.NET Regular expressions on bytes instead of chars

Question

I\'m trying to do some parsing that will be easier using regular expressions.

The input is an array (or enumeration) of bytes.

I don\'t want to convert the b

Answer 1

I personally went a different approach and wrote a small state machine that can be extended. I believe if parsing protocol data this is much more readable than regex.

bool ParseUDSResponse(PassThruMsg rxMsg, UDScmd.Mode txMode, byte txSubFunction, out UDScmd.Response functionResponse, out byte[] payload)
{
    payload = new byte[0];
    functionResponse = UDScmd.Response.UNKNOWN;
    bool positiveReponse = false;
    var rxMsgBytes = rxMsg.GetBytes();

    //Iterate the reply bytes to find the echod ECU index, response code, function response and payload data if there is any
    //If we could use some kind of HEX regex this would be a bit neater
    //Iterate until we get past any and all null padding
    int stateMachine = 0;
    for (int i = 0; i < rxMsgBytes.Length; i++)
    {
        switch (stateMachine)
        {
            case 0:
                if (rxMsgBytes[i] == 0x07) stateMachine = 1;
                break;
            case 1:
                if (rxMsgBytes[i] == 0xE8) stateMachine = 2;
                else return false;
            case 2:
                if (rxMsgBytes[i] == (byte)txMode + (byte)OBDcmd.Reponse.SUCCESS)
                {
                    //Positive response to the requested mode
                    positiveReponse = true;
                }
                else if(rxMsgBytes[i] != (byte)OBDcmd.Reponse.NEGATIVE_RESPONSE)
                {
                    //This is an invalid response, give up now
                    return false;
                }
                stateMachine = 3;
                break;
            case 3:
                functionResponse = (UDScmd.Response)rxMsgBytes[i];
                if (positiveReponse && rxMsgBytes[i] == txSubFunction)
                {
                    //We have a positive response and a positive subfunction code (subfunction is reflected)
                    int payloadLength = rxMsgBytes.Length - i;
                    if(payloadLength > 0)
                    {
                        payload = new byte[payloadLength];
                        Array.Copy(rxMsgBytes, i, payload, 0, payloadLength);
                    }
                    return true;
                } else
                {
                    //We had a positive response but a negative subfunction error
                    //we return the function error code so it can be relayed
                    return false;
                }
            default:
                return false;
        }
    }
    return false;
}