alvinalexander.com | career | drupal | java | mac | mysql | perl | scala | uml | unix  

Java example source code file (Test7190310_unsafe.java)

This example Java source code file (Test7190310_unsafe.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

class, exception, field, object, reflection, string, test7190310_unsafe, testobject, weakreference

The Test7190310_unsafe.java Java example source code

/*
 * Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * 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).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */

/*
 * @test
 * @bug 7190310
 * @summary Inlining WeakReference.get(), and hoisting $referent may lead to non-terminating loops
 * @run main/othervm -Xbatch Test7190310_unsafe
 */

import java.lang.ref.*;
import java.lang.reflect.*;
import sun.misc.Unsafe;

public class Test7190310_unsafe {

  static class TestObject {
    public String toString() {
      return "TestObject";
    }
  };

  private static TestObject str = new TestObject();
  private static final WeakReference ref = new WeakReference(str);

  private TestObject obj;

  public static void main(String[] args) throws Exception {
    Class c = Test7190310_unsafe.class.getClassLoader().loadClass("sun.misc.Unsafe");
    Field f = c.getDeclaredField("theUnsafe");
    f.setAccessible(true);
    Unsafe unsafe = (Unsafe)f.get(c);

    f = Reference.class.getDeclaredField("referent");
    f.setAccessible(true);
    long referent_offset = unsafe.objectFieldOffset(f);

    Test7190310_unsafe t = new Test7190310_unsafe();
    TestObject o = new TestObject();
    t.obj = o;

    // Warmup (compile methods)
    System.err.println("Warmup");
    Object obj = null;
    for (int i = 0; i < 11000; i++) {
      obj = getRef0(ref);
    }
    for (int i = 0; i < 11000; i++) {
      obj = getRef1(unsafe, ref, referent_offset);
    }
    for (int i = 0; i < 11000; i++) {
      obj = getRef2(unsafe, ref, referent_offset);
    }
    for (int i = 0; i < 11000; i++) {
      obj = getRef3(unsafe, ref, referent_offset);
    }
    for (int i = 0; i < 11000; i++) {
      obj = getRef4(unsafe, t, referent_offset);
    }

    // Access verification
    System.err.println("Verification");
    if (!verifyGet(referent_offset, unsafe)) {
      System.exit(97);
    }

    obj = getRef3(unsafe, t, referent_offset);
    if (obj != o) {
      System.out.println("FAILED: unsafe.getObject(Object, " + referent_offset + ") " + obj + " != " + o);
      System.exit(97);
    }
    obj = getRef4(unsafe, t, referent_offset);
    if (obj != o) {
      System.out.println("FAILED: unsafe.getObject(Test7190310, " + referent_offset + ") " + obj + " != " + o);
      System.exit(97);
    }
  }

  static boolean verifyGet(long referent_offset, Unsafe unsafe) throws Exception {
    // Access verification
    System.out.println("referent: " + str);
    Object obj = getRef0(ref);
    if (obj != str) {
      System.out.println("FAILED: weakRef.get() " + obj + " != " + str);
      return false;
    }
    obj = getRef1(unsafe, ref, referent_offset);
    if (obj != str) {
      System.out.println("FAILED: unsafe.getObject(weakRef, " + referent_offset + ") " + obj + " != " + str);
      return false;
    }
    obj = getRef2(unsafe, ref, referent_offset);
    if (obj != str) {
      System.out.println("FAILED: unsafe.getObject(abstRef, " + referent_offset + ") " + obj + " != " + str);
      return false;
    }
    obj = getRef3(unsafe, ref, referent_offset);
    if (obj != str) {
      System.out.println("FAILED: unsafe.getObject(Object, " + referent_offset + ") " + obj + " != " + str);
      return false;
    }
    return true;
  }

  static Object getRef0(WeakReference ref) throws Exception {
    return ref.get();
  }
  static Object getRef1(Unsafe unsafe, WeakReference ref, long referent_offset) throws Exception {
    return unsafe.getObject(ref, referent_offset);
  }
  static Object getRef2(Unsafe unsafe, Reference ref, long referent_offset) throws Exception {
    return unsafe.getObject(ref, referent_offset);
  }
  static Object getRef3(Unsafe unsafe, Object ref, long referent_offset) throws Exception {
    return unsafe.getObject(ref, referent_offset);
  }
  static Object getRef4(Unsafe unsafe, Test7190310_unsafe ref, long referent_offset) throws Exception {
    return unsafe.getObject(ref, referent_offset);
  }
}

Other Java examples (source code examples)

Here is a short list of links related to this Java Test7190310_unsafe.java source code file:

... this post is sponsored by my books ...

#1 New Release!

FP Best Seller

 

new blog posts

 

Copyright 1998-2021 Alvin Alexander, alvinalexander.com
All Rights Reserved.

A percentage of advertising revenue from
pages under the /java/jwarehouse URI on this website is
paid back to open source projects.