/*

 * Copyright (c) 2015, 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.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * 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

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package com.sun.org.apache.xml.internal.utils;

/**

 * This is a combination of ThreadControllerWrapper's inner class SafeThread

 * that was introduced as a fix for CR 6607339

 * and sun.misc.ManagedLocalsThread, a thread that has it's thread locals, and

 * inheritable thread locals erased on construction. Except the run method,

 * it is identical to sun.misc.ManagedLocalsThread.

 */

public class SafeThread extends Thread {

    private static final jdk.internal.misc.Unsafe UNSAFE;

    private static final long THREAD_LOCALS;

    private static final long INHERITABLE_THREAD_LOCALS;

    private volatile boolean ran = false;

    public SafeThread(Runnable target) {

        super(target);

        eraseThreadLocals();

    }

    public SafeThread(Runnable target, String name) {

        super(target, name);

        eraseThreadLocals();

    }

    public SafeThread(ThreadGroup group, Runnable target, String name) {

        super(group, target, name);

        eraseThreadLocals();

    }

    public final void run() {

        if (Thread.currentThread() != this) {

            throw new IllegalStateException("The run() method in a"

                    + " SafeThread cannot be called from another thread.");

        }

        synchronized (this) {

            if (!ran) {

                ran = true;

            } else {

                throw new IllegalStateException("The run() method in a"

                        + " SafeThread cannot be called more than once.");

            }

        }

        super.run();

    }

    /**

     * Drops all thread locals (and inherited thread locals).

     */

    public final void eraseThreadLocals() {

        UNSAFE.putObject(this, THREAD_LOCALS, null);

        UNSAFE.putObject(this, INHERITABLE_THREAD_LOCALS, null);

    }

    static {

        UNSAFE = jdk.internal.misc.Unsafe.getUnsafe();

        Class<?> t = Thread.class;

        try {

            THREAD_LOCALS = UNSAFE.objectFieldOffset(t.getDeclaredField("threadLocals"));

            INHERITABLE_THREAD_LOCALS = UNSAFE.objectFieldOffset(t.getDeclaredField("inheritableThreadLocals"));

        } catch (Exception e) {

            throw new Error(e);

        }

    }

}