base/time/clock.h

   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.h"
  10
  11 namespace 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/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/tick_clock.h) for the equivalent interface for
  27 // TimeTicks.
  28 class 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_