/// <summary>
/// Constructor for a DCB, using the DCB provided by another object.
/// </summary>
/// <param name="handle">Valid handle to a serial port object.</param>
/// <param name="state">A CommState object for which the DCB settings should be
/// taken. Note, the handle managed by the state object is ignored. If this
/// parameter is null, then a default DCB is created.</param>
internal CommState(SafeFileHandle handle, CommState state)
{
m_ComPortHandle = handle;
if (state == null)
{
m_Dcb.DCBLength = Marshal.SizeOf(m_Dcb);
GetCommState();
}
else
{
m_Dcb = state.m_Dcb;
}
}
void UpdateSettings()
{
lock (_lock)
{
// This assumes the handle is acquired.
if (!_settingsChanged)
{
return;
}
_settingsChanged = false;
var dcb = new NativeMethods.DCB();
dcb.DCBlength = Marshal.SizeOf(typeof(NativeMethods.DCB));
if (!NativeMethods.GetCommState(_handle, ref dcb))
{
int hr = Marshal.GetHRForLastWin32Error();
throw DeviceException.CreateIOException(Device, "Failed to get serial state.", hr);
}
int baudRate = _ser.BaudRate;
int dataBits = _ser.DataBits;
var parity = _ser.Parity;
int stopBits = _ser.StopBits;
SetDcbDefaults(ref dcb);
dcb.BaudRate = checked ((uint)baudRate);
dcb.ByteSize = checked ((byte)_ser.DataBits);
dcb.Parity = parity == SerialParity.Even ? NativeMethods.EVENPARITY : parity == SerialParity.Odd ? NativeMethods.ODDPARITY : NativeMethods.NOPARITY;
dcb.StopBits = stopBits == 2 ? NativeMethods.TWOSTOPBITS : NativeMethods.ONESTOPBIT;
if (!NativeMethods.SetCommState(_handle, ref dcb))
{
int hr = Marshal.GetHRForLastWin32Error();
throw DeviceException.CreateIOException(Device, "Failed to set serial state.", hr);
}
var purgeFlags = NativeMethods.PURGE_RXABORT | NativeMethods.PURGE_RXCLEAR | NativeMethods.PURGE_TXABORT | NativeMethods.PURGE_TXCLEAR;
if (!NativeMethods.PurgeComm(_handle, purgeFlags))
{
int hr = Marshal.GetHRForLastWin32Error();
throw DeviceException.CreateIOException(Device, "Failed to purge serial port.", hr);
}
}
}
static void SetDcbDefaults(ref NativeMethods.DCB dcb)
{
dcb.fFlags = 0;
dcb.fBinary = true;
}
