time: add fuzz test for Time.appendFormatRFC3339

Time.appendFormatRFC3339 is a specialized implementation of
Time.appendFormat. We expect the two to be identical.
Add a fuzz test to ensure this property.

Updates #54093

Change-Id: I0bc41ee6e016d3dac75d1ac372d8c9c7266d0299
Reviewed-on: https://go-review.googlesource.com/c/go/+/425100
Reviewed-by: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
Auto-Submit: Joseph Tsai <joetsai@digital-static.net>
Reviewed-by: Heschi Kreinick <heschi@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>

diff --git a/src/time/export_test.go b/src/time/export_test.go
index b450aec01f9bec556ffecf33eaec4f4ce365b370..afe1560dead5b21a464f1162b103fcf2c1db43a2 100644 (file)
--- a/src/time/export_test.go
+++ b/src/time/export_test.go
@@ -132,3 +132,6 @@ var StdChunkNames = map[int]string{
 }
 
 var Quote = quote
+
+var AppendFormatAny = Time.appendFormat
+var AppendFormatRFC3339 = Time.appendFormatRFC3339

diff --git a/src/time/format.go b/src/time/format.go
index c32861c6db6b166f254173a6df0700e4212841bc..6d5da323dc1cbffe8cd61b198c8202f2472b497a 100644 (file)
--- a/src/time/format.go
+++ b/src/time/format.go
@@ -618,6 +618,17 @@ func (t Time) Format(layout string) string {
 // AppendFormat is like Format but appends the textual
 // representation to b and returns the extended buffer.
 func (t Time) AppendFormat(b []byte, layout string) []byte {
+       switch layout {
+       case RFC3339:
+               return t.appendFormatRFC3339(b, false)
+       case RFC3339Nano:
+               return t.appendFormatRFC3339(b, true)
+       default:
+               return t.appendFormat(b, layout)
+       }
+}
+
+func (t Time) appendFormat(b []byte, layout string) []byte {
        var (
                name, offset, abs = t.locabs()
 
@@ -630,14 +641,6 @@ func (t Time) AppendFormat(b []byte, layout string) []byte {
                sec   int
        )
 
-       // Handle most frequent layouts separately.
-       switch layout {
-       case RFC3339:
-               return t.appendFormatRFC3339(b, abs, offset, false)
-       case RFC3339Nano:
-               return t.appendFormatRFC3339(b, abs, offset, true)
-       }
-
        // Each iteration generates one std value.
        for layout != "" {
                prefix, std, suffix := nextStdChunk(layout)
@@ -793,7 +796,9 @@ func (t Time) AppendFormat(b []byte, layout string) []byte {
        return b
 }
 
-func (t Time) appendFormatRFC3339(b []byte, abs uint64, offset int, nanos bool) []byte {
+func (t Time) appendFormatRFC3339(b []byte, nanos bool) []byte {
+       _, offset, abs := t.locabs()
+
        // Format date.
        year, month, day, _ := absDate(abs, true)
        b = appendInt(b, year, 4)

diff --git a/src/time/format_test.go b/src/time/format_test.go
index 5c18ef45deb7663176079825fd2dcd8d08c5ae72..4880e1703c15255328a8f45f1b74c9d92d3ede98 100644 (file)
--- a/src/time/format_test.go
+++ b/src/time/format_test.go
@@ -5,7 +5,9 @@
 package time_test
 
 import (
+       "bytes"
        "fmt"
+       "math"
        "strconv"
        "strings"
        "testing"
@@ -911,3 +913,45 @@ func TestParseFractionalSecondsLongerThanNineDigits(t *testing.T) {
                }
        }
 }
+
+func FuzzFormatRFC3339(f *testing.F) {
+       for _, ts := range [][2]int64{
+               {math.MinInt64, math.MinInt64}, // 292277026304-08-26T15:42:51Z
+               {-62167219200, 0},              // 0000-01-01T00:00:00Z
+               {1661201140, 676836973},        // 2022-08-22T20:45:40.676836973Z
+               {253402300799, 999999999},      // 9999-12-31T23:59:59.999999999Z
+               {math.MaxInt64, math.MaxInt64}, // -292277022365-05-08T08:17:07Z
+       } {
+               f.Add(ts[0], ts[1], true, false, 0)
+               f.Add(ts[0], ts[1], false, true, 0)
+               for _, offset := range []int{0, 60, 60 * 60, 99*60*60 + 99*60, 123456789} {
+                       f.Add(ts[0], ts[1], false, false, -offset)
+                       f.Add(ts[0], ts[1], false, false, +offset)
+               }
+       }
+
+       f.Fuzz(func(t *testing.T, sec, nsec int64, useUTC, useLocal bool, tzOffset int) {
+               var loc *Location
+               switch {
+               case useUTC:
+                       loc = UTC
+               case useLocal:
+                       loc = Local
+               default:
+                       loc = FixedZone("", tzOffset)
+               }
+               ts := Unix(sec, nsec).In(loc)
+
+               got := AppendFormatRFC3339(ts, nil, false)
+               want := AppendFormatAny(ts, nil, RFC3339)
+               if !bytes.Equal(got, want) {
+                       t.Errorf("Format(%s, RFC3339) mismatch:\n\tgot:  %s\n\twant: %s", ts, got, want)
+               }
+
+               gotNanos := AppendFormatRFC3339(ts, nil, true)
+               wantNanos := AppendFormatAny(ts, nil, RFC3339Nano)
+               if !bytes.Equal(got, want) {
+                       t.Errorf("Format(%s, RFC3339Nano) mismatch:\n\tgot:  %s\n\twant: %s", ts, gotNanos, wantNanos)
+               }
+       })
+}