com.github.benmanes.caffeine.cache.UnsafeAccess Maven / Gradle / Ivy
The newest version!
/*
* Copyright 2014 Ben Manes. All Rights Reserved.
*
* 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.github.benmanes.caffeine.cache;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import sun.misc.Unsafe;
/**
* Static access to {@link Unsafe} and convenient utility methods for performing low-level, unsafe
* operations.
*
* @author [email protected] (Ben Manes)
*/
@SuppressWarnings("restriction")
final class UnsafeAccess {
static final String ANDROID = "THE_ONE";
static final String OPEN_JDK = "theUnsafe";
/** The Unsafe instance. */
public static final Unsafe UNSAFE;
static {
try {
UNSAFE = load(OPEN_JDK, ANDROID);
} catch (Exception e) {
throw new Error("Failed to load sun.misc.Unsafe", e);
}
}
/**
* Returns the location of a given static field.
*
* @param clazz the class containing the field
* @param fieldName the name of the field
* @return the address offset of the field
*/
public static long objectFieldOffset(Class clazz, String fieldName) {
try {
return UNSAFE.objectFieldOffset(clazz.getDeclaredField(fieldName));
} catch (NoSuchFieldException | SecurityException e) {
throw new Error(e);
}
}
static Unsafe load(String openJdk, String android) throws NoSuchMethodException,
InstantiationException, IllegalAccessException, InvocationTargetException {
Field field;
try {
// try OpenJDK field name
field = Unsafe.class.getDeclaredField(openJdk);
} catch (NoSuchFieldException e) {
try {
// try Android field name
field = Unsafe.class.getDeclaredField(android);
} catch (NoSuchFieldException e2) {
// try to create a new instance
Constructor unsafeConstructor = Unsafe.class.getDeclaredConstructor();
unsafeConstructor.setAccessible(true);
return unsafeConstructor.newInstance();
}
}
field.setAccessible(true);
return (Unsafe) field.get(null);
}
private UnsafeAccess() {}
}