79 lines
2.5 KiB
C++
79 lines
2.5 KiB
C++
/*
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* Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#ifndef SYSTEM_WRAPPERS_INCLUDE_CLOCK_H_
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#define SYSTEM_WRAPPERS_INCLUDE_CLOCK_H_
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#include <stdint.h>
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#include <atomic>
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#include <memory>
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#include "api/units/timestamp.h"
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#include "rtc_base/system/rtc_export.h"
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#include "system_wrappers/include/ntp_time.h"
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namespace webrtc {
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// January 1970, in NTP seconds.
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const uint32_t kNtpJan1970 = 2208988800UL;
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// Magic NTP fractional unit.
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const double kMagicNtpFractionalUnit = 4.294967296E+9;
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// A clock interface that allows reading of absolute and relative timestamps.
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class RTC_EXPORT Clock {
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public:
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virtual ~Clock() {}
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// Return a timestamp relative to an unspecified epoch.
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virtual Timestamp CurrentTime() = 0;
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int64_t TimeInMilliseconds() { return CurrentTime().ms(); }
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int64_t TimeInMicroseconds() { return CurrentTime().us(); }
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// Retrieve an NTP absolute timestamp (with an epoch of Jan 1, 1900).
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virtual NtpTime CurrentNtpTime() = 0;
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int64_t CurrentNtpInMilliseconds() { return CurrentNtpTime().ToMs(); }
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// Returns an instance of the real-time system clock implementation.
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static Clock* GetRealTimeClock();
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};
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class SimulatedClock : public Clock {
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public:
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// The constructors assume an epoch of Jan 1, 1970.
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explicit SimulatedClock(int64_t initial_time_us);
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explicit SimulatedClock(Timestamp initial_time);
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~SimulatedClock() override;
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// Return a timestamp with an epoch of Jan 1, 1970.
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Timestamp CurrentTime() override;
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NtpTime CurrentNtpTime() override;
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// Advance the simulated clock with a given number of milliseconds or
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// microseconds.
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void AdvanceTimeMilliseconds(int64_t milliseconds);
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void AdvanceTimeMicroseconds(int64_t microseconds);
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void AdvanceTime(TimeDelta delta);
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private:
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// The time is read and incremented with relaxed order. Each thread will see
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// monotonically increasing time, and when threads post tasks or messages to
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// one another, the synchronization done as part of the message passing should
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// ensure that any causual chain of events on multiple threads also
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// corresponds to monotonically increasing time.
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std::atomic<int64_t> time_us_;
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};
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} // namespace webrtc
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#endif // SYSTEM_WRAPPERS_INCLUDE_CLOCK_H_
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