update_engine/common/clock_interface.h

//
// Copyright (C) 2013 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//

#ifndef UPDATE_ENGINE_COMMON_CLOCK_INTERFACE_H_
#define UPDATE_ENGINE_COMMON_CLOCK_INTERFACE_H_

#include <string>

#include <base/time/time.h>

namespace chromeos_update_engine {

// The clock interface allows access to various system clocks. The
// sole reason for providing this as an interface is unit testing.
// Additionally, the sole reason for the methods not being static
// is also unit testing.
class ClockInterface {
 public:
  virtual ~ClockInterface() = default;

  // Gets the current time e.g. similar to base::Time::Now().
  virtual base::Time GetWallclockTime() = 0;

  // Returns monotonic time since some unspecified starting point. It
  // is not increased when the system is sleeping nor is it affected
  // by NTP or the user changing the time.
  //
  // (This is a simple wrapper around clock_gettime(2) / CLOCK_MONOTONIC_RAW.)
  virtual base::Time GetMonotonicTime() = 0;

  // Returns monotonic time since some unspecified starting point. It
  // is increased when the system is sleeping but it's not affected
  // by NTP or the user changing the time.
  //
  // (This is a simple wrapper around clock_gettime(2) / CLOCK_BOOTTIME.)
  virtual base::Time GetBootTime() = 0;
};

}  // namespace chromeos_update_engine

#endif  // UPDATE_ENGINE_COMMON_CLOCK_INTERFACE_H_