public virtual void ReadStartMessage()
{
if (_disposed)
{
throw new ObjectDisposedException(nameof(NmeaReader));
}
if (_state != NmeaReadState.None)
{
throw new InvalidOperationException();
}
int start = _input.ReadByte();
while ((start = _input.ReadByte()) != 36 /*$*/)
{
}
_state = NmeaReadState.StartMessage;
}
private string ReadAddressCore(out byte checksum)
{
if (_state != NmeaReadState.StartMessage)
{
throw new InvalidOperationException();
}
var sb = new StringBuilder();
int b;
checksum = 0x0;
while ((b = _input.ReadByte()) != 44 /*comma*/)
{
sb.Append((char)b);
checksum ^= (byte)b;
}
_state = NmeaReadState.Address;
return(sb.ToString());
}
private string ReadDataCore(out byte checksum)
{
if (_state != NmeaReadState.Address)
{
throw new InvalidOperationException();
}
var sb = new StringBuilder();
int b;
checksum = 0x0;
while ((b = _input.ReadByte()) != 0x2a /*asterisk*/)
{
sb.Append((char)b);
checksum ^= (byte)b;
}
_state = NmeaReadState.Data;
return(sb.ToString());
}
private void ReadEndMessageCore(out int checksum)
{
if (_state != NmeaReadState.Data)
{
throw new InvalidOperationException();
}
var buffer = new byte[2];
_input.Read(buffer, 0, 2);
string checksumString = new string(new[] { (char)buffer[0], (char)buffer[1] });
if (!int.TryParse(checksumString, NumberStyles.HexNumber, CultureInfo.InvariantCulture, out checksum))
{
_state = NmeaReadState.None;
throw new InvalidDataException();
}
int cr = _input.ReadByte();
if (cr != 13 /*CR*/)
{
_state = NmeaReadState.None;
throw new InvalidDataException();
}
int LF = _input.ReadByte();
if (LF != 10 /*LF*/)
{
_state = NmeaReadState.None;
throw new InvalidDataException();
}
_state = NmeaReadState.None;
}
