Remove unnecessary *bytes.Reader in Stream.Write()

Prior to this change, each call to Stream.Write() would allocate 1 or
more *bytes.Reader instances. While these are small, it makes the Go
garbage collector do unnecessary work.

Besides the inefficiency at the machine level, it also makes no sense
at the human level to create an io.Reader and use io.Copy when a
single Write() call suffices.

session.go

@@ -80,7 +80,7 @@ type Session struct {
 // or to directly send a header
 type sendReady struct {
 	Hdr  []byte
-	Body io.Reader
+	Body []byte
 	Err  chan error
 }
 
@@ -352,7 +352,7 @@ func (s *Session) keepalive() {
 }
 
 // waitForSendErr waits to send a header, checking for a potential shutdown
-func (s *Session) waitForSend(hdr header, body io.Reader) error {
+func (s *Session) waitForSend(hdr header, body []byte) error {
 	errCh := make(chan error, 1)
 	return s.waitForSendErr(hdr, body, errCh)
 }
@@ -360,7 +360,7 @@ func (s *Session) waitForSend(hdr header, body io.Reader) error {
 // waitForSendErr waits to send a header with optional data, checking for a
 // potential shutdown. Since there's the expectation that sends can happen
 // in a timely manner, we enforce the connection write timeout here.
-func (s *Session) waitForSendErr(hdr header, body io.Reader, errCh chan error) error {
+func (s *Session) waitForSendErr(hdr header, body []byte, errCh chan error) error {
 	t := timerPool.Get()
 	timer := t.(*time.Timer)
 	timer.Reset(s.config.ConnectionWriteTimeout)
@@ -440,7 +440,7 @@ func (s *Session) send() {
 
 			// Send data from a body if given
 			if ready.Body != nil {
-				_, err := io.Copy(s.conn, ready.Body)
+				_, err := s.conn.Write(ready.Body)
 				if err != nil {
 					s.logger.Printf("[ERR] yamux: Failed to write body: %v", err)
 					asyncSendErr(ready.Err, err)

stream.go

@@ -169,7 +169,7 @@ func (s *Stream) Write(b []byte) (n int, err error) {
 func (s *Stream) write(b []byte) (n int, err error) {
 	var flags uint16
 	var max uint32
-	var body io.Reader
+	var body []byte
 START:
 	s.stateLock.Lock()
 	switch s.state {
@@ -195,7 +195,7 @@ START:
 
 	// Send up to our send window
 	max = min(window, uint32(len(b)))
-	body = bytes.NewReader(b[:max])
+	body = b[:max]
 
 	// Send the header
 	s.sendHdr.encode(typeData, flags, s.id, max)