add SendResponse::poll_reset and SendStream::poll_reset to listen for reset streams (#279)

src/proto/streams/state.rs

@@ -1,7 +1,9 @@
+use std::io;
+
 use codec::{RecvError, UserError};
 use codec::UserError::*;
 use frame::Reason;
-use proto;
+use proto::{self, PollReset};
 
 use self::Inner::*;
 use self::Peer::*;
@@ -399,8 +401,6 @@ impl State {
     }
 
     pub fn ensure_recv_open(&self) -> Result<bool, proto::Error> {
-        use std::io;
-
         // TODO: Is this correct?
         match self.inner {
             Closed(Cause::Proto(reason)) |
@@ -412,6 +412,24 @@ impl State {
             _ => Ok(true),
         }
     }
+
+    /// Returns a reason if the stream has been reset.
+    pub(super) fn ensure_reason(&self, mode: PollReset) -> Result<Option<Reason>, ::Error> {
+        match self.inner {
+            Closed(Cause::Proto(reason)) |
+            Closed(Cause::LocallyReset(reason)) |
+            Closed(Cause::Scheduled(reason)) => Ok(Some(reason)),
+            Closed(Cause::Io) => Err(proto::Error::Io(io::ErrorKind::BrokenPipe.into()).into()),
+            Open { local: Streaming, .. } |
+            HalfClosedRemote(Streaming) => match mode {
+                PollReset::AwaitingHeaders => {
+                    Err(UserError::PollResetAfterSendResponse.into())
+                },
+                PollReset::Streaming => Ok(None),
+            },
+            _ => Ok(None),
+        }
+    }
 }
 
 impl Default for State {