optimize the performance of the function appendFormatRFC3339

Author: fx408

src/time/format_rfc3339.go

@@ -18,9 +18,8 @@ import "errors"
 func (t Time) appendFormatRFC3339(b []byte, nanos bool) []byte {
 	_, offset, abs := t.locabs()
 
-	// Format date.
+	// Format date and time.
 	year, month, day := abs.days().date()
-	// Format time.
 	hour, min, sec := abs.clock()
 
 	b = appendIntWidth4(b, year)

src/time/format_test.go

@@ -1095,10 +1095,10 @@ func FuzzParseRFC3339(f *testing.F) {
 func TestAppendIntWidth(t *testing.T) {
 	values := []int{0, -1, 1, 10, -10, 99, -99, 9999, -9999, 10001}
 	for _, v := range values {
-		exp := AppendInt(nil, v, 4)
+		want := AppendInt(nil, v, 4)
 		got := AppendIntWidth4(nil, v)
-		if !bytes.Equal(got, exp) {
-			t.Errorf("AppendIntWidth4(%d) = %s, want %s", v, got, exp)
+		if !bytes.Equal(got, want) {
+			t.Errorf("AppendIntWidth4(%d) = %s, want %s", v, got, want)
 		}
 	}
 }
@@ -1107,23 +1107,23 @@ func BenchmarkAppendIntWidth4(b *testing.B) {
 	b.Run("name=AppendInt", func(b *testing.B) {
 		var buf = make([]byte, 0, 8)
 		b.ResetTimer()
-		for i := 0; i < b.N; i++ {
+		for b.Loop() {
 			buf = AppendInt(buf[:0], 360, 4)
 		}
 	})
 	b.Run("name=AppendIntWidth4", func(b *testing.B) {
 		var buf = make([]byte, 0, 8)
 		b.ResetTimer()
-		for i := 0; i < b.N; i++ {
+		for b.Loop() {
 			buf = AppendIntWidth4(buf[:0], 360)
 		}
 	})
 }
 
 func BenchmarkTimeFormatRFC3339(b *testing.B) {
-	tm := Now()
+	tm := Unix(1661201140, 676836973)
 	buf := make([]byte, 0, 64)
-	for i := 0; i < b.N; i++ {
+	for b.Loop() {
 		buf = tm.AppendFormat(buf[:0], RFC3339)
 	}
 }