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/*
* 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.
*/
#ifndef SYSTEM_WRAPPERS_INCLUDE_CLOCK_H_
#define SYSTEM_WRAPPERS_INCLUDE_CLOCK_H_
#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 {
public:
virtual ~Clock() {}
// Return a timestamp relative to an unspecified epoch.
virtual Timestamp CurrentTime() = 0;
int64_t TimeInMilliseconds() { return CurrentTime().ms(); }
int64_t TimeInMicroseconds() { return CurrentTime().us(); }
// Retrieve an NTP absolute timestamp (with an epoch of Jan 1, 1900).
NtpTime CurrentNtpTime() { return ConvertTimestampToNtpTime(CurrentTime()); }
int64_t CurrentNtpInMilliseconds() { return CurrentNtpTime().ToMs(); }
// Converts between a relative timestamp returned by this clock, to NTP time.
virtual NtpTime ConvertTimestampToNtpTime(Timestamp timestamp) = 0;
int64_t ConvertTimestampToNtpTimeInMilliseconds(int64_t timestamp_ms) {
return ConvertTimestampToNtpTime(Timestamp::Millis(timestamp_ms)).ToMs();
}
// Converts NtpTime to a Timestamp with UTC epoch.
// A `Minus Infinity` Timestamp is returned if the NtpTime is invalid.
static Timestamp NtpToUtc(NtpTime ntp_time) {
if (!ntp_time.Valid()) {
return Timestamp::MinusInfinity();
}
// Seconds since UTC epoch.
int64_t time = ntp_time.seconds() - kNtpJan1970;
// Microseconds since UTC epoch (not including NTP fraction)
time = time * 1'000'000;
// Fractions part of the NTP time, in microseconds.
int64_t time_fraction =
DivideRoundToNearest(int64_t{ntp_time.fractions()} * 1'000'000,
NtpTime::kFractionsPerSecond);
return Timestamp::Micros(time + time_fraction);
}
// Returns an instance of the real-time system clock implementation.
static Clock* GetRealTimeClock();
};
class SimulatedClock : public Clock {
public:
// The constructors assume an epoch of Jan 1, 1970.
explicit SimulatedClock(int64_t initial_time_us);
explicit SimulatedClock(Timestamp initial_time);
~SimulatedClock() override;
// Return a timestamp with an epoch of Jan 1, 1970.
Timestamp CurrentTime() override;
NtpTime ConvertTimestampToNtpTime(Timestamp timestamp) 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);
private:
// 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
#endif // SYSTEM_WRAPPERS_INCLUDE_CLOCK_H_
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