From: Matt Joiner <anacrolix@gmail.com>
Date: Fri, 30 Sep 2016 02:14:34 +0000 (+1000)
Subject: Speed up mse.handshake.establishS
X-Git-Tag: v1.0.0~567
X-Git-Url: http://www.git.stargrave.org/?a=commitdiff_plain;h=d72d93bba7e36b8fb1ca133e02f34dcd840c6922;p=btrtrc.git

Speed up mse.handshake.establishS

Remove possible slice allocation, and avoid reflect.
---

diff --git a/mse/mse.go b/mse/mse.go
index d366aa75..93a80a6b 100644
--- a/mse/mse.go
+++ b/mse/mse.go
@@ -17,7 +17,6 @@ import (
 	"strconv"
 	"sync"
 
-	"github.com/anacrolix/missinggo"
 	"github.com/bradfitz/iter"
 )
 
@@ -167,7 +166,8 @@ func (h *handshake) establishS() (err error) {
 	var Y, S big.Int
 	Y.SetBytes(b[:])
 	S.Exp(&Y, &x, &p)
-	missinggo.CopyExact(&h.s, paddedLeft(S.Bytes(), 96))
+	sBytes := S.Bytes()
+	copy(h.s[96-len(sBytes):96], sBytes)
 	return
 }