From b286aae7a4f2f13d66829d8511c5d5711eec8877 Mon Sep 17 00:00:00 2001
From: Marten Seemann <martenseemann@gmail.com>
Date: Tue, 5 Dec 2017 14:36:58 +0700
Subject: [PATCH] refactor stream ID parity check in the streams map

No functional change expected.
---
 streams_map.go      | 34 ++++++++++++++--------------------
 streams_map_test.go |  8 ++++----
 2 files changed, 18 insertions(+), 24 deletions(-)

diff --git a/streams_map.go b/streams_map.go
index df5b4c99..141d1cdb 100644
--- a/streams_map.go
+++ b/streams_map.go
@@ -73,6 +73,14 @@ func newStreamsMap(newStream newStreamLambda, pers protocol.Perspective, ver pro
 	return &sm
 }
 
+// getStreamPerspective says which side should initiate a stream
+func (m *streamsMap) streamInitiatedBy(id protocol.StreamID) protocol.Perspective {
+	if id%2 == 0 {
+		return protocol.PerspectiveServer
+	}
+	return protocol.PerspectiveClient
+}
+
 // GetOrOpenStream either returns an existing stream, a newly opened stream, or nil if a stream with the provided ID is already closed.
 // Newly opened streams should only originate from the client. To open a stream from the server, OpenStream should be used.
 func (m *streamsMap) GetOrOpenStream(id protocol.StreamID) (streamI, error) {
@@ -92,27 +100,14 @@ func (m *streamsMap) GetOrOpenStream(id protocol.StreamID) (streamI, error) {
 		return s, nil
 	}
 
-	if m.perspective == protocol.PerspectiveServer {
-		if id%2 == 0 {
-			if id <= m.nextStream { // this is a server-side stream that we already opened. Must have been closed already
-				return nil, nil
-			}
-			return nil, qerr.Error(qerr.InvalidStreamID, fmt.Sprintf("attempted to open stream %d from client-side", id))
-		}
-		if id <= m.highestStreamOpenedByPeer { // this is a client-side stream that doesn't exist anymore. Must have been closed already
+	if m.perspective == m.streamInitiatedBy(id) {
+		if id <= m.nextStream { // this is a stream opened by us. Must have been closed already
 			return nil, nil
 		}
+		return nil, qerr.Error(qerr.InvalidStreamID, fmt.Sprintf("peer attempted to open stream %d", id))
 	}
-	if m.perspective == protocol.PerspectiveClient {
-		if id%2 == 1 {
-			if id <= m.nextStream { // this is a client-side stream that we already opened.
-				return nil, nil
-			}
-			return nil, qerr.Error(qerr.InvalidStreamID, fmt.Sprintf("attempted to open stream %d from server-side", id))
-		}
-		if id <= m.highestStreamOpenedByPeer { // this is a server-side stream that doesn't exist anymore. Must have been closed already
-			return nil, nil
-		}
+	if id <= m.highestStreamOpenedByPeer { // this is a peer-initiated stream that doesn't exist anymore. Must have been closed already
+		return nil, nil
 	}
 
 	// sid is the next stream that will be opened
@@ -123,8 +118,7 @@ func (m *streamsMap) GetOrOpenStream(id protocol.StreamID) (streamI, error) {
 	}
 
 	for ; sid <= id; sid += 2 {
-		_, err := m.openRemoteStream(sid)
-		if err != nil {
+		if _, err := m.openRemoteStream(sid); err != nil {
 			return nil, err
 		}
 	}
diff --git a/streams_map_test.go b/streams_map_test.go
index 14ec0e6c..11953811 100644
--- a/streams_map_test.go
+++ b/streams_map_test.go
@@ -64,14 +64,14 @@ var _ = Describe("Streams Map", func() {
 
 				It("rejects streams with even IDs", func() {
 					_, err := m.GetOrOpenStream(6)
-					Expect(err).To(MatchError("InvalidStreamID: attempted to open stream 6 from client-side"))
+					Expect(err).To(MatchError("InvalidStreamID: peer attempted to open stream 6"))
 				})
 
 				It("rejects streams with even IDs, which are lower thatn the highest client-side stream", func() {
 					_, err := m.GetOrOpenStream(5)
 					Expect(err).NotTo(HaveOccurred())
 					_, err = m.GetOrOpenStream(4)
-					Expect(err).To(MatchError("InvalidStreamID: attempted to open stream 4 from client-side"))
+					Expect(err).To(MatchError("InvalidStreamID: peer attempted to open stream 4"))
 				})
 
 				It("gets existing streams", func() {
@@ -421,14 +421,14 @@ var _ = Describe("Streams Map", func() {
 			Context("client-side streams", func() {
 				It("rejects streams with odd IDs", func() {
 					_, err := m.GetOrOpenStream(5)
-					Expect(err).To(MatchError("InvalidStreamID: attempted to open stream 5 from server-side"))
+					Expect(err).To(MatchError("InvalidStreamID: peer attempted to open stream 5"))
 				})
 
 				It("rejects streams with odds IDs, which are lower thatn the highest server-side stream", func() {
 					_, err := m.GetOrOpenStream(6)
 					Expect(err).NotTo(HaveOccurred())
 					_, err = m.GetOrOpenStream(5)
-					Expect(err).To(MatchError("InvalidStreamID: attempted to open stream 5 from server-side"))
+					Expect(err).To(MatchError("InvalidStreamID: peer attempted to open stream 5"))
 				})
 
 				It("gets new streams", func() {