System.Net.Security.SslStreamInternal.StartFrameBody C# (CSharp) Method

        private int StartFrameBody(int readBytes, byte[] buffer, int offset, int count, AsyncProtocolRequest asyncRequest)
        {
            if (readBytes == 0)
            {
                //EOF : Reset the buffer as we did not read anything into it.
                SkipBytes(InternalBufferCount);
                asyncRequest?.CompleteUser(0);
                
                return 0;
            }

            // Now readBytes is a payload size.
            readBytes = _sslState.GetRemainingFrameSize(InternalBuffer, readBytes);

            if (readBytes < 0)
            {
                throw new IOException(SR.net_frame_read_size);
            }

            EnsureInternalBufferSize(SecureChannel.ReadHeaderSize, readBytes);

            if (asyncRequest != null)
            {
                asyncRequest.SetNextRequest(InternalBuffer, SecureChannel.ReadHeaderSize, readBytes, s_readFrameCallback);

                _reader.AsyncReadPacket(asyncRequest);

                if (!asyncRequest.MustCompleteSynchronously)
                {
                    return 0;
                }
                
                readBytes = asyncRequest.Result;
            }
            else
            {
                readBytes = _reader.ReadPacket(InternalBuffer, SecureChannel.ReadHeaderSize, readBytes);
            }
            
            return ProcessFrameBody(readBytes, buffer, offset, count, asyncRequest);
        }

        private static void ReadHeaderCallback(AsyncProtocolRequest asyncRequest)
        {
            try
            {
                SslStreamInternal sslStream    = (SslStreamInternal)asyncRequest.AsyncObject;
                BufferAsyncResult bufferResult = (BufferAsyncResult)asyncRequest.UserAsyncResult;
                if (-1 == sslStream.StartFrameBody(asyncRequest.Result, bufferResult.Buffer, bufferResult.Offset, bufferResult.Count, asyncRequest))
                {
                    // in case we decrypted 0 bytes start another reading.
                    sslStream.StartReading(bufferResult.Buffer, bufferResult.Offset, bufferResult.Count, asyncRequest);
                }
            }
            catch (Exception e)
            {
                if (asyncRequest.IsUserCompleted)
                {
                    // This will throw on a worker thread.
                    throw;
                }

                asyncRequest.CompleteUserWithError(e);
            }
        }