Add context-aware "time" library wrapper.

go/src/infra/libs/clock/testclock/testtimer.go

+// Copyright 2015 The Chromium 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 testclock
+
+import (
+        "time"
+
+        "infra/libs/clock"
+)
+
+// timer is an implementation of clock.TestTimer that uses a channel
+// to signal the timer to fire.
+//
+// The channel is buffered so it can be used without requiring a separate signalling
+// goroutine.
+type timer struct {
+        clock   *testClock     // The underlying test clock instance.
+        signalC chan time.Time // Underlying signal channel.
+
+        // Cancels callback from clock.invokeAt. Being not nil implies that the timer
+        // is active.
+        cancelFunc cancelFunc
+}
+
+var _ clock.Timer = (*timer)(nil)
+
+// NewTimer returns a new, instantiated timer.
+func newTimer(clock *testClock) clock.Timer {
+        t := timer{
+                clock: clock,
+        }
+        return &t
+}
+
+func (t *timer) GetC() (c <-chan time.Time) {
+        if t.cancelFunc != nil {
+                c = t.signalC
+        }
+        return
+}
+
+func (t *timer) Reset(d time.Duration) (active bool) {
+        now := t.clock.Now()
+        triggerTime := now.Add(d)
+
+        // Signal our timerSet callback.
+        t.clock.signalTimerSet(t)
+
+        // Stop our current polling goroutine, if it's running.
+        active = t.Stop()
+
+        // Set timer properties.
+        t.signalC = make(chan time.Time, 1)
+        t.cancelFunc = t.clock.invokeAt(triggerTime, t.signal)
+        return
+}
+
+func (t *timer) Stop() bool {
+        // If the timer is not running, we're done.
+        if t.cancelFunc == nil {
+                return false
+        }
+
+        // Clear our state.
+        t.cancelFunc()
+        t.cancelFunc = nil
+        return true
+}
+
+// Sends a single signal, clearing the channel afterwards.
+func (t *timer) signal(now time.Time) {
+        if t.signalC != nil {
+                t.signalC <- now
+        }
+}