1 files changed, 129 insertions, 0 deletions
diff --git a/common/mclock/simclock.go b/common/mclock/simclock.go
new file mode 100644
index 000000000..e014f5615
--- /dev/null
+++ b/common/mclock/simclock.go
@@ -0,0 +1,129 @@
+// 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 []event
+	mu        sync.RWMutex
+	cond      *sync.Cond
+}
+
+type event struct {
+	do func()
+	at AbsTime
+}
+
+// Run moves the clock by the given duration, executing all timers before that duration.
+func (s *Simulated) Run(d time.Duration) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.init()
+
+	end := s.now + AbsTime(d)
+	for len(s.scheduled) > 0 {
+		ev := s.scheduled[0]
+		if ev.at > end {
+			break
+		}
+		s.now = ev.at
+		ev.do()
+		s.scheduled = s.scheduled[1:]
+	}
+	s.now = end
+}
+
+func (s *Simulated) ActiveTimers() int {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+
+	return len(s.scheduled)
+}
+
+func (s *Simulated) WaitForTimers(n int) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.init()
+
+	for len(s.scheduled) < n {
+		s.cond.Wait()
+	}
+}
+
+// Now implements Clock.
+func (s *Simulated) Now() AbsTime {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+
+	return s.now
+}
+
+// Sleep implements Clock.
+func (s *Simulated) Sleep(d time.Duration) {
+	<-s.After(d)
+}
+
+// After implements Clock.
+func (s *Simulated) After(d time.Duration) <-chan time.Time {
+	after := make(chan time.Time, 1)
+	s.insert(d, func() {
+		after <- (time.Time{}).Add(time.Duration(s.now))
+	})
+	return after
+}
+
+func (s *Simulated) insert(d time.Duration, do func()) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.init()
+
+	at := s.now + AbsTime(d)
+	l, h := 0, len(s.scheduled)
+	ll := h
+	for l != h {
+		m := (l + h) / 2
+		if at < s.scheduled[m].at {
+			h = m
+		} else {
+			l = m + 1
+		}
+	}
+	s.scheduled = append(s.scheduled, event{})
+	copy(s.scheduled[l+1:], s.scheduled[l:ll])
+	s.scheduled[l] = event{do: do, at: at}
+	s.cond.Broadcast()
+}
+
+func (s *Simulated) init() {
+	if s.cond == nil {
+		s.cond = sync.NewCond(&s.mu)
+	}
+}