protected override void Decode(IChannelHandlerContext context, IByteBuffer input, List <object> output)
{
// Discard all data received if closing handshake was received before.
if (this.receivedClosingHandshake)
{
_ = input.SkipBytes(this.ActualReadableBytes);
return;
}
switch (this.state)
{
case State.ReadingFirst:
if (!input.IsReadable())
{
return;
}
this.framePayloadLength = 0;
// FIN, RSV, OPCODE
byte b = input.ReadByte();
this.frameFinalFlag = (b & 0x80) != 0;
this.frameRsv = (b & 0x70) >> 4;
this.frameOpcode = b & 0x0F;
#if DEBUG
if (Logger.TraceEnabled)
{
Logger.DecodingWebSocketFrameOpCode(this.frameOpcode);
}
#endif
this.state = State.ReadingSecond;
goto case State.ReadingSecond;
case State.ReadingSecond:
if (!input.IsReadable())
{
return;
}
// MASK, PAYLOAD LEN 1
b = input.ReadByte();
this.frameMasked = (b & 0x80) != 0;
this.framePayloadLen1 = b & 0x7F;
if (this.frameRsv != 0 && !_config.AllowExtensions)
{
this.ProtocolViolation_RSVNoExtensionNegotiated(context, input, this.frameRsv);
return;
}
if (!_config.AllowMaskMismatch && _config.ExpectMaskedFrames != this.frameMasked)
{
this.ProtocolViolation_RecAFrameThatIsNotMaskedAsExected(context, input);
return;
}
// control frame (have MSB in opcode set)
if (this.frameOpcode > 7)
{
// control frames MUST NOT be fragmented
if (!this.frameFinalFlag)
{
this.ProtocolViolation_FragmentedControlFrame(context, input);
return;
}
// control frames MUST have payload 125 octets or less
if (this.framePayloadLen1 > 125)
{
this.ProtocolViolation_ControlFrameWithPayloadLength125Octets(context, input);
return;
}
switch (this.frameOpcode)
{
// close frame : if there is a body, the first two bytes of the
// body MUST be a 2-byte unsigned integer (in network byte
// order) representing a getStatus code
case OpcodeClose:
if (this.framePayloadLen1 == 1)
{
this.ProtocolViolation_RecCloseControlFrame(context, input);
return;
}
break;
case OpcodePing:
case OpcodePong:
break;
// check for reserved control frame opcodes
default:
this.ProtocolViolation_ControlFrameUsingReservedOpcode(context, input, this.frameOpcode);
return;
}
}
else // data frame
{
switch (this.frameOpcode)
{
case OpcodeCont:
case OpcodeText:
case OpcodeBinary:
break;
// check for reserved data frame opcodes
default:
this.ProtocolViolation_DataFrameUsingReservedOpcode(context, input, this.frameOpcode);
return;
}
uint uFragmentedFramesCount = (uint)this.fragmentedFramesCount;
// check opcode vs message fragmentation state 1/2
if (0u >= uFragmentedFramesCount && this.frameOpcode == OpcodeCont)
{
this.ProtocolViolation_RecContionuationDataFrame(context, input);
return;
}
// check opcode vs message fragmentation state 2/2
if (uFragmentedFramesCount > 0u && this.frameOpcode != OpcodeCont && this.frameOpcode != OpcodePing)
{
this.ProtocolViolation_RecNonContionuationDataFrame(context, input);
return;
}
}
this.state = State.ReadingSize;
goto case State.ReadingSize;
case State.ReadingSize:
// Read frame payload length
switch (this.framePayloadLen1)
{
case 126:
if (input.ReadableBytes < 2)
{
return;
}
this.framePayloadLength = input.ReadUnsignedShort();
if (this.framePayloadLength < 126)
{
this.ProtocolViolation_InvalidDataFrameLength(context, input);
return;
}
break;
case 127:
if (input.ReadableBytes < 8)
{
return;
}
this.framePayloadLength = input.ReadLong();
// TODO: check if it's bigger than 0x7FFFFFFFFFFFFFFF, Maybe
// just check if it's negative?
if (this.framePayloadLength < 65536)
{
this.ProtocolViolation_InvalidDataFrameLength(context, input);
return;
}
break;
default:
this.framePayloadLength = this.framePayloadLen1;
break;
}
var maxFramePayloadLength = _config.MaxFramePayloadLength;
if (this.framePayloadLength > maxFramePayloadLength)
{
this.ProtocolViolation_MaxFrameLengthHasBeenExceeded(context, input, maxFramePayloadLength);
return;
}
#if DEBUG
if (Logger.TraceEnabled)
{
Logger.DecodingWebSocketFrameLength(this.framePayloadLength);
}
#endif
this.state = State.MaskingKey;
goto case State.MaskingKey;
case State.MaskingKey:
if (this.frameMasked)
{
if (input.ReadableBytes < 4)
{
return;
}
if (this.maskingKey is null)
{
this.maskingKey = new byte[4];
}
_ = input.ReadBytes(this.maskingKey);
}
this.state = State.Payload;
goto case State.Payload;
case State.Payload:
if (input.ReadableBytes < this.framePayloadLength)
{
return;
}
IByteBuffer payloadBuffer = null;
try
{
payloadBuffer = ReadBytes(context.Allocator, input, ToFrameLength(this.framePayloadLength));
// Now we have all the data, the next checkpoint must be the next
// frame
this.state = State.ReadingFirst;
// Unmask data if needed
if (this.frameMasked)
{
this.Unmask(payloadBuffer);
}
// Processing ping/pong/close frames because they cannot be
// fragmented
switch (this.frameOpcode)
{
case OpcodePing:
output.Add(new PingWebSocketFrame(this.frameFinalFlag, this.frameRsv, payloadBuffer));
payloadBuffer = null;
return;
case OpcodePong:
output.Add(new PongWebSocketFrame(this.frameFinalFlag, this.frameRsv, payloadBuffer));
payloadBuffer = null;
return;
case OpcodeClose:
this.receivedClosingHandshake = true;
this.CheckCloseFrameBody(context, payloadBuffer);
output.Add(new CloseWebSocketFrame(this.frameFinalFlag, this.frameRsv, payloadBuffer));
payloadBuffer = null;
return;
}
// Processing for possible fragmented messages for text and binary
// frames
if (this.frameFinalFlag)
{
// Final frame of the sequence. Apparently ping frames are
// allowed in the middle of a fragmented message
if (this.frameOpcode != OpcodePing)
{
this.fragmentedFramesCount = 0;
}
}
else
{
// Increment counter
this.fragmentedFramesCount++;
}
// Return the frame
switch (this.frameOpcode)
{
case OpcodeText:
output.Add(new TextWebSocketFrame(this.frameFinalFlag, this.frameRsv, payloadBuffer));
payloadBuffer = null;
return;
case OpcodeBinary:
output.Add(new BinaryWebSocketFrame(this.frameFinalFlag, this.frameRsv, payloadBuffer));
payloadBuffer = null;
return;
case OpcodeCont:
output.Add(new ContinuationWebSocketFrame(this.frameFinalFlag, this.frameRsv, payloadBuffer));
payloadBuffer = null;
return;
default:
ThrowNotSupportedException(this.frameOpcode); return;
}
}
finally
{
_ = (payloadBuffer?.Release());
}
case State.Corrupt:
if (input.IsReadable())
{
// If we don't keep reading Netty will throw an exception saying
// we can't return null if no bytes read and state not changed.
_ = input.ReadByte();
}
return;
default:
ThrowHelper.ThrowException_FrameDecoder(); break;
}
}