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   /*
    * Copyright 2012 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:
    *
    *   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.netty.handler.execution;
  
  
  import java.util.concurrent.Executor;
  import java.util.concurrent.ExecutorService;
  
  import org.jboss.netty.util.ExternalResourceReleasable;
  
  /**
   * A special {@link Executor} which allows to chain a series of
   * {@link Executor}s and {@link ChannelEventRunnableFilter}.
   */
  public class ChainedExecutor implements Executor, ExternalResourceReleasable {
  
      private final Executor cur;
      private final Executor next;
      private final ChannelEventRunnableFilter filter;
  
      /**
       * Create a new {@link ChainedExecutor} which will used the given
       * {@link ChannelEventRunnableFilter} to see if the {@link #cur} {@link Executor} should get
       * used.  Otherwise it will pass the work to the {@link #next} {@link Executor}
       *
       * @param filter  the {@link ChannelEventRunnableFilter} which will be used to check if the
       *                {@link ChannelEventRunnable} should be passed to the cur or next {@link Executor}
       * @param cur     the {@link Executor} to use if the {@link ChannelEventRunnableFilter} match
       * @param next    the {@link Executor} to use if the {@link ChannelEventRunnableFilter} does not match
       */
      public ChainedExecutor(ChannelEventRunnableFilter filter, Executor cur, Executor next) {
          if (filter == null) {
              throw new NullPointerException("filter");
          }
          if (cur == null) {
              throw new NullPointerException("cur");
          }
          if (next == null) {
              throw new NullPointerException("next");
          }
  
          this.filter = filter;
          this.cur = cur;
          this.next = next;
      }
  
      /**
       * Execute the passed {@link ChannelEventRunnable} with the current {@link Executor} if the
       * {@link ChannelEventRunnableFilter} match.  Otherwise pass it to the next {@link Executor} in
       * the chain.
       */
      public void execute(Runnable command) {
          assert command instanceof ChannelEventRunnable;
          if (filter.filter((ChannelEventRunnable) command)) {
              cur.execute(command);
          } else {
              next.execute(command);
          }
      }
  
      public void releaseExternalResources() {
          if (cur instanceof ExecutorService) {
              ((ExecutorService) cur).shutdown();
          }
          if (next instanceof ExecutorService) {
              ((ExecutorService) next).shutdown();
          }
          releaseExternal(cur);
          releaseExternal(next);
      }
  
      private static void releaseExternal(Executor executor) {
          if (executor instanceof ExternalResourceReleasable) {
              ((ExternalResourceReleasable) executor).releaseExternalResources();
          }
      }
  }