samgr_lite

• Introduction
• Directory Structure
• Constraints
• Developing a Service
• Developing a Feature of a Service
• Developing an External API for Intra-Process Communication
• Invoking a Service in the Same Process
• Developing an External API for IPC
• Invoking a Service in Another Process
• Developing a Client Proxy for Inter-Process Service Invocation
• Repositories Involved

Introduction

Due to limited platform resources, a unified system ability (SA) framework is provided to harmonize differences of hardware architectures (for example, RISC-V, Cortex-M, and Cortex-A), resources, and running modes. Two types of hardware platforms (M- and A-core) are defined.

• M-core: hardware platforms with Cortex-M or equivalent processing capabilities. The system memory is generally less than 512 KB. There is only a lightweight file system that can be used in limited scenarios, or no file system at all. M-core platforms comply with the Cortex Microcontroller Software Interface Standard (CMSIS).
• A-core: hardware platforms with Cortex-A or equivalent processing capabilities. The system memory is greater than 512 KB. There is a comprehensive file system for storing a large amount of data. A-core platforms comply with the Portable Operating System Interface (POSIX) specifications.

This service-oriented SA framework enables you to develop services, features, and external APIs, and implement multi-service process sharing and service invoking for inter-process communication (IPC). Wherein:

• M core provides services, features, external APIs, and multi-service process sharing development.
• In addition to the capabilities provided by M-core, A-core provides capabilities such as IPC service invoking, permission control for IPC service invoking, and IPC service API development.

Service-oriented architecture

• Provider: a service provider that provides capabilities (external APIs) for the system
• Consumer: a service consumer that invokes the features (external APIs) provided by the service
• Samgr: an agency that manages capabilities provided by providers and helps consumers discover providers' capabilities

Main objects of the SA framework:

• SamgrLite: provides service registration and discovery.
• Service: implements lifecycle APIs of the service during service development.
• Feature: implements lifecycle APIs of the feature during feature development.
• IUnknown: implements external APIs for services or features based on IUnknown.
• IClientProxy: implements the consumer's proxy to send messages during IPC invoking.
• IServerProxy: implements the provider's proxy during IPC invoking, which needs to be implemented by developers.

Directory Structure

Table 1 Structure of the source code directory of the SA framework

Constraints

• The SA framework is developed using the C programming language.
• Services in the same process use IUnknown for invoking. Messages are passed to the service through IUnknown.
• The service name and feature name must be constant character strings and the length must be less than 16 bytes.
• More-core depends on the Bootstrap service and calls the OHOS_SystemInit() function in the system startup function.
• A-core depends on the Samgr library and calls the SAMGR_Bootstrap() function in the main function.

Developing a Service

• Inherit and redefine a service.

  typedef struct ExampleService {
      INHERIT_SERVICE;
      INHERIT_IUNKNOWNENTRY(DefaultFeatureApi);
      Identity identity;
  } ExampleService;

• Implement the lifecycle function of the service.

  static const char *GetName(Service *service)
  {
      return EXAMPLE_SERVICE;
  }
  
  static BOOL Initialize(Service *service, Identity identity)
  {
      ExampleService *example = (ExampleService *)service;
      // Save the unique ID of the service, which is used when IUnknown is used to send messages to the service.
      example->identity = identity;
      return TRUE;
  }
  static BOOL MessageHandle(Service *service, Request *msg)
  {
      ExampleService *example = (ExampleService *)service;
      switch (msg->msgId) {
          case MSG_SYNC:
              // Process the service.
              break;
          default:break;
      }
      return FALSE;
  }
  static TaskConfig GetTaskConfig(Service *service)
  {
      TaskConfig config = {LEVEL_HIGH, PRI_BELOW_NORMAL,
                           0x800, 20, SHARED_TASK};
      return config;
  }

• Create a service object.

  static ExampleService g_example = {
      .GetName = GetName,
      .Initialize = Initialize,
      .MessageHandle = MessageHandle,
      .GetTaskConfig = GetTaskConfig,
      SERVER_IPROXY_IMPL_BEGIN,
          .Invoke = NULL,
          .SyncCall = SyncCall,
      IPROXY_END,
  };

• Register the service and API with Samgr.

  static void Init(void)
  {
      SAMGR_GetInstance()->RegisterService((Service *)&g_example);
      SAMGR_GetInstance()->RegisterDefaultFeatureApi(EXAMPLE_SERVICE, GET_IUNKNOWN(g_example));
  }

• Define the initializer of the service.

  SYSEX_SERVICE_INIT(Init);
  

Developing a Feature of a Service

• Inherit and redefine a feature.

  typedef struct DemoFeature {
      INHERIT_FEATURE;
      INHERIT_IUNKNOWNENTRY(DemoApi);
      Identity identity;
      Service *parent;
  } DemoFeature;

• Implement the lifecycle function of the feature.

  static const char *FEATURE_GetName(Feature *feature)
  {
      return EXAMPLE_FEATURE;
  }
  
  static void FEATURE_OnInitialize(Feature *feature, Service *parent, Identity identity)
  {
      DemoFeature *demoFeature = (DemoFeature *)feature;
      demoFeature->identity = identity;
      demoFeature->parent = parent;
  }
  
  static void FEATURE_OnStop(Feature *feature, Identity identity)
  {
      g_example.identity.queueId = NULL;
      g_example.identity.featureId = -1;
      g_example.identity.serviceId = -1;
  }
  
  static BOOL FEATURE_OnMessage(Feature *feature, Request *request)
  {
      if (request->msgId == MSG_PROC) {
          Response response = {.data = "Yes, you did!", .len = 0};
          SAMGR_SendResponse(request, &response);
          return TRUE;
      } else {
          if (request->msgId == MSG_TIME_PROC) {
              LOS_Msleep(WAIT_FEATURE_PROC * 10);
              if (request->msgValue) {
                  SAMGR_PrintServices();
              } else {
                  SAMGR_PrintOperations();
              }
              AsyncTimeCall(GET_IUNKNOWN(g_example));
              return FALSE;
          }
      }
      return FALSE;
  }

• Create a feature object.

  static DemoFeature g_example = {
      .GetName = FEATURE_GetName,
      .OnInitialize = FEATURE_OnInitialize,
      .OnStop = FEATURE_OnStop,
      .OnMessage = FEATURE_OnMessage,
      DEFAULT_IUNKNOWN_ENTRY_BEGIN,
          .AsyncCall = AsyncCall,
          .AsyncTimeCall = AsyncTimeCall,
          .SyncCall = SyncCall,
          .AsyncCallBack = AsyncCallBack,
      DEFAULT_IUNKNOWN_ENTRY_END,
      .identity = {-1, -1, NULL},
  };

• Register the feature and API with Samgr.

  static void Init(void){
      SAMGR_GetInstance()->RegisterFeature(EXAMPLE_SERVICE, (Feature *)&g_example);
      SAMGR_GetInstance()->RegisterFeatureApi(EXAMPLE_SERVICE, EXAMPLE_FEATURE, GET_IUNKNOWN(g_example));
  }

• Define the initializer of the feature.

  SYSEX_FEATURE_INIT(Init);
  

Developing an External API for Intra-Process Communication

• Define the IUnknown API.

  typedef struct DemoApi {
      INHERIT_IUNKNOWN;
      BOOL (*AsyncCall)(IUnknown *iUnknown, const char *buff);
      BOOL (*AsyncTimeCall)(IUnknown *iUnknown);
      BOOL (*SyncCall)(IUnknown *iUnknown, struct Payload *payload);
      BOOL (*AsyncCallBack)(IUnknown *iUnknown, const char *buff, Handler handler);
  } DemoApi;

• Define the reference object of IUnknown.

  typedef struct DemoRefApi {
      INHERIT_IUNKNOWNENTRY(DemoApi);
  } DemoRefApi;

• Initialize the object of IUnknown.

  static DemoRefApi api = {
      DEFAULT_IUNKNOWN_ENTRY_BEGIN,
          .AsyncCall = AsyncCall,
          .AsyncTimeCall = AsyncTimeCall,
          .SyncCall = SyncCall,
          .AsyncCallBack = AsyncCallBack,
      DEFAULT_IUNKNOWN_ENTRY_END,
  };

• Register the feature API.

  SAMGR_GetInstance()->RegisterFeatureApi(EXAMPLE_SERVICE, EXAMPLE_FEATURE, GET_IUNKNOWN(api));
  

Invoking a Service in the Same Process

• Obtain the external API of the service.

  DemoApi *demoApi = NULL;
  IUnknown *iUnknown = SAMGR_GetInstance()->GetFeatureApi(EXAMPLE_SERVICE, EXAMPLE_FEATURE);
  if (iUnknown == NULL) {
      return NULL;
  }
  int result = iUnknown->QueryInterface(iUnknown, DEFAULT_VERSION, (void **)&demoApi);
  if (result != 0 || demoApi == NULL) {
      return NULL;
  }

• Call the API.

  if (demoApi->AsyncCallBack == NULL) {
      return NULL;
  }
  demoApi->AsyncCallBack((IUnknown *)demoApi, "I wanna async call callback good result!", AsyncHandler);

• Release the API.

  int32 ref = demoApi->Release((IUnknown *)demoApi);
  

Developing an External API for IPC

• Inherit IServerProxy to replace IUnknown: INHERIT_SERVER_IPROXY

  typedef struct DemoFeatureApi {
      INHERIT_SERVER_IPROXY;
      BOOL (*AsyncCall)(IUnknown *iUnknown, const char *buff);
      BOOL (*AsyncTimeCall)(IUnknown *iUnknown);
      BOOL (*SyncCall)(IUnknown *iUnknown, struct Payload *payload);
      BOOL (*AsyncCallBack)(IUnknown *iUnknown, const char *buff, IOwner notify, INotifyFunc handler);
  } DemoFeatureApi;

• Initialize the IServerProxy object.

  static DemoFeature g_example = {
      SERVER_IPROXY_IMPL_BEGIN,
      .Invoke = Invoke,
      .AsyncCall = AsyncCall,
      .AsyncTimeCall = AsyncTimeCall,
      .SyncCall = SyncCall,
      .AsyncCallBack = AsyncCallBack,
      IPROXY_END,
  };

• Implement the Invoke function to process IPC messages.

  static int32 Invoke(IServerProxy *iProxy, int funcId, void *origin, IpcIo *req, IpcIo *reply)
  {
      DemoFeatureApi *api = (DemoFeatureApi *)iProxy;
      BOOL ret;
      size_t len = 0;
      switch (funcId) {
          case ID_ASYNCALL:
              ret = api->AsyncCall((IUnknown *)iProxy, (char *)IpcIoPopString(req, &len));
              IpcIoPushBool(reply, ret);
              break;
          case ID_ASYNTIMECALL:
              ret = api->AsyncTimeCall((IUnknown *)iProxy);
              IpcIoPushBool(reply, ret);
              break;
          case ID_SYNCCALL: {
              struct Payload payload;
              payload.id = IpcIoPopInt32(req);
              payload.value = IpcIoPopInt32(req);
              payload.name = (char *)IpcIoPopString(req, &len);
              ret = api->SyncCall((IUnknown *)iProxy, &payload);
              IpcIoPushString(reply, ret ? "TRUE" : "FALSE");
          }
              break;
          case ID_ASYNCCALLBACK: { // convert to sync proxy
              IpcIoPushString(reply, "Yes, you did!");
              IpcIoPushBool(reply, TRUE);
          }
              break;
          default:
              IpcIoPushBool(reply, FALSE);
              break;
      }
      return EC_SUCCESS;
  }

• Register the API. This step is same as the API registration for intra-process communication.

  SAMGR_GetInstance()->RegisterFeatureApi(EXAMPLE_SERVICE, EXAMPLE_FEATURE, GET_IUNKNOWN(g_example));
  

Invoking a Service in Another Process

• Obtain the external API of the service in another process.

  IClientProxy *demoApi = NULL;
  IUnknown *iUnknown = SAMGR_GetInstance()->GetFeatureApi(EXAMPLE_SERVICE, EXAMPLE_FEATURE);
  if (iUnknown == NULL) {
      return NULL;
  }
  int result = iUnknown->QueryInterface(iUnknown, CLIENT_PROXY_VER, (void **)&demoApi);
  if (result != 0 || demoApi == NULL) {
      return NULL;
  }

• Invoke the API for sending IPC messages.

  IpcIo request;char data[250];
  IpcIoInit(&request, data, sizeof(data), 0);
  demoApi->Invoke(demoApi, 0, &request, NULL, NULL);

• Release the API.

  int32 ref = demoApi->Release((IUnknown *)demoApi);
  

Developing a Client Proxy for Inter-Process Service Invocation

• Define a client proxy for the IPC API.

  typedef struct DemoClientProxy {
      INHERIT_CLIENT_IPROXY;
      BOOL (*AsyncCall)(IUnknown *iUnknown, const char *buff);
      BOOL (*AsyncTimeCall)(IUnknown *iUnknown);
      BOOL (*SyncCall)(IUnknown *iUnknown, struct Payload *payload);
      BOOL (*AsyncCallBack)(IUnknown *iUnknown, const char *buff, IOwner notify, INotifyFunc handler);
  } DemoClientProxy;
  typedef struct DemoClientEntry {
      INHERIT_IUNKNOWNENTRY(DemoClientProxy);
  } DemoClientEntry;

• Enable the client proxy to encapsulate the IPC message API.

  static BOOL AsyncCall(IUnknown *iUnknown, const char *buff)
  {
      DemoClientProxy *proxy = (DemoClientProxy *)iUnknown;
      IpcIo request;
      char data[MAX_DATA_LEN];
      IpcIoInit(&request, data, MAX_DATA_LEN, 0);
      IpcIoPushString(&request, buff);
      int ret = proxy->Invoke((IClientProxy *)proxy, ID_ASYNCALL, &request, NULL, NULL);
      return ret == EC_SUCCESS;
  }
  
  static BOOL AsyncTimeCall(IUnknown *iUnknown)
  {
      DemoClientProxy *proxy = (DemoClientProxy *)iUnknown;
      IpcIo request;
      char data[MAX_DATA_LEN];
      IpcIoInit(&request, data, MAX_DATA_LEN, 0);
      int ret = proxy->Invoke((IClientProxy *)proxy, ID_ASYNTIMECALL, &request, NULL, NULL);
      return ret == EC_SUCCESS;
  }
  
  static int Callback(IOwner owner, int code, IpcIo *reply)
  {
      size_t len = 0;
      return strcpy_s(owner, MAX_DATA_LEN, (char *)IpcIoPopString(reply, &len));
  }
  
  static BOOL SyncCall(IUnknown *iUnknown, struct Payload *payload)
  {
      DemoClientProxy *proxy = (DemoClientProxy *)iUnknown;
      IpcIo request;
      char data[MAX_DATA_LEN];
      IpcIoInit(&request, data, MAX_DATA_LEN, 0);
      IpcIoPushInt32(&request, payload->id);
      IpcIoPushInt32(&request, payload->value);
      IpcIoPushString(&request, payload->name);
      int ret = proxy->Invoke((IClientProxy *)proxy, ID_SYNCCALL, &request, data, Callback);
      data[MAX_DATA_LEN - 1] = 0;
      HILOG_INFO(HILOG_MODULE_APP, "[TID:0x%lx]Remote response is %s!", pthread_self(), data);
      return ret == EC_SUCCESS;
  }
  
  struct CurrentNotify {
      IOwner notify;
      INotifyFunc handler;
  };
  
  static int CurrentCallback(IOwner owner, int code, IpcIo *reply)
  {
      struct CurrentNotify *notify = (struct CurrentNotify *)owner;
      size_t len = 0;
      char *response = (char *)IpcIoPopString(reply, &len);
      HILOG_INFO(HILOG_MODULE_APP, "[TID:0x%lx]Notify Remote response is %s!", pthread_self(), response);
      notify->handler(notify->notify, response);
      return EC_SUCCESS;
  }
  
  static BOOL AsyncCallBack(IUnknown *iUnknown, const char *buff, IOwner notify, INotifyFunc handler)
  {
      struct CurrentNotify owner = {notify, handler};
      DemoClientProxy *proxy = (DemoClientProxy *)iUnknown;
      IpcIo request;
      char data[MAX_DATA_LEN];
      IpcIoInit(&request, data, MAX_DATA_LEN, 0);
      IpcIoPushString(&request, buff);
      int ret = proxy->Invoke((IClientProxy *)proxy, ID_ASYNCCALLBACK, &request, &owner, CurrentCallback);
      return ret == EC_SUCCESS;
  }

• Implement the factory method for creating the client proxy.

  void *DEMO_CreatClient(const char *service, const char *feature, uint32 size)
  {
      (void)service;
      (void)feature;
      uint32 len = size + sizeof(DemoClientEntry);
      uint8 *client = malloc(len);
      (void)memset_s(client, len, 0, len);
      DemoClientEntry *entry = (DemoClientEntry *)&client[size];
      entry->ver = ((uint16)CLIENT_PROXY_VER | (uint16)DEFAULT_VERSION);
      entry->ref = 1;
      entry->iUnknown.QueryInterface = IUNKNOWN_QueryInterface;
      entry->iUnknown.AddRef = IUNKNOWN_AddRef;
      entry->iUnknown.Release = IUNKNOWN_Release;
      entry->iUnknown.Invoke = NULL;
      entry->iUnknown.AsyncCall = AsyncCall;
      entry->iUnknown.AsyncTimeCall = AsyncTimeCall;
      entry->iUnknown.SyncCall = SyncCall;
      entry->iUnknown.AsyncCallBack = AsyncCallBack;
      return client;
  }
  void DEMO_DestroyClient(const char *service, const char *feature, void *iproxy)
  {
      free(iproxy);
  }

• Register the factory method of the client proxy with Samgr.

  SAMGR_RegisterFactory(EXAMPLE_SERVICE, EXAMPLE_FEATURE, DEMO_CreatClient, DEMO_DestroyClient);

• Obtain the external API of the service in another process.

  DemoClientProxy *demoApi = NULL;
  IUnknown *iUnknown = SAMGR_GetInstance()->GetFeatureApi(EXAMPLE_SERVICE, EXAMPLE_FEATURE);
  if (iUnknown == NULL) {
      return NULL;
  }
  int result = iUnknown->QueryInterface(iUnknown, DEFAULT_VERSION, (void **)&demoApi);
  if (result != 0 || demoApi == NULL) {
      return NULL;
  }

• Invoke the client proxy API of the service in another process.

  if (demoApi->AsyncCallBack == NULL) {
      return NULL;
  }
  demoApi->AsyncCallBack((IUnknown *)demoApi,
                         "I wanna async call callback good result!", NULL, AsyncHandler);

• Release the API.

  int32 ref = demoApi->Release((IUnknown *)demoApi);

Repositories Involved

Distributed Scheduler subsystem

samgr_lite