/// <summary>
/// Creates an event object for the overlapped structure used with
/// ReadFile. Called before the first call to ReadFile.
/// </summary>
///
/// <param name="hidOverlapped"> the overlapped structure </param>
/// <param name="eventObject"> the event object </param>
public void PrepareForOverlappedTransfer(ref FileIO.OVERLAPPED hidOverlapped, ref SafeWaitHandle eventObject)
{
try
{
// ***
// 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 = FileIO.CreateEvent(null, System.Convert.ToInt32(false), System.Convert.ToInt32(true), "");
// Debug.WriteLine(MyDebugging.ResultOfAPICall("CreateEvent"))
// Set the members of the overlapped structure.
hidOverlapped.Offset = 0;
hidOverlapped.OffsetHigh = 0;
hidOverlapped.hEvent = eventObject;
readyForOverlappedTransfer = true;
}
catch (Exception ex)
{
DisplayException(MODULE_NAME, ex);
}
}
/// <summary>
/// reads an Input report from the device using interrupt transfers.
/// </summary>
///
/// <param name="hidHandle"> the handle for learning about the device and exchanging Feature reports. </param>
/// <param name="readHandle"> the handle for reading Input reports from the device. </param>
/// <param name="writeHandle"> the handle for writing Output reports to the device. </param>
/// <param name="myDeviceDetected"> tells whether the device is currently attached. </param>
/// <param name="inputReportBuffer"> contains the requested report. </param>
/// <param name="success"> read success </param>
public override void Read(SafeFileHandle hidHandle, SafeFileHandle readHandle, SafeFileHandle writeHandle, ref Boolean myDeviceDetected, ref Byte[] inputReportBuffer, ref Boolean success)
{
SafeWaitHandle eventObject = null;
FileIO.OVERLAPPED HidOverlapped = new FileIO.OVERLAPPED();
Int32 numberOfBytesRead = 0;
Int32 result = 0;
try
{
// If it's the first attempt to read, set up the overlapped structure for ReadFile.
if (readyForOverlappedTransfer == false)
{
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.
// ***
result = FileIO.ReadFile(readHandle, inputReportBuffer, inputReportBuffer.Length, ref numberOfBytesRead, HidOverlapped);
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 = FileIO.WaitForSingleObject(eventObject, 3000);
// Find out if ReadFile completed or timeout.
switch (result)
{
case (System.Int32)FileIO.WAIT_OBJECT_0:
// ReadFile has completed
success = true;
Debug.WriteLine("ReadFile completed successfully.");
break;
case FileIO.WAIT_TIMEOUT:
// Cancel the operation on timeout
CancelTransfer(hidHandle, readHandle, writeHandle);
Debug.WriteLine("Readfile timeout");
success = false;
myDeviceDetected = false;
break;
default:
// Cancel the operation on other error.
CancelTransfer(hidHandle, readHandle, writeHandle);
Debug.WriteLine("Readfile undefined error");
success = false;
myDeviceDetected = false;
break;
}
if (result == 0)
{
success = true;
}
else
{
success = false;
}
}
catch (Exception ex)
{
DisplayException(MODULE_NAME, ex);
}
}
/// <summary>
/// reads an Input report from the device using interrupt transfers.
/// </summary>
///
/// <param name="hidHandle"> the handle for learning about the device and exchanging Feature reports. </param>
/// <param name="readHandle"> the handle for reading Input reports from the device. </param>
/// <param name="writeHandle"> the handle for writing Output reports to the device. </param>
/// <param name="myDeviceDetected"> tells whether the device is currently attached. </param>
/// <param name="inputReportBuffer"> contains the requested report. </param>
/// <param name="success"> read success </param>
public override void Read(SafeFileHandle hidHandle, SafeFileHandle readHandle, SafeFileHandle writeHandle, ref Boolean myDeviceDetected, ref Byte[] inputReportBuffer, ref Boolean success)
{
SafeWaitHandle eventObject = null;
FileIO.OVERLAPPED HidOverlapped = new FileIO.OVERLAPPED();
Int32 numberOfBytesRead = 0;
Int32 result = 0;
try
{
// If it's the first attempt to read, set up the overlapped structure for ReadFile.
if ( readyForOverlappedTransfer == false )
{
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.
// ***
result = FileIO.ReadFile(readHandle, inputReportBuffer, inputReportBuffer.Length, ref numberOfBytesRead, HidOverlapped);
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 = FileIO.WaitForSingleObject(eventObject, 3000);
// Find out if ReadFile completed or timeout.
switch ( result )
{
case (System.Int32)FileIO.WAIT_OBJECT_0:
// ReadFile has completed
success = true;
Debug.WriteLine( "ReadFile completed successfully." );
break;
case FileIO.WAIT_TIMEOUT:
// Cancel the operation on timeout
CancelTransfer( hidHandle, readHandle, writeHandle );
Debug.WriteLine( "Readfile timeout" );
success = false;
myDeviceDetected = false;
break;
default:
// Cancel the operation on other error.
CancelTransfer( hidHandle, readHandle, writeHandle );
Debug.WriteLine( "Readfile undefined error" );
success = false;
myDeviceDetected = false;
break;
}
if ( result == 0 )
{
success = true;
}
else
{
success = false;
}
}
catch ( Exception ex )
{
DisplayException( MODULE_NAME, ex );
throw ;
}
}