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- //
- // third_party_lib.cpp
- // ~~~~~~~~~~~~~~~~~~~
- //
- // Copyright (c) 2003-2019 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 <array>
- #include <iostream>
- #include <memory>
- 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)
- {
- }
- // 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_ = reading;
- std::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 std::enable_shared_from_this<connection>
- {
- public:
- connection(tcp::socket socket)
- : socket_(std::move(socket))
- {
- }
- void start()
- {
- // Put the socket into non-blocking mode.
- socket_.non_blocking(true);
- do_operations();
- }
- private:
- void do_operations()
- {
- auto self(shared_from_this());
- // 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,
- [this, self](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)
- do_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();
- });
- }
- // 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,
- [this, self](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)
- do_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_{socket_};
- bool read_in_progress_ = false;
- bool write_in_progress_ = false;
- };
- class server
- {
- public:
- server(boost::asio::io_context& io_context, unsigned short port)
- : acceptor_(io_context, {tcp::v4(), port})
- {
- do_accept();
- }
- private:
- void do_accept()
- {
- acceptor_.async_accept(
- [this](boost::system::error_code ec, tcp::socket socket)
- {
- if (!ec)
- {
- std::make_shared<connection>(std::move(socket))->start();
- }
- do_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;
- server s(io_context, std::atoi(argv[1]));
- io_context.run();
- }
- catch (std::exception& e)
- {
- std::cerr << "Exception: " << e.what() << "\n";
- }
- return 0;
- }
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