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// Package timer is a Go timer implementation with a fixed Reset behavior.
package timer
import (
"time"
)
// 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. NewStoppedTimer or AfterFunc.
type Timer struct {
C <-chan time.Time
i int // heap index.
when time.Time // Timer wakes up at when.
// f is called in a locked context on timeout. This function must not block
// and must behave well-defined.
f func(t *time.Time)
// reset is called in a locked context. This function must not block
// and must behave well-defined.
reset func()
}
// NewTimer creates a new Timer that will send the current time on its
// channel after at least duration d.
func NewTimer(d time.Duration) *Timer {
t := NewStoppedTimer()
addTimer(t, d)
return t
}
// NewStoppedTimer creates a new stopped Timer.
func NewStoppedTimer() *Timer {
c := make(chan time.Time, 1)
t := &Timer{
C: c,
f: func(t *time.Time) {
// Don't block.
select {
case c <- *t:
default:
}
},
reset: func() {
// Empty the channel if filled.
select {
case <-c:
default:
}
},
}
return t
}
// 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.
func (t *Timer) Stop() (wasActive bool) {
if t.f == nil {
panic("timer: Stop called on uninitialized Timer")
}
return delTimer(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.
// The channel t.C is cleared and calling t.Reset() behaves as creating a
// new Timer.
func (t *Timer) Reset(d time.Duration) bool {
if t.f == nil {
panic("timer: Reset called on uninitialized Timer")
}
return resetTimer(t, d)
}
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