前言
人类获取外界信息必须借助于感觉器官，而在研究自然现象和规律以及生产活动仅靠感官已经远远不够了，为了适应这种情况，出现了传感器。随着物联网，移动互联网的快速发展，在数字时代，传感器在智能交通，智能工业，智能穿戴等领域有着广阔的应用空间。
概述
传感器是检测到被测量信息，将非电量信息转换成电信号的检测装置。就像眼睛是人类心灵的窗户，传感器则是计算机感知世界万物的眼睛。
传感器用于侦测环境中所发生事件或变化，并将此消息发送至其他电子设备(如中央处理器)的设备，通常由敏感组件和转换组件组成。根据用途可分为以下六大类：
- 运动类：加速度、陀螺仪、重力、线性加速度传感器等;
- 姿态类：旋转矢量、方向传感器等;
- 环境类：磁力计、气压、湿度传感器等;
- 光线类：环境光、接近光、色温传感器等;
- 健康类：心率、心跳传感器等;
- 其它：霍尔传感器、手握传感器等;
架构层级
OpenHarmony架构图:
传感器架构图如下所示：
应用层 ：各种需要sensor的应用，例如运动健康，计步器，指南针等等。
框架层 ：
- SDK ，给应用提供标准接口，包括JS接口和C++接口。
- Framework，向应用层提供稳定的基础能力，包括Sensor列表查询、Sensor启停、Sensor订阅及去订阅，Sensor参数配置，创建数据传递通道，sensor数据上传等功能。
- Service, 提供Sensor设备管理，Sensor通用配置能力，Sensor通用数据解析能力，权限管理能力。
HDF层 ：HDF驱动框架，Sensor设备驱动的开发是基于该框架的基础上，结合操作系统适配层(OSAL)和平台驱动接口(比如I2C/SPI/UART总线等平台资源)能力，屏蔽不同操作系统和平台总线资源差异，实现Sensor驱动“一次开发，多系统部署”的目标。
Hardware层 ：各种传感器器件，例如加速度计，陀螺仪，温度，湿度等等。
Sensor子系统代码目录
- /base/sensors/sensor
- ├── frameworks # 框架代码
- │ └── native # sensor客户端代码
- ├── interfaces # 对外接口存放目录
- │ ├── native # sensor native实现
- │ └── plugin # Js API
- ├── sa_profile # 服务名称和服务的动态库的配置文件
- ├── services # 服务的代码目录
- │ └── sensor # 传感器服务，包括加速度、陀螺仪等，上报传感器数据
- └── utils # 公共代码，包括权限、通信等能力
源码分析
本文先讲解框架层的代码，HDF的部分放在下一篇文章讲解。框架层主要包含两部分：
JS应用订阅、启动sensor。
JS应用收到订阅sensor的数据信息。
1. JS应用订阅、启动Sensor
我们从JS API开放的能力开始看源码，绿色部分看作client，黄色部分看作service。
JS API的主要接口：
给JS应用提供接口的实现文件是sensor_js.cpp，我们从init开始看接口的实现：
- static napi_value Init(napi_env env, napi_value exports)
- {
- // 这里定义了三个接口，on、once、off。
- napi_property_descriptor desc[] = {
- DECLARE_NAPI_FUNCTION("on", On),
- DECLARE_NAPI_FUNCTION("once", Once),
- DECLARE_NAPI_FUNCTION("off", Off)
- };
- NAPI_CALL(env, napi_define_properties(env, exports, sizeof(desc) / sizeof(napi_property_descriptor), desc));
- return exports;
- }
- static napi_value On(napi_env env, napi_callback_info info)
- {
- ......
- // 获取JS应用传递的sensorTypeId，例如加速度计，陀螺仪等等
- int32_t sensorTypeId = GetCppInt32(args[0], env);
- ......
- AsyncCallbackInfo *asyncCallbackInfo = new AsyncCallbackInfo {
- .env = env,
- .asyncWork = nullptr,
- .deferred = nullptr,
- };
- napi_create_reference(env, args[1], 1, &asyncCallbackInfo->callback[0]);
- g_onCallbackInfos[sensorTypeId] = asyncCallbackInfo;
- // 调用SubscribeSensor函数订阅该sensor，指定sensor类型，上报频率，数据返回通过DataCallbackImpl。
- int32_t ret = SubscribeSensor(sensorTypeId, interval, DataCallbackImpl);
- ......
- HiLog::Info(LABEL, "%{public}s out", __func__);
- return nullptr;
- }
- static int32_t SubscribeSensor(int32_t sensorTypeId, int64_t interval, RecordSensorCallback callback)
- {
- HiLog::Info(LABEL, "%{public}s in, sensorTypeId: %{public}d", __func__, sensorTypeId);
- // 注一：订阅指定sensorId的传感器数据,通过user，系统将向应用上报获得的传感器数据，user实际就是callback。
- int32_t ret = SubscribeSensor(sensorTypeId, &user);
- if (ret < 0) {
- HiLog::Error(LABEL, "%{public}s subscribeSensor failed", __func__);
- return ret;
- }
- // 设置采样频率和上报频率
- ret = SetBatch(sensorTypeId, &user, interval, 0);
- if (ret < 0) {
- HiLog::Error(LABEL, "%{public}s set batch failed", __func__);
- return ret;
- }
- //注二： 启用已订阅的传感器。只有在启用传感器后，应用才能获取传感器数据。
- ret = ActivateSensor(sensorTypeId, &user);
- if (ret < 0) {
- HiLog::Error(LABEL, "%{public}s activateSensor failed", __func__);
- return ret;
- }
- return 0;
- }
注一：SubscribeSensor，订阅sensor，建立sensor数据传递频道。
- int32_t SensorAgentProxy::SubscribeSensor(int32_t sensorId, const SensorUser *user) const
- {
- HiLog::Info(LABEL, "%{public}s in, sensorId: %{public}d", __func__, sensorId);
- if (user == nullptr || sensorId < 0 || user->callback == nullptr) {
- HiLog::Error(LABEL, "%{public}s user is null or sensorId is invalid", __func__);
- return OHOS::Sensors::ERROR;
- }
- if (!g_isChannelCreated) {
- HiLog::Info(LABEL, "%{public}s channel created", __func__);
- g_isChannelCreated = true;
- // 创建sensor数据频道，通过此channel实现client和service的数据传递。
- CreateSensorDataChannel(user);
- }
- // 指定sensorId对应的callback
- g_subscribeMap[sensorId] = user;
- return OHOS::Sensors::SUCCESS;
- }
- int32_t SensorAgentProxy::CreateSensorDataChannel(const SensorUser *user) const
- {
- HiLog::Debug(LABEL, "%{public}s", __func__);
- if (dataChannel_ == nullptr) {
- HiLog::Error(LABEL, "%{public}s data channel cannot be null", __func__);
- return INVALID_POINTER;
- }
- // 注1 ，创建sensor数据传递频道，sendFd和recvFd
- auto ret = dataChannel_->CreateSensorDataChannel(HandleSensorData, nullptr);
- if (ret != ERR_OK) {
- HiLog::Error(LABEL, "%{public}s create data channel failed, ret : %{public}d", __func__, ret);
- return ret;
- }
- auto &client = SensorServiceClient::GetInstance();
- // 注2 , 将client创建的数据频道，sendFd转移到service，使得service和client可以通讯。
- ret = client.TransferDataChannel(dataChannel_);
- if (ret != ERR_OK) {
- auto destoryRet = dataChannel_->DestroySensorDataChannel();
- HiLog::Error(LABEL, "%{public}s transfer data channel failed,
- ret : %{public}d, destoryRet : %{public}d",__func__, ret, destoryRet);
- return ret;
- }
- return ERR_OK;
- }
先看注1，创建sensor数据传递频道，sendFd和receiveFd，由调用关系找到，调用SensorDataChannel::InnerSensorDataChannel()，我们来看下这个函数。
- int32_t SensorDataChannel::InnerSensorDataChannel()
- {
- std::lock_guard<std::mutex> threadLock(treadMutex_);
- // create basic data channel，通过socketpair()函数用于创建一对套接字sendFd_和receiveFd_
- int32_t ret = CreateSensorBasicChannel(SENSOR_READ_DATA_SIZE,SENSOR_READ_DATA_SIZE);
- if (ret != ERR_OK) {
- HiLog::Error(LABEL, "%{public}s create basic channel failed, ret : %{public}d", __func__, ret);
- return ret;
- }
- auto listener = std::make_shared<MyFileDescriptorListener>();
- listener->SetChannel(this);
- auto myRunner = AppExecFwk::EventRunner::Create(true);
- if (myRunner == nullptr) {
- HiLog::Error(LABEL, "%{public}s myRunner is null", __func__);
- return -1;
- }
- auto handler = std::make_shared<MyEventHandler>(myRunner);
- if (handler == nullptr) {
- HiLog::Error(LABEL, "%{public}s handler is null", __func__);
- return -1;
- }
- // receiveFd_绑定到MyFileDescriptorListener，MyFileDescriptorListener用于接收sensor数据
- receiveFd_ = GetReceiveDataFd();
- auto inResult = handler->AddFileDescriptorListener(receiveFd_, AppExecFwk::FILE_DESCRIPTOR_INPUT_EVENT, listener);
- ……
- }
再看注2，如何将sendFd_转移给service，作为sensor数据的发送端?
- ErrCode SensorServiceProxy::TransferDataChannel(const sptr<SensorBasicDataChannel> &sensorBasicDataChannel,
- const sptr<IRemoteObject> &sensorClient)
- {
- HiLog::Debug(LABEL, "%{public}s sendFd: %{public}d", __func__, sensorBasicDataChannel->GetSendDataFd());
- if (sensorBasicDataChannel == nullptr || sensorClient == nullptr) {
- HiLog::Error(LABEL, "%{public}s sensorBasicDataChannel or sensorClient cannot be null", __func__);
- return OBJECT_NULL;
- }
- MessageParcel data;
- MessageParcel reply;
- MessageOption option;
- if (!data.WriteInterfaceToken(SensorServiceProxy::GetDescriptor())) {
- HiLog::Error(LABEL, "%{public}s write descriptor failed", __func__);
- return WRITE_MSG_ERR;
- }
- // 将sendFd_写入parcel，会通过SendRequest，传递给service
- sensorBasicDataChannel->SendToBinder(data);
- if (!data.WriteRemoteObject(sensorClient)) {
- HiLog::Error(LABEL, "%{public}s write sensorClient failed", __func__);
- return WRITE_MSG_ERR;
- }
- // IPC通讯机制，执行此处会调用service的CreateDataChannelInner
- int32_t ret = Remote()->SendRequest(ISensorService::TRANSFER_DATA_CHANNEL, data, reply, option);
- if (ret != NO_ERROR) {
- DmdReport::ReportException(SENSOR_SERVICE_IPC_EXCEPTION, "TransferDataChannel", ret);
- HiLog::Error(LABEL, "%{public}s failed, ret : %{public}d", __func__, ret);
- }
- sensorBasicDataChannel->CloseSendFd();
- return static_cast<ErrCode>(ret);
- }
由SendRequest，指定ISensorService::TRANSFER_DATA_CHANNEL会调用到CreateDataChannelInner，这个函数主要的作用是CreateSensorBasicChannel，service端获取到sendFd_。
- ErrCode SensorServiceStub::CreateDataChannelInner(MessageParcel &data, MessageParcel &reply)
- {
- (void)reply;
- sptr<SensorBasicDataChannel> sensorChannel = new (std::nothrow)SensorBasicDataChannel();
- if (sensorChannel == nullptr) {
- HiLog::Error(LABEL, "%{public}s sensorChannel cannot be null", __func__);
- return OBJECT_NULL;
- }
- auto ret = sensorChannel->CreateSensorBasicChannel(data);
- if (ret != ERR_OK) {
- HiLog::Error(LABEL, "%{public}s CreateSensorBasicChannel ret : %{public}d",__func__, ret);
- return OBJECT_NULL;
- }
- sptr<IRemoteObject> sensorClient = data.ReadRemoteObject();
- if (sensorClient == nullptr) {
- HiLog::Error(LABEL, "%{public}s sensorClient cannot be null", __func__);
- return OBJECT_NULL;
- }
- return TransferDataChannel(sensorChannel, sensorClient);
- }
- int32_t SensorBasicDataChannel::CreateSensorBasicChannel(MessageParcel &data)
- {
- HiLog::Debug(LABEL, "%{public}s begin", __func__);
- if ((sendFd_ != INVALID_FD) || (receiveFd_ != INVALID_FD)) {
- HiLog::Debug(LABEL, "%{public}s already create socketpair", __func__);
- return ERR_OK;
- }
- int32_t tmpFd = data.ReadFileDescriptor();
- if (tmpFd < 0) {
- HiLog::Error(LABEL, "%{public}s ReadFileDescriptor failed", __func__);
- sendFd_ = INVALID_FD;
- return SENSOR_CHANNEL_DUP_ERR;
- }
- // service的sendFd，和前面的receiveFd对应，用于传递sensor数据。
- sendFd_ = dup(tmpFd);
- HiLog::Error(LABEL, "%{public}s sendFd: %{public}d", __func__, sendFd_);
- if (sendFd_ < 0) {
- HiLog::Error(LABEL, "%{public}s dup FileDescriptor failed", __func__);
- sendFd_ = INVALID_FD;
- return SENSOR_CHANNEL_DUP_ERR;
- }
- return ERR_OK;
- }
至此client和service跨进程传递Sensor数据的通道建立完成了。
注二： 启用已订阅的传感器。
- int32_t ActivateSensor(int32_t sensorId, const SensorUser *user)
- {
- HiLog::Info(LABEL, "%{public}s begin", __func__);
- const SensorAgentProxy *proxy = GetInstance();
- if (proxy == NULL) {
- HiLog::Error(LABEL, "%s proxy is null", __func__);
- return OHOS::Sensors::ERROR;
- }
- // 调用SensorAgentProxy的ActivateSensor函数，指定sendorId和user，开启sensor
- return proxy->ActivateSensor(sensorId, user);
- }
- int32_t SensorAgentProxy::ActivateSensor(int32_t sensorId, const SensorUser *user) const
- {
- if (user == NULL || sensorId < 0) {
- HiLog::Error(LABEL, "%{public}s user is null or sensorId is invalid",__func__);
- return OHOS::Sensors::ERROR;
- }
- if (g_samplingInterval < 0 || g_reportInterval < 0) {
- HiLog::Error(LABEL, "%{public}s samplingPeroid or g_reportInterval is invalid", __func__);
- return OHOS::Sensors::ERROR;
- }
- if ((g_subscribeMap.find(sensorId) == g_subscribeMap.end()) || (g_subscribeMap.at(sensorId) != user)) {
- HiLog::Error(LABEL, "%{public}s subscribe sensorId first", __func__);
- return OHOS::Sensors::ERROR;
- }
- SensorServiceClient &client = SensorServiceClient::GetInstance();
- // 调用SensorServiceClient的 EnableSensor，指定sensorId，采样频率设上报频率。
- int32_t ret = client.EnableSensor(sensorId, g_samplingInterval, g_reportInterval);
- g_samplingInterval = -1;
- g_reportInterval = -1;
- if (ret != 0) {
- HiLog::Error(LABEL, "%{public}s enable sensor failed, ret: %{public}d",__func__, ret);
- return OHOS::Sensors::ERROR;
- }
- return OHOS::Sensors::SUCCESS;
- }
最终会调用到SensorServiceImpl::EnableSensor，这里主要是调用HDF提供的标准接口，打开sensor，下一篇文章会讲述HDF的内容。
- ErrCode SensorServiceImpl::EnableSensor(uint32_t sensorId) const
- {
- HiLog::Info(LABEL, "%{public}s begin", __func__);
- int32_t ret = sensorInterface_->Enable(sensorId);
- if (ret < 0) {
- HiLog::Error(LABEL, "%{public}s is failed", __func__);
- return -1;
- }
- HiLog::Info(LABEL, "%{public}s end", __func__);
- return ERR_OK;
- }
2. JS应用接收订阅的sensor数据
Sensor打开之后，就会有sensor数据按照上报频率上报给应用。我们下面看下，数据是如何上报的?
前面看到传递的数据通道在订阅时已经创建好了，SensorService::EnableSensor时，在其内部还调用了SaveSubscriber。
- ErrCode SensorService::EnableSensor(uint32_t sensorId, int64_t samplingPeriodNs, int64_t maxReportDelayNs)
- {
- ......
- auto ret = SaveSubscriber(sensorId, samplingPeriodNs, maxReportDelayNs);
- if (ret != ERR_OK) {
- HiLog::Error(LABEL, "%{public}s SaveSubscriber failed", __func__);
- return ret;
- }
- ret = sensorServiceImpl_.EnableSensor(sensorId);
- if (ret != ERR_OK) {
- HiLog::Error(LABEL, "%{public}s EnableSensor failed", __func__);
- clientInfo_.RemoveSubscriber(sensorId, this->GetCallingPid());
- return ENABLE_SENSOR_ERR;
- }
- return ret;
- }
SaveSubscriber 做了两件事情：
1、调用SensorManager::SaveSubscriber管理sensor订阅信息。
2、开启sensor数据上报的线程。
- ErrCode SensorService::SaveSubscriber(uint32_t sensorId, int64_t samplingPeriodNs, int64_t maxReportDelayNs)
- {
- auto ret = sensorManager_.SaveSubscriber(sensorId, this->GetCallingPid(), samplingPeriodNs, maxReportDelayNs);
- if (ret != ERR_OK) {
- HiLog::Error(LABEL, "%{public}s SaveSubscriber failed", __func__);
- return ret;
- }
- sensorManager_.StartDataReportThread();
- if (!sensorManager_.SetBestSensorParams(sensorId, samplingPeriodNs, maxReportDelayNs)) {
- HiLog::Error(LABEL, "%{public}s SetBestSensorParams failed", __func__);
- clientInfo_.RemoveSubscriber(sensorId, this->GetCallingPid());
- return ENABLE_SENSOR_ERR;
- }
- return ret;
- }
- void SensorManager::StartDataReportThread()
- {
- HiLog::Debug(LABEL, "%{public}s begin", __func__);
- if (!dataThread_.joinable()) {
- HiLog::Warn(LABEL, "%{public}s dataThread_ started", __func__);
- std::thread senocdDataThread(SensorDataProcesser::DataThread, sensorDataProcesser_, reportDataCallback_);
- dataThread_ = std::move(senocdDataThread);
- }
- HiLog::Debug(LABEL, "%{public}s end", __func__);
- }
- int32_t SensorDataProcesser::DataThread(sptr<SensorDataProcesser>dataProcesser, sptr<ReportDataCallback> dataCallback)
- {
- HiLog::Debug(LABEL, "%{public}s begin", __func__);
- do {
- if (dataProcesser->ProcessEvents(dataCallback) == INVALID_POINTER) {
- HiLog::Error(LABEL, "%{public}s callback cannot be null", __func__);
- return INVALID_POINTER;
- }
- } while (1);
- }
- int32_t SensorDataProcesser::ProcessEvents(sptr<ReportDataCallback>dataCallback)
- {
- if (dataCallback == nullptr) {
- HiLog::Error(LABEL, "%{public}s dataCallback cannot be null", __func__);
- return INVALID_POINTER;
- }
- std::unique_lock<std::mutex> lk(SensorServiceImpl::dataMutex_);
- // 使用std::condition_variable::wait()，处于阻塞状态，
- // 当其它线程调用notify_one()或者notify_all()函数，wait()会结束阻塞。
- SensorServiceImpl::dataCondition_.wait(lk);
- ......
- return SUCCESS;
- }
看到这里，我们发现SaveSubscriber创建了sensor数据处理的线程，并使用SensorServiceImpl::dataCondition_.wait(lk)进入阻塞状态，我们看下何时使用notify_one()来激活该线程上报数据的?
系统开机启动时，hsensors进程启动，也就是SensorService启动。
- on post-fs-data
- start hsensors
- service hsensors /system/bin/sa_main /system/profile/hsensors.xml
- class hsensors
- user system
- group system shell
- seclabel u:r:foundation:s0
SensorService启动后，会将ZReportDataCallback 注册到HDF，看下面的代码：
- void SensorService::OnStart()
- {
- if (state_ == SensorServiceState::STATE_RUNNING) {
- HiLog::Warn(LABEL, "%{public}s SensorService has already started", __func__);
- return;
- }
- // 调用HDF标准接口，初始化
- if (!InitInterface()) {
- HiLog::Error(LABEL, "%{public}s Init interface error", __func__);
- return;
- }
- // 注册数据返回的callback，初始化
- if (!InitDataCallback()) {
- HiLog::Error(LABEL, "%{public}s Init data callback error", __func__);
- return;
- }
- ......
- }
- bool SensorService::InitDataCallback()
- {
- reportDataCallback_ = new (std::nothrow) ReportDataCallback();
- if (reportDataCallback_ == nullptr) {
- HiLog::Error(LABEL, "%{public}s failed, reportDataCallback_ cannot be null",__func__);
- return false;
- }
- // 将ZReportDataCallback通过RegisteDataReport赋值给reportDataCb_,sensor数据上报会触发ZReportDataCallback
- // new ReportDataCallback传递到sensorServiceImpl_，为了调用reportDataCb_
- ZReportDataCb cb = &ReportDataCallback::ZReportDataCallback;
- auto ret = sensorServiceImpl_.RegisteDataReport(cb, reportDataCallback_);
- if (ret != ERR_OK) {
- HiLog::Error(LABEL, "%{public}s RegisterDataReport failed", __func__);
- return false;
- }
- return true;
- }
- ErrCode SensorServiceImpl::RegisteDataReport(ZReportDataCb cb, sptr<ReportDataCallback> reportDataCallback)
- {
- HiLog::Info(LABEL, "%{public}s begin", __func__);
- if (reportDataCallback == nullptr) {
- HiLog::Error(LABEL, "%{public}s failed, reportDataCallback cannot be null",__func__);
- return ERR_NO_INIT;
- }
- // 注册callback到HDF
- Register(SensorDataCallback);
- reportDataCb_ = cb;
- reportDataCallback_ = reportDataCallback;
- HiLog::Info(LABEL, "%{public}s end", __func__);
- return ERR_OK;
- }
- ErrCode SensorServiceImpl::Register(RecordDataCallback cb) const
- {
- HiLog::Info(LABEL, "%{public}s begin", __func__);
- if (sensorInterface_ == nullptr) {
- HiLog::Error(LABEL, " %{public}s,", "test sensorHdi get Module instance failed\n\r");
- return ERR_INVALID_VALUE;
- }
- // 通过HDF提供的标准接口，注册到HDF
- int32_t ret = sensorInterface_->Register(cb);
- if (ret < 0) {
- HiLog::Error(LABEL, "%{public}s failed", __func__);
- return ERR_INVALID_VALUE;
- }
- HiLog::Info(LABEL, "%{public}s end", __func__);
- return ERR_OK;
- }
当JS应用订阅了传感器，并且启用了传感器，传感器数据就从SensorServiceImpl::SensorDataCallback向上传递，我们看下这函数的实现，主要做了两件事情：
1、调用ReportDataCallback::ZreportDataCallback将sensor数据写入cb->eventsBuf_。
2、调用dataCondition_.notify_one()激活数据上报的线程。
- int32_t SensorServiceImpl::SensorDataCallback(const struct SensorEvents *event)
- {
- HiLog::Debug(LABEL, "%{public}s begin", __func__);
- const int32_t SENSOR_AXISZ = 2;
- if ((event == nullptr) || (event->dataLen == 0)) {
- HiLog::Error(LABEL, "%{public}s event is NULL", __func__);
- return ERR_INVALID_VALUE;
- }
- float *data = (float*)event->data;
- if (reportDataCb_ == nullptr) {
- HiLog::Error(LABEL, "%{public}s reportDataCb_ cannot be null", __func__);
- return ERR_INVALID_VALUE;
- }
- // 调用ReportDataCallback::ZReportDataCallback方法，存入eventsBuf_
- (void)(reportDataCallback_->*reportDataCb_)(reinterpret_cast<const structSensorEvent*>(event), reportDataCallback_);
- // 激活sensor数据上报线程
- dataCondition_.notify_one();
- return ERR_OK;
- }
- int32_t ReportDataCallback::ZReportDataCallback(const struct SensorEvent *event, sptr<ReportDataCallback> cb)
- {
- float *data = (float*)event->data;
- if (cb == nullptr || cb->eventsBuf_.circularBuf == nullptr || event == nullptr) {
- HiLog::Error(LABEL, "%{public}s callback or circularBuf or event cannot be null", __func__);
- return ERROR;
- }
- struct SensorEvent eventCopy = {
- .sensorTypeId = event->sensorTypeId,
- .version = event->version,
- .timestamp = event->timestamp,
- .option = event->option,
- .mode = event->mode,
- .dataLen = event->dataLen
- };
- eventCopy.data = new uint8_t[SENSOR_DATA_LENGHT];
- if (memcpy_s(eventCopy.data, event->dataLen, event->data, event->dataLen) != EOK) {
- HiLog::Error(LABEL, "%{public}s copy data failed", __func__);
- return COPY_ERR;
- }
- // 将SensorEvent的数据存入到ReportDataCallback的变量eventsBuf_里面
- int32_t leftSize = CIRCULAR_BUF_LEN - cb->eventsBuf_.eventNum;
- int32_t toEndLen = CIRCULAR_BUF_LEN - cb->eventsBuf_.writePosition;
- if (toEndLen == 0) {
- cb->eventsBuf_.circularBuf[0] = eventCopy;
- cb->eventsBuf_.writePosition = 1 - toEndLen;
- } else {
- cb->eventsBuf_.circularBuf[cb->eventsBuf_.writePosition] = eventCopy;
- cb->eventsBuf_.writePosition += 1;
- }
- ……
- }
至此，回过头来再看SensorDataProcesser::ProcessEvents，lock锁激活后，获取到eventsBuf_。
- int32_t SensorDataProcesser::ProcessEvents(sptr<ReportDataCallback>dataCallback)
- {
- if (dataCallback == nullptr) {
- HiLog::Error(LABEL, "%{public}s dataCallback cannot be null", __func__);
- return INVALID_POINTER;
- }
- std::unique_lock<std::mutex> lk(SensorServiceImpl::dataMutex_);
- SensorServiceImpl::dataCondition_.wait(lk);
- auto &eventsBuf = dataCallback->GetEventData();
- if (eventsBuf.eventNum <= 0) {
- HiLog::Error(LABEL, "%{public}s data cannot be empty", __func__);
- return NO_EVENT;
- }
- int32_t eventNum = eventsBuf.eventNum;
- for (int32_t i = 0; i < eventNum; i++) {
- // 通过EventFilter report eventsBuf数据
- EventFilter(eventsBuf);
- delete eventsBuf.circularBuf[eventsBuf.readPosition].data;
- eventsBuf.circularBuf[eventsBuf.readPosition].data = nullptr;
- eventsBuf.readPosition++;
- if (eventsBuf.readPosition == CIRCULAR_BUF_LEN) {
- eventsBuf.readPosition = 0;
- }
- eventsBuf.eventNum--;
- }
- return SUCCESS;
- }
EventFilter最终会调用SendRawData，通过该函数的channel->SendData，调用Socket send函数发送sensor数据。这里的sendFd_就是前面创建的。(中间的调用过程请看前面的时序图)
- int32_t SensorBasicDataChannel::SendData(const void *vaddr, size_t size)
- {
- if (vaddr == nullptr || sendFd_ < 0) {
- HiLog::Error(LABEL, "%{public}s failed, param is invalid", __func__);
- return SENSOR_CHANNEL_SEND_ADDR_ERR;
- }
- ssize_t length;
- do {
- length = send(sendFd_, vaddr, size, MSG_DONTWAIT | MSG_NOSIGNAL);
- } while (errno == EINTR);
- if (length < 0) {
- HiLog::Error(LABEL, "%{public}s send fail : %{public}d, length = %{public}d", __func__, errno, (int32_t)length);
- return SENSOR_CHANNEL_SEND_DATA_ERR;
- }
- return ERR_OK;
- }
- void MyFileDescriptorListener::OnReadable(int32_t fileDescriptor)
- {
- if (fileDescriptor < 0) {
- HiLog::Error(LABEL, "%{public}s fileDescriptor: %{public}d", __func__, fileDescriptor);
- return;
- }
- FileDescriptorListener::OnReadable(fileDescriptor);
- struct TransferSensorEvents *receiveDataBuff_
- = new (std::nothrow) TransferSensorEvents[sizeof(struct TransferSensorEvents) * RECEIVE_DATA_SIZE];
- // 接收sensor数据，这里的fileDescriptor就是receiveFd_
- int32_t len = recv(fileDescriptor, receiveDataBuff_, sizeof(struct TransferSensorEvents) * RECEIVE_DATA_SIZE, NULL);
- while (len > 0) {
- int32_t eventSize = sizeof(struct TransferSensorEvents);
- int32_t num = len / eventSize;
- for (int i = 0; i < num; i++) {
- SensorEvent event = {
- .sensorTypeId = receiveDataBuff_[i].sensorTypeId,
- .version = receiveDataBuff_[i].version,
- .timestamp = receiveDataBuff_[i].timestamp,
- .option = receiveDataBuff_[i].option,
- .mode = receiveDataBuff_[i].mode,
- .dataLen = receiveDataBuff_[i].dataLen,
- .data = receiveDataBuff_[i].data
- };
- float *data = (float *)(event.data);
- // 通过dataCB_将数据再往上层传递，dataCB_即SensorAgentProxy::HandleSensorData
- channel_->dataCB_(&event, 1, channel_->privateData_);
- }
- len = recv(fileDescriptor, receiveDataBuff_, sizeof(struct TransferSensorEvents) * RECEIVE_DATA_SIZE, NULL);
- }
- }
- void SensorAgentProxy::HandleSensorData(struct SensorEvent *events, int32_t num, void *data)
- {
- if (events == nullptr || num <= 0) {
- HiLog::Error(LABEL, "%{public}s events is null or num is invalid", __func__);
- return;
- }
- struct SensorEvent eventStream;
- for (int32_t i = 0; i < num; ++i) {
- eventStream = events[i];
- if (eventStream.data == nullptr || g_subscribeMap[eventStream.sensorTypeId] == nullptr) {
- HiLog::Error(LABEL, "%{public}s data or sensorUser is nullptr", __func__);
- return;
- }
- if (g_subscribeMap.find(eventStream.sensorTypeId) == g_subscribeMap.end()) {
- HiLog::Error(LABEL, "%{public}s sensorTypeId not in g_subscribeMap", __func__);
- return;
- }
- // 这里的callback调用的是sensor_js.cpp DataCallbackImpl函数
- g_subscribeMap[eventStream.sensorTypeId]->callback(&eventStream);
- }
- }
通过DataCallbackImpl将数据上报给JS应用。以加速度计为例，会出现下面的log打印。
- sensor.on(sensor.SensorType.SENSOR_TYPE_ID_ACCELEROMETER, (error, data) => {
- if (error) {
- console.error("Failed to subscribe to acceleration data. Error code: " +
- error.code + "; message: " + error.message);
- return;
- }
- console.info("Acceleration data obtained. x: " + data.x + "; y: " + data.y + ";z: " + data.z);
- }, {'interval':200000000});
总结
本文主要和大家分享传感器应用到框架层的实现，重点分析了传感器订阅、启动以及接收订阅传感器数据，做了较为详细的代码说明，希望通过本文您能初步掌握JS应用开发到框架层开发的步骤与流程。关于传感器HDF框架和驱动的分析，请关注后续文章。
