private EncodeResult EncodeFrame(ProtocolFramework.Buffer data, out ProtocolFramework.Buffer encoded, WebSocketOpCode opCode)
{
int size = data == null ? 0 : data.Size;
encoded = new ProtocolFramework.Buffer(2 + 8 + size); // max possible length of header
const bool isLastFrame = true;
byte finBitSetAsByte = isLastFrame ? (byte)0x80 : (byte)0x00;
byte byte1 = (byte)(finBitSetAsByte | (byte)opCode);
encoded.Append(byte1);
if (size < 126)
{
encoded.Append((byte)size);
}
else if (size <= ushort.MaxValue)
{
encoded.Append(126);
byte[] buffer = BitConverter.GetBytes((ushort)size);
Array.Reverse(buffer);
encoded.Append(buffer, 0, buffer.Length);
}
else
{
encoded.Append(127);
byte[] buffer = BitConverter.GetBytes((ulong)size);
Array.Reverse(buffer);
encoded.Append(buffer, 0, buffer.Length);
}
if (data != null)
{
encoded.Append(data);
}
return(EncodeResult.Success);
}
public override DecodeResult TryDecode(object connectionToken, out ProtocolFramework.Buffer decodedBytes, out ProtocolFramework.Buffer outputBytes)
{
decodedBytes = null;
outputBytes = null;
ConnectionToken token = (ConnectionToken)connectionToken;
if (token.PendingData.Empty())
{
return(DecodeResult.WantMoreData);
}
if (!token.IsNegociationEnded)
{
return(this.TryDecodeHandshakeData(token, out decodedBytes, out outputBytes));
}
// We start interpreting two bytes.
int headerSize = 2;
if (token.PendingData.Size < headerSize)
{
return(DecodeResult.WantMoreData);
}
// First byte = Fin (1 bit) + Flags (3 bits) + opcodes (4 bits):
byte byte1 = token.PendingData.Data[0];
const byte finBitFlag = 0x80;
const byte opCodeFlag = 0x0F;
const byte reservedBitsFlag = 0x70;
bool isFinBitSet = (byte1 & finBitFlag) == finBitFlag;
int reservedBits = (byte1 & reservedBitsFlag);
if (reservedBits != 0)
{
Console.WriteLine("Reserved bits not zeros");
return(DecodeResult.Failure);
}
WebSocketOpCode opCode = (WebSocketOpCode)(byte1 & opCodeFlag);
if (!WebsocketProtocol.IsValidCode(opCode))
{
Console.WriteLine("Invalid opCode: " + opCode);
return(DecodeResult.Failure);
}
// Second byte is Mask (1 bit) + Payload Size (7 bits)
byte byte2 = token.PendingData.Data[1];
const byte maskFlag = 0x80;
bool isMaskBitSet = (byte2 & maskFlag) == maskFlag;
const byte payloadLenFlag = 0x7F;
uint len = (uint)(byte2 & payloadLenFlag);
int payloadSize = 0;
if (len <= 125)
{
payloadSize = (int)len;
}
if (len == 126)
{
headerSize += 2;
if (token.PendingData.Size < headerSize)
{
return(DecodeResult.WantMoreData);
}
byte[] lenBuffer = new byte[2];
Array.Copy(token.PendingData.Data, 2, lenBuffer, 0, 2);
Array.Reverse(lenBuffer); // big endian
payloadSize = (int)BitConverter.ToUInt16(lenBuffer, 0);
}
else if (len == 127)
{
headerSize += 8;
if (token.PendingData.Size < headerSize)
{
return(DecodeResult.WantMoreData);
}
byte[] lenBuffer = new byte[8];
Array.Copy(token.PendingData.Data, 2, lenBuffer, 0, 8);
Array.Reverse(lenBuffer); // big endian
payloadSize = (int)BitConverter.ToUInt64(lenBuffer, 0);
}
if (WebsocketProtocol.IsControlFrame(opCode) && payloadSize > 125)
{
Console.WriteLine("Large control frame payload");
return(DecodeResult.Failure);
}
int totalSize = headerSize + (isMaskBitSet ? 4 : 0) + (int)payloadSize;
if (token.PendingData.Size < totalSize)
{
return(DecodeResult.WantMoreData);
}
ProtocolFramework.Buffer payloadBuffer = new ProtocolFramework.Buffer(payloadSize);
int payloadOffset = headerSize + (isMaskBitSet ? 4 : 0);
payloadBuffer.Append(token.PendingData.Data, payloadOffset, (int)payloadSize);
if (isMaskBitSet)
{
const int maskKeyLen = 4;
byte[] maskKey = new byte[4];
Array.Copy(token.PendingData.Data, headerSize, maskKey, 0, 4);
// apply the mask key
for (int i = 0; i < payloadBuffer.Size; i++)
{
payloadBuffer.Data[i] = (Byte)(payloadBuffer.Data[i] ^ maskKey[i % maskKeyLen]);
}
}
token.PendingData.PopAndAdjust(payloadOffset + (int)payloadSize);
if (opCode == WebSocketOpCode.ConnectionClose)
{
this.EncodeFrame(null, out outputBytes, WebSocketOpCode.ConnectionClose);
return(DecodeResult.Failure); // TODO.
}
else if (opCode == WebSocketOpCode.Pong)
{
return(DecodeResult.Success);
}
else if (opCode == WebSocketOpCode.Ping)
{
this.EncodeFrame(payloadBuffer, out outputBytes, WebSocketOpCode.Pong);
return(DecodeResult.Success);
}
else
{
token.LastReceivedOpCode = opCode;
decodedBytes = payloadBuffer;
return(DecodeResult.Success);
}
}