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/*
* Copyright 2023 Code Intelligence GmbH
*
* 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.code_intelligence.jazzer.utils;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodHandles.Lookup;
import java.lang.reflect.Array;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.Arrays;
import java.util.Optional;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.Opcodes;
public final class UnsafeUtils {
/**
* Dynamically creates a concrete class implementing the given abstract class.
*
* <p>The returned class will not be functional and should only be used to construct instances
* via {@link sun.misc.Unsafe#allocateInstance(Class)}.
*/
public static <T> Class<? extends T> defineAnonymousConcreteSubclass(Class<T> abstractClass) {
if (!Modifier.isAbstract(abstractClass.getModifiers())) {
throw new IllegalArgumentException(abstractClass + " is not abstract");
}
ClassWriter cw = new ClassWriter(0);
String superClassName = abstractClass.getName().replace('.', '/');
// Only the package of the class name matters, the actual name is generated. defineHiddenClass
// requires the package of the new class to match the one of the lookup.
String className = UnsafeUtils.class.getPackage().getName().replace('.', '/') + "/Anonymous";
cw.visit(Opcodes.V1_8, 0, className, null, superClassName, null);
cw.visitEnd();
try {
Optional<Method> defineHiddenClass =
Arrays.stream(Lookup.class.getMethods())
.filter(method -> method.getName().equals("defineHiddenClass"))
.findFirst();
Optional<Class<?>> classOption =
Arrays.stream(Lookup.class.getClasses())
.filter(clazz -> clazz.getSimpleName().equals("ClassOption"))
.findFirst();
// MethodHandles.Lookup#defineHiddenClass is available as of Java 15.
// Unsafe#defineAnonymousClass has been removed in Java 17.
if (defineHiddenClass.isPresent() && classOption.isPresent()) {
return ((MethodHandles.Lookup) defineHiddenClass.get().invoke(MethodHandles.lookup(),
cw.toByteArray(), true, Array.newInstance(classOption.get(), 0)))
.lookupClass()
.asSubclass(abstractClass);
} else {
return (Class<? extends T>) UnsafeProvider.getUnsafe()
.getClass()
.getMethod("defineAnonymousClass", Class.class, byte[].class, Object[].class)
.invoke(UnsafeProvider.getUnsafe(), UnsafeUtils.class, cw.toByteArray(), null);
}
} catch (IllegalAccessException | InvocationTargetException | NoSuchMethodException e) {
throw new IllegalStateException(e);
}
}
private UnsafeUtils() {}
}
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