net/http: use standard time formatting methods

time.Time has had an AppendFormat method since go1.5 so there's no
need to carry around a custom implementation.

Change-Id: I8e7e5a9ac34e8bf251f5d70555405777ce4e22a8
Reviewed-on: https://go-review.googlesource.com/c/go/+/647955
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Damien Neil <dneil@google.com>
Auto-Submit: Ian Lance Taylor <iant@golang.org>

3 files changed, 1 insertions, 37 deletions

diff --git a/src/net/http/export_test.go b/src/net/http/export_test.go
index 56ebda180b..f2aa663a99 100644
--- a/src/net/http/export_test.go
+++ b/src/net/http/export_test.go
@@ -21,7 +21,6 @@ import (
 var (
 	DefaultUserAgent                  = defaultUserAgent
 	NewLoggingConn                    = newLoggingConn
-	ExportAppendTime                  = appendTime
 	ExportRefererForURL               = refererForURL
 	ExportServerNewConn               = (*Server).newConn
 	ExportCloseWriteAndWait           = (*conn).closeWriteAndWait
diff --git a/src/net/http/serve_test.go b/src/net/http/serve_test.go
index 0c46b1ecc3..e551732016 100644
--- a/src/net/http/serve_test.go
+++ b/src/net/http/serve_test.go
@@ -4302,19 +4302,6 @@ func TestResponseWriterWriteString(t *testing.T) {
 	}
 }
 
-func TestAppendTime(t *testing.T) {
-	var b [len(TimeFormat)]byte
-	t1 := time.Date(2013, 9, 21, 15, 41, 0, 0, time.FixedZone("CEST", 2*60*60))
-	res := ExportAppendTime(b[:0], t1)
-	t2, err := ParseTime(string(res))
-	if err != nil {
-		t.Fatalf("Error parsing time: %s", err)
-	}
-	if !t1.Equal(t2) {
-		t.Fatalf("Times differ; expected: %v, got %v (%s)", t1, t2, string(res))
-	}
-}
-
 func TestServerConnState(t *testing.T) { run(t, testServerConnState, []testMode{http1Mode}) }
 func testServerConnState(t *testing.T, mode testMode) {
 	handler := map[string]func(w ResponseWriter, r *Request){
diff --git a/src/net/http/server.go b/src/net/http/server.go
index cbdc9dd0e3..439efa0c75 100644
--- a/src/net/http/server.go
+++ b/src/net/http/server.go
@@ -991,28 +991,6 @@ func (ecr *expectContinueReader) Close() error {
 // For parsing this time format, see [ParseTime].
 const TimeFormat = "Mon, 02 Jan 2006 15:04:05 GMT"
 
-// appendTime is a non-allocating version of []byte(t.UTC().Format(TimeFormat))
-func appendTime(b []byte, t time.Time) []byte {
-	const days = "SunMonTueWedThuFriSat"
-	const months = "JanFebMarAprMayJunJulAugSepOctNovDec"
-
-	t = t.UTC()
-	yy, mm, dd := t.Date()
-	hh, mn, ss := t.Clock()
-	day := days[3*t.Weekday():]
-	mon := months[3*(mm-1):]
-
-	return append(b,
-		day[0], day[1], day[2], ',', ' ',
-		byte('0'+dd/10), byte('0'+dd%10), ' ',
-		mon[0], mon[1], mon[2], ' ',
-		byte('0'+yy/1000), byte('0'+(yy/100)%10), byte('0'+(yy/10)%10), byte('0'+yy%10), ' ',
-		byte('0'+hh/10), byte('0'+hh%10), ':',
-		byte('0'+mn/10), byte('0'+mn%10), ':',
-		byte('0'+ss/10), byte('0'+ss%10), ' ',
-		'G', 'M', 'T')
-}
-
 var errTooLarge = errors.New("http: request too large")
 
 // Read next request from connection.
@@ -1506,7 +1484,7 @@ func (cw *chunkWriter) writeHeader(p []byte) {
 	}
 
 	if !header.has("Date") {
-		setHeader.date = appendTime(cw.res.dateBuf[:0], time.Now())
+		setHeader.date = time.Now().UTC().AppendFormat(cw.res.dateBuf[:0], TimeFormat)
 	}
 
 	if hasCL && hasTE && te != "identity" {