From bf0fbf3de3b8e3f37aec9ce13f25e7187b9d05a1 Mon Sep 17 00:00:00 2001
From: Matt Joiner <anacrolix@gmail.com>
Date: Mon, 26 Feb 2024 09:28:05 +1100
Subject: [PATCH] Remove mutex in MSE cipher reader
It has a very noticeable overhead when the race detector is running. It probably has some unattributed performance impact otherwise.
---
mse/mse.go | 21 ++++-----------------
1 file changed, 4 insertions(+), 17 deletions(-)
diff --git a/mse/mse.go b/mse/mse.go
index c3a9f3d3..582a451f 100644
--- a/mse/mse.go
+++ b/mse/mse.go
@@ -87,28 +87,15 @@ func newEncrypt(initer bool, s, skey []byte) (c *rc4.Cipher) {
type cipherReader struct {
c *rc4.Cipher
r io.Reader
- mu sync.Mutex
be []byte
}
func (cr *cipherReader) Read(b []byte) (n int, err error) {
- var be []byte
- cr.mu.Lock()
- if len(cr.be) >= len(b) {
- be = cr.be
- cr.be = nil
- cr.mu.Unlock()
- } else {
- cr.mu.Unlock()
- be = make([]byte, len(b))
- }
- n, err = cr.r.Read(be[:len(b)])
- cr.c.XORKeyStream(b[:n], be[:n])
- cr.mu.Lock()
- if len(be) > len(cr.be) {
- cr.be = be
+ if cap(cr.be) < len(b) {
+ cr.be = make([]byte, len(b))
}
- cr.mu.Unlock()
+ n, err = cr.r.Read(cr.be[:len(b)])
+ cr.c.XORKeyStream(b[:n], cr.be[:n])
return
}
--
2.51.0