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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:
    *
    *   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.channel.local;
  
  import io.netty.channel.AbstractServerChannel;
  import io.netty.channel.ChannelConfig;
  import io.netty.channel.ChannelPipeline;
  import io.netty.channel.DefaultChannelConfig;
  import io.netty.channel.EventLoop;
  import io.netty.channel.PreferHeapByteBufAllocator;
  import io.netty.channel.RecvByteBufAllocator;
  import io.netty.channel.ServerChannel;
  import io.netty.channel.ServerChannelRecvByteBufAllocator;
  import io.netty.channel.SingleThreadEventLoop;
  import io.netty.util.concurrent.SingleThreadEventExecutor;
  
  import java.net.SocketAddress;
  import java.util.ArrayDeque;
  import java.util.Queue;
  
  /**
   * A {@link ServerChannel} for the local transport which allows in VM communication.
   */
  public class LocalServerChannel extends AbstractServerChannel {
  
      private final ChannelConfig config =
              new DefaultChannelConfig(this, new ServerChannelRecvByteBufAllocator()) { };
      private final Queue<Object> inboundBuffer = new ArrayDeque<Object>();
      private final Runnable shutdownHook = new Runnable() {
          @Override
          public void run() {
              unsafe().close(unsafe().voidPromise());
          }
      };
  
      private volatile int state; // 0 - open, 1 - active, 2 - closed
      private volatile LocalAddress localAddress;
      private volatile boolean acceptInProgress;
  
      public LocalServerChannel() {
          config().setAllocator(new PreferHeapByteBufAllocator(config.getAllocator()));
      }
  
      @Override
      public ChannelConfig config() {
          return config;
      }
  
      @Override
      public LocalAddress localAddress() {
          return (LocalAddress) super.localAddress();
      }
  
      @Override
      public LocalAddress remoteAddress() {
          return (LocalAddress) super.remoteAddress();
      }
  
      @Override
      public boolean isOpen() {
          return state < 2;
      }
  
      @Override
      public boolean isActive() {
          return state == 1;
      }
  
      @Override
      protected boolean isCompatible(EventLoop loop) {
          return loop instanceof SingleThreadEventLoop;
      }
  
      @Override
      protected SocketAddress localAddress0() {
          return localAddress;
      }
  
      @Override
      protected void doRegister() throws Exception {
          ((SingleThreadEventExecutor) eventLoop()).addShutdownHook(shutdownHook);
      }
  
      @Override
      protected void doBind(SocketAddress localAddress) throws Exception {
          this.localAddress = LocalChannelRegistry.register(this, this.localAddress, localAddress);
         state = 1;
     }
 
     @Override
     protected void doClose() throws Exception {
         if (state <= 1) {
             // Update all internal state before the closeFuture is notified.
             if (localAddress != null) {
                 LocalChannelRegistry.unregister(localAddress);
                 localAddress = null;
             }
             state = 2;
         }
     }
 
     @Override
     protected void doDeregister() throws Exception {
         ((SingleThreadEventExecutor) eventLoop()).removeShutdownHook(shutdownHook);
     }
 
     @Override
     protected void doBeginRead() throws Exception {
         if (acceptInProgress) {
             return;
         }
 
         Queue<Object> inboundBuffer = this.inboundBuffer;
         if (inboundBuffer.isEmpty()) {
             acceptInProgress = true;
             return;
         }
 
         readInbound();
     }
 
     LocalChannel serve(final LocalChannel peer) {
         final LocalChannel child = newLocalChannel(peer);
         if (eventLoop().inEventLoop()) {
             serve0(child);
         } else {
             eventLoop().execute(new Runnable() {
                 @Override
                 public void run() {
                     serve0(child);
                 }
             });
         }
         return child;
     }
 
     private void readInbound() {
         RecvByteBufAllocator.Handle handle = unsafe().recvBufAllocHandle();
         handle.reset(config());
         ChannelPipeline pipeline = pipeline();
         do {
             Object m = inboundBuffer.poll();
             if (m == null) {
                 break;
             }
             pipeline.fireChannelRead(m);
         } while (handle.continueReading());
         handle.readComplete();
         pipeline.fireChannelReadComplete();
     }
 
     /**
      * A factory method for {@link LocalChannel}s. Users may override it
      * to create custom instances of {@link LocalChannel}s.
      */
     protected LocalChannel newLocalChannel(LocalChannel peer) {
         return new LocalChannel(this, peer);
     }
 
     private void serve0(final LocalChannel child) {
         inboundBuffer.add(child);
         if (acceptInProgress) {
             acceptInProgress = false;
 
             readInbound();
         }
     }
 }