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// Copyright 2018 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 (
"sync"
"time"
)
// Simulated implements a virtual Clock for reproducible time-sensitive tests. It
// simulates a scheduler on a virtual timescale where actual processing takes zero time.
//
// The virtual clock doesn't advance on its own, call Run to advance it and execute timers.
// Since there is no way to influence the Go scheduler, testing timeout behaviour involving
// goroutines needs special care. A good way to test such timeouts is as follows: First
// perform the action that is supposed to time out. Ensure that the timer you want to test
// is created. Then run the clock until after the timeout. Finally observe the effect of
// the timeout using a channel or semaphore.
type Simulated struct {
now AbsTime
scheduled []*simTimer
mu sync.RWMutex
cond *sync.Cond
lastId uint64
}
// simTimer implements Timer on the virtual clock.
type simTimer struct {
do func()
at AbsTime
id uint64
s *Simulated
}
// Run moves the clock by the given duration, executing all timers before that duration.
func (s *Simulated) Run(d time.Duration) {
s.mu.Lock()
s.init()
end := s.now + AbsTime(d)
var do []func()
for len(s.scheduled) > 0 {
ev := s.scheduled[0]
if ev.at > end {
break
}
s.now = ev.at
do = append(do, ev.do)
s.scheduled = s.scheduled[1:]
}
s.now = end
s.mu.Unlock()
for _, fn := range do {
fn()
}
}
// ActiveTimers returns the number of timers that haven't fired.
func (s *Simulated) ActiveTimers() int {
s.mu.RLock()
defer s.mu.RUnlock()
return len(s.scheduled)
}
// WaitForTimers waits until the clock has at least n scheduled timers.
func (s *Simulated) WaitForTimers(n int) {
s.mu.Lock()
defer s.mu.Unlock()
s.init()
for len(s.scheduled) < n {
s.cond.Wait()
}
}
// Now returns the current virtual time.
func (s *Simulated) Now() AbsTime {
s.mu.RLock()
defer s.mu.RUnlock()
return s.now
}
// Sleep blocks until the clock has advanced by d.
func (s *Simulated) Sleep(d time.Duration) {
<-s.After(d)
}
// After returns a channel which receives the current time after the clock
// has advanced by d.
func (s *Simulated) After(d time.Duration) <-chan time.Time {
after := make(chan time.Time, 1)
s.AfterFunc(d, func() {
after <- (time.Time{}).Add(time.Duration(s.now))
})
return after
}
// AfterFunc runs fn after the clock has advanced by d. Unlike with the system
// clock, fn runs on the goroutine that calls Run.
func (s *Simulated) AfterFunc(d time.Duration, fn func()) Timer {
s.mu.Lock()
defer s.mu.Unlock()
s.init()
at := s.now + AbsTime(d)
s.lastId++
id := s.lastId
l, h := 0, len(s.scheduled)
ll := h
for l != h {
m := (l + h) / 2
if (at < s.scheduled[m].at) || ((at == s.scheduled[m].at) && (id < s.scheduled[m].id)) {
h = m
} else {
l = m + 1
}
}
ev := &simTimer{do: fn, at: at, s: s}
s.scheduled = append(s.scheduled, nil)
copy(s.scheduled[l+1:], s.scheduled[l:ll])
s.scheduled[l] = ev
s.cond.Broadcast()
return ev
}
func (ev *simTimer) Stop() bool {
s := ev.s
s.mu.Lock()
defer s.mu.Unlock()
for i := 0; i < len(s.scheduled); i++ {
if s.scheduled[i] == ev {
s.scheduled = append(s.scheduled[:i], s.scheduled[i+1:]...)
s.cond.Broadcast()
return true
}
}
return false
}
func (s *Simulated) init() {
if s.cond == nil {
s.cond = sync.NewCond(&s.mu)
}
}