webrtc/test/drifting_clock.cc

/*
 *  Copyright (c) 2016 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 "webrtc/test/drifting_clock.h"
#include "webrtc/base/checks.h"

namespace webrtc {
namespace test {
const float DriftingClock::kDoubleSpeed = 2.0f;
const float DriftingClock::kNoDrift = 1.0f;
const float DriftingClock::kHalfSpeed = 0.5f;

DriftingClock::DriftingClock(Clock* clock, float speed)
    : clock_(clock),
      drift_(speed - 1.0f),
      start_time_(clock_->TimeInMicroseconds()) {
  RTC_CHECK(clock);
  RTC_CHECK_GT(speed, 0.0f);
}

float DriftingClock::Drift() const {
  int64_t now = clock_->TimeInMicroseconds();
  RTC_DCHECK_GE(now, start_time_);
  return (now - start_time_) * drift_;
}

int64_t DriftingClock::TimeInMilliseconds() const {
  return clock_->TimeInMilliseconds() + Drift() / 1000.;
}

int64_t DriftingClock::TimeInMicroseconds() const {
  return clock_->TimeInMicroseconds() + Drift();
}

void DriftingClock::CurrentNtp(uint32_t& seconds, uint32_t& fractions) const {
  // NTP precision is 1/2^32 seconds, i.e. 2^32 ntp fractions = 1 second.
  const double kNtpFracPerMicroSecond = 4294.967296;  // = 2^32 / 10^6

  clock_->CurrentNtp(seconds, fractions);
  uint64_t total_fractions = (static_cast<uint64_t>(seconds) << 32) | fractions;
  total_fractions += Drift() * kNtpFracPerMicroSecond;
  seconds = total_fractions >> 32;
  fractions = static_cast<uint32_t>(total_fractions);
}

int64_t DriftingClock::CurrentNtpInMilliseconds() const {
  return clock_->CurrentNtpInMilliseconds() + Drift() / 1000.;
}
}  // namespace test
}  // namespace webrtc