nchronous operations, in a way that is transparent
            to the user of the socket object. The following example illustrates how
            Linux's <code class="computeroutput">sendfile</code> system call might be encapsulated:
          </p>
<pre class="programlisting">template &lt;typename Handler&gt;
struct sendfile_op
{
  tcp::socket&amp; sock_;
  int fd_;
  Handler handler_;
  off_t offset_;
  std::size_t total_bytes_transferred_;

  // Function call operator meeting WriteHandler requirements.
 