[sensors] Introduce Generic Sensor API interfaces

device/generic_sensor/platform_sensor_provider.cc

+// 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 "device/generic_sensor/platform_sensor_provider.h"
+
+#include <utility>
+
+namespace device {
+
+// static
+PlatformSensorProvider* PlatformSensorProvider::Create(
+    uint64_t shared_buffer_size) {
+  // TODO(shalamov): Add platform-specific PlatformSensorProvider
+  // implementations here.
+  return nullptr;
+}
+
+PlatformSensorProvider::PlatformSensorProvider(uint64_t shared_buffer_size)
+    : shared_buffer_size_(shared_buffer_size) {}
+
+PlatformSensorProvider::~PlatformSensorProvider() = default;
+
+scoped_refptr<PlatformSensor> PlatformSensorProvider::CreateSensor(
+    mojom::SensorType type,
+    uint64_t size,
+    uint64_t offset) {
+  DCHECK(CalledOnValidThread());
+
+  if (!CreateSharedBufferIfNeeded())
+    return nullptr;
+
+  mojo::ScopedSharedBufferMapping mapping =
+      shared_buffer_handle_->MapAtOffset(size, offset);
+  if (!mapping)
+    return nullptr;
+
+  // Create new platform sensor instance.

[Reilly Grant (use Gerrit), 2016/08/11 20:59:37]

This comment is unnecessary.

[Mikhail, 2016/08/12 10:21:48]

Done.

+  scoped_refptr<PlatformSensor> new_sensor =
+      CreateSensor(type, std::move(mapping), size);
+  if (!new_sensor)
+    return nullptr;
+
+  const auto& add_result =
+      sensor_map_.insert(std::make_pair(type, new_sensor.get()));
+  DCHECK(add_result.second);

[Reilly Grant (use Gerrit), 2016/08/11 20:59:37]

It's a little shorter/clearer to write:

DCHECK(!ContainsKey(sensor_map_, type));
sensor_map_[type] = new_sensor.get();

[Mikhail, 2016/08/12 10:21:48]

Done.

+
+  return new_sensor;
+}
+
+scoped_refptr<PlatformSensor> PlatformSensorProvider::GetSensor(
+    mojom::SensorType type) {
+  DCHECK(CalledOnValidThread());
+
+  auto it = sensor_map_.find(type);
+  if (it != sensor_map_.end())
+    return it->second;
+  return nullptr;
+}
+
+bool PlatformSensorProvider::CreateSharedBufferIfNeeded() {
+  DCHECK(CalledOnValidThread());
+  if (shared_buffer_handle_.is_valid())
+    return true;
+
+  shared_buffer_handle_ = mojo::SharedBufferHandle::Create(shared_buffer_size_);
+  return shared_buffer_handle_.is_valid();
+}
+
+void PlatformSensorProvider::RemoveSensor(mojom::SensorType type) {
+  DCHECK(CalledOnValidThread());
+  auto it = sensor_map_.find(type);
+  if (it != sensor_map_.end())
+    sensor_map_.erase(it);

[Reilly Grant (use Gerrit), 2016/08/11 20:59:37]

sensor_map_.erase(type) is simpler.

[Mikhail, 2016/08/12 10:21:48]

Done.

+
+  if (sensor_map_.empty() && shared_buffer_handle_->is_valid())
+    shared_buffer_handle_.reset();
+}
+
+mojo::ScopedSharedBufferHandle
+PlatformSensorProvider::GetClonedSharedBufferHandle() {
+  DCHECK(CalledOnValidThread());
+  CreateSharedBufferIfNeeded();
+  return shared_buffer_handle_->Clone();
+}
+
+}  // namespace device