurityManager() != null || mn == null) {

            URL url = findResource(mn, name);

            return (url != null) ? url.openStream() : null;

        }

        // find in module defined to this loader, no security manager

        ModuleReference mref = nameToModule.get(mn);

        if (mref != null) {

            return moduleReaderFor(mref).open(name).orElse(null);

        } else {

            return null;

        }

    }

    /**

     * Finds a resource with the given name in the modules defined to this

     * class loader or its class path.

     */

    @Override

    public URL findResource(String name) {

        String pn = Resources.toPackageName(name);

        LoadedModule module = packageToModule.get(pn);

        if (module != null) {

            // resource is in a package of a module defined to this loader

            if (module.loader() == this) {

                URL url;

                try {

                    url = findResource(module.name(), name); // checks URL

                } catch (IOException ioe) {

                    return null;

                }

                if (url != null

                    && (name.endsWith(".class")

                        || url.toString().endsWith("/")

                        || isOpen(module.mref(), pn))) {

                    return url;

                }

            }

        } else {

            // not in a module package but may be in module defined to this loader

            try {

                List<URL> urls = findMiscResource(name);

                if (!urls.isEmpty()) {

                    URL url = urls.get(0);

                    if (url != null) {

                        return checkURL(url); // check access before returning

                    }

                }

            } catch (IOException ioe) {

                return null;

            }

        }

        // search class path

        URL url = findResourceOnClassPath(name);

        return checkURL(url);

    }

    /**

     * Returns an enumeration of URL objects to all the resources with the

     * given name in modules defined to this class loader or on the class

     * path of this loader.

     */

    @Override

    public Enumeration<URL> findResources(String name) throws IOException {

        List<URL> checked = new ArrayList<>();  // list of checked URLs

        String pn = Resources.toPackageName(name);

        LoadedModule module = packageToModule.get(pn);

        if (module != null) {

            // resource is in a package of a module defined to this loader

            if (module.loader() == this) {

                URL url = findResource(module.name(), name); // checks URL

                if (url != null

                    && (name.endsWith(".class")

                        || url.toString().endsWith("/")

                        || isOpen(module.mref(), pn))) {

                    checked.add(url);

                }

            }

        } else {

            // not in a package of a module defined to this loader

            for (URL url : findMiscResource(name)) {

                url = checkURL(url);

                if (url != null) {

                    checked.add(url);

                }

            }

        }

        // class path (not checked)

        Enumeration<URL> e = findResourcesOnClassPath(name);

        // concat the checked URLs and the (not checked) class path

        return new Enumeration<>() {

            final Iterator<URL> iterator = checked.iterator();

            URL next;

            private boolean hasNext() {

                if (next != null) {

                    return true;

                } else if (iterator.hasNext()) {

                    next = iterator.next();

                    return true;

                } else {

                    // need to check each URL

                    while (e.hasMoreElements() && next == null) {

                        next = checkURL(e.nextElement());

                    }

                    return next != null;

                }

            }

            @Override

            public boolean hasMoreElements() {

                return hasNext();

            }

            @Override

            public URL nextElement() {

                if (hasNext()) {

                    URL result = next;

                    next = null;

                    return result;

                } else {

                    throw new NoSuchElementException();

                }

            }

        };

    }

    /**

     * Returns the list of URLs to a "miscellaneous" resource in modules

     * defined to this loader. A miscellaneous resource is not in a module

     * package, e.g. META-INF/services/p.S.

     *

     * The cache used by this method avoids repeated searching of all modules.

     */

    private List<URL> findMiscResource(String name) throws IOException {

        SoftReference<Map<String, List<URL>>> ref = this.resourceCache;

        Map<String, List<URL>> map = (ref != null) ? ref.get() : null;

        if (map == null) {

            map = new ConcurrentHashMap<>();

            this.resourceCache = new SoftReference<>(map);

        } else {

            List<URL> urls = map.get(name);

            if (urls != null)

                return urls;

        }

        // search all modules for the resource

        List<URL> urls;

        try {

            urls = AccessController.doPrivileged(

                new PrivilegedExceptionAction<>() {

                    @Override

                    public List<URL> run() throws IOException {

                        List<URL> result = null;

                        for (ModuleReference mref : nameToModule.values()) {

                            URI u = moduleReaderFor(mref).find(name).orElse(null);

                            if (u != null) {

                                try {

                                    if (result == null)

                                        result = new ArrayList<>();

                                    result.add(u.toURL());

                                } catch (MalformedURLException |

                                         IllegalArgumentException e) {

                                }

                            }

                        }

                        return (result != null) ? result : Collections.emptyList();

                    }

                });

        } catch (PrivilegedActionException pae) {

            throw (IOException) pae.getCause();

        }

        // only cache resources after VM is fully initialized

        if (VM.isModuleSystemInited()) {

            map.putIfAbsent(name, urls);

        }

        return urls;

    }

    /**

     * Returns the URL to a resource in a module or {@code null} if not found.

     */

    private URL findResource(ModuleReference mref, String name) throws IOException {

        URI u;

        if (System.getSecurityManager() == null) {

            u = moduleReaderFor(mref).find(name).orElse(null);

        } else {

            try {

                u = AccessController.doPrivileged(new PrivilegedExceptionAction<> () {

                    @Override

                    public URI run() throws IOException {

                        return moduleReaderFor(mref).find(name).orElse(null);

                    }

                });

            } catch (PrivilegedActionException pae) {

                throw (IOException) pae.getCause();

            }

        }

        if (u != null) {

            try {

                return u.toURL();

            } catch (MalformedURLException | IllegalArgumentException e) { }

        }

        return null;

    }

    /**

     * Returns the URL to a resource in a module. Returns {@code null} if not found

     * or an I/O error occurs.

     */

    private URL findResourceOrNull(ModuleReference mref, String name) {

        try {

            return findResource(mref, name);

        } catch (IOException ignore) {

            return null;

        }

    }

    /**

     * Returns a URL to a resource on the class path.

     */

    private URL findResourceOnClassPath(String name) {

        if (hasClassPath()) {

            if (System.getSecurityManager() == null) {

                return ucp.findResource(name, false);

            } else {

                PrivilegedAction<URL> pa = () -> ucp.findResource(name, false);

                return AccessController.doPrivileged(pa);