Frank v Hoof Frank v Hoof - 28 days ago 23
C# Question

Createfile works, but handle is invalid on FileStream Construction

I'm trying to connect to a Wiimote in Unity3D through HID.

When I call

CreateFile()
(from kernel32) a "valid" pointer is returned, and I can even get the Wiimote's capabilities through
HidD_GetPreparsedData
and
HidP_GetCaps
. Buffer-size etc. is returned, and is the size that I'm expecting. However, when I try to open a
FileStream
on the handle, it errors with "Invalid Handle".

How can this handle be invalid here if I can
GetCaps
?
Marshal32.GetLastWinError()
is also returning 0.

Relevant code:

int i = 0;
foreach (string devPath in devicePaths)
{
Debug.Log(i);
i++;
if (devPath.Contains(VID_NINTENDO))
if (devPath.Contains(PID_WIIMOTE)) // ADD OTHER PID (IF EVER FOUND)
{
try
{
IntPtr dev_Handle = CreateFile(devPath, FileAccess.Read | FileAccess.Write, FileShare.Read | FileShare.Write, IntPtr.Zero, FileMode.Open, FILE_FLAG_OVERLAPPED, IntPtr.Zero); // Gives a "Valid" pointer
IntPtr device_data = IntPtr.Zero;
int inputLength = 0;
try
{
if (!HidD_GetPreparsedData(dev_Handle, out device_data))
{
throw new HIDException("Unable to get Preparsed data from device");
}
HidCaps device_capabilities; // Struct to contain inputlength etc.
HidP_GetCaps(device_data, out device_capabilities);
inputLength = device_capabilities.InputReportByteLength;
int outputLength = device_capabilities.OutputReportByteLength;
FileStream stream = new FileStream(dev_Handle, FileAccess.Read | FileAccess.Write, true, inputLength); // INVALID HANDLE
//FileStream stream = new FileStream(new SafeFileHandle(dev_Handle, false), FileAccess.Read | FileAccess.Write, inputLength, true); // Invalid Handle
//FileStream stream = new FileStream(dev_Handle, FileAccess.Read | FileAccess.Write, true, inputLength); // Invalid Handle
//FileStream stream = new FileStream(devPath, FileMode.Open, FileAccess.Read | FileAccess.Write, FileShare.Read | FileShare.Write, inputLength); // nullref (The file isnt being created in this path)
Debug.Log(dev_Handle);
}
catch (Exception e)
{
HandleException(e, "HIDException");
}
finally
{
HidD_FreePreparsedData(ref device_data);
}
}
catch (Exception e)
{
HandleException(e, "HIDException");
}
}
}


Also, in a regular C# project it simply works :( (although I did have to set useAsync = true in the FileStream Constructor (still
Invalid Handle
in Unity though)

Answer

Finally got it working through the use of kernel32.dll's ReadFile Method... Apparently Unity has problems with SafeFileHandles.. :S Using this API: http://buiba.blogspot.nl/2009/06/using-winapi-createfile-readfile.html Makes reading possible