private Task SendFrameLockAcquiredNonCancelableAsync()

in src/Microsoft.Azure.Relay/WebSockets/NetStandard20/ManagedWebSocket.cs [390:449]
44 lines of code
7 McCabe index (conditional complexity)

        private Task SendFrameLockAcquiredNonCancelableAsync(MessageOpcode opcode, bool endOfMessage, ArraySegment<byte> payloadBuffer)
        {
            Debug.Assert(_sendFrameAsyncLock.CurrentCount == 0, "Caller should hold the _sendFrameAsyncLock");

            // If we get here, the cancellation token is not cancelable so we don't have to worry about it,
            // and we own the semaphore, so we don't need to asynchronously wait for it.
            Task writeTask = null;
            bool releaseSemaphoreAndSendBuffer = true;
            try
            {
                // Write the payload synchronously to the buffer, then write that buffer out to the network.
                int sendBytes = WriteFrameToSendBuffer(opcode, endOfMessage, payloadBuffer);
                writeTask = _stream.WriteAsync(_sendBuffer, 0, sendBytes, CancellationToken.None);

                // If the operation happens to complete synchronously (or, more specifically, by
                // the time we get from the previous line to here, release the semaphore, propagate
                // exceptions, and we're done.
                if (writeTask.IsCompleted)
                {
                    writeTask.GetAwaiter().GetResult(); // propagate any exceptions
                    return Task.CompletedTask;
                }

                // Up until this point, if an exception occurred (such as when accessing _stream or when
                // calling GetResult), we want to release the semaphore and the send buffer. After this point,
                // both need to be held until writeTask completes.
                releaseSemaphoreAndSendBuffer = false;
            }
            catch (Exception exc)
            {
                return Task.FromException(_state == WebSocketState.Aborted ?
                    CreateOperationCanceledException(exc) :
                    new WebSocketException(WebSocketError.ConnectionClosedPrematurely, exc));
            }
            finally
            {
                if (releaseSemaphoreAndSendBuffer)
                {
                    _sendFrameAsyncLock.Release();
                    ReleaseSendBuffer();
                }
            }

            // The write was not yet completed.  Create and return a continuation that will
            // release the semaphore and translate any exception that occurred.
            return writeTask.ContinueWith((t, s) =>
            {
                var thisRef = (ManagedWebSocket)s;
                thisRef._sendFrameAsyncLock.Release();
                thisRef.ReleaseSendBuffer();

                try { t.GetAwaiter().GetResult(); }
                catch (Exception exc)
                {
                    throw thisRef._state == WebSocketState.Aborted ?
                        CreateOperationCanceledException(exc) :
                        new WebSocketException(WebSocketError.ConnectionClosedPrematurely, exc);
                }
            }, this, CancellationToken.None, TaskContinuationOptions.ExecuteSynchronously, TaskScheduler.Default);
        }