time: format negative monotonic times correctly in Time.String

Fixes #18993

Change-Id: Ia1fa20b6d82384b07e9ba5512b909439e0bec2a5
Reviewed-on: https://go-review.googlesource.com/36611
Run-TryBot: Caleb Spare <cespare@gmail.com>
Reviewed-by: Russ Cox <rsc@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

diff --git a/src/time/format.go b/src/time/format.go
index 7fe5b51bca48e0307148ff321d5df83632cc45b5..37e759f890dbc81512ccb91ecf209779632c5df0 100644 (file)
--- a/src/time/format.go
+++ b/src/time/format.go
@@ -433,17 +433,13 @@ func (t Time) String() string {
 
        // Format monotonic clock reading as m=±ddd.nnnnnnnnn.
        if t.wall&hasMonotonic != 0 {
-               m2 := t.ext
-               m1, m2 := m2/1e9, m2%1e9
-               if m2 < 0 {
-                       m2 += 1e9
-                       m1--
-               }
+               m2 := uint64(t.ext)
                sign := byte('+')
-               if m1 < 0 {
+               if t.ext < 0 {
                        sign = '-'
-                       m1 = -m1
+                       m2 = -m2
                }
+               m1, m2 := m2/1e9, m2%1e9
                m0, m1 := m1/1e9, m1%1e9
                var buf []byte
                buf = append(buf, " m="...)

diff --git a/src/time/mono_test.go b/src/time/mono_test.go
index 0bbb5c11f045cea391803b47910a62c7f3f327ed..b5ae24f0ab3a0b0a9c9aa8ebceaa9c9f9deb8f8d 100644 (file)
--- a/src/time/mono_test.go
+++ b/src/time/mono_test.go
@@ -5,7 +5,7 @@
 package time_test
 
 import (
-       "regexp"
+       "strings"
        "testing"
        . "time"
 )
@@ -231,22 +231,28 @@ func TestMonotonicOverflow(t *testing.T) {
        }
 }
 
-func TestMonotonicString(t *testing.T) {
-       t1 := Now()
-       re := regexp.MustCompile(` m=\+[0-9]+\.[0-9]{9}$`)
-       if !re.MatchString(t1.String()) {
-               t.Errorf("Now().String() = %q, want match for /%s/", t1.String(), re)
-       }
-
-       t2 := Now().Add(-5 * Hour)
-       re = regexp.MustCompile(` m=-[0-9]+\.[0-9]{9}$`)
-       if !re.MatchString(t2.String()) {
-               t.Errorf("Now().Add(-5*Hour).String() = %q, want match for /%s/", t2.String(), re)
-       }
+var monotonicStringTests = []struct {
+       mono int64
+       want string
+}{
+       {0, "m=+0.000000000"},
+       {123456789, "m=+0.123456789"},
+       {-123456789, "m=-0.123456789"},
+       {123456789000, "m=+123.456789000"},
+       {-123456789000, "m=-123.456789000"},
+       {9e18, "m=+9000000000.000000000"},
+       {-9e18, "m=-9000000000.000000000"},
+       {-1 << 63, "m=-9223372036.854775808"},
+}
 
-       t3 := Now().Add(1.2e18)
-       re = regexp.MustCompile(` m=\+120[0-9]{7}\.[0-9]{9}$`)
-       if !re.MatchString(t3.String()) {
-               t.Errorf("Now().Add(12e17).String() = %q, want match for /%s/", t3.String(), re)
+func TestMonotonicString(t *testing.T) {
+       for _, tt := range monotonicStringTests {
+               t1 := Now()
+               SetMono(&t1, tt.mono)
+               s := t1.String()
+               got := s[strings.LastIndex(s, " ")+1:]
+               if got != tt.want {
+                       t.Errorf("with mono=%d: got %q; want %q", tt.mono, got, tt.want)
+               }
        }
 }