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_CLOCK_H_
6#define BASE_CLOCK_H_
7
8#include "base/base_export.h"
9#include "base/time/time.h"
10
11namespace base {
12
13// A Clock is an interface for objects that vend Times.  It is
14// intended to be able to test the behavior of classes with respect to
15// time.
16//
17// See DefaultClock (base/time/default_clock.h) for the default
18// implementation that simply uses Time::Now().
19//
20// (An implementation that uses Time::SystemTime() should be added as
21// needed.)
22//
23// See SimpleTestClock (base/test/simple_test_clock.h) for a simple
24// test implementation.
25//
26// See TickClock (base/time/tick_clock.h) for the equivalent interface for
27// TimeTicks.
28class BASE_EXPORT Clock {
29 public:
30  virtual ~Clock();
31
32  // Now() must be safe to call from any thread.  The caller cannot
33  // make any ordering assumptions about the returned Time.  For
34  // example, the system clock may change to an earlier time.
35  virtual Time Now() = 0;
36};
37
38}  // namespace base
39
40#endif  // BASE_CLOCK_H_
41