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   /*
    * Copyright 2016 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.kqueue;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.channel.Channel;
  import io.netty.channel.ChannelOutboundBuffer;
  import io.netty.channel.socket.InternetProtocolFamily;
  import io.netty.channel.socket.ServerSocketChannel;
  import io.netty.channel.socket.SocketChannel;
  import io.netty.channel.unix.IovArray;
  import io.netty.util.concurrent.GlobalEventExecutor;
  import io.netty.util.internal.UnstableApi;
  
  import java.net.InetSocketAddress;
  import java.net.SocketAddress;
  import java.util.concurrent.Executor;
  
  @UnstableApi
  public final class KQueueSocketChannel extends AbstractKQueueStreamChannel implements SocketChannel {
      private final KQueueSocketChannelConfig config;
  
      public KQueueSocketChannel() {
          super(null, BsdSocket.newSocketStream(), false);
          config = new KQueueSocketChannelConfig(this);
      }
  
      public KQueueSocketChannel(InternetProtocolFamily protocol) {
          super(null, BsdSocket.newSocketStream(protocol), false);
          config = new KQueueSocketChannelConfig(this);
      }
  
      public KQueueSocketChannel(int fd) {
          super(new BsdSocket(fd));
          config = new KQueueSocketChannelConfig(this);
      }
  
      KQueueSocketChannel(Channel parent, BsdSocket fd, InetSocketAddress remoteAddress) {
          super(parent, fd, remoteAddress);
          config = new KQueueSocketChannelConfig(this);
      }
  
      @Override
      public InetSocketAddress remoteAddress() {
          return (InetSocketAddress) super.remoteAddress();
      }
  
      @Override
      public InetSocketAddress localAddress() {
          return (InetSocketAddress) super.localAddress();
      }
  
      @Override
      public KQueueSocketChannelConfig config() {
          return config;
      }
  
      @Override
      public ServerSocketChannel parent() {
          return (ServerSocketChannel) super.parent();
      }
  
      @Override
      protected boolean doConnect0(SocketAddress remoteAddress, SocketAddress localAddress) throws Exception {
          if (config.isTcpFastOpenConnect()) {
              ChannelOutboundBuffer outbound = unsafe().outboundBuffer();
              outbound.addFlush();
              Object curr;
              if ((curr = outbound.current()) instanceof ByteBuf) {
                  ByteBuf initialData = (ByteBuf) curr;
                  // Don't bother with TCP FastOpen if we don't have any initial data to send anyway.
                  if (initialData.isReadable()) {
                      IovArray iov = new IovArray(config.getAllocator().directBuffer());
                      try {
                          iov.add(initialData, initialData.readerIndex(), initialData.readableBytes());
                          int bytesSent = socket.connectx(
                                  (InetSocketAddress) localAddress, (InetSocketAddress) remoteAddress, iov, true);
                          writeFilter(true);
                          outbound.removeBytes(Math.abs(bytesSent));
                          // The `connectx` method returns a negative number if connection is in-progress.
                          // So we should return `true` to indicate that connection was established, if it's positive.
                          return bytesSent > 0;
                      } finally {
                          iov.release();
                      }
                  }
             }
         }
         return super.doConnect0(remoteAddress, localAddress);
     }
 
     @Override
     protected AbstractKQueueUnsafe newUnsafe() {
         return new KQueueSocketChannelUnsafe();
     }
 
     private final class KQueueSocketChannelUnsafe extends KQueueStreamUnsafe {
         @Override
         protected Executor prepareToClose() {
             try {
                 // Check isOpen() first as otherwise it will throw a RuntimeException
                 // when call getSoLinger() as the fd is not valid anymore.
                 if (isOpen() && config().getSoLinger() > 0) {
                     // We need to cancel this key of the channel so we may not end up in a eventloop spin
                     // because we try to read or write until the actual close happens which may be later due
                     // SO_LINGER handling.
                     // See https://github.com/netty/netty/issues/4449
                     ((KQueueEventLoop) eventLoop()).remove(KQueueSocketChannel.this);
                     return GlobalEventExecutor.INSTANCE;
                 }
             } catch (Throwable ignore) {
                 // Ignore the error as the underlying channel may be closed in the meantime and so
                 // getSoLinger() may produce an exception. In this case we just return null.
                 // See https://github.com/netty/netty/issues/4449
             }
             return null;
         }
     }
 }