#星光计划1.0# OpenHarmony 源码解析之Sensor子系统（上）原创精华

深开鸿

发布于 2021-11-3 17:52

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1 简介

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。

1.1 OpenHarmony架构图

#星光计划1.0# OpenHarmony 源码解析之Sensor子系统（上）-鸿蒙开发者社区

2 基础知识

2.1 传感器概述

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;

2.2 传感器架构图

#星光计划1.0# OpenHarmony 源码解析之Sensor子系统（上）-鸿蒙开发者社区

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。

2.3 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

3 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。

3.1 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。

#星光计划1.0# OpenHarmony 源码解析之Sensor子系统（上）-鸿蒙开发者社区

JS API的主要接口：

接口名	描述
on(type: SensorType, callback: AsyncCallback<Response>, options?: Options)	监听传感器数据变化。SensorType为支持订阅的传感器类型，callback表示订阅传感器的回调函数，options为设置传感器数据上报的时间间隔。
once(type: SensorType, callback: AsyncCallback<Response>)	监听传感器数据变化一次。SensorType为支持订阅的传感器类型，callback表示订阅传感器的回调函数。
off(type: SensorType, callback: AsyncCallback<void>)	取消订阅传感器数据。SensorType为支持的取消订阅的传感器类型，callback表示取消订阅传感器是否成功。

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;
}

3.2 JS应用接收订阅的sensor数据

#星光计划1.0# OpenHarmony 源码解析之Sensor子系统（上）-鸿蒙开发者社区

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});