boost_1_45_0/libs/asio/doc/overview/reactor.qbk

[/
 / Copyright (c) 2003-2010 Christopher M. Kohlhoff (chris at kohlhoff dot com)
 /
 / Distributed under the Boost Software License, Version 1.0. (See accompanying
 / file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
 /]

[section:reactor Reactor-Style Operations]

Sometimes a program must be integrated with a third-party library that wants to
perform the I/O operations itself. To facilitate this, Boost.Asio includes a
`null_buffers` type that can be used with both read and write operations. A
`null_buffers` operation doesn't return until the I/O object is "ready" to
perform the operation.

As an example, to perform a non-blocking read something like the
following may be used:

  ip::tcp::socket socket(my_io_service);
  ...
  ip::tcp::socket::non_blocking nb(true);
  socket.io_control(nb);
  ...
  socket.async_read_some(null_buffers(), read_handler);
  ...
  void read_handler(boost::system::error_code ec)
  {
    if (!ec)
    {
      std::vector<char> buf(socket.available());
      socket.read_some(buffer(buf));
    }
  }
  
These operations are supported for sockets on all platforms, and for the POSIX
stream-oriented descriptor classes.

[heading See Also]

[link boost_asio.reference.null_buffers null_buffers],
[link boost_asio.examples.nonblocking nonblocking example].

[endsect]