From 4983a0b75b40448d3245811ddcf682a9c86fc975 Mon Sep 17 00:00:00 2001 From: Joe Tsai Date: Fri, 16 Aug 2019 03:16:34 +0000 Subject: [PATCH] Revert "time: optimize Sub" 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 TryBot-Result: Gobot Gobot Reviewed-by: Emmanuel Odeke Reviewed-by: Andrew Bonventre --- src/time/time.go | 33 ++++++++------------------------- src/time/time_test.go | 10 +--------- 2 files changed, 9 insertions(+), 34 deletions(-) diff --git a/src/time/time.go b/src/time/time.go index c8116a74f4..0d1cb9e5a1 100644 --- a/src/time/time.go +++ b/src/time/time.go @@ -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. diff --git a/src/time/time_test.go b/src/time/time_test.go index dd3a8160cd..0ac3c3a27f 100644 --- a/src/time/time_test.go +++ b/src/time/time_test.go @@ -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