joystick.cc

#include <iomanip>
#include <iostream>
#include <boost/asio.hpp>
#include <boost/bind.hpp>

extern "C" {
#include <fcntl.h>
#include <linux/joystick.h>
#include <sys/ioctl.h>
#include <unistd.h>
}

class joystick {
public:
  joystick(boost::asio::io_service& io_service, int fd) : joystick_(io_service, fd) {
    boost::asio::async_read(
        joystick_, buffer_, boost::asio::transfer_exactly(sizeof(js_event)),
        boost::bind(&joystick::handle_read, this, boost::asio::placeholders::error,
                    boost::asio::placeholders::bytes_transferred));
  }

  ~joystick() {
    joystick_.close();
  }

private:
  void handle_read(const boost::system::error_code& error, std::size_t bytes_transferred) {
    if (error) {
      std::cerr << "error: " << error.message() << std::endl;
      return;
    }

    if (bytes_transferred == sizeof(js_event)) {
      auto jse = boost::asio::buffer_cast<const js_event*>(buffer_.data());

      switch (jse->type & ~JS_EVENT_INIT) {
        case JS_EVENT_BUTTON:
          std::cout << "button: ";
          break;
        case JS_EVENT_AXIS:
          std::cout << "  axis: ";
          break;
      }

      std::cout << std::setw(2) << static_cast<int>(jse->number) << ", value: " << jse->value
                << std::endl;
    }

    buffer_.consume(bytes_transferred);

    boost::asio::async_read(
        joystick_, buffer_, boost::asio::transfer_exactly(sizeof(js_event)),
        boost::bind(&joystick::handle_read, this, boost::asio::placeholders::error,
                    boost::asio::placeholders::bytes_transferred));
  }

  boost::asio::posix::stream_descriptor joystick_;
  boost::asio::streambuf buffer_;
};

auto main(int argc, char** argv) -> int {
  if (argc != 2) {
    std::cerr << "Usage: " << argv[0] << " <device>" << std::endl;
    return -1;
  }

  const auto fd = open(argv[1], O_RDONLY);
  if (fd < 0) {
    std::cerr << "Cannot open " << argv[1] << ": " << strerror(errno) << std::endl;
    return -1;
  }

  {
    char name[255];
    int axes, buttons;
    ioctl(fd, JSIOCGNAME(255), name);
    ioctl(fd, JSIOCGAXES, &axes);
    ioctl(fd, JSIOCGBUTTONS, &buttons);

    std::cout << name << ": " << axes << " axes/" << buttons << " buttons" << std::endl;
  }

  boost::asio::io_service io_service;

  joystick j(io_service, fd);

  io_service.run();
}