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Revert "time: optimize Sub"

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This reverts commit CL 131196 because there is a bug
in the calculation of nanoseconds.

Fixes #33677

Change-Id: Ic8e94c547ee29b8aeda1b9a5cb9764dbf47b14b4
Reviewed-on: https://go-review.googlesource.com/c/go/+/190497
Run-TryBot: Andrew Bonventre <andybons@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
Reviewed-by: Andrew Bonventre <andybons@golang.org>
This commit is contained in:
Joe Tsai 2019-08-16 03:16:34 +00:00
parent 0212f0410f
commit 4983a0b75b
2 changed files with 9 additions and 34 deletions
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33
src/time/time.go
View File

@ -906,33 +906,16 @@ func (t Time) Sub(u Time) Duration {
}
return d
}
ts, us := t.sec(), u.sec()
var sec, nsec, d int64
ssub := ts - us
if (ssub < ts) != (us > 0) {
goto overflow
}
if ssub < int64(minDuration/Second) || ssub > int64(maxDuration/Second) {
goto overflow
}
sec = ssub * int64(Second)
nsec = int64(t.nsec() - u.nsec())
d = sec + nsec
if (d > sec) != (nsec > 0) {
goto overflow
}
return Duration(d)
overflow:
if t.Before(u) {
d := Duration(t.sec()-u.sec())*Second + Duration(t.nsec()-u.nsec())
// Check for overflow or underflow.
switch {
case u.Add(d).Equal(t):
return d // d is correct
case t.Before(u):
return minDuration // t - u is negative out of range
default:
return maxDuration // t - u is positive out of range
}
return maxDuration // t - u is positive out of range
}
// Since returns the time elapsed since t.

10
src/time/time_test.go
View File

@ -690,7 +690,7 @@ var gobTests = []Time{
Date(0, 1, 2, 3, 4, 5, 6, UTC),
Date(7, 8, 9, 10, 11, 12, 13, FixedZone("", 0)),
Unix(81985467080890095, 0x76543210), // Time.sec: 0x0123456789ABCDEF
{}, // nil location
{}, // nil location
Date(1, 2, 3, 4, 5, 6, 7, FixedZone("", 32767*60)),
Date(1, 2, 3, 4, 5, 6, 7, FixedZone("", -32768*60)),
}
@ -1008,14 +1008,6 @@ func TestSub(t *testing.T) {
}
}
func BenchmarkSub(b *testing.B) {
for i := 0; i < b.N; i++ {
for _, st := range subTests {
st.t.Sub(st.u)
}
}
}
var nsDurationTests = []struct {
d Duration
want int64