blob: 3c60f63da8201779ff7c53e06e6a228d5b4f38dd [file] [log] [blame]
* Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
#include <stdint.h>
#include <atomic>
#include <memory>
#include "api/units/timestamp.h"
#include "rtc_base/system/rtc_export.h"
#include "system_wrappers/include/ntp_time.h"
namespace webrtc {
// January 1970, in NTP seconds.
const uint32_t kNtpJan1970 = 2208988800UL;
// Magic NTP fractional unit.
const double kMagicNtpFractionalUnit = 4.294967296E+9;
// A clock interface that allows reading of absolute and relative timestamps.
class RTC_EXPORT Clock {
virtual ~Clock() {}
// Return a timestamp relative to an unspecified epoch.
virtual Timestamp CurrentTime() {
return Timestamp::Micros(TimeInMicroseconds());
virtual int64_t TimeInMilliseconds() { return CurrentTime().ms(); }
virtual int64_t TimeInMicroseconds() { return CurrentTime().us(); }
// Retrieve an NTP absolute timestamp.
virtual NtpTime CurrentNtpTime() = 0;
// Retrieve an NTP absolute timestamp in milliseconds.
virtual int64_t CurrentNtpInMilliseconds() = 0;
// Converts an NTP timestamp to a millisecond timestamp.
static int64_t NtpToMs(uint32_t seconds, uint32_t fractions) {
return NtpTime(seconds, fractions).ToMs();
// Returns an instance of the real-time system clock implementation.
static Clock* GetRealTimeClock();
class SimulatedClock : public Clock {
explicit SimulatedClock(int64_t initial_time_us);
explicit SimulatedClock(Timestamp initial_time);
~SimulatedClock() override;
// Return a timestamp relative to some arbitrary source; the source is fixed
// for this clock.
Timestamp CurrentTime() override;
// Retrieve an NTP absolute timestamp.
NtpTime CurrentNtpTime() override;
// Converts an NTP timestamp to a millisecond timestamp.
int64_t CurrentNtpInMilliseconds() override;
// Advance the simulated clock with a given number of milliseconds or
// microseconds.
void AdvanceTimeMilliseconds(int64_t milliseconds);
void AdvanceTimeMicroseconds(int64_t microseconds);
void AdvanceTime(TimeDelta delta);
// The time is read and incremented with relaxed order. Each thread will see
// monotonically increasing time, and when threads post tasks or messages to
// one another, the synchronization done as part of the message passing should
// ensure that any causual chain of events on multiple threads also
// corresponds to monotonically increasing time.
std::atomic<int64_t> time_us_;
} // namespace webrtc