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// 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
import "errors"
// A Ticker holds a synchronous channel that delivers `ticks' of a clock
// at intervals.
type Ticker struct {
C <-chan int64 // The channel on which the ticks are delivered.
r runtimeTimer
}
// NewTicker returns a new Ticker containing a channel that will
// send the time, in nanoseconds, every ns nanoseconds. It adjusts the
// intervals to make up for pauses in delivery of the ticks. The value of
// ns must be greater than zero; if not, NewTicker will panic.
func NewTicker(ns int64) *Ticker {
if ns <= 0 {
panic(errors.New("non-positive interval for NewTicker"))
}
// Give the channel a 1-element time buffer.
// If the client falls behind while reading, we drop ticks
// on the floor until the client catches up.
c := make(chan int64, 1)
t := &Ticker{
C: c,
r: runtimeTimer{
when: Nanoseconds() + ns,
period: ns,
f: sendTime,
arg: c,
},
}
startTimer(&t.r)
return t
}
// Stop turns off a ticker. After Stop, no more ticks will be sent.
func (t *Ticker) Stop() {
stopTimer(&t.r)
}
// Tick is a convenience wrapper for NewTicker providing access to the ticking
// channel only. Useful for clients that have no need to shut down the ticker.
func Tick(ns int64) <-chan int64 {
if ns <= 0 {
return nil
}
return NewTicker(ns).C
}
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