Implement Device Orientation using shared memory in content/renderer.

content/renderer/device_orientation/device_sensor_event_pump.cc

+// Copyright 2013 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 "device_sensor_event_pump.h"
+
+#include "base/logging.h"
+#include "content/public/renderer/render_thread.h"
+
+namespace content {
+
+const int DeviceSensorEventPump::kDefaultPumpDelayMillis = 40;
+
+int DeviceSensorEventPump::GetDelayMillis() const {
+  return pump_delay_millis_;
+}
+
+DeviceSensorEventPump::DeviceSensorEventPump()
+    : pump_delay_millis_(kDefaultPumpDelayMillis),
+      state_(STOPPED) {
+}
+
+DeviceSensorEventPump::DeviceSensorEventPump(int pump_delay_millis)
+    : pump_delay_millis_(pump_delay_millis),
+      state_(STOPPED) {
+  DCHECK(pump_delay_millis_ > 0);
+}
+
+DeviceSensorEventPump::~DeviceSensorEventPump() {
+}
+
+bool DeviceSensorEventPump::RequestStart() {
+  DVLOG(2) << "requested start";
+
+  if (state_ != STOPPED)
+    return false;
+
+  DCHECK(!timer_.IsRunning());
+
+  if (SendStartMessage()) {
+    state_ = PENDING_START;
+    return true;
+  }
+  return false;
+}
+
+bool DeviceSensorEventPump::Stop() {
+  DVLOG(2) << "stop";
+
+  if (state_ == STOPPED)
+    return true;
+
+  DCHECK((state_ == PENDING_START && !timer_.IsRunning()) ||
+      (state_ == RUNNING && timer_.IsRunning()));
+
+  if (timer_.IsRunning())
+    timer_.Stop();
+  SendStopMessage();
+  state_ = STOPPED;
+  return true;
+}
+
+void DeviceSensorEventPump::Attach(RenderThread* thread) {
+  if (!thread)
+    return;
+  thread->AddObserver(this);
+}
+
+void DeviceSensorEventPump::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::FromMilliseconds(GetDelayMillis()),
+                 this, &DeviceSensorEventPump::FireEvent);
+    state_ = RUNNING;
+  }
+}
+
+}  // namespace content