runtime: implement resetTimer

Author: joeshaw

src/runtime/time.go

@@ -13,6 +13,7 @@ func (t *timerNode) whenTicks() timeUnit {
 }
 
 // Defined in the time package, implemented here in the runtime.
+//
 //go:linkname startTimer time.startTimer
 func startTimer(tim *timer) {
 	addTimer(&timerNode{
@@ -48,3 +49,11 @@ func timerCallback(tn *timerNode) {
 func stopTimer(tim *timer) bool {
 	return removeTimer(tim)
 }
+
+//go:linkname resetTimer time.resetTimer
+func resetTimer(tim *timer, when int64) bool {
+	tim.when = when
+	removed := removeTimer(tim)
+	startTimer(tim)
+	return removed
+}

testdata/timers.go

@@ -37,5 +37,16 @@ func main() {
 	}()
 	<-timer.C
 	println("waited on timer at 250ms")
+	reset := timer.Reset(time.Millisecond * 250)
+	println("timer reset:", reset)
+	println("waiting on timer")
+	go func() {
+		time.Sleep(time.Millisecond * 125)
+		println(" - after 125ms")
+		time.Sleep(time.Millisecond * 250)
+		println(" - after 250ms")
+	}()
+	<-timer.C
+	println("waited on timer at 250ms")
 	time.Sleep(time.Millisecond * 250)
 }

testdata/timers.txt

@@ -9,3 +9,8 @@ waiting on timer
  - after 125ms
 waited on timer at 250ms
  - after 250ms
+timer reset: true
+waiting on timer
+ - after 125ms
+waited on timer at 250ms
+ - after 250ms