fn send_internal()

in neqo-transport/src/send_stream.rs [1246:1293]
43 lines of code
7 McCabe index (conditional complexity)

    fn send_internal(&mut self, buf: &[u8], atomic: bool) -> Res<usize> {
        if buf.is_empty() {
            qerror!("[{self}] zero-length send on stream");
            return Err(Error::InvalidInput);
        }

        if let SendStreamState::Ready { fc, conn_fc } = &mut self.state {
            let owned_fc = mem::replace(fc, SenderFlowControl::new(self.stream_id, 0));
            let owned_conn_fc = Rc::clone(conn_fc);
            self.state.transition(SendStreamState::Send {
                fc: owned_fc,
                conn_fc: owned_conn_fc,
                send_buf: TxBuffer::new(),
            });
        }

        if !matches!(self.state, SendStreamState::Send { .. }) {
            return Err(Error::FinalSizeError);
        }

        let buf = if self.avail() == 0 {
            return Ok(0);
        } else if self.avail() < buf.len() {
            if atomic {
                self.send_blocked_if_space_needed(buf.len());
                return Ok(0);
            }

            &buf[..self.avail()]
        } else {
            buf
        };

        match &mut self.state {
            SendStreamState::Ready { .. } => unreachable!(),
            SendStreamState::Send {
                fc,
                conn_fc,
                send_buf,
            } => {
                let sent = send_buf.send(buf);
                fc.consume(sent);
                conn_fc.borrow_mut().consume(sent);
                Ok(sent)
            }
            _ => Err(Error::FinalSizeError),
        }
    }