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tailscale/tstest/clock.go

62 lines
1.3 KiB
Go

// Copyright (c) 2020 Tailscale Inc & 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 tstest
import (
"sync"
"time"
)
// Clock is a testing clock that advances every time its Now method is
// called, beginning at Start.
//
// The zero value starts virtual time at an arbitrary value recorded
// in Start on the first call to Now, and time never advances.
type Clock struct {
// Start is the first value returned by Now.
Start time.Time
// Step is how much to advance with each Now call.
Step time.Duration
// Present is the time that the next Now call will receive.
Present time.Time
sync.Mutex
}
// Now returns the virtual clock's current time, and advances it
// according to its step configuration.
func (c *Clock) Now() time.Time {
c.Lock()
defer c.Unlock()
c.initLocked()
step := c.Step
ret := c.Present
c.Present = c.Present.Add(step)
return ret
}
func (c *Clock) Advance(d time.Duration) {
c.Lock()
defer c.Unlock()
c.initLocked()
c.Present = c.Present.Add(d)
}
func (c *Clock) initLocked() {
if c.Start.IsZero() {
c.Start = time.Now()
}
if c.Present.Before(c.Start) {
c.Present = c.Start
}
}
// Reset rewinds the virtual clock to its start time.
func (c *Clock) Reset() {
c.Lock()
defer c.Unlock()
c.Present = c.Start
}