time: add Timer.Reset

Fixes #4412.

R=adg, rsc, rogpeppe, andrewdg, bradfitz
CC=golang-dev
https://golang.org/cl/7086050

diff --git a/src/pkg/time/sleep.go b/src/pkg/time/sleep.go
index 657e25410312767912b0f7a9b921086e20e7989f..1e6b4f2e44250794ea82c4adb76948c5df6ba533 100644 (file)
--- a/src/pkg/time/sleep.go
+++ b/src/pkg/time/sleep.go
@@ -35,10 +35,10 @@ type Timer struct {
 
 // Stop prevents the Timer from firing.
 // It returns true if the call stops the timer, false if the timer has already
-// expired or stopped.
+// expired or been stopped.
 // Stop does not close the channel, to prevent a read from the channel succeeding
 // incorrectly.
-func (t *Timer) Stop() (ok bool) {
+func (t *Timer) Stop() bool {
        return stopTimer(&t.r)
 }
 
@@ -58,6 +58,17 @@ func NewTimer(d Duration) *Timer {
        return t
 }
 
+// Reset changes the timer to expire after duration d.
+// It returns true if the timer had been active, false if the timer had
+// expired or been stopped.
+func (t *Timer) Reset(d Duration) bool {
+       when := nano() + int64(d)
+       active := stopTimer(&t.r)
+       t.r.when = when
+       startTimer(&t.r)
+       return active
+}
+
 func sendTime(now int64, c interface{}) {
        // Non-blocking send of time on c.
        // Used in NewTimer, it cannot block anyway (buffer).

diff --git a/src/pkg/time/sleep_test.go b/src/pkg/time/sleep_test.go
index e05773df6e1bc9607eaf723df281f351596ded82..3e4b6c072c5d7b03d8ceb2be8efce23a72096b64 100644 (file)
--- a/src/pkg/time/sleep_test.go
+++ b/src/pkg/time/sleep_test.go
@@ -245,3 +245,27 @@ func TestSleepZeroDeadlock(t *testing.T) {
        }
        <-c
 }
+
+func TestReset(t *testing.T) {
+       t0 := NewTimer(100 * Millisecond)
+       Sleep(50 * Millisecond)
+       if t0.Reset(150*Millisecond) != true {
+               t.Fatalf("resetting unfired timer returned false")
+       }
+       Sleep(100 * Millisecond)
+       select {
+       case <-t0.C:
+               t.Fatalf("timer fired early")
+       default:
+       }
+       Sleep(100 * Millisecond)
+       select {
+       case <-t0.C:
+       default:
+               t.Fatalf("reset timer did not fire")
+       }
+
+       if t0.Reset(50*Millisecond) != false {
+               t.Fatalf("resetting expired timer returned true")
+       }
+}