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/*
 * JBoss, Home of Professional Open Source.
 * Copyright 2017 Red Hat, Inc., and individual contributors
 * as indicated by the @author tags.
 *
 * 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 org.jboss.threads;

import java.lang.reflect.Field;
import java.security.AccessController;

final class ThreadLocalResetter implements Runnable {
    private static final ThreadLocalResetter INSTANCE = new ThreadLocalResetter();

    private static final long threadLocalMapOffs;
    private static final long inheritableThreadLocalMapOffs;

    static {
        final Field threadLocals = AccessController.doPrivileged(new DeclaredFieldAction(Thread.class, "threadLocals"));
        threadLocalMapOffs = threadLocals == null ? 0 : JBossExecutors.unsafe.objectFieldOffset(threadLocals);
        final Field inheritableThreadLocals = AccessController.doPrivileged(new DeclaredFieldAction(Thread.class, "inheritableThreadLocals"));
        inheritableThreadLocalMapOffs = inheritableThreadLocals == null ? 0 : JBossExecutors.unsafe.objectFieldOffset(inheritableThreadLocals);
    }

    static ThreadLocalResetter getInstance() {
        return INSTANCE;
    }

    private ThreadLocalResetter() {
    }

    public void run() {
        final Thread thread = Thread.currentThread();
        if (threadLocalMapOffs != 0) JBossExecutors.unsafe.putObject(thread, threadLocalMapOffs, null);
        if (inheritableThreadLocalMapOffs != 0) JBossExecutors.unsafe.putObject(thread, inheritableThreadLocalMapOffs, null);
    }

    public String toString() {
        return "Thread-local resetting Runnable";
    }
}