// 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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import "errors"
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// A Ticker holds a channel that delivers `ticks' of a clock
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// at intervals.
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type Ticker struct {
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C <-chan Time // The channel on which the ticks are delivered.
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r runtimeTimer
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}
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// NewTicker returns a new Ticker containing a channel that will send the
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// time with a period specified by the duration argument.
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// It adjusts the intervals or drops ticks to make up for slow receivers.
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// The duration d must be greater than zero; if not, NewTicker will panic.
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// Stop the ticker to release associated resources.
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func NewTicker(d Duration) *Ticker {
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if d <= 0 {
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panic(errors.New("non-positive interval for NewTicker"))
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}
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// Give the channel a 1-element time buffer.
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// If the client falls behind while reading, we drop ticks
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// on the floor until the client catches up.
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c := make(chan Time, 1)
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t := &Ticker{
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C: c,
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r: runtimeTimer{
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when: when(d),
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period: int64(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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// Stop turns off a ticker. After Stop, no more ticks will be sent.
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// Stop does not close the channel, to prevent a concurrent goroutine
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// reading from the channel from seeing an erroneous "tick".
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func (t *Ticker) Stop() {
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stopTimer(&t.r)
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}
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// Tick is a convenience wrapper for NewTicker providing access to the ticking
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// channel only. While Tick is useful for clients that have no need to shut down
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// the Ticker, be aware that without a way to shut it down the underlying
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// Ticker cannot be recovered by the garbage collector; it "leaks".
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// Unlike NewTicker, Tick will return nil if d <= 0.
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func Tick(d Duration) <-chan Time {
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if d <= 0 {
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return nil
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}
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return NewTicker(d).C
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}
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