1 // Copyright (C) 2019 Google LLC 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // http://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 15 #ifndef ICING_UTIL_CLOCK_H_ 16 #define ICING_UTIL_CLOCK_H_ 17 18 #include <cstdint> 19 #include <memory> 20 21 namespace icing { 22 namespace lib { 23 24 // Returns the current steady time in nanoseconds. The steady clock is different 25 // from the system clock. It's monotonic and never returns a lower value than a 26 // previous call, while a system clock can be occasionally adjusted. 27 int64_t GetSteadyTimeNanoseconds(); 28 29 // Returns the current steady time in Milliseconds. The steady clock is 30 // different from the system clock. It's monotonic and never returns a lower 31 // value than a previous call, while a system clock can be occasionally 32 // adjusted. 33 int64_t GetSteadyTimeMilliseconds(); 34 35 // Used to calculate the elapsed time. 36 class Timer { 37 public: 38 // Creates and starts the timer. Timer()39 Timer() : start_timestamp_nanoseconds_(GetSteadyTimeNanoseconds()) {} 40 41 virtual ~Timer() = default; 42 43 // Returns the elapsed time from when timer started. GetElapsedMilliseconds()44 virtual int64_t GetElapsedMilliseconds() { 45 return GetElapsedNanoseconds() / 1000000; 46 } 47 48 // Returns the elapsed time from when timer started. GetElapsedNanoseconds()49 virtual int64_t GetElapsedNanoseconds() { 50 return GetSteadyTimeNanoseconds() - start_timestamp_nanoseconds_; 51 } 52 53 private: 54 int64_t start_timestamp_nanoseconds_; 55 }; 56 57 // Wrapper around real-time clock functions. This is separated primarily so 58 // tests can override this clock and inject it into the class under test. 59 class Clock { 60 public: 61 virtual ~Clock() = default; 62 63 // Returns the current time in milliseconds, it's guaranteed that the return 64 // value is non-negative. 65 virtual int64_t GetSystemTimeMilliseconds() const; 66 67 // Returns a timer used to calculate the elapsed time. The timer starts when 68 // the method returns. 69 virtual std::unique_ptr<Timer> GetNewTimer() const; 70 }; 71 72 } // namespace lib 73 } // namespace icing 74 75 #endif // ICING_UTIL_CLOCK_H_ 76