1// Copyright (c) 2012 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#ifndef BASE_TICK_CLOCK_H_
6#define BASE_TICK_CLOCK_H_
7
8#include "base/base_export.h"
9#include "base/time/time.h"
10
11namespace base {
12
13// A TickClock is an interface for objects that vend TimeTicks.  It is
14// intended to be able to test the behavior of classes with respect to
15// non-decreasing time.
16//
17// See DefaultTickClock (base/time/default_tick_clock.h) for the default
18// implementation that simply uses TimeTicks::Now().
19//
20// (Other implementations that use TimeTicks::HighResNow() or
21// TimeTicks::NowFromSystemTime() should be added as needed.)
22//
23// See SimpleTestTickClock (base/test/simple_test_tick_clock.h) for a
24// simple test implementation.
25//
26// See Clock (base/time/clock.h) for the equivalent interface for Times.
27class BASE_EXPORT TickClock {
28 public:
29  virtual ~TickClock();
30
31  // NowTicks() must be safe to call from any thread.  The caller may
32  // assume that NowTicks() is monotonic (but not strictly monotonic).
33  // In other words, the returned TimeTicks will never decrease with
34  // time, although they might "stand still".
35  virtual TimeTicks NowTicks() = 0;
36};
37
38}  // namespace base
39
40#endif  // BASE_TICK_CLOCK_H_
41