鸿蒙源码分析（六十九）

service剩下函数分析

我们知道该模块下经常出现的任务概念，这里我们也可以理解为消息。这里有消息的处理函数。
任务或者消息通过iunknown接口发送，这个函数就是默认的处理该接口发送过来的消息。先根据参数identity来判断身份是否合法。如果合法调用相应的函数来处理消息。其中还需要判断是service还是feature，根据不同情况调用不同处理函数。
参数参数：

• serviceImpl：服务实例
• identity：身份信息标识
• msg：消息数据

void DEFAULT_MessageHandle(ServiceImpl *serviceImpl, const Identity *identity, Request *msg)
{
    //参数检查
    if (serviceImpl->serviceId != identity->serviceId) {
        //身份标识identity中指示的serviceId与当前服务不匹配
        return;
    }
    if (identity->featureId < 0) {
        //未指定feature，则调用service的消息处理函数
        if (serviceImpl->service->MessageHandle != NULL) {
            //用于处理调用者发送的请求
            serviceImpl->service->MessageHandle(serviceImpl->service, msg);
        }
        return;
    }
    //有指定featureid，则调用对应的feature处理消息
    //判断featureid是否合法
    if (VECTOR_Size(&serviceImpl->features) <= identity->featureId) {
        return;
    }
    //根据featureid返回对应的featureImpl对象，featureid对应于features中的feature的下标
    FeatureImpl *featureImpl = (FeatureImpl *)VECTOR_At(&(serviceImpl->features), identity->featureId);
    if (featureImpl == NULL) {
        return;
    }
    //通过对应的feature处理消息，用于处理调用者发送的请求
    featureImpl->feature->OnMessage(featureImpl->feature, msg);
}
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服务的停止
该函数就是为了停止一个服务，最后将服务状态置为INIT。

void DEFAULT_StopService(ServiceImpl *service)
{
    if (service == NULL) {
        return;
    }
    //配置身份标识
    Identity id = {service->serviceId, INVALID_INDEX, (service->taskPool != NULL) ? service->taskPool->queueId : NULL};
    //获取features中feature的个数
    int16 size = VECTOR_Size(&service->features);
    int16 i;
    //遍历features集合
    for (i = 0; i < size; ++i) {
        //根据下标返回FeatureImpl对象
        FeatureImpl *featureImpl = (FeatureImpl *)VECTOR_At(&(service->features), i);
        if (featureImpl == NULL) {
            continue;
        }
        //标识指定的feature
        id.featureId = i;
        //停止feature
        featureImpl->feature->OnStop(featureImpl->feature, id);
    }
    //更新状态为SVC_INIT
    service->inited = SVC_INIT;
}
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获取feature实例
这里的原理就是根据feature的name来匹配对应实例的下标pos，最后返回feature实例。

/*  
    函数功能：获取featureimpl对象
    函数描述：查询并返回serviceimpl的features中指定name的featureimpl对象
*/
FeatureImpl *DEFAULT_GetFeature(ServiceImpl *serviceImpl, const char *featureName)
{
    //参数检查
    if (serviceImpl == NULL || featureName == NULL) {
        return NULL;
    }
    //根据featureName查询，返回相应元素下标
    short pos = VECTOR_FindByKey(&(serviceImpl->features), (void *)featureName);
    //返回指定下标的FeatureImpl对象
    return (FeatureImpl *)VECTOR_At(&(serviceImpl->features), pos);
}
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feature的删除

//删除serviceImpl中名称为featureName的feature，删除的同时停止feature
Feature *DEFAULT_DeleteFeature(ServiceImpl *serviceImpl, const char *featureName)
{
    //参数检查
    if (serviceImpl == NULL || featureName == NULL) {
        return NULL;
    }
    //获取指定featureName在features中的下标
    int16 pos = VECTOR_FindByKey(&(serviceImpl->features), (void *)featureName);
    if (pos < 0 || !SAMGR_IsNoInterface((FeatureImpl *)VECTOR_At(&serviceImpl->features, pos))) {
        //下标不合法，或者featureImpl不为NULL且featureImpl的接口不为NULL
        return NULL;
    }
    //将features中指定下标的元素与NULL值交换，起到删除的作用。
    //成功 返回被替换的元素，失败 返回NULL
    FeatureImpl *featureImpl = (FeatureImpl *)VECTOR_Swap(&(serviceImpl->features), pos, NULL);
    if (featureImpl == NULL) {
        return NULL;
    }
    //标识服务ID
    Identity id = {serviceImpl->serviceId, INVALID_INDEX, NULL};
    //停止指定的feature
    featureImpl->feature->OnStop(featureImpl->feature, id);
    //返回feature，并释放featureImpl占用的空间
    Feature *feature = featureImpl->feature;
    SAMGR_Free(featureImpl);
    return feature;
}
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获取featurename
这个和之前获取实例的相反，这个是根据feature实例获取featurename，之前是根据featurename来获取实例。刚好实现功能相反

static const char *GetFeatureName(const FeatureImpl *featureImpl)
{
    if (featureImpl == NULL) {
        return NULL;
    }
    //获取feature的name并返回
    return featureImpl->feature->GetName(featureImpl->feature);
}
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