/*

 * Copyright (c) 2010, 2013, 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

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 */

package jdk.nashorn.internal.runtime.linker;

import java.security.AccessControlContext;

import java.security.AccessController;

import java.security.PrivilegedAction;

import java.security.ProtectionDomain;

import java.security.SecureClassLoader;

import jdk.internal.dynalink.beans.StaticClass;

/**

 * This class encapsulates the bytecode of the adapter class and can be used to load it into the JVM as an actual Class.

 * It can be invoked repeatedly to create multiple adapter classes from the same bytecode; adapter classes that have

 * class-level overrides must be re-created for every set of such overrides. Note that while this class is named

 * "class loader", it does not, in fact, extend {@code ClassLoader}, but rather uses them internally. Instances of this

 * class are normally created by {@link JavaAdapterBytecodeGenerator}.

 */

@SuppressWarnings("javadoc")

final class JavaAdapterClassLoader {

    private static final AccessControlContext CREATE_LOADER_ACC_CTXT = ClassAndLoader.createPermAccCtxt("createClassLoader");

    private final String className;

    private final byte[] classBytes;

    JavaAdapterClassLoader(String className, byte[] classBytes) {

        this.className = className.replace('/', '.');

        this.classBytes = classBytes;

    }

    /**

     * Loads the generated adapter class into the JVM.

     * @param parentLoader the parent class loader for the generated class loader

     * @param protectionDomain the protection domain for the generated class

     * @return the generated adapter class

     */

    StaticClass generateClass(final ClassLoader parentLoader, final ProtectionDomain protectionDomain) {

        assert protectionDomain != null;

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

            @Override

            public StaticClass run() {

                try {

                    return StaticClass.forClass(Class.forName(className, true, createClassLoader(parentLoader, protectionDomain)));

                } catch (final ClassNotFoundException e) {

                    throw new AssertionError(e); // cannot happen

                }

            }

        }, CREATE_LOADER_ACC_CTXT);

    }

    // Note that the adapter class is created in the protection domain of the class/interface being

    // extended/implemented, and only the privileged global setter action class is generated in the protection domain

    // of Nashorn itself. Also note that the creation and loading of the global setter is deferred until it is

    // required by JVM linker, which will only happen on first invocation of any of the adapted method. We could defer

    // it even more by separating its invocation into a separate static method on the adapter class, but then someone

    // with ability to introspect on the class and use setAccessible(true) on it could invoke the method. It's a

    // security tradeoff...

    private ClassLoader createClassLoader(final ClassLoader parentLoader, final ProtectionDomain protectionDomain) {

        return new SecureClassLoader(parentLoader) {

            private final ClassLoader myLoader = getClass().getClassLoader();

            @Override

            public Class<?> loadClass(final String name, final boolean resolve) throws ClassNotFoundException {

                try {

                    return super.loadClass(name, resolve);

                } catch (final SecurityException se) {

                    // we may be implementing an interface or extending a class that was

                    // loaded by a loader that prevents package.access. If so, it'd throw

                    // SecurityException for nashorn's classes!. For adapter's to work, we

                        return myLoader.loadClass(name);

                    }

                    throw se;

                }

            }

            @Override

            protected Class<?> findClass(final String name) throws ClassNotFoundException {

                if(name.equals(className)) {

                    assert classBytes != null : "what? already cleared .class bytes!!";

                    return defineClass(name, classBytes, 0, classBytes.length, protectionDomain);

                }

                throw new ClassNotFoundException(name);

            }

        };

    }

}