com.google.inject.internal.aop.HiddenClassDefiner Maven / Gradle / Ivy
/*
* Copyright (C) 2021 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.inject.internal.aop;
import java.lang.invoke.MethodHandles.Lookup;
import java.lang.reflect.Array;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
/**
* {@link ClassDefiner} that defines classes using {@code MethodHandles.Lookup#defineHiddenClass}.
*
* @author [email protected] (Stuart McCulloch)
*/
final class HiddenClassDefiner implements ClassDefiner {
private static final Object THE_UNSAFE;
private static final Object TRUSTED_LOOKUP_BASE;
private static final Object TRUSTED_LOOKUP_OFFSET;
private static final Method GET_OBJECT_METHOD;
private static final Object HIDDEN_CLASS_OPTIONS;
private static final Method HIDDEN_DEFINE_METHOD;
static {
try {
Class unsafeType = Class.forName("sun.misc.Unsafe");
Field theUnsafeField = unsafeType.getDeclaredField("theUnsafe");
theUnsafeField.setAccessible(true);
THE_UNSAFE = theUnsafeField.get(null);
Field trustedLookupField = Lookup.class.getDeclaredField("IMPL_LOOKUP");
Method baseMethod = unsafeType.getMethod("staticFieldBase", Field.class);
TRUSTED_LOOKUP_BASE = baseMethod.invoke(THE_UNSAFE, trustedLookupField);
Method offsetMethod = unsafeType.getMethod("staticFieldOffset", Field.class);
TRUSTED_LOOKUP_OFFSET = offsetMethod.invoke(THE_UNSAFE, trustedLookupField);
GET_OBJECT_METHOD = unsafeType.getMethod("getObject", Object.class, long.class);
HIDDEN_CLASS_OPTIONS = classOptions("NESTMATE");
HIDDEN_DEFINE_METHOD =
Lookup.class.getMethod(
"defineHiddenClass", byte[].class, boolean.class, HIDDEN_CLASS_OPTIONS.getClass());
} catch (ReflectiveOperationException e) {
throw new ExceptionInInitializerError(e);
}
}
@Override
public Class define(Class hostClass, byte[] bytecode) throws Exception {
Lookup trustedLookup =
(Lookup) GET_OBJECT_METHOD.invoke(THE_UNSAFE, TRUSTED_LOOKUP_BASE, TRUSTED_LOOKUP_OFFSET);
Lookup definedLookup =
(Lookup)
HIDDEN_DEFINE_METHOD.invoke(
trustedLookup.in(hostClass), bytecode, false, HIDDEN_CLASS_OPTIONS);
return definedLookup.lookupClass();
}
/** Creates {@link MethodHandles.Lookup.ClassOption} array with the named options. */
@SuppressWarnings("unchecked")
private static Object classOptions(String... options) throws ClassNotFoundException {
@SuppressWarnings("rawtypes") // Unavoidable, only way to use Enum.valueOf
Class optionClass = Class.forName(Lookup.class.getName() + "$ClassOption");
Object classOptions = Array.newInstance(optionClass, options.length);
for (int i = 0; i < options.length; i++) {
Array.set(classOptions, i, Enum.valueOf(optionClass, options[i]));
}
return classOptions;
}
}