private async Task <object> ReadAsync()
{
//Read a chunk
var readBuffer = await _HidDevice.ReadAsync();
TMessageType messageType;
//Check to see that this is a valid first chunk
var firstByteNot63 = readBuffer[0] != (byte)'?';
var secondByteNot35 = readBuffer[1] != 35;
var thirdByteNot35 = readBuffer[2] != 35;
if (firstByteNot63 || secondByteNot35 || thirdByteNot35)
{
var message = $"An error occurred while attempting to read the message from the device. The last written message was a {_LastWrittenMessage?.GetType().Name}. In the first chunk of data ";
if (firstByteNot63)
{
message += "the first byte was not 63";
}
if (secondByteNot35)
{
message += "the second byte was not 35";
}
if (thirdByteNot35)
{
message += "the third byte was not 35";
}
throw new ReadException(message, readBuffer, _LastWrittenMessage);
}
//Looks like the message type is at index 4
var messageTypeInt = readBuffer[4];
if (!Enum.IsDefined(MessageTypeType, (int)messageTypeInt))
{
throw new Exception($"The number {messageTypeInt} is not a valid MessageType");
}
//Get the message type
var messageTypeValueName = Enum.GetName(MessageTypeType, messageTypeInt);
messageType = (TMessageType)Enum.Parse(MessageTypeType, messageTypeValueName);
//msgLength:= int(binary.BigEndian.Uint32(buf[i + 4 : i + 8]))
//TODO: Is this correct?
var remainingDataLength = ((readBuffer[5] & 0xFF) << 24)
+ ((readBuffer[6] & 0xFF) << 16)
+ ((readBuffer[7] & 0xFF) << 8)
+ (readBuffer[8] & 0xFF);
var length = Math.Min(readBuffer.Length - (FirstChunkStartIndex), remainingDataLength);
//This is the first chunk so read from 9-64
var allData = GetRange(readBuffer, FirstChunkStartIndex, length);
remainingDataLength -= allData.Length;
_InvalidChunksCounter = 0;
while (remainingDataLength > 0)
{
//Read a chunk
readBuffer = await _HidDevice.ReadAsync();
//check that there was some data returned
if (readBuffer.Length <= 0)
{
continue;
}
//Check what's smaller, the buffer or the remaining data length
length = Math.Min(readBuffer.Length, remainingDataLength);
if (readBuffer[0] != (byte)'?')
{
if (_InvalidChunksCounter++ > 5)
{
throw new Exception("messageRead: too many invalid chunks (2)");
}
}
allData = Append(allData, GetRange(readBuffer, 1, length - 1));
//Decrement the length of the data to be read
remainingDataLength -= (length - 1);
//Super hack! Fix this!
if (remainingDataLength != 1)
{
continue;
}
allData = Append(allData, GetRange(readBuffer, length, 1));
remainingDataLength = 0;
}
var msg = Deserialize(messageType, allData);
Logger.Log($"Read: {msg}", null, LogSection);
return(msg);
}
