1 /* 2 * Copyright (c) 2013 The WebRTC project authors. All Rights Reserved. 3 * 4 * Use of this source code is governed by a BSD-style license 5 * that can be found in the LICENSE file in the root of the source 6 * tree. An additional intellectual property rights grant can be found 7 * in the file PATENTS. All contributing project authors may 8 * be found in the AUTHORS file in the root of the source tree. 9 */ 10 11 #ifndef SYSTEM_WRAPPERS_INCLUDE_CLOCK_H_ 12 #define SYSTEM_WRAPPERS_INCLUDE_CLOCK_H_ 13 14 #include <stdint.h> 15 16 #include <atomic> 17 #include <memory> 18 19 #include "api/units/timestamp.h" 20 #include "rtc_base/system/rtc_export.h" 21 #include "system_wrappers/include/ntp_time.h" 22 23 namespace webrtc { 24 25 // January 1970, in NTP seconds. 26 const uint32_t kNtpJan1970 = 2208988800UL; 27 28 // Magic NTP fractional unit. 29 const double kMagicNtpFractionalUnit = 4.294967296E+9; 30 31 // A clock interface that allows reading of absolute and relative timestamps. 32 class RTC_EXPORT Clock { 33 public: ~Clock()34 virtual ~Clock() {} 35 36 // Return a timestamp relative to an unspecified epoch. 37 virtual Timestamp CurrentTime() = 0; TimeInMilliseconds()38 int64_t TimeInMilliseconds() { return CurrentTime().ms(); } TimeInMicroseconds()39 int64_t TimeInMicroseconds() { return CurrentTime().us(); } 40 41 // Retrieve an NTP absolute timestamp (with an epoch of Jan 1, 1900). CurrentNtpTime()42 NtpTime CurrentNtpTime() { return ConvertTimestampToNtpTime(CurrentTime()); } CurrentNtpInMilliseconds()43 int64_t CurrentNtpInMilliseconds() { return CurrentNtpTime().ToMs(); } 44 45 // Converts between a relative timestamp returned by this clock, to NTP time. 46 virtual NtpTime ConvertTimestampToNtpTime(Timestamp timestamp) = 0; ConvertTimestampToNtpTimeInMilliseconds(int64_t timestamp_ms)47 int64_t ConvertTimestampToNtpTimeInMilliseconds(int64_t timestamp_ms) { 48 return ConvertTimestampToNtpTime(Timestamp::Millis(timestamp_ms)).ToMs(); 49 } 50 51 // Returns an instance of the real-time system clock implementation. 52 static Clock* GetRealTimeClock(); 53 }; 54 55 class SimulatedClock : public Clock { 56 public: 57 // The constructors assume an epoch of Jan 1, 1970. 58 explicit SimulatedClock(int64_t initial_time_us); 59 explicit SimulatedClock(Timestamp initial_time); 60 ~SimulatedClock() override; 61 62 // Return a timestamp with an epoch of Jan 1, 1970. 63 Timestamp CurrentTime() override; 64 65 NtpTime ConvertTimestampToNtpTime(Timestamp timestamp) override; 66 67 // Advance the simulated clock with a given number of milliseconds or 68 // microseconds. 69 void AdvanceTimeMilliseconds(int64_t milliseconds); 70 void AdvanceTimeMicroseconds(int64_t microseconds); 71 void AdvanceTime(TimeDelta delta); 72 73 private: 74 // The time is read and incremented with relaxed order. Each thread will see 75 // monotonically increasing time, and when threads post tasks or messages to 76 // one another, the synchronization done as part of the message passing should 77 // ensure that any causual chain of events on multiple threads also 78 // corresponds to monotonically increasing time. 79 std::atomic<int64_t> time_us_; 80 }; 81 82 } // namespace webrtc 83 84 #endif // SYSTEM_WRAPPERS_INCLUDE_CLOCK_H_ 85