Method poll_next

arrow-flight/src/encode.rs:396–437

(
        mut self: Pin<&mut Self>,
        cx: &mut std::task::Context<'_>,
    )

    type Item = Result<FlightData>;

    fn poll_next(
        mut self: Pin<&mut Self>,
        cx: &mut std::task::Context<'_>,
    ) -> Poll<Option<Self::Item>> {
        loop {
            if self.done && self.queue.is_empty() {
                return Poll::Ready(None);
            }

            // Any messages queued to send?
            if let Some(data) = self.queue.pop_front() {
                return Poll::Ready(Some(Ok(data)));
            }

            // Get next batch
            let batch = ready!(self.inner.poll_next_unpin(cx));

            match batch {
                None => {
                    // inner is done
                    self.done = true;
                    // queue must also be empty so we are done
                    assert!(self.queue.is_empty());
                    return Poll::Ready(None);
                }
                Some(Err(e)) => {
                    // error from inner
                    self.done = true;
                    self.queue.clear();
                    return Poll::Ready(Some(Err(e)));
                }
                Some(Ok(batch)) => {
                    // had data, encode into the queue
                    if let Err(e) = self.encode_batch(batch) {
                        self.done = true;
                        self.queue.clear();
                        return Poll::Ready(Some(Err(e)));
                    }
                }
            }
        }
    }
}

/// Defines how a [`FlightDataEncoder`] encodes [`DictionaryArray`]s