156 lines
4.4 KiB
Go
156 lines
4.4 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package time
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// Sleep pauses the current goroutine for at least the duration d.
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// A negative or zero duration causes Sleep to return immediately.
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func Sleep(d Duration)
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// runtimeNano returns the current value of the runtime clock in nanoseconds.
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func runtimeNano() int64
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// Interface to timers implemented in package runtime.
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// Must be in sync with ../runtime/runtime.h:/^struct.Timer$
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type runtimeTimer struct {
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i int
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when int64
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period int64
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f func(interface{}, uintptr) // NOTE: must not be closure
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arg interface{}
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seq uintptr
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}
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// when is a helper function for setting the 'when' field of a runtimeTimer.
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// It returns what the time will be, in nanoseconds, Duration d in the future.
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// If d is negative, it is ignored. If the returned value would be less than
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// zero because of an overflow, MaxInt64 is returned.
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func when(d Duration) int64 {
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if d <= 0 {
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return runtimeNano()
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}
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t := runtimeNano() + int64(d)
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if t < 0 {
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t = 1<<63 - 1 // math.MaxInt64
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}
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return t
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}
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func startTimer(*runtimeTimer)
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func stopTimer(*runtimeTimer) bool
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// The Timer type represents a single event.
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// When the Timer expires, the current time will be sent on C,
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// unless the Timer was created by AfterFunc.
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// A Timer must be created with NewTimer or AfterFunc.
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type Timer struct {
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C <-chan Time
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r runtimeTimer
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}
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// Stop prevents the Timer from firing.
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// It returns true if the call stops the timer, false if the timer has already
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// expired or been stopped.
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// Stop does not close the channel, to prevent a read from the channel succeeding
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// incorrectly.
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//
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// To prevent the timer firing after a call to Stop,
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// check the return value and drain the channel. For example:
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// if !t.Stop() {
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// <-t.C
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// }
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// This cannot be done concurrent to other receives from the Timer's
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// channel.
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func (t *Timer) Stop() bool {
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if t.r.f == nil {
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panic("time: Stop called on uninitialized Timer")
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}
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return stopTimer(&t.r)
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}
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// NewTimer creates a new Timer that will send
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// the current time on its channel after at least duration d.
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func NewTimer(d Duration) *Timer {
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c := make(chan Time, 1)
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t := &Timer{
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C: c,
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r: runtimeTimer{
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when: when(d),
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f: sendTime,
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arg: c,
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},
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}
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startTimer(&t.r)
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return t
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}
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// Reset changes the timer to expire after duration d.
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// It returns true if the timer had been active, false if the timer had
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// expired or been stopped.
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//
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// To reuse an active timer, always call its Stop method first and—if it had
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// expired—drain the value from its channel. For example:
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// if !t.Stop() {
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// <-t.C
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// }
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// t.Reset(d)
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// This should not be done concurrent to other receives from the Timer's
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// channel.
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//
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// Note that it is not possible to use Reset's return value correctly, as there
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// is a race condition between draining the channel and the new timer expiring.
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// Reset should always be used in concert with Stop, as described above.
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// The return value exists to preserve compatibility with existing programs.
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func (t *Timer) Reset(d Duration) bool {
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if t.r.f == nil {
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panic("time: Reset called on uninitialized Timer")
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}
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w := when(d)
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active := stopTimer(&t.r)
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t.r.when = w
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startTimer(&t.r)
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return active
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}
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func sendTime(c interface{}, seq uintptr) {
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// Non-blocking send of time on c.
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// Used in NewTimer, it cannot block anyway (buffer).
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// Used in NewTicker, dropping sends on the floor is
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// the desired behavior when the reader gets behind,
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// because the sends are periodic.
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select {
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case c.(chan Time) <- Now():
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default:
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}
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}
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// After waits for the duration to elapse and then sends the current time
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// on the returned channel.
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// It is equivalent to NewTimer(d).C.
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// The underlying Timer is not recovered by the garbage collector
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// until the timer fires. If efficiency is a concern, use NewTimer
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// instead and call Timer.Stop if the timer is no longer needed.
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func After(d Duration) <-chan Time {
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return NewTimer(d).C
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}
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// AfterFunc waits for the duration to elapse and then calls f
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// in its own goroutine. It returns a Timer that can
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// be used to cancel the call using its Stop method.
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func AfterFunc(d Duration, f func()) *Timer {
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t := &Timer{
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r: runtimeTimer{
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when: when(d),
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f: goFunc,
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arg: f,
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},
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}
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startTimer(&t.r)
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return t
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}
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func goFunc(arg interface{}, seq uintptr) {
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go arg.(func())()
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}
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