Port série tout ça : LA solution propre via BOOST::ASIO

Marsh Posté le 07-10-2008 à 08:47:39

J'en avais un peu plein les fesses de ces 901085401654.464 topic sur le port série en C ou en C++.
Je reporte ici un exemple minimaliste proposé par Jeff Gray sur la mailing list boost
qui utilise ASIO pour faire ce genre de chose.

Il nécessite boost 1.36 ou ultérieur pour compiler.

Code :

/* minicom.cpp
A simple demonstration minicom client with Boost asio
Parameters:
baud rate
serial port (eg /dev/ttyS0 or COM1)
To end the application, send Ctrl-C on standard input
*/
#include <deque>
#include <iostream>
#include <boost/bind.hpp>
#include <boost/asio.hpp>
#include <boost/asio/serial_port.hpp>
#include <boost/thread.hpp>
#include <boost/lexical_cast.hpp>
#include <boost/date_time/posix_time/posix_time_types.hpp>
#ifdef POSIX
#include <termios.h>
#endif
using namespace std;
class minicom_client
{
public:
minicom_client(boost::asio::io_service& io_service, unsigned int baud, const string& device)
: active_(true),
io_service_(io_service),
serialPort(io_service, device)
{
if (!serialPort.is_open())
{
cerr << "Failed to open serial port\n";
return;
}
boost::asio::serial_port_base::baud_rate baud_option(baud);
serialPort.set_option(baud_option); // set the baud rate after the port has been opened
read_start();
}
void write(const char msg) // pass the write data to the do_write function via the io service in the other thread
{
io_service_.post(boost::bind(&minicom_client::do_write, this, msg));
}
void close() // call the do_close function via the io service in the other thread
{
io_service_.post(boost::bind(&minicom_client::do_close, this, boost::system::error_code()));
}
bool active() // return true if the socket is still active
{
return active_;
}
private:
static const int max_read_length = 512; // maximum amount of data to read in one operation
void read_start(void)
{ // Start an asynchronous read and call read_complete when it completes or fails
serialPort.async_read_some(boost::asio::buffer(read_msg_, max_read_length),
boost::bind(&minicom_client::read_complete,
this,
boost::asio::placeholders::error,
boost::asio::placeholders::bytes_transferred));
}
void read_complete(const boost::system::error_code& error, size_t bytes_transferred)
{ // the asynchronous read operation has now completed or failed and returned an error
if (!error)
{ // read completed, so process the data
cout.write(read_msg_, bytes_transferred); // echo to standard output
read_start(); // start waiting for another asynchronous read again
}
else
do_close(error);
}
void do_write(const char msg)
{ // callback to handle write call from outside this class
bool write_in_progress = !write_msgs_.empty(); // is there anything currently being written?
write_msgs_.push_back(msg); // store in write buffer
if (!write_in_progress) // if nothing is currently being written, then start
write_start();
}
void write_start(void)
{ // Start an asynchronous write and call write_complete when it completes or fails
boost::asio::async_write(serialPort,
boost::asio::buffer(&write_msgs_.front(), 1),
boost::bind(&minicom_client::write_complete,
this,
boost::asio::placeholders::error));
}
void write_complete(const boost::system::error_code& error)
{ // the asynchronous read operation has now completed or failed and returned an error
if (!error)
{ // write completed, so send next write data
write_msgs_.pop_front(); // remove the completed data
if (!write_msgs_.empty()) // if there is anthing left to be written
write_start(); // then start sending the next item in the buffer
}
else
do_close(error);
}
void do_close(const boost::system::error_code& error)
{ // something has gone wrong, so close the socket & make this object inactive
if (error == boost::asio::error::operation_aborted) // if this call is the result of a timer cancel()
return; // ignore it because the connection cancelled the timer
if (error)
cerr << "Error: " << error.message() << endl; // show the error message
else
cout << "Error: Connection did not succeed.\n";
cout << "Press Enter to exit\n";
serialPort.close();
active_ = false;
}
private:
bool active_; // remains true while this object is still operating
boost::asio::io_service& io_service_; // the main IO service that runs this connection
boost::asio::serial_port serialPort; // the serial port this instance is connected to
char read_msg_[max_read_length]; // data read from the socket
deque<char> write_msgs_; // buffered write data
};
int main(int argc, char* argv[])
{
// on Unix POSIX based systems, turn off line buffering of input, so cin.get() returns after every keypress
// On other systems, you'll need to look for an equivalent
#ifdef POSIX
termios stored_settings;
tcgetattr(0, &stored_settings);
termios new_settings = stored_settings;
new_settings.c_lflag &= (~ICANON);
new_settings.c_lflag &= (~ISIG); // don't automatically handle control-C
tcsetattr(0, TCSANOW, &new_settings);
#endif
try
{
if (argc != 3)
{
cerr << "Usage: minicom <baud> <device>\n";
return 1;
}
boost::asio::io_service io_service;
// define an instance of the main class of this program
minicom_client c(io_service, boost::lexical_cast<unsigned int>(argv[1]), argv[2]);
// run the IO service as a separate thread, so the main thread can block on standard input
boost::thread t(boost::bind(&boost::asio::io_service::run, &io_service));
while (c.active()) // check the internal state of the connection to make sure it's still running
{
char ch;
cin.get(ch); // blocking wait for standard input
if (ch == 3) // ctrl-C to end program
break;
c.write(ch);
}
c.close(); // close the minicom client connection
t.join(); // wait for the IO service thread to close
}
catch (exception& e)
{
cerr << "Exception: " << e.what() << "\n";
}
#ifdef POSIX // restore default buffering of standard input
tcsetattr(0, TCSANOW, &stored_settings);
#endif
return 0;
}

Le code devrait être assez claire au vue des noms des méthodes et des commentaires.

Marsh Posté le 07-10-2008 à 08:47:39

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