doc/html/boost_asio/example/cpp03/nonblocking/third_party_lib.cpp
//
// third_party_lib.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 <boost/asio.hpp>
#include <boost/array.hpp>
#include <boost/bind/bind.hpp>
#include <boost/shared_ptr.hpp>
#include <boost/enable_shared_from_this.hpp>
#include <iostream>
using boost::asio::ip::tcp;
namespace third_party_lib {
// Simulation of a third party library that wants to perform read and write
// operations directly on a socket. It needs to be polled to determine whether
// it requires a read or write operation, and notified when the socket is ready
// for reading or writing.
class session
{
public:
session(tcp::socket& socket)
: socket_(socket),
state_(reading)
{
}
// Returns true if the third party library wants to be notified when the
// socket is ready for reading.
bool want_read() const
{
return state_ == reading;
}
// Notify that third party library that it should perform its read operation.
void do_read(boost::system::error_code& ec)
{
if (std::size_t len = socket_.read_some(boost::asio::buffer(data_), ec))
{
write_buffer_ = boost::asio::buffer(data_, len);
state_ = writing;
}
}
// Returns true if the third party library wants to be notified when the
// socket is ready for writing.
bool want_write() const
{
return state_ == writing;
}
// Notify that third party library that it should perform its write operation.
void do_write(boost::system::error_code& ec)
{
if (std::size_t len = socket_.write_some(
boost::asio::buffer(write_buffer_), ec))
{
write_buffer_ = write_buffer_ + len;
state_ = boost::asio::buffer_size(write_buffer_) > 0 ? writing : reading;
}
}
private:
tcp::socket& socket_;
enum { reading, writing } state_;
boost::array<char, 128> data_;
boost::asio::const_buffer write_buffer_;
};
} // namespace third_party_lib
// The glue between asio's sockets and the third party library.
class connection
: public boost::enable_shared_from_this<connection>
{
public:
typedef boost::shared_ptr<connection> pointer;
static pointer create(const boost::asio::any_io_executor& ex)
{
return pointer(new connection(ex));
}
tcp::socket& socket()
{
return socket_;
}
void start()
{
// Put the socket into non-blocking mode.
socket_.non_blocking(true);
start_operations();
}
private:
connection(const boost::asio::any_io_executor& ex)
: socket_(ex),
session_impl_(socket_),
read_in_progress_(false),
write_in_progress_(false)
{
}
void start_operations()
{
// Start a read operation if the third party library wants one.
if (session_impl_.want_read() && !read_in_progress_)
{
read_in_progress_ = true;
socket_.async_wait(tcp::socket::wait_read,
boost::bind(&connection::handle_read,
shared_from_this(),
boost::asio::placeholders::error));
}
// Start a write operation if the third party library wants one.
if (session_impl_.want_write() && !write_in_progress_)
{
write_in_progress_ = true;
socket_.async_wait(tcp::socket::wait_write,
boost::bind(&connection::handle_write,
shared_from_this(),
boost::asio::placeholders::error));
}
}
void handle_read(boost::system::error_code ec)
{
read_in_progress_ = false;
// Notify third party library that it can perform a read.
if (!ec)
session_impl_.do_read(ec);
// The third party library successfully performed a read on the socket.
// Start new read or write operations based on what it now wants.
if (!ec || ec == boost::asio::error::would_block)
start_operations();
// Otherwise, an error occurred. Closing the socket cancels any outstanding
// asynchronous read or write operations. The connection object will be
// destroyed automatically once those outstanding operations complete.
else
socket_.close();
}
void handle_write(boost::system::error_code ec)
{
write_in_progress_ = false;
// Notify third party library that it can perform a write.
if (!ec)
session_impl_.do_write(ec);
// The third party library successfully performed a write on the socket.
// Start new read or write operations based on what it now wants.
if (!ec || ec == boost::asio::error::would_block)
start_operations();
// Otherwise, an error occurred. Closing the socket cancels any outstanding
// asynchronous read or write operations. The connection object will be
// destroyed automatically once those outstanding operations complete.
else
socket_.close();
}
private:
tcp::socket socket_;
third_party_lib::session session_impl_;
bool read_in_progress_;
bool write_in_progress_;
};
class server
{
public:
server(boost::asio::io_context& io_context, unsigned short port)
: acceptor_(io_context, tcp::endpoint(tcp::v4(), port))
{
start_accept();
}
private:
void start_accept()
{
connection::pointer new_connection =
connection::create(acceptor_.get_executor());
acceptor_.async_accept(new_connection->socket(),
boost::bind(&server::handle_accept, this, new_connection,
boost::asio::placeholders::error));
}
void handle_accept(connection::pointer new_connection,
const boost::system::error_code& error)
{
if (!error)
{
new_connection->start();
}
start_accept();
}
tcp::acceptor acceptor_;
};
int main(int argc, char* argv[])
{
try
{
if (argc != 2)
{
std::cerr << "Usage: third_party_lib <port>\n";
return 1;
}
boost::asio::io_context io_context;
using namespace std; // For atoi.
server s(io_context, atoi(argv[1]));
io_context.run();
}
catch (std::exception& e)
{
std::cerr << "Exception: " << e.what() << "\n";
}
return 0;
}