System.Net.WebSockets.ManagedWebSocket.TryParseMessageHeaderFromReceiveBuffer C# (CSharp) Method

        private bool TryParseMessageHeaderFromReceiveBuffer(out MessageHeader resultHeader)
        {
            Debug.Assert(_receiveBufferCount >= 2, $"Expected to at least have the first two bytes of the header.");

            var header = new MessageHeader();

            header.Fin = (_receiveBuffer[_receiveBufferOffset] & 0x80) != 0;
            bool reservedSet = (_receiveBuffer[_receiveBufferOffset] & 0x70) != 0;
            header.Opcode = (MessageOpcode)(_receiveBuffer[_receiveBufferOffset] & 0xF);

            bool masked = (_receiveBuffer[_receiveBufferOffset + 1] & 0x80) != 0;
            header.PayloadLength = _receiveBuffer[_receiveBufferOffset + 1] & 0x7F;

            ConsumeFromBuffer(2);

            // Read the remainder of the payload length, if necessary
            if (header.PayloadLength == 126)
            {
                Debug.Assert(_receiveBufferCount >= 2, $"Expected to have two bytes for the payload length.");
                header.PayloadLength = (_receiveBuffer[_receiveBufferOffset] << 8) | _receiveBuffer[_receiveBufferOffset + 1];
                ConsumeFromBuffer(2);
            }
            else if (header.PayloadLength == 127)
            {
                Debug.Assert(_receiveBufferCount >= 8, $"Expected to have eight bytes for the payload length.");
                header.PayloadLength = 0;
                for (int i = 0; i < 8; i++)
                {
                    header.PayloadLength = (header.PayloadLength << 8) | _receiveBuffer[_receiveBufferOffset + i];
                }
                ConsumeFromBuffer(8);
            }

            bool shouldFail = reservedSet;
            if (masked)
            {
                if (!_isServer)
                {
                    shouldFail = true;
                }
                header.Mask = CombineMaskBytes(_receiveBuffer, _receiveBufferOffset);

                // Consume the mask bytes
                ConsumeFromBuffer(4);
            }

            // Do basic validation of the header
            switch (header.Opcode)
            {
                case MessageOpcode.Continuation:
                    if (_lastReceiveHeader.Fin)
                    {
                        // Can't continue from a final message
                        shouldFail = true;
                    }
                    break;

                case MessageOpcode.Binary:
                case MessageOpcode.Text:
                    if (!_lastReceiveHeader.Fin)
                    {
                        // Must continue from a non-final message
                        shouldFail = true;
                    }
                    break;

                case MessageOpcode.Close:
                case MessageOpcode.Ping:
                case MessageOpcode.Pong:
                    if (header.PayloadLength > MaxControlPayloadLength || !header.Fin)
                    {
                        // Invalid control messgae
                        shouldFail = true;
                    }
                    break;

                default:
                    // Unknown opcode
                    shouldFail = true;
                    break;
            }

            // Return the read header
            resultHeader = header;
            return !shouldFail;
        }