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/*
* Copyright 2014 The Netty Project
*
* The Netty Project licenses this file to you 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:
*
*   https://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 io.netty.util.concurrent;

import io.netty.util.internal.InternalThreadLocalMap;
import io.netty.util.internal.UnstableApi;
import io.netty.util.internal.logging.InternalLogger;
import io.netty.util.internal.logging.InternalLoggerFactory;

/**
 * A special {@link Thread} that provides fast access to {@link FastThreadLocal} variables.
 */
public class FastThreadLocalThread extends Thread {

    private static final InternalLogger logger = InternalLoggerFactory.getInstance(FastThreadLocalThread.class);

    // This will be set to true if we have a chance to wrap the Runnable.
    private final boolean cleanupFastThreadLocals;

    private InternalThreadLocalMap threadLocalMap;

    public FastThreadLocalThread() {
        cleanupFastThreadLocals = false;
    }

    public FastThreadLocalThread(Runnable target) {
        super(FastThreadLocalRunnable.wrap(target));
        cleanupFastThreadLocals = true;
    }

    public FastThreadLocalThread(ThreadGroup group, Runnable target) {
        super(group, FastThreadLocalRunnable.wrap(target));
        cleanupFastThreadLocals = true;
    }

    public FastThreadLocalThread(String name) {
        super(name);
        cleanupFastThreadLocals = false;
    }

    public FastThreadLocalThread(ThreadGroup group, String name) {
        super(group, name);
        cleanupFastThreadLocals = false;
    }

    public FastThreadLocalThread(Runnable target, String name) {
        super(FastThreadLocalRunnable.wrap(target), name);
        cleanupFastThreadLocals = true;
    }

    public FastThreadLocalThread(ThreadGroup group, Runnable target, String name) {
        super(group, FastThreadLocalRunnable.wrap(target), name);
        cleanupFastThreadLocals = true;
    }

    public FastThreadLocalThread(ThreadGroup group, Runnable target, String name, long stackSize) {
        super(group, FastThreadLocalRunnable.wrap(target), name, stackSize);
        cleanupFastThreadLocals = true;
    }

    /**
     * Returns the internal data structure that keeps the thread-local variables bound to this thread.
     * Note that this method is for internal use only, and thus is subject to change at any time.
     */
    public final InternalThreadLocalMap threadLocalMap() {
        if (this != Thread.currentThread() && logger.isWarnEnabled()) {
            logger.warn(new RuntimeException("It's not thread-safe to get 'threadLocalMap' " +
                    "which doesn't belong to the caller thread"));
        }
        return threadLocalMap;
    }

    /**
     * Sets the internal data structure that keeps the thread-local variables bound to this thread.
     * Note that this method is for internal use only, and thus is subject to change at any time.
     */
    public final void setThreadLocalMap(InternalThreadLocalMap threadLocalMap) {
        if (this != Thread.currentThread() && logger.isWarnEnabled()) {
            logger.warn(new RuntimeException("It's not thread-safe to set 'threadLocalMap' " +
                    "which doesn't belong to the caller thread"));
        }
        this.threadLocalMap = threadLocalMap;
    }

    /**
     * Returns {@code true} if {@link FastThreadLocal#removeAll()} will be called once {@link #run()} completes.
     */
    @UnstableApi
    public boolean willCleanupFastThreadLocals() {
        return cleanupFastThreadLocals;
    }

    /**
     * Returns {@code true} if {@link FastThreadLocal#removeAll()} will be called once {@link Thread#run()} completes.
     */
    @UnstableApi
    public static boolean willCleanupFastThreadLocals(Thread thread) {
        return thread instanceof FastThreadLocalThread &&
                ((FastThreadLocalThread) thread).willCleanupFastThreadLocals();
    }

    /**
     * Query whether this thread is allowed to perform blocking calls or not.
     * {@link FastThreadLocalThread}s are often used in event-loops, where blocking calls are forbidden in order to
     * prevent event-loop stalls, so this method returns {@code false} by default.
     * 
     * Subclasses of {@link FastThreadLocalThread} can override this method if they are not meant to be used for
     * running event-loops.
     *
     * @return {@code false}, unless overriden by a subclass.
     */
    public boolean permitBlockingCalls() {
        return false;
    }
}