jdk

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/*
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 * Copyright (c) 2014, 2022, Oracle and/or its affiliates. All rights reserved.
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 *
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 * This code is free software; you can redistribute it and/or modify it
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 * under the terms of the GNU General Public License version 2 only, as
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 * published by the Free Software Foundation.
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 *
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 * This code is distributed in the hope that it will be useful, but WITHOUT
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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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 * version 2 for more details (a copy is included in the LICENSE file that
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 * accompanied this code).
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 *
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 * You should have received a copy of the GNU General Public License version
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 * 2 along with this work; if not, write to the Free Software Foundation,
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 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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 *
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 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 * or visit www.oracle.com if you need additional information or have any
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 * questions.
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 */
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import java.lang.instrument.Instrumentation;
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import java.lang.instrument.ClassDefinition;
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import jdk.test.lib.compiler.InMemoryJavaCompiler;
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import jdk.test.lib.helpers.ClassFileInstaller;
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/*
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 * Helper class to write tests that redefine classes.
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 * When main method is run, it will create a redefineagent.jar that can be used
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 * with the -javaagent option to support redefining classes in jtreg tests.
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 *
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 * See sample test in test/testlibrary_tests/RedefineClassTest.java
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 */
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public class RedefineClassHelper {
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    public static Instrumentation instrumentation;
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    public static void premain(String agentArgs, Instrumentation inst) {
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        instrumentation = inst;
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    }
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    /**
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     * Redefine a class
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     *
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     * @param clazz Class to redefine
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     * @param javacode String with the new java code for the class to be redefined
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     */
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    public static void redefineClass(Class<?> clazz, String javacode) throws Exception {
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        byte[] bytecode = InMemoryJavaCompiler.compile(clazz.getName(), javacode);
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        redefineClass(clazz, bytecode);
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    }
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    /**
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     * Redefine a class
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     *
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     * @param clazz Class to redefine
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     * @param bytecode byte[] with the new class
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     */
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    public static void redefineClass(Class<?> clazz, byte[] bytecode) throws Exception {
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        instrumentation.redefineClasses(new ClassDefinition(clazz, bytecode));
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    }
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    /**
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     * Main method to be invoked before test to create the redefineagent.jar
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     */
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    public static void main(String[] args) throws Exception {
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        String manifest = "Premain-Class: RedefineClassHelper\nCan-Redefine-Classes: true\n";
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        ClassFileInstaller.writeJar("redefineagent.jar", ClassFileInstaller.Manifest.fromString(manifest), "RedefineClassHelper");
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    }
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}
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