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   /*
    * Copyright 2014 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.example.file;
  
  import io.netty.channel.ChannelFutureListener;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.channel.DefaultFileRegion;
  import io.netty.channel.SimpleChannelInboundHandler;
  import io.netty.handler.ssl.SslHandler;
  import io.netty.handler.stream.ChunkedFile;
  
  import java.io.RandomAccessFile;
  
  public class FileServerHandler extends SimpleChannelInboundHandler<String> {
  
      @Override
      public void channelActive(ChannelHandlerContext ctx) {
          ctx.writeAndFlush("HELLO: Type the path of the file to retrieve.\n");
      }
  
      @Override
      public void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
          RandomAccessFile raf = null;
          long length = -1;
          try {
              raf = new RandomAccessFile(msg, "r");
              length = raf.length();
          } catch (Exception e) {
              ctx.writeAndFlush("ERR: " + e.getClass().getSimpleName() + ": " + e.getMessage() + '\n');
              return;
          } finally {
              if (length < 0 && raf != null) {
                  raf.close();
              }
          }
  
          ctx.write("OK: " + raf.length() + '\n');
          if (ctx.pipeline().get(SslHandler.class) == null) {
              // SSL not enabled - can use zero-copy file transfer.
              ctx.write(new DefaultFileRegion(raf.getChannel(), 0, length));
          } else {
              // SSL enabled - cannot use zero-copy file transfer.
              ctx.write(new ChunkedFile(raf));
          }
          ctx.writeAndFlush("\n");
      }
  
      @Override
      public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
          cause.printStackTrace();
  
          if (ctx.channel().isActive()) {
              ctx.writeAndFlush("ERR: " +
                      cause.getClass().getSimpleName() + ": " +
                      cause.getMessage() + '\n').addListener(ChannelFutureListener.CLOSE);
          }
      }
  }