// Create a new inotify poller.
// This creates an inotify handler, and an epoll handler.
func newFdPoller(fd int) (*fdPoller, error) {
var errno error
poller := emptyPoller(fd)
defer func() {
if errno != nil {
poller.close()
}
}()
poller.fd = fd
// Create epoll fd
poller.epfd, errno = unix.EpollCreate1(0)
if poller.epfd == -1 {
return nil, errno
}
// Create pipe; pipe[0] is the read end, pipe[1] the write end.
errno = unix.Pipe2(poller.pipe[:], unix.O_NONBLOCK)
if errno != nil {
return nil, errno
}
// Register inotify fd with epoll
event := unix.EpollEvent{
Fd: int32(poller.fd),
Events: unix.EPOLLIN,
}
errno = unix.EpollCtl(poller.epfd, unix.EPOLL_CTL_ADD, poller.fd, &event)
if errno != nil {
return nil, errno
}
// Register pipe fd with epoll
event = unix.EpollEvent{
Fd: int32(poller.pipe[0]),
Events: unix.EPOLLIN,
}
errno = unix.EpollCtl(poller.epfd, unix.EPOLL_CTL_ADD, poller.pipe[0], &event)
if errno != nil {
return nil, errno
}
return poller, 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
}