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// Copyright (c) 2011 The Chromium OS Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// Timer - class that provides timer tracking.
#include <string>
#include <base/macros.h>
#include <base/memory/scoped_ptr.h>
#include <base/time/time.h>
#include <gtest/gtest_prod.h> // for FRIEND_TEST
class MetricsLibraryInterface;
namespace chromeos_metrics {
class TimerInterface {
virtual ~TimerInterface() {}
virtual bool Start() = 0;
virtual bool Stop() = 0;
virtual bool Reset() = 0;
virtual bool HasStarted() const = 0;
// Wrapper for calls to the system clock.
class ClockWrapper {
ClockWrapper() {}
virtual ~ClockWrapper() {}
// Returns the current time from the system.
virtual base::TimeTicks GetCurrentTime() const;
// Implements a Timer.
class Timer : public TimerInterface {
virtual ~Timer() {}
// Starts the timer. If a timer is already running, also resets current
// timer. Always returns true.
virtual bool Start();
// Stops the timer and calculates the total time elapsed between now and when
// Start() was called. Note that this method needs a prior call to Start().
// Otherwise, it fails (returns false).
virtual bool Stop();
// Pauses a timer. If the timer is stopped, this call starts the timer in
// the paused state. Fails (returns false) if the timer is already paused.
virtual bool Pause();
// Restarts a paused timer (or starts a stopped timer). This method fails
// (returns false) if the timer is already running; otherwise, returns true.
virtual bool Resume();
// Resets the timer, erasing the current duration being tracked. Always
// returns true.
virtual bool Reset();
// Returns whether the timer has started or not.
virtual bool HasStarted() const;
// Stores the current elapsed time in |elapsed_time|. If timer is stopped,
// stores the elapsed time from when Stop() was last called. Otherwise,
// calculates and stores the elapsed time since the last Start().
// Returns false if the timer was never Start()'ed or if called with a null
// pointer argument.
virtual bool GetElapsedTime(base::TimeDelta* elapsed_time) const;
enum TimerState { kTimerStopped, kTimerRunning, kTimerPaused };
friend class TimerTest;
friend class TimerReporterTest;
FRIEND_TEST(TimerReporterTest, StartStopReport);
FRIEND_TEST(TimerTest, InvalidElapsedTime);
FRIEND_TEST(TimerTest, InvalidStop);
FRIEND_TEST(TimerTest, PauseResumeStop);
FRIEND_TEST(TimerTest, PauseStartStopResume);
FRIEND_TEST(TimerTest, PauseStop);
FRIEND_TEST(TimerTest, Reset);
FRIEND_TEST(TimerTest, ReStart);
FRIEND_TEST(TimerTest, ResumeStartStopPause);
FRIEND_TEST(TimerTest, SeparatedTimers);
FRIEND_TEST(TimerTest, StartPauseResumePauseResumeStop);
FRIEND_TEST(TimerTest, StartPauseResumePauseStop);
FRIEND_TEST(TimerTest, StartPauseResumeStop);
FRIEND_TEST(TimerTest, StartPauseStop);
FRIEND_TEST(TimerTest, StartResumeStop);
FRIEND_TEST(TimerTest, StartStop);
// Elapsed time of the last use of the timer.
base::TimeDelta elapsed_time_;
// Starting time value.
base::TimeTicks start_time_;
// Whether the timer is running, stopped, or paused.
TimerState timer_state_;
// Wrapper for the calls to the system clock.
scoped_ptr<ClockWrapper> clock_wrapper_;
// Extends the Timer class to report the elapsed time in milliseconds through
// the UMA metrics library.
class TimerReporter : public Timer {
// Initializes the timer by providing a |histogram_name| to report to with
// |min|, |max| and |num_buckets| attributes for the histogram.
TimerReporter(const std::string& histogram_name, int min, int max,
int num_buckets);
virtual ~TimerReporter() {}
// Sets the metrics library used by all instances of this class.
static void set_metrics_lib(MetricsLibraryInterface* metrics_lib) {
metrics_lib_ = metrics_lib;
// Reports the current duration to UMA, in milliseconds. Returns false if
// there is nothing to report, e.g. a metrics library is not set.
virtual bool ReportMilliseconds() const;
// Accessor methods.
const std::string& histogram_name() const { return histogram_name_; }
int min() const { return min_; }
int max() const { return max_; }
int num_buckets() const { return num_buckets_; }
friend class TimerReporterTest;
FRIEND_TEST(TimerReporterTest, StartStopReport);
FRIEND_TEST(TimerReporterTest, InvalidReport);
static MetricsLibraryInterface* metrics_lib_;
std::string histogram_name_;
int min_;
int max_;
int num_buckets_;
} // namespace chromeos_metrics
#endif // METRICS_TIMER_H_