ln.http/websocket/WebSocketFrame.cs

using System;
using System.IO;
using System.Text;
using ln.types;
using ln.logging;
namespace ln.http.websocket
{
    public class WebSocketFrame
    {
        public bool FIN;
        public bool RSV1;
        public bool RSV2;
        public bool RSV3;

        public WebSocketOpcode Opcode = WebSocketOpcode.INVALIDOPCODE;

        public bool Mask;

        public int MaskingKey;

        public byte[] ExtensionData;
        public byte[] ApplicationData;

        public byte[] Payload => ExtensionData.Concat(ApplicationData); 

        public WebSocketFrame()
        {
            ExtensionData = new byte[0];
            ApplicationData = new byte[0];
        }

        public WebSocketFrame(WebSocketOpcode opcode)
            :this(opcode,new byte[0])
        {
        }
        public WebSocketFrame(WebSocketOpcode opcode,byte[] applicationData)
        {
            Opcode = opcode;
            ExtensionData = new byte[0];
            ApplicationData = applicationData;
        }

        public WebSocketFrame(string applicationData)
            :this(Encoding.UTF8.GetBytes(applicationData),new byte[0])
        {
            Opcode = WebSocketOpcode.TEXT;
        }
        public WebSocketFrame(byte[] applicationData)
            : this(applicationData, new byte[0]) { }
        public WebSocketFrame(byte[] applicationData,byte[] extensionData)
        {
            FIN = true;
            Opcode = WebSocketOpcode.BINARY;
            ExtensionData = extensionData;
            ApplicationData = applicationData;
        }

        public WebSocketFrame(Stream stream)
        {
            ReadFrom(stream);
        }

        public void ReadFrom(Stream stream)
        {
            int firstByte = stream.ReadByte();
            if (firstByte == -1)
                throw new IOException();

            FIN = (firstByte & 0x80) != 0;
            RSV1 = (firstByte & 0x40) != 0;
            RSV3 = (firstByte & 0x20) != 0;
            RSV1 = (firstByte & 0x10) != 0;

            Opcode = (WebSocketOpcode)(firstByte & 0x0F);

            int secondByte = stream.ReadByte();
            if (secondByte == -1)
                throw new IOException();

            Mask = (secondByte & 0x80) != 0;

            int pLength = (secondByte) & 0x7F;
            if (pLength == 126)
            {
                pLength = stream.ReadUShort(true);
            }
            else if (pLength == 127)
            {
                ulong ulpLength = stream.ReadULong(true);
                if (ulpLength > int.MaxValue)
                    throw new NotSupportedException(String.Format("Maximum supported frame size is: {0} bytes", int.MaxValue));

                pLength = (int)ulpLength;
            }

            if (Mask)
            {
                MaskingKey = stream.ReadInteger();
            }

            ExtensionData = new byte[0];
            ApplicationData = stream.ReadBytes(pLength);

            if (Mask)
            {
                MaskPayload(ApplicationData, MaskingKey);
            }
        }

        public void WriteTo(Stream stream)
        {
            stream.WriteByte(
                (byte)(
                    (FIN ? 0x80 : 0x00) |
                    (RSV1 ? 0x40 : 0x00) |
                    (RSV2 ? 0x20 : 0x00) |
                    (RSV3 ? 0x10 : 0x00) |
                    (((int)Opcode) & 0x0F)
                )
            );

            int dLength = ExtensionData.Length + ApplicationData.Length;
            int pLength = 0;

            if (dLength < 126)
            {
                pLength = (dLength) | (Mask ? 0x80 : 0x00);

                stream.WriteByte((byte)pLength);

            } else if (dLength < (1U<<16))
            {
                pLength = (126) | (Mask ? 0x80 : 0x00);

                stream.WriteByte((byte)pLength);
                stream.WriteBytes(((ushort)dLength).GetBytes(true));
            }
            else
            {
                pLength = (127) | (Mask ? 0x80 : 0x00);

                stream.WriteByte((byte)pLength);
                stream.WriteBytes(((ulong)dLength).GetBytes(true));
            }

            byte[] payload = Payload;

            if (Mask)
            {
                stream.WriteBytes(MaskingKey.GetBytes());
                MaskPayload(payload, MaskingKey);
            }

            stream.WriteBytes(payload);

            stream.Flush();
        }

        public static void MaskPayload(byte[] data,int maskingKey)
        {
            byte[] mk = BitConverter.GetBytes(maskingKey);
            for (int n = 0; n < data.Length; n++)
            {
                data[n] = (byte)(data[n] ^ mk[n % 4]);
            }
        }


        static Random random = new Random();
    }
}