llgo/runtime/internal/lib/time/sleep.go

// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package time

import (
	"sync"
	"unsafe"

	c "github.com/goplus/llgo/runtime/internal/clite"
	"github.com/goplus/llgo/runtime/internal/clite/libuv"
)

// Sleep pauses the current goroutine for at least the duration d.
// A negative or zero duration causes Sleep to return immediately.
func Sleep(d Duration) {
	c.Usleep(c.Uint(d.Nanoseconds()))
}

// Interface to timers implemented in package runtime.
// Must be in sync with ../runtime/time.go:/^type timer
type runtimeTimer struct {
	libuv.Timer
	when int64
	f    func(any, uintptr)
	arg  any
}

// when is a helper function for setting the 'when' field of a runtimeTimer.
// It returns what the time will be, in nanoseconds, Duration d in the future.
// If d is negative, it is ignored. If the returned value would be less than
// zero because of an overflow, MaxInt64 is returned.
func when(d Duration) int64 {
	if d <= 0 {
		return runtimeNano()
	}
	t := runtimeNano() + int64(d)
	if t < 0 {
		// N.B. runtimeNano() and d are always positive, so addition
		// (including overflow) will never result in t == 0.
		t = 1<<63 - 1 // math.MaxInt64
	}
	return t
}

/* TODO(xsw):
func modTimer(t *runtimeTimer, when, period int64, f func(any, uintptr), arg any, seq uintptr) {
	panic("todo: time.modTimer")
}
*/

// The Timer type represents a single event.
// When the Timer expires, the current time will be sent on C,
// unless the Timer was created by AfterFunc.
// A Timer must be created with NewTimer or AfterFunc.
type Timer struct {
	C <-chan Time
	r runtimeTimer
}

// Stop prevents the Timer from firing.
// It returns true if the call stops the timer, false if the timer has already
// expired or been stopped.
// Stop does not close the channel, to prevent a read from the channel succeeding
// incorrectly.
//
// To ensure the channel is empty after a call to Stop, check the
// return value and drain the channel.
// For example, assuming the program has not received from t.C already:
//
//	if !t.Stop() {
//		<-t.C
//	}
//
// This cannot be done concurrent to other receives from the Timer's
// channel or other calls to the Timer's Stop method.
//
// For a timer created with AfterFunc(d, f), if t.Stop returns false, then the timer
// has already expired and the function f has been started in its own goroutine;
// Stop does not wait for f to complete before returning.
// If the caller needs to know whether f is completed, it must coordinate
// with f explicitly.
func (t *Timer) Stop() bool {
	return stopTimer(&t.r)
}

// NewTimer creates a new Timer that will send
// the current time on its channel after at least duration d.
func NewTimer(d Duration) *Timer {
	c := make(chan Time, 1)
	t := &Timer{
		C: c,
		r: runtimeTimer{
			when: when(d),
			f:    sendTime,
			arg:  c,
		},
	}
	startTimer(&t.r)
	return t
}

// Reset changes the timer to expire after duration d.
// It returns true if the timer had been active, false if the timer had
// expired or been stopped.
//
// For a Timer created with NewTimer, Reset should be invoked only on
// stopped or expired timers with drained channels.
//
// If a program has already received a value from t.C, the timer is known
// to have expired and the channel drained, so t.Reset can be used directly.
// If a program has not yet received a value from t.C, however,
// the timer must be stopped and—if Stop reports that the timer expired
// before being stopped—the channel explicitly drained:
//
//	if !t.Stop() {
//		<-t.C
//	}
//	t.Reset(d)
//
// This should not be done concurrent to other receives from the Timer's
// channel.
//
// Note that it is not possible to use Reset's return value correctly, as there
// is a race condition between draining the channel and the new timer expiring.
// Reset should always be invoked on stopped or expired channels, as described above.
// The return value exists to preserve compatibility with existing programs.
//
// For a Timer created with AfterFunc(d, f), Reset either reschedules
// when f will run, in which case Reset returns true, or schedules f
// to run again, in which case it returns false.
// When Reset returns false, Reset neither waits for the prior f to
// complete before returning nor does it guarantee that the subsequent
// goroutine running f does not run concurrently with the prior
// one. If the caller needs to know whether the prior execution of
// f is completed, it must coordinate with f explicitly.
func (t *Timer) Reset(d Duration) bool {
	w := when(d)
	return resetTimer(&t.r, w)
}

// sendTime does a non-blocking send of the current time on c.
func sendTime(c any, seq uintptr) {
	select {
	case c.(chan Time) <- Now():
	default:
	}
}

// After waits for the duration to elapse and then sends the current time
// on the returned channel.
// It is equivalent to NewTimer(d).C.
// The underlying Timer is not recovered by the garbage collector
// until the timer fires. If efficiency is a concern, use NewTimer
// instead and call Timer.Stop if the timer is no longer needed.
func After(d Duration) <-chan Time {
	return NewTimer(d).C
}

// AfterFunc waits for the duration to elapse and then calls f
// in its own goroutine. It returns a Timer that can
// be used to cancel the call using its Stop method.
func AfterFunc(d Duration, f func()) *Timer {
	t := &Timer{
		r: runtimeTimer{
			when: when(d),
			f:    goFunc,
			arg:  f,
		},
	}
	startTimer(&t.r)
	return t
}

func goFunc(arg any, seq uintptr) {
	go arg.(func())()
}

var (
	timerLoop *libuv.Loop
	timerOnce sync.Once
)

func init() {
	timerOnce.Do(func() {
		timerLoop = libuv.LoopNew()
	})
	go func() {
		timerLoop.Run(libuv.RUN_DEFAULT)
	}()
}

// cross thread
func timerEvent(async *libuv.Async) {
	a := (*asyncTimerEvent)(unsafe.Pointer(async))
	a.cb()
	a.Close(nil)
}

type asyncTimerEvent struct {
	libuv.Async
	cb func()
}

func timerCallback(t *libuv.Timer) {
}

func startTimer(r *runtimeTimer) {
	asyncTimer := &asyncTimerEvent{
		cb: func() {
			libuv.InitTimer(timerLoop, &r.Timer)
			r.Start(timerCallback, uint64(r.when), 0)
		},
	}
	timerLoop.Async(&asyncTimer.Async, timerEvent)
	asyncTimer.Send()
}

func stopTimer(r *runtimeTimer) bool {
	asyncTimer := &asyncTimerEvent{
		cb: func() {
			r.Stop()
		},
	}
	timerLoop.Async(&asyncTimer.Async, timerEvent)
	return asyncTimer.Send() == 0
}

func resetTimer(r *runtimeTimer, when int64) bool {
	asyncTimer := &asyncTimerEvent{
		cb: func() {
			r.Stop()
			r.Start(timerCallback, uint64(when), 0)
		},
	}
	timerLoop.Async(&asyncTimer.Async, timerEvent)
	return asyncTimer.Send() == 0
}