ServerManagers/src/QueryMaster/UdpQuery.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using Ionic.BZip2;
using System.Net;
using Ionic.Crc;

namespace QueryMaster
{
    internal class UdpQuery : ServerSocket
    {
        private const int SinglePacket = -1;
        private const int MultiPacket = -2;
        private EngineType Type;
        internal UdpQuery(IPEndPoint address, int sendTimeOut, int receiveTimeOut)
            : base(SocketType.Udp)
        {
            Connect(address);
            socket.SendTimeout = sendTimeOut;
            socket.ReceiveTimeout = receiveTimeOut;
        }

        internal byte[] GetResponse(byte[] msg, EngineType type)
        {
            Type = type;
            byte[] recvData;
            SendData(msg);
            recvData = ReceiveData();
            try
            {
                int header = BitConverter.ToInt32(recvData, 0);
                switch (header)
                {
                    case SinglePacket: return ParseSinglePkt(recvData);
                    case MultiPacket: return ParseMultiPkt(recvData);
                    default: throw new InvalidHeaderException("Protocol header is not valid");
                }
            }
            catch (Exception e)
            {
                e.Data.Add("ReceivedData", recvData);
                throw;
            }
        }

        private byte[] ParseSinglePkt(byte[] data)
        {
            return data.Skip(4).ToArray();
        }

        private byte[] ParseMultiPkt(byte[] data)
        {
            switch (Type)
            {
                case EngineType.Source: return SourcePackets(data);
                case EngineType.GoldSource: return GoldSourcePackets(data);
                default: throw new ArgumentException("An invalid EngineType was specified.");
            }
        }

        private byte[] GoldSourcePackets(byte[] data)
        {
            var pktCount = data[8] & 0x0F;
            List<KeyValuePair<int, byte[]>> pktList = new List<KeyValuePair<int, byte[]>>(pktCount);
            pktList.Add(new KeyValuePair<int, byte[]>(data[8] >> 4, data));

            byte[] recvData;
            for (int i = 1; i < pktCount; i++)
            {
                recvData = new byte[BufferSize];
                recvData = ReceiveData();
                pktList.Add(new KeyValuePair<int, byte[]>(recvData[8] >> 4, recvData));
            }

            pktList.Sort((x, y) => x.Key.CompareTo(y.Key));
            List<byte> byteList = new List<byte>();
            byteList.AddRange(pktList[0].Value.Skip(13));

            for (int i = 1; i < pktList.Count; i++)
            {
                byteList.AddRange(pktList[i].Value.Skip(9));
            }
            return byteList.ToArray<byte>();
        }

        private byte[] SourcePackets(byte[] data)
        {
            byte pktCount = data[8];
            List<KeyValuePair<byte, byte[]>> pktList = new List<KeyValuePair<byte, byte[]>>(pktCount);
            pktList.Add(new KeyValuePair<byte, byte[]>(data[9], data));

            byte[] recvData;
            for (int i = 1; i < pktCount; i++)
            {
                recvData = ReceiveData();
                pktList.Add(new KeyValuePair<byte, byte[]>(recvData[9], recvData));
            }

            pktList.Sort((x, y) => x.Key.CompareTo(y.Key));
            Parser parser = null;
            bool isCompressed = false;
            int checksum = 0;
            List<byte> recvList = new List<byte>();
            parser = new Parser(pktList[0].Value);
            parser.Skip(4);//header
            if (parser.ReadInt() < 0)//ID
                isCompressed = true;
            parser.ReadByte();//total
            int pktId = parser.ReadByte();// packet id
            parser.ReadShort();//size
            if (isCompressed)
            {
                parser.Skip(2);//[this is not equal to decompressed length of data]
                checksum = parser.ReadInt();//Checksum
            }
            recvList.AddRange(parser.GetUnParsedData());

            for (int i = 1; i < pktList.Count; i++)
            {
                parser = new Parser(pktList[i].Value);
                parser.Skip(12);//multipacket header only
                recvList.AddRange(parser.GetUnParsedData());
            }
            recvData = recvList.ToArray<byte>();
            if (isCompressed)
            {
                recvData = Decompress(recvData);
                if (!IsValid(recvData, checksum))
                    throw new InvalidPacketException("packet's checksum value does not match with the calculated checksum");
            }
            return recvData.Skip(4).ToArray<byte>();
        }

        private byte[] Decompress(byte[] data)
        {
            using (var input = new MemoryStream(data))
            using (var output = new MemoryStream())
            using (var unZip = new BZip2InputStream(input))
            {
                int ch = unZip.ReadByte();

                while (ch != -1)
                {
                    output.WriteByte((byte)ch);
                    ch = unZip.ReadByte();
                }
                output.Flush();
                return output.ToArray();
            }
        }

        private bool IsValid(byte[] data, int Checksum)
        {
            using (var Input = new MemoryStream(data))
            {
                if (Checksum == new CRC32().GetCrc32(Input))
                    return true;
                return false;
            }
        }


    }
}