我如何找到计时器启动的剩余时间？

Question

I need to run a function after x seconds, with some ability to control (reset the timer, stop the timer, find time remaining for execution). time.Timer is a close fit - the only thing missing is that it seems to provide no way of finding how much time is left.

What options do I have?

At the moment, I'm thinking of something like:

package main

import "time"

type SecondsTimer struct {
    T       time.Duration
    C       chan time.Time
    control chan time.Duration
    running bool
}

func (s *SecondsTimer) run() {
    for s.T.Seconds() > 0 {
        time.Sleep(time.Second)
        select {
        case f := <-s.control:
            if f > 0 {
                s.T = f
            } else {
                s.running = false
                break
            }
        default:
            s.T = s.T - 1
        }
    }
    s.C <- time.Now()
}
func (s *SecondsTimer) Reset(t time.Duration) {
    if s.running {
        s.control <- t
    } else {
        s.T = t
        go s.run()
    }

}
func (s *SecondsTimer) Stop() {
    if s.running {
        s.control <- 0
    }
}
func NewSecondsTimer(t time.Duration) *SecondsTimer {
    time := SecondsTimer{t, make(chan time.Time), make(chan time.Duration), false}
    go time.run()
    return &time
}

Now I can use s.T.Seconds() as needed.

But I'm wary of race conditions and other such problems. Is this the way to go, or is there something more native I can use?

Answer 1

There is a simpler way. You can still use a time.Timer to accomplish what you want, you just need to keep track of end time.Time:

type SecondsTimer struct {
    timer *time.Timer
    end   time.Time
}

func NewSecondsTimer(t time.Duration) *SecondsTimer {
    return &SecondsTimer{time.NewTimer(t), time.Now().Add(t)}
}

func (s *SecondsTimer) Reset(t time.Duration) {
    s.timer.Reset(t)
    s.end = time.Now().Add(t)
}

func (s *SecondsTimer) Stop() {
    s.timer.Stop()
}

so time remaining is easy:

func (s *SecondsTimer) TimeRemaining() time.Duration {
    return s.end.Sub(time.Now())
}