1 files changed, 65 insertions, 147 deletions
diff --git a/src/pkg/time/sleep.go b/src/pkg/time/sleep.go
index 314622d0d..27820b0ea 100644
--- a/src/pkg/time/sleep.go
+++ b/src/pkg/time/sleep.go
@@ -4,174 +4,92 @@
 
 package time
 
-import (
-	"container/heap"
-	"sync"
-)
+// Sleep pauses the current goroutine for the duration d.
+func Sleep(d Duration)
 
-// The Timer type represents a single event.
-// When the Timer expires, the current time will be sent on C
-// unless the Timer represents an AfterFunc event.
-type Timer struct {
-	C <-chan int64
-	t int64       // The absolute time that the event should fire.
-	f func(int64) // The function to call when the event fires.
-	i int         // The event's index inside eventHeap.
-}
-
-type timerHeap []*Timer
-
-// forever is the absolute time (in ns) of an event that is forever away.
-const forever = 1 << 62
-
-// maxSleepTime is the maximum length of time that a sleeper
-// sleeps for before checking if it is defunct.
-const maxSleepTime = 1e9
-
-var (
-	// timerMutex guards the variables inside this var group.
-	timerMutex sync.Mutex
-
-	// timers holds a binary heap of pending events, terminated with a sentinel.
-	timers timerHeap
-
-	// currentSleeper is an ever-incrementing counter which represents
-	// the current sleeper. It allows older sleepers to detect that they are
-	// defunct and exit.
-	currentSleeper int64
-)
-
-func init() {
-	timers.Push(&Timer{t: forever}) // sentinel
+func nano() int64 {
+	sec, nsec := now()
+	return sec*1e9 + int64(nsec)
 }
 
-// NewTimer creates a new Timer that will send
-// the current time on its channel after at least ns nanoseconds.
-func NewTimer(ns int64) *Timer {
-	c := make(chan int64, 1)
-	e := after(ns, func(t int64) { c <- t })
-	e.C = c
-	return e
+// Interface to timers implemented in package runtime.
+// Must be in sync with ../runtime/runtime.h:/^struct.Timer$
+type runtimeTimer struct {
+	i      int32
+	when   int64
+	period int64
+	f      func(int64, interface{})
+	arg    interface{}
 }
 
-// After waits at least ns nanoseconds before sending the current time
-// on the returned channel.
-// It is equivalent to NewTimer(ns).C.
-func After(ns int64) <-chan int64 {
-	return NewTimer(ns).C
-}
+func startTimer(*runtimeTimer)
+func stopTimer(*runtimeTimer) bool
 
-// AfterFunc waits at least ns nanoseconds before calling f
-// in its own goroutine. It returns a Timer that can
-// be used to cancel the call using its Stop method.
-func AfterFunc(ns int64, f func()) *Timer {
-	return after(ns, func(_ int64) {
-		go f()
-	})
+// The Timer type represents a single event.
+// When the Timer expires, the current time will be sent on C,
+// unless the Timer was created by AfterFunc.
+type Timer struct {
+	C <-chan Time
+	r runtimeTimer
 }
 
 // Stop prevents the Timer from firing.
 // It returns true if the call stops the timer, false if the timer has already
 // expired or stopped.
-func (e *Timer) Stop() (ok bool) {
-	timerMutex.Lock()
-	// Avoid removing the first event in the queue so that
-	// we don't start a new sleeper unnecessarily.
-	if e.i > 0 {
-		heap.Remove(timers, e.i)
-	}
-	ok = e.f != nil
-	e.f = nil
-	timerMutex.Unlock()
-	return
+func (t *Timer) Stop() (ok bool) {
+	return stopTimer(&t.r)
 }
 
-// after is the implementation of After and AfterFunc.
-// When the current time is after ns, it calls f with the current time.
-// It assumes that f will not block.
-func after(ns int64, f func(int64)) (e *Timer) {
-	now := Nanoseconds()
-	t := now + ns
-	if ns > 0 && t < now {
-		panic("time: time overflow")
-	}
-	timerMutex.Lock()
-	t0 := timers[0].t
-	e = &Timer{nil, t, f, -1}
-	heap.Push(timers, e)
-	// Start a new sleeper if the new event is before
-	// the first event in the queue. If the length of time
-	// until the new event is at least maxSleepTime,
-	// then we're guaranteed that the sleeper will wake up
-	// in time to service it, so no new sleeper is needed.
-	if t0 > t && (t0 == forever || ns < maxSleepTime) {
-		currentSleeper++
-		go sleeper(currentSleeper)
+// NewTimer creates a new Timer that will send
+// the current time on its channel after at least duration d.
+func NewTimer(d Duration) *Timer {
+	c := make(chan Time, 1)
+	t := &Timer{
+		C: c,
+		r: runtimeTimer{
+			when: nano() + int64(d),
+			f:    sendTime,
+			arg:  c,
+		},
 	}
-	timerMutex.Unlock()
-	return
+	startTimer(&t.r)
+	return t
 }
 
-// sleeper continually looks at the earliest event in the queue, waits until it happens,
-// then removes any events in the queue that are due. It stops when the queue
-// is empty or when another sleeper has been started.
-func sleeper(sleeperId int64) {
-	timerMutex.Lock()
-	e := timers[0]
-	t := Nanoseconds()
-	for e.t != forever {
-		if dt := e.t - t; dt > 0 {
-			if dt > maxSleepTime {
-				dt = maxSleepTime
-			}
-			timerMutex.Unlock()
-			sysSleep(dt)
-			timerMutex.Lock()
-			if currentSleeper != sleeperId {
-				// Another sleeper has been started, making this one redundant.
-				break
-			}
-		}
-		e = timers[0]
-		t = Nanoseconds()
-		for t >= e.t {
-			if e.f != nil {
-				e.f(t)
-				e.f = nil
-			}
-			heap.Pop(timers)
-			e = timers[0]
-		}
+func sendTime(now int64, c interface{}) {
+	// Non-blocking send of time on c.
+	// Used in NewTimer, it cannot block anyway (buffer).
+	// Used in NewTicker, dropping sends on the floor is
+	// the desired behavior when the reader gets behind,
+	// because the sends are periodic.
+	select {
+	case c.(chan Time) <- Unix(0, now):
+	default:
 	}
-	timerMutex.Unlock()
-}
-
-func (timerHeap) Len() int {
-	return len(timers)
-}
-
-func (timerHeap) Less(i, j int) bool {
-	return timers[i].t < timers[j].t
 }
 
-func (timerHeap) Swap(i, j int) {
-	timers[i], timers[j] = timers[j], timers[i]
-	timers[i].i = i
-	timers[j].i = j
+// After waits for the duration to elapse and then sends the current time
+// on the returned channel.
+// It is equivalent to NewTimer(d).C.
+func After(d Duration) <-chan Time {
+	return NewTimer(d).C
 }
 
-func (timerHeap) Push(x interface{}) {
-	e := x.(*Timer)
-	e.i = len(timers)
-	timers = append(timers, e)
+// AfterFunc waits for the duration to elapse and then calls f
+// in its own goroutine. It returns a Timer that can
+// be used to cancel the call using its Stop method.
+func AfterFunc(d Duration, f func()) *Timer {
+	t := &Timer{
+		r: runtimeTimer{
+			when: nano() + int64(d),
+			f:    goFunc,
+			arg:  f,
+		},
+	}
+	startTimer(&t.r)
+	return t
 }
 
-func (timerHeap) Pop() interface{} {
-	// TODO: possibly shrink array.
-	n := len(timers) - 1
-	e := timers[n]
-	timers[n] = nil
-	timers = timers[0:n]
-	e.i = -1
-	return e
+func goFunc(now int64, arg interface{}) {
+	go arg.(func())()
 }