b59e9045bf
The timestamps returned by the clocks do not have an epoch. Each clock should be able to convert a timestamp it returns to an NTP time. The default implementation for querying for an NTP time is converting the current timestamp. This is favored over returning the offset between the relative and the NTP time because there is a field trial that makes the real clock revert to using system dependent methods for getting the NTP time. Bug: webrtc:11327 Change-Id: Ia139b2744b407cae94420bf9112212ec577efb16 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/219687 Reviewed-by: Minyue Li <minyue@webrtc.org> Reviewed-by: Niels Moller <nisse@webrtc.org> Commit-Queue: Paul Hallak <phallak@google.com> Cr-Commit-Position: refs/heads/master@{#34071}
93 lines
3.2 KiB
C++
93 lines
3.2 KiB
C++
/*
|
|
* 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).
|
|
// TODO(bugs.webrtc.org/11327): Make this non-virtual once
|
|
// "WebRTC-SystemIndependentNtpTimeKillSwitch" is removed.
|
|
virtual NtpTime CurrentNtpTime() {
|
|
return ConvertTimestampToNtpTime(CurrentTime());
|
|
}
|
|
int64_t CurrentNtpInMilliseconds() { return CurrentNtpTime().ToMs(); }
|
|
|
|
// Converts between a relative timestamp returned by this clock, to NTP time.
|
|
// TODO(bugs.webrtc.org/11327): Make this method pure virtual,
|
|
// and delete default dummy implementation.
|
|
virtual NtpTime ConvertTimestampToNtpTime(Timestamp timestamp) {
|
|
return NtpTime();
|
|
}
|
|
int64_t ConvertTimestampToNtpTimeInMilliseconds(int64_t timestamp_ms) {
|
|
return ConvertTimestampToNtpTime(Timestamp::Millis(timestamp_ms)).ToMs();
|
|
}
|
|
|
|
// 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_
|