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228 lines
4.9 KiB
228 lines
4.9 KiB
package common
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import (
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"sync"
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"time"
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)
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// Used by RepeatTimer the first time,
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// and every time it's Reset() after Stop().
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type TickerMaker func(dur time.Duration) Ticker
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// Ticker is a basic ticker interface.
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type Ticker interface {
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// Never changes, never closes.
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Chan() <-chan time.Time
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// Stopping a stopped Ticker will panic.
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Stop()
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}
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//----------------------------------------
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// defaultTickerMaker
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func defaultTickerMaker(dur time.Duration) Ticker {
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ticker := time.NewTicker(dur)
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return (*defaultTicker)(ticker)
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}
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type defaultTicker time.Ticker
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// Implements Ticker
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func (t *defaultTicker) Chan() <-chan time.Time {
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return t.C
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}
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// Implements Ticker
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func (t *defaultTicker) Stop() {
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((*time.Ticker)(t)).Stop()
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}
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//----------------------------------------
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// LogicalTickerMaker
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// Construct a TickerMaker that always uses `source`.
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// It's useful for simulating a deterministic clock.
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func NewLogicalTickerMaker(source chan time.Time) TickerMaker {
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return func(dur time.Duration) Ticker {
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return newLogicalTicker(source, dur)
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}
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}
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type logicalTicker struct {
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source <-chan time.Time
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ch chan time.Time
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quit chan struct{}
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}
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func newLogicalTicker(source <-chan time.Time, interval time.Duration) Ticker {
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lt := &logicalTicker{
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source: source,
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ch: make(chan time.Time),
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quit: make(chan struct{}),
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}
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go lt.fireRoutine(interval)
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return lt
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}
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// We need a goroutine to read times from t.source
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// and fire on t.Chan() when `interval` has passed.
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func (t *logicalTicker) fireRoutine(interval time.Duration) {
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source := t.source
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// Init `lasttime`
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lasttime := time.Time{}
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select {
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case lasttime = <-source:
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case <-t.quit:
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return
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}
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// Init `lasttime` end
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timeleft := interval
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for {
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select {
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case newtime := <-source:
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elapsed := newtime.Sub(lasttime)
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timeleft -= elapsed
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if timeleft <= 0 {
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// Block for determinism until the ticker is stopped.
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select {
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case t.ch <- newtime:
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case <-t.quit:
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return
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}
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// Reset timeleft.
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// Don't try to "catch up" by sending more.
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// "Ticker adjusts the intervals or drops ticks to make up for
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// slow receivers" - https://golang.org/pkg/time/#Ticker
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timeleft = interval
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}
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case <-t.quit:
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return // done
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}
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}
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}
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// Implements Ticker
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func (t *logicalTicker) Chan() <-chan time.Time {
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return t.ch // immutable
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}
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// Implements Ticker
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func (t *logicalTicker) Stop() {
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close(t.quit) // it *should* panic when stopped twice.
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}
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//---------------------------------------------------------------------
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/*
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RepeatTimer repeatedly sends a struct{}{} to `.Chan()` after each `dur`
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period. (It's good for keeping connections alive.)
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A RepeatTimer must be stopped, or it will keep a goroutine alive.
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*/
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type RepeatTimer struct {
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name string
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ch chan time.Time
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tm TickerMaker
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mtx sync.Mutex
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dur time.Duration
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ticker Ticker
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quit chan struct{}
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}
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// NewRepeatTimer returns a RepeatTimer with a defaultTicker.
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func NewRepeatTimer(name string, dur time.Duration) *RepeatTimer {
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return NewRepeatTimerWithTickerMaker(name, dur, defaultTickerMaker)
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}
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// NewRepeatTimerWithTicker returns a RepeatTimer with the given ticker
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// maker.
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func NewRepeatTimerWithTickerMaker(name string, dur time.Duration, tm TickerMaker) *RepeatTimer {
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var t = &RepeatTimer{
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name: name,
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ch: make(chan time.Time),
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tm: tm,
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dur: dur,
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ticker: nil,
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quit: nil,
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}
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t.reset()
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return t
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}
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func (t *RepeatTimer) fireRoutine(ch <-chan time.Time, quit <-chan struct{}) {
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for {
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select {
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case t_ := <-ch:
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t.ch <- t_
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case <-quit: // NOTE: `t.quit` races.
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return
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}
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}
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}
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func (t *RepeatTimer) Chan() <-chan time.Time {
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return t.ch
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}
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func (t *RepeatTimer) Stop() {
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t.mtx.Lock()
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defer t.mtx.Unlock()
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t.stop()
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}
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// Wait the duration again before firing.
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func (t *RepeatTimer) Reset() {
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t.mtx.Lock()
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defer t.mtx.Unlock()
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t.reset()
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}
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//----------------------------------------
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// Misc.
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// CONTRACT: (non-constructor) caller should hold t.mtx.
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func (t *RepeatTimer) reset() {
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if t.ticker != nil {
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t.stop()
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}
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t.ticker = t.tm(t.dur)
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t.quit = make(chan struct{})
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go t.fireRoutine(t.ticker.Chan(), t.quit)
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}
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// CONTRACT: caller should hold t.mtx.
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func (t *RepeatTimer) stop() {
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if t.ticker == nil {
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/*
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Similar to the case of closing channels twice:
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https://groups.google.com/forum/#!topic/golang-nuts/rhxMiNmRAPk
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Stopping a RepeatTimer twice implies that you do
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not know whether you are done or not.
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If you're calling stop on a stopped RepeatTimer,
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you probably have race conditions.
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*/
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panic("Tried to stop a stopped RepeatTimer")
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}
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t.ticker.Stop()
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t.ticker = nil
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/*
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XXX
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From https://golang.org/pkg/time/#Ticker:
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"Stop the ticker to release associated resources"
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"After Stop, no more ticks will be sent"
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So we shouldn't have to do the below.
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select {
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case <-t.ch:
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// read off channel if there's anything there
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default:
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}
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*/
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close(t.quit)
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}
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