use poll instead of select in waitForFrame to allow for large fds

Fixes #65

.gitignore

@@ -0,0 +1 @@
+.DS_Store

go.mod

@@ -0,0 +1,5 @@
+module github.com/blackjack/webcam
+
+go 1.18
+
+require golang.org/x/sys v0.14.0

go.sum

@@ -0,0 +1,2 @@
+golang.org/x/sys v0.14.0 h1:Vz7Qs629MkJkGyHxUlRHizWJRG2j8fbQKjELVSNhy7Q=
+golang.org/x/sys v0.14.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=

v4l2.go

@@ -557,19 +557,9 @@ func stopStreaming(fd uintptr) (err error) {
 
 }
 
-func waitForFrame(fd uintptr, timeout uint32) (count int, err error) {
-
+func waitForFrame(pollFds []unix.PollFd, timeout uint32) (count int, err error) {
 	for {
-		fds := &unix.FdSet{}
-		fds.Set(int(fd))
-
-		var oneSecInNsec int64 = 1e9
-		timeoutNsec := int64(timeout) * oneSecInNsec
-		nativeTimeVal := unix.NsecToTimeval(timeoutNsec)
-		tv := &nativeTimeVal
-
-		count, err = unix.Select(int(fd+1), fds, nil, nil, tv)
-
+		count, err = unix.Poll(pollFds, int(timeout*1000))
 		if count < 0 && err == unix.EINTR {
 			continue
 		}

webcam.go

@@ -17,6 +17,7 @@ type Webcam struct {
 	bufcount  uint32
 	buffers   [][]byte
 	streaming bool
+	pollFds   []unix.PollFd
 }
 
 type ControlID uint32
@@ -58,6 +59,7 @@ func Open(path string) (*Webcam, error) {
 	w := new(Webcam)
 	w.fd = fd
 	w.bufcount = 256
+	w.pollFds = []unix.PollFd{{Fd: int32(fd), Events: unix.POLLIN}}
 	return w, nil
 }
 
@@ -294,7 +296,7 @@ func (w *Webcam) ReleaseFrame(index uint32) error {
 // Wait until frame could be read
 func (w *Webcam) WaitForFrame(timeout uint32) error {
 
-	count, err := waitForFrame(w.fd, timeout)
+	count, err := waitForFrame(w.pollFds, timeout)
 
 	if count < 0 || err != nil {
 		return err