func (m Monitor) Fd() error {
err := C.udev_monitor_get_fd(m.ptr)
if err == 0 {
return nil
}
return Error(err)
}
func MonitorUdev(subsystem string) (*Monitor, error) {
cName := C.CString("udev")
defer C.free(unsafe.Pointer(cName))
udev := C.udev_new()
udev_monitor := C.udev_monitor_new_from_netlink(udev, cName)
if udev_monitor == nil {
C.udev_unref(udev)
return nil, Error{"udev_monitor_new_from_netlink"}
}
if subsystem != "" {
cSubsystem := C.CString(subsystem)
defer C.free(unsafe.Pointer(cSubsystem))
if C.udev_monitor_filter_add_match_subsystem_devtype(udev_monitor, cSubsystem, nil) < 0 {
C.udev_monitor_unref(udev_monitor)
C.udev_unref(udev)
return nil, Error{"udev_monitor_filter_add_match_subsystem_devtype"}
}
}
if C.udev_monitor_enable_receiving(udev_monitor) < 0 {
C.udev_monitor_unref(udev_monitor)
C.udev_unref(udev)
return nil, Error{"udev_monitor_enable_receiving"}
}
// set blocking
if fd := C.udev_monitor_get_fd(udev_monitor); fd < 0 {
C.udev_monitor_unref(udev_monitor)
C.udev_unref(udev)
return nil, Error{"udev_monitor_get_fd"}
} else if err := syscall.SetNonblock(int(fd), false); err != nil {
C.udev_monitor_unref(udev_monitor)
C.udev_unref(udev)
return nil, err
}
return &Monitor{udev, udev_monitor}, nil
}
// DeviceChan binds the udev_monitor socket to the event source and spawns a
// goroutine. The goroutine efficiently waits on the monitor socket using epoll.
// Data is received from the udev monitor socket and a new Device is created
// with the data received. Pointers to the device are sent on the returned channel.
// The function takes a done signalling channel as a parameter, which when
// triggered will stop the goroutine and close the device channel.
// Only socket connections with uid=0 are accepted.
func (m *Monitor) DeviceChan(done <-chan struct{}) (<-chan *Device, error) {
var event unix.EpollEvent
var events [maxEpollEvents]unix.EpollEvent
// Lock the context
m.lock()
defer m.unlock()
// Enable receiving
if C.udev_monitor_enable_receiving(m.ptr) != 0 {
return nil, errors.New("udev: udev_monitor_enable_receiving failed")
}
// Set the fd to non-blocking
fd := C.udev_monitor_get_fd(m.ptr)
if e := unix.SetNonblock(int(fd), true); e != nil {
return nil, errors.New("udev: unix.SetNonblock failed")
}
// Create an epoll fd
epfd, e := unix.EpollCreate1(0)
if e != nil {
return nil, errors.New("udev: unix.EpollCreate1 failed")
}
// Add the fd to the epoll fd
event.Events = unix.EPOLLIN | unix.EPOLLET
event.Fd = int32(fd)
if e = unix.EpollCtl(epfd, unix.EPOLL_CTL_ADD, int(fd), &event); e != nil {
return nil, errors.New("udev: unix.EpollCtl failed")
}
// Create the channel
ch := make(chan *Device)
// Create goroutine to epoll the fd
go func(done <-chan struct{}, fd int32) {
// Close the epoll fd when goroutine exits
defer unix.Close(epfd)
// Close the channel when goroutine exits
defer close(ch)
// Loop forever
for {
// Poll the file descriptor
nevents, e := unix.EpollWait(epfd, events[:], epollTimeout)
if e != nil {
return
}
// Process events
for ev := 0; ev < nevents; ev++ {
if events[ev].Fd == fd {
if (events[ev].Events & unix.EPOLLIN) != 0 {
for d := m.receiveDevice(); d != nil; d = m.receiveDevice() {
ch <- d
}
}
}
}
// Check for done signal
select {
case <-done:
return
default:
}
}
}(done, int32(fd))
return ch, nil
}