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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).
 *
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 * 2 along with this work; if not, write to the Free Software Foundation,
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package jdk.nashorn.internal.runtime.linker;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.security.AccessControlContext;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.security.ProtectionDomain;
import java.security.SecureClassLoader;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;
import jdk.dynalink.beans.StaticClass;
import jdk.nashorn.internal.codegen.DumpBytecode;
import jdk.nashorn.internal.runtime.Context;
import jdk.nashorn.internal.runtime.JSType;
import jdk.nashorn.internal.runtime.ScriptFunction;
import jdk.nashorn.internal.runtime.ScriptObject;

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 ClassLoader, but rather uses them internally. Instances of this class are normally created by JavaAdapterBytecodeGenerator. /**
 * 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 {@code JavaAdapterBytecodeGenerator}.
 */
final class JavaAdapterClassLoader {
    private static final Module NASHORN_MODULE = Context.class.getModule();

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

    private static final Collection<String> VISIBLE_INTERNAL_CLASS_NAMES = Collections.unmodifiableCollection(new HashSet<>(
            Arrays.asList(JavaAdapterServices.class.getName(), ScriptObject.class.getName(), ScriptFunction.class.getName(), JSType.class.getName())));

    private final String className;
    private final byte[] classBytes;

    JavaAdapterClassLoader(final String className, final byte[] classBytes) {
        this.className = className.replace('/', '.');
        this.classBytes = classBytes;
    }

    
Loads the generated adapter class into the JVM.
Params:
parentLoader – the parent class loader for the generated class loader
protectionDomain – the protection domain for the generated class
Returns:
the generated adapter class/**
     * 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();

            // the unnamed module into which adapter is loaded!
            private final Module adapterModule = getUnnamedModule();

            {
                // specific exports from nashorn to the new adapter module
                NASHORN_MODULE.addExports("jdk.nashorn.internal.runtime", adapterModule);
                NASHORN_MODULE.addExports("jdk.nashorn.internal.runtime.linker", adapterModule);

                // nashorn should be be able to read methods of classes loaded in adapter module
                NASHORN_MODULE.addReads(adapterModule);
            }

            @Override
            public Class<?> loadClass(final String name, final boolean resolve) throws ClassNotFoundException {
                try {
                    final int i = name.lastIndexOf('.');
                    if(i != -1){
                        final String pkgName = name.substring(0,i);
                        Context.checkPackageAccess(pkgName);
                    }
                    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
                    // should be able to refer to the few classes it needs in its implementation.
                    if(VISIBLE_INTERNAL_CLASS_NAMES.contains(name)) {
                        return myLoader != null? myLoader.loadClass(name) : Class.forName(name, false, myLoader);
                    }
                    throw se;
                }
            }

            @Override
            protected Class<?> findClass(final String name) throws ClassNotFoundException {
                if(name.equals(className)) {
                    assert classBytes != null : "what? already cleared .class bytes!!";

                    final Context ctx = AccessController.doPrivileged(new PrivilegedAction<Context>() {
                        @Override
                        public Context run() {
                            return Context.getContext();
                        }
                    }, GET_CONTEXT_ACC_CTXT);
                    DumpBytecode.dumpBytecode(ctx.getEnv(), ctx.getLogger(jdk.nashorn.internal.codegen.Compiler.class), classBytes, name);
                    return defineClass(name, classBytes, 0, classBytes.length, protectionDomain);
                }
                throw new ClassNotFoundException(name);
            }
        };
    }
}