1 files changed, 45 insertions, 12 deletions

diff --git a/src/send.rs b/src/send.rs
index d927d98..780bbcf 100644
--- a/src/send.rs
+++ b/src/send.rs
@@ -22,6 +22,7 @@ use crate::stream::*;
 //		CHUNK_HAS_CONTINUATION when this is not the last chunk of the stream
 //		ERROR_MARKER 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:
@@ -35,8 +36,14 @@ pub(crate) const MAX_CHUNK_LENGTH: ChunkLength = 0x3FF0;
 pub(crate) const ERROR_MARKER: ChunkLength = 0x4000;
 pub(crate) const CHUNK_HAS_CONTINUATION: ChunkLength = 0x8000;
 pub(crate) const CHUNK_LENGTH_MASK: ChunkLength = 0x3FFF;
+pub(crate) const CANCEL_REQUEST: ChunkLength = 0xFFFF;
 
-pub(crate) type SendStream = (RequestID, RequestPriority, Option<OrderTag>, ByteStream);
+pub(crate) enum SendItem {
+	Stream(RequestID, RequestPriority, Option<OrderTag>, ByteStream),
+	Cancel(RequestID),
+}
+
+// ----
 
 struct SendQueue {
 	items: Vec<(u8, SendQueuePriority)>,
@@ -71,6 +78,11 @@ impl SendQueue {
 		};
 		self.items[pos_prio].1.push(item);
 	}
+	fn remove(&mut self, id: RequestID) {
+		for (_, prioq) in self.items.iter_mut() {
+			prioq.remove(id);
+		}
+	}
 	fn is_empty(&self) -> bool {
 		self.items.iter().all(|(_k, v)| v.is_empty())
 	}
@@ -96,6 +108,16 @@ impl SendQueuePriority {
 		}
 		self.items.push_back(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();
+			}
+		}
+	}
 	fn is_empty(&self) -> bool {
 		self.items.is_empty()
 	}
@@ -229,7 +251,7 @@ impl DataFrame {
 pub(crate) trait SendLoop: Sync {
 	async fn send_loop<W>(
 		self: Arc<Self>,
-		msg_recv: mpsc::UnboundedReceiver<SendStream>,
+		msg_recv: mpsc::UnboundedReceiver<SendItem>,
 		mut write: BoxStreamWrite<W>,
 		debug_name: String,
 	) -> Result<(), Error>
@@ -264,16 +286,27 @@ pub(crate) trait SendLoop: Sync {
 			tokio::select! {
 				biased;	// always read incomming channel first if it has data
 				sth = recv_fut => {
-					if let Some((id, prio, order_tag, data)) = sth {
-						trace!("send_loop({}): add stream {} to send", debug_name, id);
-						sending.push(SendQueueItem {
-							id,
-							prio,
-							order_tag,
-							data: ByteStreamReader::new(data),
-						});
-					} else {
-						msg_recv = None;
+					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),
+							})
+						}
+						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 => {