doc/html/boost_asio/example/cpp03/http/server4/server.cpp
//
// server.cpp
// ~~~~~~~~~~
//
// Copyright (c) 2003-2023 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)
//
#include "server.hpp"
#include "request.hpp"
#include "reply.hpp"
namespace http {
namespace server4 {
server::server(boost::asio::io_context& io_context,
const std::string& address, const std::string& port,
boost::function<void(const request&, reply&)> request_handler)
: request_handler_(request_handler)
{
tcp::resolver resolver(io_context);
boost::asio::ip::tcp::endpoint endpoint =
*resolver.resolve(address, port).begin();
acceptor_.reset(new tcp::acceptor(io_context, endpoint));
}
// Enable the pseudo-keywords reenter, yield and fork.
#include <boost/asio/yield.hpp>
void server::operator()(boost::system::error_code ec, std::size_t length)
{
// In this example we keep the error handling code in one place by
// hoisting it outside the coroutine. An alternative approach would be to
// check the value of ec after each yield for an asynchronous operation.
if (!ec)
{
// On reentering a coroutine, control jumps to the location of the last
// yield or fork. The argument to the "reenter" pseudo-keyword can be a
// pointer or reference to an object of type coroutine.
reenter (this)
{
// Loop to accept incoming connections.
do
{
// Create a new socket for the next incoming connection.
socket_.reset(new tcp::socket(acceptor_->get_executor()));
// Accept a new connection. The "yield" pseudo-keyword saves the current
// line number and exits the coroutine's "reenter" block. We use the
// server coroutine as the completion handler for the async_accept
// operation. When the asynchronous operation completes, the io_context
// invokes the function call operator, we "reenter" the coroutine, and
// then control resumes at the following line.
yield acceptor_->async_accept(*socket_, *this);
// We "fork" by cloning a new server coroutine to handle the connection.
// After forking we have a parent coroutine and a child coroutine. Both
// parent and child continue execution at the following line. They can
// be distinguished using the functions coroutine::is_parent() and
// coroutine::is_child().
fork server(*this)();
// The parent continues looping to accept the next incoming connection.
// The child exits the loop and processes the connection.
} while (is_parent());
// Create the objects needed to receive a request on the connection.
buffer_.reset(new boost::array<char, 8192>);
request_.reset(new request);
// Loop until a complete request (or an invalid one) has been received.
do
{
// Receive some more data. When control resumes at the following line,
// the ec and length parameters reflect the result of the asynchronous
// operation.
yield socket_->async_read_some(boost::asio::buffer(*buffer_), *this);
// Parse the data we just received.
boost::tie(valid_request_, boost::tuples::ignore)
= request_parser_.parse(*request_,
buffer_->data(), buffer_->data() + length);
// An indeterminate result means we need more data, so keep looping.
} while (boost::indeterminate(valid_request_));
// Create the reply object that will be sent back to the client.
reply_.reset(new reply);
if (valid_request_)
{
// A valid request was received. Call the user-supplied function object
// to process the request and compose a reply.
request_handler_(*request_, *reply_);
}
else
{
// The request was invalid.
*reply_ = reply::stock_reply(reply::bad_request);
}
// Send the reply back to the client.
yield boost::asio::async_write(*socket_, reply_->to_buffers(), *this);
// Initiate graceful connection closure.
socket_->shutdown(tcp::socket::shutdown_both, ec);
}
}
// If an error occurs then the coroutine is not reentered. Consequently, no
// new asynchronous operations are started. This means that all shared_ptr
// references will disappear and the resources associated with the coroutine
// will be destroyed automatically after this function call returns.
}
// Disable the pseudo-keywords reenter, yield and fork.
#include <boost/asio/unyield.hpp>
} // namespace server4
} // namespace http