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//
// protocol.hpp
// ~~~~~~~~~~~~
//
// Copyright (c) 2003-2012 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 PORTHOPPER_PROTOCOL_HPP
#define PORTHOPPER_PROTOCOL_HPP
#include <boost/array.hpp>
#include <boost/asio.hpp>
#include <cstring>
#include <iomanip>
#include <string>
#include <strstream>
// This request is sent by the client to the server over a TCP connection.
// The client uses it to perform three functions:
// - To request that data start being sent to a given port.
// - To request that data is no longer sent to a given port.
// - To change the target port to another.
class control_request
{
public:
// Construct an empty request. Used when receiving.
control_request()
{
}
// Create a request to start sending data to a given port.
static const control_request start(unsigned short port)
{
return control_request(0, port);
}
// Create a request to stop sending data to a given port.
static const control_request stop(unsigned short port)
{
return control_request(port, 0);
}
// Create a request to change the port that data is sent to.
static const control_request change(
unsigned short old_port, unsigned short new_port)
{
return control_request(old_port, new_port);
}
// Get the old port. Returns 0 for start requests.
unsigned short old_port() const
{
std::istrstream is(data_, encoded_port_size);
unsigned short port = 0;
is >> std::setw(encoded_port_size) >> std::hex >> port;
return port;
}
// Get the new port. Returns 0 for stop requests.
unsigned short new_port() const
{
std::istrstream is(data_ + encoded_port_size, encoded_port_size);
unsigned short port = 0;
is >> std::setw(encoded_port_size) >> std::hex >> port;
return port;
}
// Obtain buffers for reading from or writing to a socket.
boost::array<boost::asio::mutable_buffer, 1> to_buffers()
{
boost::array<boost::asio::mutable_buffer, 1> buffers
= { { boost::asio::buffer(data_) } };
return buffers;
}
private:
// Construct with specified old and new ports.
control_request(unsigned short old_port_number,
unsigned short new_port_number)
{
std::ostrstream os(data_, control_request_size);
os << std::setw(encoded_port_size) << std::hex << old_port_number;
os << std::setw(encoded_port_size) << std::hex << new_port_number;
}
// The length in bytes of a control_request and its components.
enum
{
encoded_port_size = 4, // 16-bit port in hex.
control_request_size = encoded_port_size * 2
};
// The encoded request data.
char data_[control_request_size];
};
// This frame is sent from the server to subscribed clients over UDP.
class frame
{
public:
// The maximum allowable length of the payload.
enum { payload_size = 32 };
// Construct an empty frame. Used when receiving.
frame()
{
}
// Construct a frame with specified frame number and payload.
frame(unsigned long frame_number, const std::string& payload_data)
{
std::ostrstream os(data_, frame_size);
os << std::setw(encoded_number_size) << std::hex << frame_number;
os << std::setw(payload_size)
<< std::setfill(' ') << payload_data.substr(0, payload_size);
}
// Get the frame number.
unsigned long number() const
{
std::istrstream is(data_, encoded_number_size);
unsigned long frame_number = 0;
is >> std::setw(encoded_number_size) >> std::hex >> frame_number;
return frame_number;
}
// Get the payload data.
const std::string payload() const
{
return std::string(data_ + encoded_number_size, payload_size);
}
// Obtain buffers for reading from or writing to a socket.
boost::array<boost::asio::mutable_buffer, 1> to_buffers()
{
boost::array<boost::asio::mutable_buffer, 1> buffers
= { { boost::asio::buffer(data_) } };
return buffers;
}
private:
// The length in bytes of a frame and its components.
enum
{
encoded_number_size = 8, // Frame number in hex.
frame_size = encoded_number_size + payload_size
};
// The encoded frame data.
char data_[frame_size];
};
#endif // PORTHOPPER_PROTOCOL_HPP
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