public static QueryHeader ParseQueryHeader(byte[] buffer)
{
//https://tools.ietf.org/html/rfc1035#section-4.1.1
var header = new QueryHeader();
//this is the first place I was bitten by endianness
header.ID = endianBitConverter.ToUInt16(buffer, 0); //first 2 bytes is the ID
//and this is the second
BitArray byteTwo = new BitArray(new byte[] { buffer[2] });
byteTwo.Reverse();
BitArray byteThree = new BitArray(new byte[] { buffer[3] });
byteThree.Reverse();
header.QueryResponse = byteTwo[0]; //Query Response bit
//chop up the next nybble as we'll use it to get the opcode itself
var opcodeArray = new BitArray(4);
opcodeArray[0] = byteTwo[1];
opcodeArray[1] = byteTwo[2];
opcodeArray[2] = byteTwo[3];
opcodeArray[3] = byteTwo[4];
//Look away, children!
//I'm converting the BitArray to a string (1010), then to a short, then to my OpCode value
//todo: use bitmasking to do this
header.OPCODE = (OpCode)Convert.ToInt16(opcodeArray.ToBitString(), 2);
//this takes us to position 5 of the second byte
header.AuthoritativeAnswer = byteTwo[5];
header.Truncation = byteTwo[6];
header.RecursionDesired = byteTwo[7];
//next!
header.RecursionAvailable = byteThree[0];
header.Z = byteThree[1];
//header.ResponseCode //bits two through 5
header.QuestionCount = endianBitConverter.ToUInt16(buffer, 4);
header.AnswerCount = endianBitConverter.ToUInt16(buffer, 6);
header.NameServerCount = endianBitConverter.ToUInt16(buffer, 8);
header.AdditonalRecordCount = endianBitConverter.ToUInt16(buffer, 10); //wtf happened with endianness here?
return header;
}