initial commit

vidnumerator.go

@@ -0,0 +1,92 @@
+package vidnumerator
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+	"unsafe"
+
+	"golang.org/x/sys/unix"
+)
+
+const (
+	IOCNrBits   = 8
+	IOCTypeBits = 8
+	IOCSizeBits = 14
+	IOCDirBits  = 2
+	IOCNone     = 0
+	IOCWrite    = 1
+	IOCRead     = 2
+	IOCNrShift  = 0
+
+	IOCTypeShift = (IOCNrShift + IOCNrBits)
+	IOCSizeShift = (IOCTypeShift + IOCTypeBits)
+	IOCDirShift  = (IOCSizeShift + IOCSizeBits)
+
+	VidIOCQueryCap = (IOCRead << IOCDirShift) |
+		(uintptr('V') << IOCTypeShift) |
+		(0 << IOCNrShift) |
+		(unsafe.Sizeof(cap{}) << IOCSizeShift)
+)
+
+type cap struct {
+	driver       [16]uint8
+	card         [32]uint8
+	busInfo      [32]uint8
+	version      uint32
+	capabilities uint32
+	deviceCaps   uint32
+	reserved     [3]uint32
+}
+
+func (r *cap) QueryFd(fileDesciptor int) error {
+	if r == nil {
+		return fmt.Errorf("nil receiver")
+	}
+	_, _, errorNumber := unix.Syscall(
+		unix.SYS_IOCTL,
+		uintptr(fileDesciptor),
+		VidIOCQueryCap,
+		uintptr(unsafe.Pointer(r)),
+	)
+	if errorNumber != 0 {
+		return errorNumber
+	}
+	return nil
+}
+
+// this function checks the ioctl for VIDIOC_QUERYCAP to see if the device is a video capture device
+func EnumeratedVideoDevices() []string {
+	// list all files in the /dev directory
+	d, err := os.ReadDir("/dev")
+	if err != nil {
+		return []string{}
+	}
+	// iterate over the files in the directory
+	devNames := []string{}
+	for _, file := range d {
+		if file.IsDir() {
+			continue
+		}
+		fname := file.Name()
+		if !strings.HasPrefix(fname, "video") {
+			continue
+		}
+		fname = filepath.Join("/dev/", fname)
+		f, err := os.OpenFile(fname, os.O_RDONLY, 0o755)
+		if err != nil {
+			continue
+		}
+		fd := f.Fd()
+		ic := cap{}
+		err = ic.QueryFd(int(fd))
+		if err != nil {
+			continue
+		}
+		if ic.deviceCaps == 69206017 {
+			devNames = append(devNames, fname)
+		}
+	}
+	return devNames
+}