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// Copyright 2020 The gVisor Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package faketime provides a fake clock that implements tcpip.Clock interface.
package faketime
import (
"container/heap"
"sync"
"time"
"github.com/dpjacques/clockwork"
"gvisor.dev/gvisor/pkg/tcpip"
)
// NullClock implements a clock that never advances.
type NullClock struct{}
var _ tcpip.Clock = (*NullClock)(nil)
// NowNanoseconds implements tcpip.Clock.NowNanoseconds.
func (*NullClock) NowNanoseconds() int64 {
return 0
}
// NowMonotonic implements tcpip.Clock.NowMonotonic.
func (*NullClock) NowMonotonic() int64 {
return 0
}
// AfterFunc implements tcpip.Clock.AfterFunc.
func (*NullClock) AfterFunc(time.Duration, func()) tcpip.Timer {
return nil
}
// ManualClock implements tcpip.Clock and only advances manually with Advance
// method.
type ManualClock struct {
clock clockwork.FakeClock
// mu protects the fields below.
mu sync.RWMutex
// times is min-heap of times. A heap is used for quick retrieval of the next
// upcoming time of scheduled work.
times *timeHeap
// waitGroups stores one WaitGroup for all work scheduled to execute at the
// same time via AfterFunc. This allows parallel execution of all functions
// passed to AfterFunc scheduled for the same time.
waitGroups map[time.Time]*sync.WaitGroup
}
// NewManualClock creates a new ManualClock instance.
func NewManualClock() *ManualClock {
return &ManualClock{
clock: clockwork.NewFakeClock(),
times: &timeHeap{},
waitGroups: make(map[time.Time]*sync.WaitGroup),
}
}
var _ tcpip.Clock = (*ManualClock)(nil)
// NowNanoseconds implements tcpip.Clock.NowNanoseconds.
func (mc *ManualClock) NowNanoseconds() int64 {
return mc.clock.Now().UnixNano()
}
// NowMonotonic implements tcpip.Clock.NowMonotonic.
func (mc *ManualClock) NowMonotonic() int64 {
return mc.NowNanoseconds()
}
// AfterFunc implements tcpip.Clock.AfterFunc.
func (mc *ManualClock) AfterFunc(d time.Duration, f func()) tcpip.Timer {
until := mc.clock.Now().Add(d)
wg := mc.addWait(until)
return &manualTimer{
clock: mc,
until: until,
timer: mc.clock.AfterFunc(d, func() {
defer wg.Done()
f()
}),
}
}
// addWait adds an additional wait to the WaitGroup for parallel execution of
// all work scheduled for t. Returns a reference to the WaitGroup modified.
func (mc *ManualClock) addWait(t time.Time) *sync.WaitGroup {
mc.mu.RLock()
wg, ok := mc.waitGroups[t]
mc.mu.RUnlock()
if ok {
wg.Add(1)
return wg
}
mc.mu.Lock()
heap.Push(mc.times, t)
mc.mu.Unlock()
wg = &sync.WaitGroup{}
wg.Add(1)
mc.mu.Lock()
mc.waitGroups[t] = wg
mc.mu.Unlock()
return wg
}
// removeWait removes a wait from the WaitGroup for parallel execution of all
// work scheduled for t.
func (mc *ManualClock) removeWait(t time.Time) {
mc.mu.RLock()
defer mc.mu.RUnlock()
wg := mc.waitGroups[t]
wg.Done()
}
// Advance executes all work that have been scheduled to execute within d from
// the current time. Blocks until all work has completed execution.
func (mc *ManualClock) Advance(d time.Duration) {
// Block until all the work is done
until := mc.clock.Now().Add(d)
for {
mc.mu.Lock()
if mc.times.Len() == 0 {
mc.mu.Unlock()
break
}
t := heap.Pop(mc.times).(time.Time)
if t.After(until) {
// No work to do
heap.Push(mc.times, t)
mc.mu.Unlock()
break
}
mc.mu.Unlock()
diff := t.Sub(mc.clock.Now())
mc.clock.Advance(diff)
mc.mu.RLock()
wg := mc.waitGroups[t]
mc.mu.RUnlock()
wg.Wait()
mc.mu.Lock()
delete(mc.waitGroups, t)
mc.mu.Unlock()
}
if now := mc.clock.Now(); until.After(now) {
mc.clock.Advance(until.Sub(now))
}
}
type manualTimer struct {
clock *ManualClock
timer clockwork.Timer
mu sync.RWMutex
until time.Time
}
var _ tcpip.Timer = (*manualTimer)(nil)
// Reset implements tcpip.Timer.Reset.
func (t *manualTimer) Reset(d time.Duration) {
if !t.timer.Reset(d) {
return
}
t.mu.Lock()
defer t.mu.Unlock()
t.clock.removeWait(t.until)
t.until = t.clock.clock.Now().Add(d)
t.clock.addWait(t.until)
}
// Stop implements tcpip.Timer.Stop.
func (t *manualTimer) Stop() bool {
if !t.timer.Stop() {
return false
}
t.mu.RLock()
defer t.mu.RUnlock()
t.clock.removeWait(t.until)
return true
}
type timeHeap []time.Time
var _ heap.Interface = (*timeHeap)(nil)
func (h timeHeap) Len() int {
return len(h)
}
func (h timeHeap) Less(i, j int) bool {
return h[i].Before(h[j])
}
func (h timeHeap) Swap(i, j int) {
h[i], h[j] = h[j], h[i]
}
func (h *timeHeap) Push(x interface{}) {
*h = append(*h, x.(time.Time))
}
func (h *timeHeap) Pop() interface{} {
last := (*h)[len(*h)-1]
*h = (*h)[:len(*h)-1]
return last
}
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