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//
// connection.hpp
// ~~~~~~~~~~~~~~
//
// Copyright (c) 2003-2018 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(boost::asio::io_context& io_context)
: socket_(io_context)
{
}
/// 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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