1 // Copyright 2009 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 package time 6 7 // Sleep pauses the current goroutine for at least the duration d. 8 // A negative or zero duration causes Sleep to return immediately. 9 func Sleep(d Duration) 10 11 // runtimeNano returns the current value of the runtime clock in nanoseconds. 12 func runtimeNano() int64 13 14 // Interface to timers implemented in package runtime. 15 // Must be in sync with ../runtime/runtime.h:/^struct.Timer$ 16 type runtimeTimer struct { 17 i int 18 when int64 19 period int64 20 f func(interface{}, uintptr) // NOTE: must not be closure 21 arg interface{} 22 seq uintptr 23 } 24 25 // when is a helper function for setting the 'when' field of a runtimeTimer. 26 // It returns what the time will be, in nanoseconds, Duration d in the future. 27 // If d is negative, it is ignored. If the returned value would be less than 28 // zero because of an overflow, MaxInt64 is returned. 29 func when(d Duration) int64 { 30 if d <= 0 { 31 return runtimeNano() 32 } 33 t := runtimeNano() + int64(d) 34 if t < 0 { 35 t = 1<<63 - 1 // math.MaxInt64 36 } 37 return t 38 } 39 40 func startTimer(*runtimeTimer) 41 func stopTimer(*runtimeTimer) bool 42 43 // The Timer type represents a single event. 44 // When the Timer expires, the current time will be sent on C, 45 // unless the Timer was created by AfterFunc. 46 // A Timer must be created with NewTimer or AfterFunc. 47 type Timer struct { 48 C <-chan Time 49 r runtimeTimer 50 } 51 52 // Stop prevents the Timer from firing. 53 // It returns true if the call stops the timer, false if the timer has already 54 // expired or been stopped. 55 // Stop does not close the channel, to prevent a read from the channel succeeding 56 // incorrectly. 57 func (t *Timer) Stop() bool { 58 if t.r.f == nil { 59 panic("time: Stop called on uninitialized Timer") 60 } 61 return stopTimer(&t.r) 62 } 63 64 // NewTimer creates a new Timer that will send 65 // the current time on its channel after at least duration d. 66 func NewTimer(d Duration) *Timer { 67 c := make(chan Time, 1) 68 t := &Timer{ 69 C: c, 70 r: runtimeTimer{ 71 when: when(d), 72 f: sendTime, 73 arg: c, 74 }, 75 } 76 startTimer(&t.r) 77 return t 78 } 79 80 // Reset changes the timer to expire after duration d. 81 // It returns true if the timer had been active, false if the timer had 82 // expired or been stopped. 83 func (t *Timer) Reset(d Duration) bool { 84 if t.r.f == nil { 85 panic("time: Reset called on uninitialized Timer") 86 } 87 w := when(d) 88 active := stopTimer(&t.r) 89 t.r.when = w 90 startTimer(&t.r) 91 return active 92 } 93 94 func sendTime(c interface{}, seq uintptr) { 95 // Non-blocking send of time on c. 96 // Used in NewTimer, it cannot block anyway (buffer). 97 // Used in NewTicker, dropping sends on the floor is 98 // the desired behavior when the reader gets behind, 99 // because the sends are periodic. 100 select { 101 case c.(chan Time) <- Now(): 102 default: 103 } 104 } 105 106 // After waits for the duration to elapse and then sends the current time 107 // on the returned channel. 108 // It is equivalent to NewTimer(d).C. 109 func After(d Duration) <-chan Time { 110 return NewTimer(d).C 111 } 112 113 // AfterFunc waits for the duration to elapse and then calls f 114 // in its own goroutine. It returns a Timer that can 115 // be used to cancel the call using its Stop method. 116 func AfterFunc(d Duration, f func()) *Timer { 117 t := &Timer{ 118 r: runtimeTimer{ 119 when: when(d), 120 f: goFunc, 121 arg: f, 122 }, 123 } 124 startTimer(&t.r) 125 return t 126 } 127 128 func goFunc(arg interface{}, seq uintptr) { 129 go arg.(func())() 130 } 131
