62 lines
1.3 KiB
Go
62 lines
1.3 KiB
Go
// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package tstest
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import (
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"sync"
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"time"
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)
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// Clock is a testing clock that advances every time its Now method is
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// called, beginning at Start.
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//
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// The zero value starts virtual time at an arbitrary value recorded
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// in Start on the first call to Now, and time never advances.
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type Clock struct {
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// Start is the first value returned by Now.
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Start time.Time
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// Step is how much to advance with each Now call.
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Step time.Duration
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// Present is the time that the next Now call will receive.
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Present time.Time
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sync.Mutex
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}
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// Now returns the virtual clock's current time, and avances it
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// according to its step configuration.
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func (c *Clock) Now() time.Time {
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c.Lock()
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defer c.Unlock()
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c.initLocked()
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step := c.Step
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ret := c.Present
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c.Present = c.Present.Add(step)
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return ret
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}
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func (c *Clock) Advance(d time.Duration) {
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c.Lock()
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defer c.Unlock()
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c.initLocked()
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c.Present = c.Present.Add(d)
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}
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func (c *Clock) initLocked() {
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if c.Start.IsZero() {
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c.Start = time.Now()
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}
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if c.Present.Before(c.Start) {
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c.Present = c.Start
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}
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}
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// Reset rewinds the virtual clock to its start time.
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func (c *Clock) Reset() {
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c.Lock()
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defer c.Unlock()
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c.Present = c.Start
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}
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