1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
|
// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package time
// Sleep pauses the current goroutine for at least the duration d.
// A negative or zero duration causes Sleep to return immediately.
func Sleep(d Duration)
// Interface to timers implemented in package runtime.
// Must be in sync with ../runtime/time.go:/^type timer
type runtimeTimer struct {
pp uintptr
when int64
period int64
f func(any, uintptr) // NOTE: must not be closure
arg any
seq uintptr
nextwhen int64
status uint32
}
// when is a helper function for setting the 'when' field of a runtimeTimer.
// It returns what the time will be, in nanoseconds, Duration d in the future.
// If d is negative, it is ignored. If the returned value would be less than
// zero because of an overflow, MaxInt64 is returned.
func when(d Duration) int64 {
if d <= 0 {
return runtimeNano()
}
t := runtimeNano() + int64(d)
if t < 0 {
// N.B. runtimeNano() and d are always positive, so addition
// (including overflow) will never result in t == 0.
t = 1<<63 - 1 // math.MaxInt64
}
return t
}
func startTimer(*runtimeTimer)
func stopTimer(*runtimeTimer) bool
func resetTimer(*runtimeTimer, int64) bool
func modTimer(t *runtimeTimer, when, period int64, f func(any, uintptr), arg any, seq uintptr)
// 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.
// A Timer must be created with NewTimer or 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 been stopped.
// Stop does not close the channel, to prevent a read from the channel succeeding
// incorrectly.
//
// To ensure the channel is empty after a call to Stop, check the
// return value and drain the channel.
// For example, assuming the program has not received from t.C already:
//
// if !t.Stop() {
// <-t.C
// }
//
// This cannot be done concurrent to other receives from the Timer's
// channel or other calls to the Timer's Stop method.
//
// For a timer created with AfterFunc(d, f), if t.Stop returns false, then the timer
// has already expired and the function f has been started in its own goroutine;
// Stop does not wait for f to complete before returning.
// If the caller needs to know whether f is completed, it must coordinate
// with f explicitly.
func (t *Timer) Stop() bool {
if t.r.f == nil {
panic("time: Stop called on uninitialized Timer")
}
return stopTimer(&t.r)
}
// 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: when(d),
f: sendTime,
arg: c,
},
}
startTimer(&t.r)
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.
//
// For a Timer created with NewTimer, Reset should be invoked only on
// stopped or expired timers with drained channels.
//
// If a program has already received a value from t.C, the timer is known
// to have expired and the channel drained, so t.Reset can be used directly.
// If a program has not yet received a value from t.C, however,
// the timer must be stopped and—if Stop reports that the timer expired
// before being stopped—the channel explicitly drained:
//
// if !t.Stop() {
// <-t.C
// }
// t.Reset(d)
//
// This should not be done concurrent to other receives from the Timer's
// channel.
//
// Note that it is not possible to use Reset's return value correctly, as there
// is a race condition between draining the channel and the new timer expiring.
// Reset should always be invoked on stopped or expired channels, as described above.
// The return value exists to preserve compatibility with existing programs.
//
// For a Timer created with AfterFunc(d, f), Reset either reschedules
// when f will run, in which case Reset returns true, or schedules f
// to run again, in which case it returns false.
// When Reset returns false, Reset neither waits for the prior f to
// complete before returning nor does it guarantee that the subsequent
// goroutine running f does not run concurrently with the prior
// one. If the caller needs to know whether the prior execution of
// f is completed, it must coordinate with f explicitly.
func (t *Timer) Reset(d Duration) bool {
if t.r.f == nil {
panic("time: Reset called on uninitialized Timer")
}
w := when(d)
return resetTimer(&t.r, w)
}
// sendTime does a non-blocking send of the current time on c.
func sendTime(c any, seq uintptr) {
select {
case c.(chan Time) <- Now():
default:
}
}
// After waits for the duration to elapse and then sends the current time
// on the returned channel.
// It is equivalent to NewTimer(d).C.
// The underlying Timer is not recovered by the garbage collector
// until the timer fires. If efficiency is a concern, use NewTimer
// instead and call Timer.Stop if the timer is no longer needed.
func After(d Duration) <-chan Time {
return NewTimer(d).C
}
// 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: when(d),
f: goFunc,
arg: f,
},
}
startTimer(&t.r)
return t
}
func goFunc(arg any, seq uintptr) {
go arg.(func())()
}
|
