git ch

k94314517

2024-04-01 a7d11031939ddb31a11f62e4a48b4a068b6e7db4

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/*
 * Copyright (C) 2011 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 cn.emay.sdk.util.json.gson.internal;
 
import java.io.ObjectInputStream;
import java.io.ObjectStreamClass;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
 
/**
 * Do sneaky things to allocate objects without invoking their constructors.
 *
 * @author Joel Leitch
 * @author Jesse Wilson
 */
public abstract class UnsafeAllocator {
    public abstract <T> T newInstance(Class<T> c) throws Exception;
 
    public static UnsafeAllocator create() {
        // try JVM
        // public class Unsafe {
        // public Object allocateInstance(Class<?> type);
        // }
        try {
            Class<?> unsafeClass = Class.forName("sun.misc.Unsafe");
            Field f = unsafeClass.getDeclaredField("theUnsafe");
            f.setAccessible(true);
            final Object unsafe = f.get(null);
            final Method allocateInstance = unsafeClass.getMethod("allocateInstance", Class.class);
            return new UnsafeAllocator() {
                @Override
                @SuppressWarnings("unchecked")
                public <T> T newInstance(Class<T> c) throws Exception {
                    return (T) allocateInstance.invoke(unsafe, c);
                }
            };
        } catch (Exception ignored) {
        }
 
        // try dalvikvm, post-gingerbread
        // public class ObjectStreamClass {
        // private static native int getConstructorId(Class<?> c);
        // private static native Object newInstance(Class<?> instantiationClass, int
        // methodId);
        // }
        try {
            Method getConstructorId = ObjectStreamClass.class.getDeclaredMethod("getConstructorId", Class.class);
            getConstructorId.setAccessible(true);
            final int constructorId = (Integer) getConstructorId.invoke(null, Object.class);
            final Method newInstance = ObjectStreamClass.class.getDeclaredMethod("newInstance", Class.class, int.class);
            newInstance.setAccessible(true);
            return new UnsafeAllocator() {
                @Override
                @SuppressWarnings("unchecked")
                public <T> T newInstance(Class<T> c) throws Exception {
                    return (T) newInstance.invoke(null, c, constructorId);
                }
            };
        } catch (Exception ignored) {
        }
 
        // try dalvikvm, pre-gingerbread
        // public class ObjectInputStream {
        // private static native Object newInstance(
        // Class<?> instantiationClass, Class<?> constructorClass);
        // }
        try {
            final Method newInstance = ObjectInputStream.class.getDeclaredMethod("newInstance", Class.class, Class.class);
            newInstance.setAccessible(true);
            return new UnsafeAllocator() {
                @Override
                @SuppressWarnings("unchecked")
                public <T> T newInstance(Class<T> c) throws Exception {
                    return (T) newInstance.invoke(null, c, Object.class);
                }
            };
        } catch (Exception ignored) {
        }
 
        // give up
        return new UnsafeAllocator() {
            @Override
            public <T> T newInstance(Class<T> c) {
                throw new UnsupportedOperationException("Cannot allocate " + c);
            }
        };
    }
}