From f1f17ffdbc4f43defc857db305019214db201a8d Mon Sep 17 00:00:00 2001
From: Michael Haro <mharo@google.com>
Date: Mon, 23 Feb 2015 23:11:31 -0800
Subject: [PATCH] Split Copy into Copy and CopyTo.

CopyTo allows bypassing allocating a new Msg to work towards less
allocation GC churn.
---
 msg.go | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/msg.go b/msg.go
index 209e63ed..0b63e986 100644
--- a/msg.go
+++ b/msg.go
@@ -1915,7 +1915,11 @@ func Copy(r RR) RR {
 
 // Copy returns a new *Msg which is a deep-copy of dns.
 func (dns *Msg) Copy() *Msg {
-	r1 := new(Msg)
+	return dns.CopyTo(new(Msg))
+}
+
+// CopyTo copies the contents to the provided message using a deep-copy and returns the copy.
+func (dns *Msg) CopyTo(r1 *Msg) *Msg {
 	r1.MsgHdr = dns.MsgHdr
 	r1.Compress = dns.Compress