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- //
- // connection.hpp
- // ~~~~~~~~~~~~~~
- //
- // 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)
- //
- #ifndef SERIALIZATION_CONNECTION_HPP
- #define SERIALIZATION_CONNECTION_HPP
- #include <boost/asio.hpp>
- #include <boost/archive/text_iarchive.hpp>
- #include <boost/archive/text_oarchive.hpp>
- #include <boost/bind.hpp>
- #include <boost/shared_ptr.hpp>
- #include <boost/tuple/tuple.hpp>
- #include <iomanip>
- #include <string>
- #include <sstream>
- #include <vector>
- namespace s11n_example {
- /// The connection class provides serialization primitives on top of a socket.
- /**
- * Each message sent using this class consists of:
- * @li An 8-byte header containing the length of the serialized data in
- * hexadecimal.
- * @li The serialized data.
- */
- class connection
- {
- public:
- /// Constructor.
- connection(const boost::asio::executor& ex)
- : socket_(ex)
- {
- }
- /// Get the underlying socket. Used for making a connection or for accepting
- /// an incoming connection.
- boost::asio::ip::tcp::socket& socket()
- {
- return socket_;
- }
- /// Asynchronously write a data structure to the socket.
- template <typename T, typename Handler>
- void async_write(const T& t, Handler handler)
- {
- // Serialize the data first so we know how large it is.
- std::ostringstream archive_stream;
- boost::archive::text_oarchive archive(archive_stream);
- archive << t;
- outbound_data_ = archive_stream.str();
- // Format the header.
- std::ostringstream header_stream;
- header_stream << std::setw(header_length)
- << std::hex << outbound_data_.size();
- if (!header_stream || header_stream.str().size() != header_length)
- {
- // Something went wrong, inform the caller.
- boost::system::error_code error(boost::asio::error::invalid_argument);
- boost::asio::post(socket_.get_executor(), boost::bind(handler, error));
- return;
- }
- outbound_header_ = header_stream.str();
- // Write the serialized data to the socket. We use "gather-write" to send
- // both the header and the data in a single write operation.
- std::vector<boost::asio::const_buffer> buffers;
- buffers.push_back(boost::asio::buffer(outbound_header_));
- buffers.push_back(boost::asio::buffer(outbound_data_));
- boost::asio::async_write(socket_, buffers, handler);
- }
- /// Asynchronously read a data structure from the socket.
- template <typename T, typename Handler>
- void async_read(T& t, Handler handler)
- {
- // Issue a read operation to read exactly the number of bytes in a header.
- void (connection::*f)(
- const boost::system::error_code&,
- T&, boost::tuple<Handler>)
- = &connection::handle_read_header<T, Handler>;
- boost::asio::async_read(socket_, boost::asio::buffer(inbound_header_),
- boost::bind(f,
- this, boost::asio::placeholders::error, boost::ref(t),
- boost::make_tuple(handler)));
- }
- /// Handle a completed read of a message header. The handler is passed using
- /// a tuple since boost::bind seems to have trouble binding a function object
- /// created using boost::bind as a parameter.
- template <typename T, typename Handler>
- void handle_read_header(const boost::system::error_code& e,
- T& t, boost::tuple<Handler> handler)
- {
- if (e)
- {
- boost::get<0>(handler)(e);
- }
- else
- {
- // Determine the length of the serialized data.
- std::istringstream is(std::string(inbound_header_, header_length));
- std::size_t inbound_data_size = 0;
- if (!(is >> std::hex >> inbound_data_size))
- {
- // Header doesn't seem to be valid. Inform the caller.
- boost::system::error_code error(boost::asio::error::invalid_argument);
- boost::get<0>(handler)(error);
- return;
- }
- // Start an asynchronous call to receive the data.
- inbound_data_.resize(inbound_data_size);
- void (connection::*f)(
- const boost::system::error_code&,
- T&, boost::tuple<Handler>)
- = &connection::handle_read_data<T, Handler>;
- boost::asio::async_read(socket_, boost::asio::buffer(inbound_data_),
- boost::bind(f, this,
- boost::asio::placeholders::error, boost::ref(t), handler));
- }
- }
- /// Handle a completed read of message data.
- template <typename T, typename Handler>
- void handle_read_data(const boost::system::error_code& e,
- T& t, boost::tuple<Handler> handler)
- {
- if (e)
- {
- boost::get<0>(handler)(e);
- }
- else
- {
- // Extract the data structure from the data just received.
- try
- {
- std::string archive_data(&inbound_data_[0], inbound_data_.size());
- std::istringstream archive_stream(archive_data);
- boost::archive::text_iarchive archive(archive_stream);
- archive >> t;
- }
- catch (std::exception& e)
- {
- // Unable to decode data.
- boost::system::error_code error(boost::asio::error::invalid_argument);
- boost::get<0>(handler)(error);
- return;
- }
- // Inform caller that data has been received ok.
- boost::get<0>(handler)(e);
- }
- }
- private:
- /// The underlying socket.
- boost::asio::ip::tcp::socket socket_;
- /// The size of a fixed length header.
- enum { header_length = 8 };
- /// Holds an outbound header.
- std::string outbound_header_;
- /// Holds the outbound data.
- std::string outbound_data_;
- /// Holds an inbound header.
- char inbound_header_[header_length];
- /// Holds the inbound data.
- std::vector<char> inbound_data_;
- };
- typedef boost::shared_ptr<connection> connection_ptr;
- } // namespace s11n_example
- #endif // SERIALIZATION_CONNECTION_HPP
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