com.mchange.sc.v1.util.concurrent.RestrictToThreadInvoker.scala Maven / Gradle / Ivy

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/*
 * Distributed as part of mchange-commons-scala v0.4.0
 *
 * Copyright (C) 2015 Machinery For Change, Inc.
 *
 * Author: Steve Waldman 
 *
 * This library is free software; you can redistribute it and/or modify
 * it under the terms of EITHER:
 *
 *     1) The GNU Lesser General Public License (LGPL), version 2.1, as 
 *        published by the Free Software Foundation
 *
 * OR
 *
 *     2) The Eclipse Public License (EPL), version 1.0
 *
 * You may choose which license to accept if you wish to redistribute
 * or modify this work. You may offer derivatives of this work
 * under the license you have chosen, or you may provide the same
 * choice of license which you have been offered here.
 *
 * This software 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.
 *
 * You should have received copies of both LGPL v2.1 and EPL v1.0
 * along with this software; see the files LICENSE-EPL and LICENSE-LGPL.
 * If not, the text of these licenses are currently available at
 *
 * LGPL v2.1: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html
 *  EPL v1.0: http://www.eclipse.org/org/documents/epl-v10.php 
 * 
 */

package com.mchange.sc.v1.util.concurrent;

import java.util.concurrent._;
import com.mchange.sc.v1.util.NullFunction;

class RestrictToThreadInvoker( threadName : String ) extends Invoker {

  val latch = new CountDownLatch(1);
  var myThread : Thread = _;

  private def used = (latch.getCount == 0);

  val executorService  =  {
    val tf = new ThreadFactory {
      def newThread( runnable : Runnable ) : Thread = {
	if (! used) {
	  latch.countDown();
	  myThread = {
	    val out = new Thread(runnable);
	    out.setName( threadName );
	    out.setDaemon(true);
	    out;
	  }
	  myThread
	} else {
	  throw new RuntimeException("Unsupported: Trying to re-create a Thread for a SingleThreadExecutor.");
	}
      }
    }
    val exe = Executors.newSingleThreadExecutor( tf );
    exe.submit( NullFunction ); //prime, start the Thread immediately on construction, bind to a lazy var if you want lazy
    exe
  }

  def invokeAndWait[T]( callable : Callable[T] ) : T = {
    latch.await;
    if ( Thread.currentThread == myThread ) callable.call else executorService.submit( callable ).get();
  }

  def invokeAndWait( runnable : Runnable ) : Unit = {
    latch.await;
    if ( Thread.currentThread == myThread ) runnable.run else executorService.submit( runnable ).get();
  }

  def invokeLater( runnable : Runnable ) : Unit = {
    latch.await;
    if ( Thread.currentThread == myThread ) runnable.run else executorService.submit( runnable );
  }

  def shutdown : Unit = executorService.shutdown();

  def close : Unit = shutdown;
}