internal void PrepareForOverlappedTransfer(ref kernel32.OVERLAPPED hidOverlapped, ref IntPtr eventObject) { // Purpose : Creates an event object for the overlapped structure used with // : ReadFile. // ; Called before the first call to ReadFile. kernel32.SECURITY_ATTRIBUTES Security = new kernel32.SECURITY_ATTRIBUTES(); try { // Values for the SECURITY_ATTRIBUTES structure: Security.lpSecurityDescriptor = 0; Security.bInheritHandle = System.Convert.ToInt32(true); Security.nLength = Marshal.SizeOf(Security); // *** // API function: CreateEvent // Purpose: Creates an event object for the overlapped structure used with ReadFile. // Accepts: // A security attributes structure. // Manual Reset = False (The system automatically resets the state to nonsignaled // after a waiting thread has been released.) // Initial state = True (signaled) // An event object name (optional) // Returns: a handle to the event object // *** eventObject = kernel32.CreateEvent(ref Security, System.Convert.ToInt32(false), System.Convert.ToInt32(true), ""); Debug.WriteLine(Debugging.ResultOfAPICall("CreateEvent")); Debug.WriteLine(""); // Set the members of the overlapped structure. hidOverlapped.Offset = 0; hidOverlapped.OffsetHigh = 0; hidOverlapped.hEvent = eventObject; ReadyForOverlappedTransfer = true; } catch (Exception ex) { HandleException(ModuleName + ":" + System.Reflection.MethodBase.GetCurrentMethod(), ex); } }
protected override void ProtectedRead(IntPtr readHandle, IntPtr hidHandle, IntPtr writeHandle, ref bool myDeviceDetected, ref byte[] inputReportBuffer, ref bool success) { // Purpose : reads an Input report from the device using interrupt transfers. // Accepts : readHandle - the handle for reading from the device. // hidHandle - the handle for other device communications. // myDeviceDetected - tells whether the device is currently attached. // readBuffer - contains the requested report. // success - read success IntPtr EventObject = IntPtr.Zero; kernel32.OVERLAPPED HIDOverlapped = new kernel32.OVERLAPPED(); int NumberOfBytesRead = 0; long Result = 0; try { // If it's the first attempt to read, set up the overlapped structure for ReadFile. if (!ReadyForOverlappedTransfer) { PrepareForOverlappedTransfer(ref HIDOverlapped, ref EventObject); } // *** // API function: ReadFile // Purpose: Attempts to read an Input report from the device. // Accepts: // A device handle returned by CreateFile // (for overlapped I/O, CreateFile must have been called with FILE_FLAG_OVERLAPPED), // A pointer to a buffer for storing the report. // The Input report length in bytes returned by HidP_GetCaps, // A pointer to a variable that will hold the number of bytes read. // An overlapped structure whose hEvent member is set to an event object. // Returns: the report in ReadBuffer. // The overlapped call returns immediately, even if the data hasn't been received yet. // To read multiple reports with one ReadFile, increase the size of ReadBuffer // and use NumberOfBytesRead to determine how many reports were returned. // Use a larger buffer if the application can't keep up with reading each report // individually. // *** Debug.Write("input report length = " + inputReportBuffer.Length); Result = kernel32.ReadFile(readHandle, ref inputReportBuffer[0], inputReportBuffer.Length, ref NumberOfBytesRead, ref HIDOverlapped); Debug.WriteLine(Debugging.ResultOfAPICall("ReadFile")); Debug.WriteLine(""); Debug.WriteLine("waiting for ReadFile"); // API function: WaitForSingleObject // Purpose: waits for at least one report or a timeout. // Used with overlapped ReadFile. // Accepts: // An event object created with CreateEvent // A timeout value in milliseconds. // Returns: A result code. Result = kernel32.WaitForSingleObject(EventObject, 3000); Debug.WriteLine(Debugging.ResultOfAPICall("WaitForSingleObject")); Debug.WriteLine(""); // Find out if ReadFile completed or timeout. switch (Result) { case kernel32.WAIT_OBJECT_0: // ReadFile has completed Debug.WriteLine(""); success = true; Debug.WriteLine("ReadFile completed successfully."); break; case kernel32.WAIT_TIMEOUT: // Cancel the operation on timeout CancelTransfer(readHandle, hidHandle); Debug.WriteLine("Readfile timeout"); Debug.WriteLine(""); success = false; myDeviceDetected = false; break; default: // Cancel the operation on other error. CancelTransfer(readHandle, hidHandle); Debug.WriteLine(""); Debug.WriteLine("Readfile undefined error"); success = false; myDeviceDetected = false; break; } success = (Result == 0) ? true : false; } catch (Exception ex) { HandleException(ModuleName + ":" + System.Reflection.MethodBase.GetCurrentMethod(), ex); } }