From e9ad39d87c837d0e7a8646b19f4971cc79ee15dc Mon Sep 17 00:00:00 2001
From: Eric Daniels <eric@erdaniels.com>
Date: Sun, 5 Nov 2023 17:42:46 -0500
Subject: [PATCH] use poll instead of select in waitForFrame to allow for large
 fds

Fixes #65
---
 .gitignore |  1 +
 go.mod     |  5 +++++
 go.sum     |  2 ++
 v4l2.go    | 14 ++------------
 webcam.go  |  4 +++-
 5 files changed, 13 insertions(+), 13 deletions(-)
 create mode 100644 .gitignore
 create mode 100644 go.mod
 create mode 100644 go.sum

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..e43b0f9
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+.DS_Store
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..72cb8e7
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,5 @@
+module github.com/blackjack/webcam
+
+go 1.18
+
+require golang.org/x/sys v0.14.0
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..5867dc0
--- /dev/null
+++ b/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=
diff --git a/v4l2.go b/v4l2.go
index 7e538fe..79dc65d 100644
--- a/v4l2.go
+++ b/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
 		}
diff --git a/webcam.go b/webcam.go
index dcb5ca5..cc3adfa 100644
--- a/webcam.go
+++ b/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