[Sensors] Improvements in fetching reading for sensors with continuous reporting mode

third_party/WebKit/Source/modules/sensor/SensorPollingStrategy.cpp

-// Copyright 2016 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#include "modules/sensor/SensorPollingStrategy.h"
-
-#include "wtf/CurrentTime.h"
-
-namespace blink {
-
-SensorPollingStrategy::SensorPollingStrategy(
-    double pollingPeriod,
-    std::unique_ptr<Function<void()>> func)
-    : m_pollingPeriod(pollingPeriod),
-      m_pollFunc(std::move(func)),
-      m_timer(this, &SensorPollingStrategy::pollForData) {}
-
-SensorPollingStrategy::~SensorPollingStrategy() = default;
-
-// Polls the buffer continuously using the given 'pollingPeriod'.
-class ContiniousSensorPollingStrategy : public SensorPollingStrategy {
- public:
-  ContiniousSensorPollingStrategy(double pollingPeriod,
-                                  std::unique_ptr<Function<void()>> func)
-      : SensorPollingStrategy(pollingPeriod, std::move(func)) {}
-
- private:
-  // SensorPollingStrategy overrides.
-  void startPolling() override;
-  void stopPolling() override;
-
-  void pollForData(TimerBase*) override;
-};
-
-void ContiniousSensorPollingStrategy::startPolling() {
-  (*m_pollFunc)();
-  m_timer.startRepeating(m_pollingPeriod, BLINK_FROM_HERE);
-}
-
-void ContiniousSensorPollingStrategy::stopPolling() {
-  m_timer.stop();
-}
-
-void ContiniousSensorPollingStrategy::pollForData(TimerBase*) {
-  (*m_pollFunc)();
-}
-
-// Polls the buffer on signal from platform but not more frequently
-// than the given 'pollingPeriod'.
-class OnChangeSensorPollingStrategy : public SensorPollingStrategy {
- public:
-  OnChangeSensorPollingStrategy(double pollingPeriod,
-                                std::unique_ptr<Function<void()>> func)
-      : SensorPollingStrategy(pollingPeriod, std::move(func)),
-        m_polling(false),
-        m_lastPollingTimestamp(0.0) {}
-
- private:
-  // SensorPollingStrategy overrides.
-  void startPolling() override;
-  void stopPolling() override;
-  void onSensorReadingChanged() override;
-
-  void pollForData(TimerBase*) override;
-
-  bool m_polling;
-  double m_lastPollingTimestamp;
-};
-
-void OnChangeSensorPollingStrategy::startPolling() {
-  (*m_pollFunc)();
-  m_polling = true;
-}
-
-void OnChangeSensorPollingStrategy::stopPolling() {
-  m_polling = false;
-}
-
-void OnChangeSensorPollingStrategy::onSensorReadingChanged() {
-  if (!m_polling || m_timer.isActive())
-    return;
-  double elapsedTime =
-      WTF::monotonicallyIncreasingTime() - m_lastPollingTimestamp;
-
-  if (elapsedTime >= m_pollingPeriod) {
-    m_lastPollingTimestamp = WTF::monotonicallyIncreasingTime();
-    (*m_pollFunc)();
-  } else {
-    m_timer.startOneShot(m_pollingPeriod - elapsedTime, BLINK_FROM_HERE);
-  }
-}
-
-void OnChangeSensorPollingStrategy::pollForData(TimerBase*) {
-  if (!m_polling)
-    return;
-  m_lastPollingTimestamp = WTF::monotonicallyIncreasingTime();
-  (*m_pollFunc)();
-}
-
-// static
-std::unique_ptr<SensorPollingStrategy> SensorPollingStrategy::create(
-    double pollingPeriod,
-    std::unique_ptr<Function<void()>> func,
-    device::mojom::blink::ReportingMode mode) {
-  if (mode == device::mojom::blink::ReportingMode::CONTINUOUS)
-    return std::unique_ptr<SensorPollingStrategy>(
-        new ContiniousSensorPollingStrategy(pollingPeriod, std::move(func)));
-
-  return std::unique_ptr<SensorPollingStrategy>(
-      new OnChangeSensorPollingStrategy(pollingPeriod, std::move(func)));
-}
-
-}  // namespace blink