/// <summary>
/// This event is called whenever new data is available on our
/// serial port. This method is responsible for managing the input
/// buffer and turning the bytes into strings that downstream methods
/// can parse.
/// </summary>
/// <param name="ignored1">not used</param>
/// <param name="ignored2">not used</param>
private void serialPort_DataReceived(object ignored1, SerialDataReceivedEventArgs ignored2)
{
lock (this)
{
// if the buffer was all scanned and not useful then dump it
if (m_bufferUsed == m_buffer.Length)
{
m_bufferUsed = 0;
}
// assume that all of the existing buffer was already scanned
// for newlines. We will scan what we just received.
int lastScanIndex = this.m_bufferUsed;
// this hack backs up our scan by one byte if we saw the CR,
// but didn't find the LF because it's in the next byte
if (this.m_bufferUsed > 0 && this.m_buffer[this.m_bufferUsed - 1] == '\r')
{
lastScanIndex--;
}
// read all of the data that is avaiable
int toRead = System.Math.Min(this.m_serialPort.BytesToRead, (this.m_buffer.Length - this.m_bufferUsed));
int bytesRead = this.m_serialPort.Read(this.m_buffer, this.m_bufferUsed, toRead);
// publish the debug event if one is registered
if (this.RawDataDebugEvent != null)
{
byte[] rawDataBuffer = new byte[bytesRead];
Array.Copy(m_buffer, m_bufferUsed, rawDataBuffer, 0, bytesRead);
var rawData = new NmeaInputDebugEventArgs(rawDataBuffer);
RawDataDebugEvent(this, rawData);
}
this.m_startProcessing = DateTime.Now.Ticks;
this.m_bufferUsed += bytesRead;
// loop looking for newlines
bool foundNewline = true;
while (foundNewline)
{
// scan the buffer for a new line from the last point scanned
int nextNewline = 0;
int pastNewline = 0;
int i;
for (i = lastScanIndex; i < this.m_bufferUsed; i++)
{
// check for a \r\n line ending.
if ((this.m_bufferUsed - i) >= 2 &&
(this.m_buffer[i] == (byte)'\r' && this.m_buffer[i + 1] == (byte)'\n'))
{
nextNewline = i;
pastNewline = i + 2;
break;
}
// check for a \n line ending
else if (this.m_buffer[i] == (byte)'\n')
{
nextNewline = i;
pastNewline = i + 1;
break;
}
}
// we found a line ending
if (nextNewline > 0)
{
char[] chars = System.Text.Encoding.UTF8.GetChars(this.m_buffer, 0, nextNewline);
string line = new string(chars);
if (line != null)
{
ParseNmeaSentence(line);
m_startProcessing = DateTime.Now.Ticks;
}
// shuffle the buffer. not very efficient, we really should use a circular array
int toCopy = this.m_bufferUsed - pastNewline;
if (toCopy == 0)
{
// we used the whole buffer, just reset what we've got
this.m_bufferUsed = 0;
}
else
{
var newBuffer = new byte[this.m_buffer.Length];
Array.Copy(this.m_buffer, pastNewline, newBuffer, 0, this.m_buffer.Length - pastNewline);
this.m_bufferUsed = toCopy + 1;
this.m_buffer = newBuffer;
}
}
else
{
foundNewline = false;
}
}
}
}
void m_nmeaInputPort_RawDataDebugEvent(object sender, NmeaInputDebugEventArgs args)
{
char[] chars = System.Text.Encoding.UTF8.GetChars(args.RawData, 0, args.RawData.Length);
m_oled.DrawStringAndScroll(m_debugFont, 0, 63, new string(chars));
}