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/*
* Copyright (c) 2001, 2011, Oracle and/or its affiliates. All rights reserved.
* 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,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
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*/
package sun.reflect;
import java.security.AccessController;
import java.security.PrivilegedAction;
import sun.misc.Unsafe;
/** Utility class which assists in calling Unsafe.defineClass() by
creating a new class loader which delegates to the one needed in
order for proper resolution of the given bytecodes to occur. */
class ClassDefiner {
static final Unsafe unsafe = Unsafe.getUnsafe();
/** We define generated code into a new class loader which
delegates to the defining loader of the target class. It is
necessary for the VM to be able to resolve references to the
target class from the generated bytecodes, which could not occur
if the generated code was loaded into the bootstrap class
loader.
There are two primary reasons for creating a new loader
instead of defining these bytecodes directly into the defining
loader of the target class: first, it avoids any possible
security risk of having these bytecodes in the same loader.
Second, it allows the generated bytecodes to be unloaded earlier
than would otherwise be possible, decreasing run-time
footprint.
*/
static Class defineClass(String name, byte[] bytes, int off, int len,
final ClassLoader parentClassLoader)
{
ClassLoader newLoader = AccessController.doPrivileged(
new PrivilegedAction() {
public ClassLoader run() {
return new DelegatingClassLoader(parentClassLoader);
}
});
return unsafe.defineClass(name, bytes, off, len, newLoader, null);
}
}
// NOTE: this class's name and presence are known to the virtual
// machine as of the fix for 4474172.
class DelegatingClassLoader extends ClassLoader {
DelegatingClassLoader(ClassLoader parent) {
super(parent);
}
}