1 files changed, 356 insertions, 0 deletions
diff --git a/src/send.rs b/src/send.rs
new file mode 100644
index 0000000..0db0ba7
--- /dev/null
+++ b/src/send.rs
@@ -0,0 +1,356 @@
+use std::collections::{HashMap, VecDeque};
+use std::pin::Pin;
+use std::sync::Arc;
+use std::task::{Context, Poll};
+
+use async_trait::async_trait;
+use bytes::{BufMut, Bytes, BytesMut};
+use log::*;
+
+use futures::{AsyncWriteExt, Future};
+use kuska_handshake::async_std::BoxStreamWrite;
+use tokio::sync::mpsc;
+
+use crate::error::*;
+use crate::message::*;
+use crate::stream::*;
+
+// Messages are sent by chunks
+// Chunk format:
+// - u32 BE: request id (same for request and response)
+// - u16 BE: chunk length + flags:
+//		CHUNK_FLAG_HAS_CONTINUATION when this is not the last chunk of the stream
+//		CHUNK_FLAG_ERROR if this chunk denotes an error
+//		(these two flags are exclusive, an error denotes the end of the stream)
+//		**special value** 0xFFFF indicates a CANCEL message
+// - [u8; chunk_length], either
+//   - if not error: chunk data
+//   - if error:
+//       - u8: error kind, encoded using error::io_errorkind_to_u8
+//       - rest: error message
+//   - absent for cancel messag
+
+pub(crate) type RequestID = u32;
+pub(crate) type ChunkLength = u16;
+
+pub(crate) const MAX_CHUNK_LENGTH: ChunkLength = 0x3FF0;
+pub(crate) const CHUNK_FLAG_ERROR: ChunkLength = 0x4000;
+pub(crate) const CHUNK_FLAG_HAS_CONTINUATION: ChunkLength = 0x8000;
+pub(crate) const CHUNK_LENGTH_MASK: ChunkLength = 0x3FFF;
+pub(crate) const CANCEL_REQUEST: ChunkLength = 0xFFFF;
+
+pub(crate) enum SendItem {
+	Stream(RequestID, RequestPriority, Option<OrderTag>, ByteStream),
+	Cancel(RequestID),
+}
+
+// ----
+
+struct SendQueue {
+	items: Vec<(u8, SendQueuePriority)>,
+}
+
+struct SendQueuePriority {
+	items: VecDeque<SendQueueItem>,
+	order: HashMap<u64, VecDeque<u64>>,
+}
+
+struct SendQueueItem {
+	id: RequestID,
+	prio: RequestPriority,
+	order_tag: Option<OrderTag>,
+	data: ByteStreamReader,
+	sent: usize,
+}
+
+impl SendQueue {
+	fn new() -> Self {
+		Self {
+			items: Vec::with_capacity(64),
+		}
+	}
+	fn push(&mut self, item: SendQueueItem) {
+		let prio = item.prio;
+		let pos_prio = match self.items.binary_search_by(|(p, _)| p.cmp(&prio)) {
+			Ok(i) => i,
+			Err(i) => {
+				self.items.insert(i, (prio, SendQueuePriority::new()));
+				i
+			}
+		};
+		self.items[pos_prio].1.push(item);
+	}
+	fn remove(&mut self, id: RequestID) {
+		for (_, prioq) in self.items.iter_mut() {
+			prioq.remove(id);
+		}
+		self.items.retain(|(_prio, q)| !q.is_empty());
+	}
+	fn is_empty(&self) -> bool {
+		self.items.iter().all(|(_k, v)| v.is_empty())
+	}
+
+	// this is like an async fn, but hand implemented
+	fn next_ready(&mut self) -> SendQueuePollNextReady<'_> {
+		SendQueuePollNextReady { queue: self }
+	}
+}
+
+impl SendQueuePriority {
+	fn new() -> Self {
+		Self {
+			items: VecDeque::new(),
+			order: HashMap::new(),
+		}
+	}
+	fn push(&mut self, item: SendQueueItem) {
+		if let Some(OrderTag(stream, order)) = item.order_tag {
+			let order_vec = self.order.entry(stream).or_default();
+			let i = order_vec.iter().take_while(|o2| **o2 < order).count();
+			order_vec.insert(i, order);
+		}
+		self.items.push_front(item);
+	}
+	fn remove(&mut self, id: RequestID) {
+		if let Some(i) = self.items.iter().position(|x| x.id == id) {
+			let item = self.items.remove(i).unwrap();
+			if let Some(OrderTag(stream, order)) = item.order_tag {
+				let order_vec = self.order.get_mut(&stream).unwrap();
+				let j = order_vec.iter().position(|x| *x == order).unwrap();
+				order_vec.remove(j).unwrap();
+				if order_vec.is_empty() {
+					self.order.remove(&stream);
+				}
+			}
+		}
+	}
+	fn is_empty(&self) -> bool {
+		self.items.is_empty()
+	}
+	fn poll_next_ready(&mut self, ctx: &mut Context<'_>) -> Poll<(RequestID, DataFrame)> {
+		for (j, item) in self.items.iter_mut().enumerate() {
+			if let Some(OrderTag(stream, order)) = item.order_tag {
+				if order > *self.order.get(&stream).unwrap().front().unwrap() {
+					continue;
+				}
+			}
+
+			let mut item_reader = item.data.read_exact_or_eos(MAX_CHUNK_LENGTH as usize);
+			if let Poll::Ready(bytes_or_err) = Pin::new(&mut item_reader).poll(ctx) {
+				let id = item.id;
+				let eos = item.data.eos();
+
+				let packet = bytes_or_err.map_err(|e| match e {
+					ReadExactError::Stream(err) => err,
+					_ => unreachable!(),
+				});
+
+				let is_err = packet.is_err();
+				let data_frame = DataFrame::from_packet(packet, !eos);
+				item.sent += data_frame.data().len();
+
+				if eos || is_err {
+					// If item had an order tag, remove it from the corresponding ordering list
+					if let Some(OrderTag(stream, order)) = item.order_tag {
+						let order_stream = self.order.get_mut(&stream).unwrap();
+						assert_eq!(order_stream.pop_front(), Some(order));
+						if order_stream.is_empty() {
+							self.order.remove(&stream);
+						}
+					}
+					// Remove item from sending queue
+					self.items.remove(j);
+				} else {
+					// Move item later in send queue to implement LAS scheduling
+					// (LAS = Least Attained Service)
+					for k in j..self.items.len() - 1 {
+						if self.items[k].sent >= self.items[k + 1].sent {
+							self.items.swap(k, k + 1);
+						} else {
+							break;
+						}
+					}
+				}
+
+				return Poll::Ready((id, data_frame));
+			}
+		}
+
+		Poll::Pending
+	}
+	fn dump(&self, prio: u8) -> String {
+		self.items
+			.iter()
+			.map(|i| format!("[{} {} {:?} @{}]", prio, i.id, i.order_tag, i.sent))
+			.collect::<Vec<_>>()
+			.join(" ")
+	}
+}
+
+struct SendQueuePollNextReady<'a> {
+	queue: &'a mut SendQueue,
+}
+
+impl<'a> futures::Future for SendQueuePollNextReady<'a> {
+	type Output = (RequestID, DataFrame);
+
+	fn poll(mut self: Pin<&mut Self>, ctx: &mut Context<'_>) -> Poll<Self::Output> {
+		for (i, (_prio, items_at_prio)) in self.queue.items.iter_mut().enumerate() {
+			if let Poll::Ready(res) = items_at_prio.poll_next_ready(ctx) {
+				if items_at_prio.is_empty() {
+					self.queue.items.remove(i);
+				}
+				return Poll::Ready(res);
+			}
+		}
+		// If the queue is empty, this futures is eternally pending.
+		// This is ok because we use it in a select with another future
+		// that can interrupt it.
+		Poll::Pending
+	}
+}
+
+enum DataFrame {
+	/// a fixed size buffer containing some data + a boolean indicating whether
+	/// there may be more data comming from this stream. Can be used for some
+	/// optimization. It's an error to set it to false if there is more data, but it is correct
+	/// (albeit sub-optimal) to set it to true if there is nothing coming after
+	Data(Bytes, bool),
+	/// An error code automatically signals the end of the stream
+	Error(Bytes),
+}
+
+impl DataFrame {
+	fn from_packet(p: Packet, has_cont: bool) -> Self {
+		match p {
+			Ok(bytes) => {
+				assert!(bytes.len() <= MAX_CHUNK_LENGTH as usize);
+				Self::Data(bytes, has_cont)
+			}
+			Err(e) => {
+				let mut buf = BytesMut::new();
+				buf.put_u8(io_errorkind_to_u8(e.kind()));
+
+				let msg = format!("{}", e).into_bytes();
+				if msg.len() > (MAX_CHUNK_LENGTH - 1) as usize {
+					buf.put(&msg[..(MAX_CHUNK_LENGTH - 1) as usize]);
+				} else {
+					buf.put(&msg[..]);
+				}
+
+				Self::Error(buf.freeze())
+			}
+		}
+	}
+
+	fn header(&self) -> [u8; 2] {
+		let header_u16 = match self {
+			DataFrame::Data(data, false) => data.len() as u16,
+			DataFrame::Data(data, true) => data.len() as u16 | CHUNK_FLAG_HAS_CONTINUATION,
+			DataFrame::Error(msg) => msg.len() as u16 | CHUNK_FLAG_ERROR,
+		};
+		ChunkLength::to_be_bytes(header_u16)
+	}
+
+	fn data(&self) -> &[u8] {
+		match self {
+			DataFrame::Data(ref data, _) => &data[..],
+			DataFrame::Error(ref msg) => &msg[..],
+		}
+	}
+}
+
+/// The SendLoop trait, which is implemented both by the client and the server
+/// connection objects (ServerConna and ClientConn) adds a method `.send_loop()`
+/// that takes a channel of messages to send and an asynchronous writer,
+/// and sends messages from the channel to the async writer, putting them in a queue
+/// before being sent and doing the round-robin sending strategy.
+///
+/// The `.send_loop()` exits when the sending end of the channel is closed,
+/// or if there is an error at any time writing to the async writer.
+#[async_trait]
+pub(crate) trait SendLoop: Sync {
+	async fn send_loop<W>(
+		self: Arc<Self>,
+		msg_recv: mpsc::UnboundedReceiver<SendItem>,
+		mut write: BoxStreamWrite<W>,
+		debug_name: String,
+	) -> Result<(), Error>
+	where
+		W: AsyncWriteExt + Unpin + Send + Sync,
+	{
+		let mut sending = SendQueue::new();
+		let mut msg_recv = Some(msg_recv);
+		while msg_recv.is_some() || !sending.is_empty() {
+			trace!(
+				"send_loop({}): queue = {:?}",
+				debug_name,
+				sending
+					.items
+					.iter()
+					.map(|(prio, i)| i.dump(*prio))
+					.collect::<Vec<_>>()
+					.join(" ; ")
+			);
+
+			let recv_fut = async {
+				if let Some(chan) = &mut msg_recv {
+					chan.recv().await
+				} else {
+					futures::future::pending().await
+				}
+			};
+			let send_fut = sending.next_ready();
+
+			// recv_fut is cancellation-safe according to tokio doc,
+			// send_fut is cancellation-safe as implemented above?
+			tokio::select! {
+				biased;	// always read incomming channel first if it has data
+				sth = recv_fut => {
+					match sth {
+						Some(SendItem::Stream(id, prio, order_tag, data)) => {
+							trace!("send_loop({}): add stream {} to send", debug_name, id);
+							sending.push(SendQueueItem {
+								id,
+								prio,
+								order_tag,
+								data: ByteStreamReader::new(data),
+								sent: 0,
+							})
+						}
+						Some(SendItem::Cancel(id)) => {
+							trace!("send_loop({}): cancelling {}", debug_name, id);
+							sending.remove(id);
+							let header_id = RequestID::to_be_bytes(id);
+							write.write_all(&header_id[..]).await?;
+							write.write_all(&ChunkLength::to_be_bytes(CANCEL_REQUEST)).await?;
+							write.flush().await?;
+						}
+						None => {
+							msg_recv = None;
+						}
+					};
+				}
+				(id, data) = send_fut => {
+					trace!(
+						"send_loop({}): id {}, send {} bytes, header_size {}",
+						debug_name,
+						id,
+						data.data().len(),
+						hex::encode(data.header())
+					);
+
+					let header_id = RequestID::to_be_bytes(id);
+					write.write_all(&header_id[..]).await?;
+
+					write.write_all(&data.header()).await?;
+					write.write_all(data.data()).await?;
+					write.flush().await?;
+				}
+			}
+		}
+
+		let _ = write.goodbye().await;
+		Ok(())
+	}
+}