364 lines
8.6 KiB
Go
364 lines
8.6 KiB
Go
package clock
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import (
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"runtime"
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"sort"
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"sync"
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"time"
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)
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// Clock represents an interface to the functions in the standard library time
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// package. Two implementations are available in the clock package. The first
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// is a real-time clock which simply wraps the time package's functions. The
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// second is a mock clock which will only make forward progress when
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// programmatically adjusted.
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type Clock interface {
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After(d time.Duration) <-chan time.Time
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AfterFunc(d time.Duration, f func()) *Timer
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Now() time.Time
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Sleep(d time.Duration)
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Tick(d time.Duration) <-chan time.Time
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Ticker(d time.Duration) *Ticker
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Timer(d time.Duration) *Timer
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}
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// New returns an instance of a real-time clock.
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func New() Clock {
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return &clock{}
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}
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// clock implements a real-time clock by simply wrapping the time package functions.
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type clock struct{}
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func (c *clock) After(d time.Duration) <-chan time.Time { return time.After(d) }
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func (c *clock) AfterFunc(d time.Duration, f func()) *Timer {
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return &Timer{timer: time.AfterFunc(d, f)}
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}
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func (c *clock) Now() time.Time { return time.Now() }
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func (c *clock) Sleep(d time.Duration) { time.Sleep(d) }
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func (c *clock) Tick(d time.Duration) <-chan time.Time { return time.Tick(d) }
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func (c *clock) Ticker(d time.Duration) *Ticker {
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t := time.NewTicker(d)
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return &Ticker{C: t.C, ticker: t}
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}
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func (c *clock) Timer(d time.Duration) *Timer {
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t := time.NewTimer(d)
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return &Timer{C: t.C, timer: t}
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}
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// Mock represents a mock clock that only moves forward programmically.
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// It can be preferable to a real-time clock when testing time-based functionality.
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type Mock struct {
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mu sync.Mutex
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now time.Time // current time
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timers clockTimers // tickers & timers
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calls Calls
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waiting []waiting
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callsMutex sync.Mutex
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}
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// NewMock returns an instance of a mock clock.
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// The current time of the mock clock on initialization is the Unix epoch.
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func NewMock() *Mock {
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return &Mock{now: time.Unix(0, 0)}
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}
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// Add moves the current time of the mock clock forward by the duration.
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// This should only be called from a single goroutine at a time.
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func (m *Mock) Add(d time.Duration) {
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// Calculate the final current time.
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t := m.now.Add(d)
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// Continue to execute timers until there are no more before the new time.
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for {
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if !m.runNextTimer(t) {
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break
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}
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}
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// Ensure that we end with the new time.
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m.mu.Lock()
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m.now = t
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m.mu.Unlock()
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// Give a small buffer to make sure the other goroutines get handled.
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gosched()
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}
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// runNextTimer executes the next timer in chronological order and moves the
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// current time to the timer's next tick time. The next time is not executed if
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// it's next time if after the max time. Returns true if a timer is executed.
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func (m *Mock) runNextTimer(max time.Time) bool {
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m.mu.Lock()
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// Sort timers by time.
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sort.Sort(m.timers)
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// If we have no more timers then exit.
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if len(m.timers) == 0 {
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m.mu.Unlock()
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return false
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}
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// Retrieve next timer. Exit if next tick is after new time.
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t := m.timers[0]
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if t.Next().After(max) {
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m.mu.Unlock()
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return false
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}
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// Move "now" forward and unlock clock.
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m.now = t.Next()
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m.mu.Unlock()
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// Execute timer.
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t.Tick(m.now)
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return true
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}
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// After waits for the duration to elapse and then sends the current time on the returned channel.
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func (m *Mock) After(d time.Duration) <-chan time.Time {
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defer m.inc(&m.calls.After)
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return m.Timer(d).C
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}
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// AfterFunc waits for the duration to elapse and then executes a function.
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// A Timer is returned that can be stopped.
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func (m *Mock) AfterFunc(d time.Duration, f func()) *Timer {
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defer m.inc(&m.calls.AfterFunc)
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t := m.Timer(d)
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t.C = nil
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t.fn = f
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return t
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}
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// Now returns the current wall time on the mock clock.
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func (m *Mock) Now() time.Time {
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defer m.inc(&m.calls.Now)
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m.mu.Lock()
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defer m.mu.Unlock()
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return m.now
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}
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// Sleep pauses the goroutine for the given duration on the mock clock.
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// The clock must be moved forward in a separate goroutine.
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func (m *Mock) Sleep(d time.Duration) {
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defer m.inc(&m.calls.Sleep)
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<-m.After(d)
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}
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// Tick is a convenience function for Ticker().
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// It will return a ticker channel that cannot be stopped.
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func (m *Mock) Tick(d time.Duration) <-chan time.Time {
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defer m.inc(&m.calls.Tick)
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return m.Ticker(d).C
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}
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// Ticker creates a new instance of Ticker.
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func (m *Mock) Ticker(d time.Duration) *Ticker {
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defer m.inc(&m.calls.Ticker)
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m.mu.Lock()
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defer m.mu.Unlock()
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ch := make(chan time.Time)
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t := &Ticker{
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C: ch,
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c: ch,
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mock: m,
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d: d,
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next: m.now.Add(d),
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}
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m.timers = append(m.timers, (*internalTicker)(t))
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return t
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}
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// Timer creates a new instance of Timer.
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func (m *Mock) Timer(d time.Duration) *Timer {
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defer m.inc(&m.calls.Timer)
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m.mu.Lock()
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defer m.mu.Unlock()
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ch := make(chan time.Time)
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t := &Timer{
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C: ch,
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c: ch,
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mock: m,
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next: m.now.Add(d),
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}
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m.timers = append(m.timers, (*internalTimer)(t))
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return t
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}
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func (m *Mock) removeClockTimer(t clockTimer) {
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m.mu.Lock()
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defer m.mu.Unlock()
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for i, timer := range m.timers {
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if timer == t {
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copy(m.timers[i:], m.timers[i+1:])
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m.timers[len(m.timers)-1] = nil
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m.timers = m.timers[:len(m.timers)-1]
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break
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}
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}
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sort.Sort(m.timers)
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}
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func (m *Mock) inc(addr *uint32) {
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m.callsMutex.Lock()
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defer m.callsMutex.Unlock()
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*addr++
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var newWaiting []waiting
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for _, w := range m.waiting {
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if m.calls.atLeast(w.expected) {
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close(w.done)
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continue
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}
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newWaiting = append(newWaiting, w)
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}
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m.waiting = newWaiting
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}
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// Wait waits for at least the relevant calls before returning. The expected
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// Calls are always over the lifetime of the Mock. Values in the Calls struct
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// are used as the minimum number of calls, this allows you to wait for only
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// the calls you care about.
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func (m *Mock) Wait(s Calls) {
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m.callsMutex.Lock()
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if m.calls.atLeast(s) {
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m.callsMutex.Unlock()
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return
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}
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done := make(chan struct{})
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m.waiting = append(m.waiting, waiting{expected: s, done: done})
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m.callsMutex.Unlock()
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<-done
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}
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// clockTimer represents an object with an associated start time.
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type clockTimer interface {
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Next() time.Time
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Tick(time.Time)
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}
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// clockTimers represents a list of sortable timers.
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type clockTimers []clockTimer
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func (a clockTimers) Len() int { return len(a) }
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func (a clockTimers) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
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func (a clockTimers) Less(i, j int) bool { return a[i].Next().Before(a[j].Next()) }
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// Timer represents a single event.
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// The current time will be sent on C, unless the timer was created by AfterFunc.
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type Timer struct {
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C <-chan time.Time
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c chan time.Time
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timer *time.Timer // realtime impl, if set
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next time.Time // next tick time
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mock *Mock // mock clock, if set
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fn func() // AfterFunc function, if set
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}
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// Stop turns off the ticker.
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func (t *Timer) Stop() {
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if t.timer != nil {
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t.timer.Stop()
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} else {
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t.mock.removeClockTimer((*internalTimer)(t))
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}
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}
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type internalTimer Timer
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func (t *internalTimer) Next() time.Time { return t.next }
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func (t *internalTimer) Tick(now time.Time) {
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if t.fn != nil {
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t.fn()
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} else {
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t.c <- now
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}
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t.mock.removeClockTimer((*internalTimer)(t))
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gosched()
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}
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// Ticker holds a channel that receives "ticks" at regular intervals.
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type Ticker struct {
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C <-chan time.Time
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c chan time.Time
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ticker *time.Ticker // realtime impl, if set
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next time.Time // next tick time
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mock *Mock // mock clock, if set
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d time.Duration // time between ticks
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}
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// Stop turns off the ticker.
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func (t *Ticker) Stop() {
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if t.ticker != nil {
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t.ticker.Stop()
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} else {
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t.mock.removeClockTimer((*internalTicker)(t))
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}
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}
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type internalTicker Ticker
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func (t *internalTicker) Next() time.Time { return t.next }
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func (t *internalTicker) Tick(now time.Time) {
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select {
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case t.c <- now:
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case <-time.After(1 * time.Millisecond):
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}
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t.next = now.Add(t.d)
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gosched()
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}
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// Sleep momentarily so that other goroutines can process.
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func gosched() { runtime.Gosched() }
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// Calls keeps track of the count of calls for each of the methods on the Clock
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// interface.
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type Calls struct {
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After uint32
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AfterFunc uint32
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Now uint32
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Sleep uint32
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Tick uint32
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Ticker uint32
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Timer uint32
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}
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// atLeast returns true if at least the number of calls in o have been made.
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func (c Calls) atLeast(o Calls) bool {
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if c.After < o.After {
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return false
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}
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if c.AfterFunc < o.AfterFunc {
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return false
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}
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if c.Now < o.Now {
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return false
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}
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if c.Sleep < o.Sleep {
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return false
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}
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if c.Tick < o.Tick {
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return false
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}
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if c.Ticker < o.Ticker {
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return false
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}
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if c.Timer < o.Timer {
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return false
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}
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return true
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}
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type waiting struct {
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expected Calls
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done chan struct{}
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}
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