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A reactive Java web server.
There is a newer version: 1.0.1
/*
 * Copyright (c) 1998-2015 Caucho Technology -- all rights reserved
 *
 * This file is part of Baratine(TM)(TM)
 *
 * Each copy or derived work must preserve the copyright notice and this
 * notice unmodified.
 *
 * Baratine is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * Baratine 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, or any warranty
 * of NON-INFRINGEMENT.  See the GNU General Public License for more
 * details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Baratine; if not, write to the
 *
 *   Free Software Foundation, Inc.
 *   59 Temple Place, Suite 330
 *   Boston, MA 02111-1307  USA
 *
 * @author Scott Ferguson
 */

package com.caucho.v5.amp.queue;

import java.util.concurrent.BlockingQueue;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicReference;
import java.util.concurrent.locks.LockSupport;

import com.caucho.v5.util.CurrentTime;

/**
 * Ring blocking algorithm.
 */
public class RingBlockerSinglePoller extends RingBlockerBasic
{
  private final AtomicReference _pollThreadRef
    = new AtomicReference<>();
  
  // true if the poll has ever needed to wait, used to avoid slow reads
  // on queues that never fill.
  private BlockingQueue _queue;
  
  public void setQueue(BlockingQueue queue)
  {
    _queue = queue;
  }

  @Override
  public final boolean pollWait(long sequence,
                                long timeout,
                                TimeUnit unit)
  {
    if (! _queue.isEmpty()) {
      return true;
    }
    
    if (timeout <= 0) {
      return false;
    }
    

    Thread thread = Thread.currentThread();
    
    Thread oldThread = _pollThreadRef.getAndSet(thread);
    
    if (oldThread != null) {
      LockSupport.unpark(oldThread);
    }
    
    long expires = CurrentTime.getCurrentTimeActual() + unit.toMillis(timeout);
    
    while (_queue.isEmpty() && CurrentTime.getCurrentTimeActual() < expires) {
      try {
        Thread.interrupted();
        
        LockSupport.parkUntil(expires);
      } catch (Exception e) {
        
      }
    }
    
    _pollThreadRef.compareAndSet(thread, null);
    
    return ! _queue.isEmpty();
  }

  @Override
  public final void pollWake()
  {
    Thread thread = _pollThreadRef.get();
    
    if (thread != null) {
      LockSupport.unpark(thread);
    }
  }
}