net: combine append calls in reverseaddr

Combined appends lead to fewer machine code and faster performance.
Some may even say that it makes code more readable.

Running revAddrTests over reverseaddr gives measurable improvements:

	name              old time/op  new time/op  delta
	ReverseAddress-8  4.10µs ± 3%  3.94µs ± 1%  -3.81%  (p=0.000 n=10+9)

Change-Id: I9bda7a20f802bcdffc6e948789765d04c6da04e7
Reviewed-on: https://go-review.googlesource.com/117615
Run-TryBot: Iskander Sharipov <iskander.sharipov@intel.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

diff --git a/src/net/dnsclient.go b/src/net/dnsclient.go
index 2e4bffaab8b85b9ad29d5570de95aca5efeb45fe..e3524280b6aaff7ad96dc77b3dd86bc9c8c63bac 100644 (file)
--- a/src/net/dnsclient.go
+++ b/src/net/dnsclient.go
@@ -27,10 +27,10 @@ func reverseaddr(addr string) (arpa string, err error) {
        // Add it, in reverse, to the buffer
        for i := len(ip) - 1; i >= 0; i-- {
                v := ip[i]
-               buf = append(buf, hexDigit[v&0xF])
-               buf = append(buf, '.')
-               buf = append(buf, hexDigit[v>>4])
-               buf = append(buf, '.')
+               buf = append(buf, hexDigit[v&0xF],
+                       '.',
+                       hexDigit[v>>4],
+                       '.')
        }
        // Append "ip6.arpa." and return (buf already has the final .)
        buf = append(buf, "ip6.arpa."...)