loop.go

package portal

import (
	"time"
)

// Rate converts a frequency in hertz to a time duration.
func Rate(hz int) time.Duration {
	return time.Second / time.Duration(hz)
}

// RatePrecise converts a frequency in hertz to a time duration with the highest precision that Go can muster.
func RatePrecise(hz float64) time.Duration {
	return time.Second / time.Duration(hz)
}

// Loop runs a thread with a minimum granularity in timing, optionally detaching into goroutines.
func Loop(granularity *time.Duration, detach bool, fnc func()) (stopper chan bool, lastLoop *time.Time) {
	stopper = make(chan bool)
	now := time.Now()
	loopThread(stopper, granularity, detach, &now, fnc)
	return stopper, &now
}

func loopThread(stopper chan bool, granularity *time.Duration, detach bool, lastLoop *time.Time, fnc func()) {
	go func(stopper chan bool, granularity *time.Duration, lastLoop *time.Time, fnc func()) {
		for {
			if detach {
				go fnc()
			} else {
				fnc()
			}

			if since := time.Since(*lastLoop); since < *granularity {
				rest := *granularity - since
				time.Sleep(rest)
				*lastLoop = time.Now()
			}

			select {
			case <-stopper:
				close(stopper)
				return
			default:
			}
		}
	}(stopper, granularity, lastLoop, fnc)
}