private ChannelFuture sendFile(ChannelHandlerContext ctx, Channel ch, FileChunk file)
      throws IOException {
    RandomAccessFile raf;
    try {
      raf = new RandomAccessFile(file.getFile(), "r");
    } catch (FileNotFoundException fnfe) {
      return null;
    }

    ChannelFuture writeFuture;
    if (ch.getPipeline().get(SslHandler.class) != null) {
      // Cannot use zero-copy with HTTPS.
      writeFuture = ch.write(new ChunkedFile(raf, file.startOffset(), file.length(), 8192));
    } else {
      // No encryption - use zero-copy.
      final FileRegion region =
          new DefaultFileRegion(raf.getChannel(), file.startOffset(), file.length());
      writeFuture = ch.write(region);
      writeFuture.addListener(
          new ChannelFutureListener() {
            public void operationComplete(ChannelFuture future) {
              region.releaseExternalResources();
            }
          });
    }

    return writeFuture;
  }