golang timer 源码

(1)使用方法

timer := time.NewTicker(time.Duration(GAP) * time.Second)
for {
       select {
       case now := <-timer.C:
              fmt.Println(now)
       }
}

(2)NewTicker 函数

func NewTicker(d Duration) *Ticker {
        if d <= 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 Time, 1)
        t := &Ticker{
                C: c,
                r: runtimeTimer{
                        when:   when(d),  //下一次要触发的纳秒级时间，绝对时间（当前纳秒级时间+d）
                        period: int64(d),   //每次时间间隔，即d
                        f:      sendTime,   //写channel 函数
                        arg:    c,               //这里把c作为参数，有个细节的原因是Ticker.C 是receive-only type chan
                },
        }
        startTimer(&t.r)
        return t
}
type Ticker struct {
        C <-chan Time   //定时满足后，执行runtimeTimer 中 f 函数 写channel
        r runtimeTimer
}

type runtimeTimer struct {
        tb uintptr
        i  int
        when   int64         
        period int64
        f      func(interface{}, uintptr) // NOTE: must not be closure
        arg    interface{}
        seq    uintptr
}
func sendTime(c interface{}, seq uintptr) {
     select {
     case c.(chan Time) <- Now():
     default:
     }   
}  

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