private unsafe IAsyncResult BeginReadCore(byte[] array, int offset, int count, AsyncCallback userCallback, Object stateObject)
{
Debug.Assert(userCallback == null);
Debug.Assert(stateObject == null);
CheckParametersForBegin(array, offset, count);
AsyncFileStream_AsyncResult asyncResult = new AsyncFileStream_AsyncResult(userCallback, stateObject, false);
if (count == 0)
{
asyncResult.SignalCompleted( );
}
else
{
// Keep the array in one location in memory until the OS writes the
// relevant data into the array. Free GCHandle later.
asyncResult.PinBuffer(array);
int totalRead = 0;
int availableToTransfer = 0;
fixed(byte *dst = array)
{
// if we already have available data, then we need to use it
lock ( syncRW )
{
System.Diagnostics.Debug.Assert(count == m_bytesAvailable);
if (m_bytesAvailable > 0)
{
// truncate
availableToTransfer = Math.Min(count, ( int )m_bytesAvailable);
// copy over to the application buffer
Marshal.Copy(m_buffer, 0, new IntPtr(dst + offset), availableToTransfer);
// update the available bytes count
m_bytesAvailable -= ( uint )availableToTransfer;
totalRead += availableToTransfer;
// adjust the buffering if there is a left over
// this will never happen if application call AvailableBytes and the reads them
if (m_bytesAvailable > 0)
{
fixed(byte *copy = m_buffer)
{
Marshal.Copy(new IntPtr(copy), m_buffer, ( int )availableToTransfer, ( int )m_bytesAvailable);
}
}
}
}
// if we need to read more, then we should go to the stream directly
int remainder = count - availableToTransfer;
if (remainder > 0)
{
byte[] byteArray = new byte[remainder];
Array.Clear(byteArray, 0, byteArray.Length);
fixed(byte *p = byteArray)
{
uint numBytesRead = 0;
var res = m_winUsbDevice.ReadPipe(Convert.ToByte(m_winUsbDevice.DeviceInfo.bulkInPipe)
, byteArray
, ( uint )remainder
, ref numBytesRead
, IntPtr.Zero
);
if (!res)
{
if (HandleErrorSituation("BeginRead", false))
{
asyncResult.SignalCompleted( );
}
else
{
m_outstandingRequests.Add(asyncResult);
}
}
else
{
Marshal.Copy(byteArray, 0, new IntPtr(dst + totalRead + offset), ( int )numBytesRead);
totalRead += ( int )numBytesRead;
}
}
}
if (totalRead > 0)
{
asyncResult.m_numBytes = totalRead;
asyncResult.SignalCompleted( );
}
}
}
return(asyncResult);
}
