From 2321642f3cf6d6371f638126d713e645311994ed Mon Sep 17 00:00:00 2001
From: David Fifield <david@bamsoftware.com>
Date: Thu, 22 Sep 2022 15:53:04 -0600
Subject: [PATCH] Hoist temporary buffers outside the loop.
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Otherwise the buffers are re-allocated on every iteration, which is a
surprise to me. I thought the compiler would do this transformation
itself.

Now there is just one allocation per client←server read (one
messageReader) and two allocations per server←client read (one
messageReader and one messageWriter).

	$ go test -bench=BenchmarkReadWrite -benchmem -benchtime=5s
	BenchmarkReadWrite/c←s_150-4              481054             12849 ns/op          11.67 MB/s           8 B/op          1 allocs/op
	BenchmarkReadWrite/s←c_150-4              421809             14095 ns/op          10.64 MB/s          56 B/op          2 allocs/op
	BenchmarkReadWrite/c←s_3000-4             208564             28003 ns/op         107.13 MB/s          16 B/op          2 allocs/op
	BenchmarkReadWrite/s←c_3000-4             186320             30576 ns/op          98.12 MB/s         112 B/op          4 allocs/op
---
 common/websocketconn/websocketconn.go | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/common/websocketconn/websocketconn.go b/common/websocketconn/websocketconn.go
index 3fdcb79..e5256df 100644
--- a/common/websocketconn/websocketconn.go
+++ b/common/websocketconn/websocketconn.go
@@ -42,6 +42,7 @@ func (conn *Conn) SetDeadline(t time.Time) error {
 }
 
 func readLoop(w io.Writer, ws *websocket.Conn) error {
+	var buf [2048]byte
 	for {
 		messageType, r, err := ws.NextReader()
 		if err != nil {
@@ -50,7 +51,6 @@ func readLoop(w io.Writer, ws *websocket.Conn) error {
 		if messageType != websocket.BinaryMessage && messageType != websocket.TextMessage {
 			continue
 		}
-		var buf [2048]byte
 		_, err = io.CopyBuffer(w, r, buf[:])
 		if err != nil {
 			return err
@@ -59,8 +59,8 @@ func readLoop(w io.Writer, ws *websocket.Conn) error {
 }
 
 func writeLoop(ws *websocket.Conn, r io.Reader) error {
+	var buf [2048]byte
 	for {
-		var buf [2048]byte
 		n, err := r.Read(buf[:])
 		if err != nil {
 			return err