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The coroutine
class provides support for stackless coroutines. Stackless coroutines enable
programs to implement asynchronous logic in a synchronous manner, with
minimal overhead, as shown in the following example:
struct session : boost::asio::coroutine
{
boost::shared_ptr<tcp::socket> socket_;
boost::shared_ptr<std::vector<char> > buffer_;
session(boost::shared_ptr<tcp::socket> socket)
: socket_(socket),
buffer_(new std::vector<char>(1024))
{
}
void operator()(boost::system::error_code ec = boost::system::error_code(), std::size_t n = 0)
{
if (!ec) reenter (this)
{
for (;;)
{
yield socket_->async_read_some(boost::asio::buffer(*buffer_), *this);
yield boost::asio::async_write(*socket_, boost::asio::buffer(*buffer_, n), *this);
}
}
}
};
The coroutine class is used in conjunction with the pseudo-keywords
reenter, yield and fork. These are
preprocessor macros, and are implemented in terms of a switch
statement using a technique similar to Duff's Device. The coroutine
class's documentation provides a complete description of these pseudo-keywords.