107 lines
2.9 KiB
Go
107 lines
2.9 KiB
Go
// Copyright 2022 The go-ethereum Authors
|
|
// This file is part of the go-ethereum library.
|
|
//
|
|
// The go-ethereum library is free software: you can redistribute it and/or modify
|
|
// it under the terms of the GNU Lesser General Public License as published by
|
|
// the Free Software Foundation, either version 3 of the License, or
|
|
// (at your option) any later version.
|
|
//
|
|
// The go-ethereum library is distributed in the hope that it will be useful,
|
|
// but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
// GNU Lesser General Public License for more details.
|
|
//
|
|
// You should have received a copy of the GNU Lesser General Public License
|
|
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
|
|
|
|
package mclock
|
|
|
|
import (
|
|
"time"
|
|
)
|
|
|
|
// Alarm sends timed notifications on a channel. This is very similar to a regular timer,
|
|
// but is easier to use in code that needs to re-schedule the same timer over and over.
|
|
//
|
|
// When scheduling an Alarm, the channel returned by C() will receive a value no later
|
|
// than the scheduled time. An Alarm can be reused after it has fired and can also be
|
|
// canceled by calling Stop.
|
|
type Alarm struct {
|
|
ch chan struct{}
|
|
clock Clock
|
|
timer Timer
|
|
deadline AbsTime
|
|
}
|
|
|
|
// NewAlarm creates an Alarm.
|
|
func NewAlarm(clock Clock) *Alarm {
|
|
if clock == nil {
|
|
panic("nil clock")
|
|
}
|
|
return &Alarm{
|
|
ch: make(chan struct{}, 1),
|
|
clock: clock,
|
|
}
|
|
}
|
|
|
|
// C returns the alarm notification channel. This channel remains identical for
|
|
// the entire lifetime of the alarm, and is never closed.
|
|
func (e *Alarm) C() <-chan struct{} {
|
|
return e.ch
|
|
}
|
|
|
|
// Stop cancels the alarm and drains the channel.
|
|
// This method is not safe for concurrent use.
|
|
func (e *Alarm) Stop() {
|
|
// Clear timer.
|
|
if e.timer != nil {
|
|
e.timer.Stop()
|
|
}
|
|
e.deadline = 0
|
|
|
|
// Drain the channel.
|
|
select {
|
|
case <-e.ch:
|
|
default:
|
|
}
|
|
}
|
|
|
|
// Schedule sets the alarm to fire no later than the given time. If the alarm was already
|
|
// scheduled but has not fired yet, it may fire earlier than the newly-scheduled time.
|
|
func (e *Alarm) Schedule(time AbsTime) {
|
|
now := e.clock.Now()
|
|
e.schedule(now, time)
|
|
}
|
|
|
|
func (e *Alarm) schedule(now, newDeadline AbsTime) {
|
|
if e.timer != nil {
|
|
if e.deadline > now && e.deadline <= newDeadline {
|
|
// Here, the current timer can be reused because it is already scheduled to
|
|
// occur earlier than the new deadline.
|
|
//
|
|
// The e.deadline > now part of the condition is important. If the old
|
|
// deadline lies in the past, we assume the timer has already fired and needs
|
|
// to be rescheduled.
|
|
return
|
|
}
|
|
e.timer.Stop()
|
|
}
|
|
|
|
// Set the timer.
|
|
d := time.Duration(0)
|
|
if newDeadline < now {
|
|
newDeadline = now
|
|
} else {
|
|
d = newDeadline.Sub(now)
|
|
}
|
|
e.timer = e.clock.AfterFunc(d, e.send)
|
|
e.deadline = newDeadline
|
|
}
|
|
|
|
func (e *Alarm) send() {
|
|
select {
|
|
case e.ch <- struct{}{}:
|
|
default:
|
|
}
|
|
}
|