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// Copyright 2014 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.
#ifndef CONTENT_RENDERER_DEVICE_SENSORS_DEVICE_SENSOR_EVENT_PUMP_H_
#define CONTENT_RENDERER_DEVICE_SENSORS_DEVICE_SENSOR_EVENT_PUMP_H_
#include "base/memory/shared_memory.h"
#include "base/time/time.h"
#include "base/timer/timer.h"
#include "content/public/renderer/platform_event_observer.h"
namespace content {
template <typename ListenerType>
class CONTENT_EXPORT DeviceSensorEventPump
: NON_EXPORTED_BASE(public PlatformEventObserver<ListenerType>) {
public:
// Default rate for firing events.
static const int kDefaultPumpFrequencyHz = 60;
static const int kDefaultPumpDelayMicroseconds =
base::Time::kMicrosecondsPerSecond / kDefaultPumpFrequencyHz;
// PlatformEventObserver
virtual void Start(blink::WebPlatformEventListener* listener) override {
DVLOG(2) << "requested start";
if (state_ != STOPPED)
return;
DCHECK(!timer_.IsRunning());
PlatformEventObserver<ListenerType>::Start(listener);
state_ = PENDING_START;
}
virtual void Stop() override {
DVLOG(2) << "stop";
if (state_ == STOPPED)
return;
DCHECK((state_ == PENDING_START && !timer_.IsRunning()) ||
(state_ == RUNNING && timer_.IsRunning()));
if (timer_.IsRunning())
timer_.Stop();
PlatformEventObserver<ListenerType>::Stop();
state_ = STOPPED;
}
protected:
explicit DeviceSensorEventPump(RenderThread* thread)
: PlatformEventObserver<ListenerType>(thread),
pump_delay_microseconds_(kDefaultPumpDelayMicroseconds),
state_(STOPPED) {}
virtual ~DeviceSensorEventPump() {
PlatformEventObserver<ListenerType>::StopIfObserving();
}
// The pump is a tri-state automaton with allowed transitions as follows:
// STOPPED -> PENDING_START
// PENDING_START -> RUNNING
// PENDING_START -> STOPPED
// RUNNING -> STOPPED
enum PumpState {
STOPPED,
RUNNING,
PENDING_START
};
void OnDidStart(base::SharedMemoryHandle handle) {
DVLOG(2) << "did start sensor event pump";
if (state_ != PENDING_START)
return;
DCHECK(!timer_.IsRunning());
if (InitializeReader(handle)) {
timer_.Start(FROM_HERE,
base::TimeDelta::FromMicroseconds(pump_delay_microseconds_),
this,
&DeviceSensorEventPump::FireEvent);
state_ = RUNNING;
}
}
virtual void FireEvent() = 0;
virtual bool InitializeReader(base::SharedMemoryHandle handle) = 0;
int pump_delay_microseconds_;
PumpState state_;
base::RepeatingTimer<DeviceSensorEventPump> timer_;
DISALLOW_COPY_AND_ASSIGN(DeviceSensorEventPump);
};
} // namespace content
#endif // CONTENT_RENDERER_DEVICE_SENSORS_DEVICE_SENSOR_EVENT_PUMP_H_
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