Passing a Task with the Specified Priority to an ArkTS Thread from an Asynchronous Thread Using Node-API

You can use napi_call_threadsafe_function_with_priority to pass a task to an ArkTS thread from an asynchronous thread in a thread-safe manner. Then, the task will be processed based on its priority and enqueuing mode.

Function Description

napi_status napi_call_threadsafe_function_with_priority(napi_threadsafe_function func,
                                                        void *data,
                                                        napi_task_priority priority,
                                                        bool isTail);

Name	Description
func	Thread-safe function to call.
data	Data to be passed from the asynchronous thread to the main thread.
priority	Priority of the task. For details, see napi_task_priority.
isTail	Whether to add the task to the end (tail) of the task queue. The value true means to add the task to the end of the task queue; the value false means to add the task to the head of the queue.

When to Use

Pass a task to the ArkTS main thread from an asynchronous thread in a thread-safe manner. Then, the task will be processed based on its priority and enqueuing mode.

Calling an ArkTS API Asynchronously

Example

• Register the module.

   // napi_init.cpp
   #include "napi/native_api.h"
   #include <string.h>
   #include <stdlib.h>
  
   struct CallbackData {
       napi_threadsafe_function tsfn;
       napi_async_work work;
   };
   // Callback implementation in the ArkTS thread.
   static void CallJs(napi_env env, napi_value jsCb, void *context, void *data) {
       if (env == nullptr) {
           return;
       }
       napi_value resultNumber = nullptr;
       napi_value undefined = nullptr;
       napi_get_undefined(env, &undefined);
       napi_value number1 = nullptr;
       napi_create_int32(env, 12, &number1);
       napi_value number2 = nullptr;
       napi_create_int32(env, 15, &number2);
       napi_value argv[2] = {number1, number2};
       napi_call_function(env, undefined, jsCb, 2, argv, &resultNumber);
       int32_t res = 0;
       napi_get_value_int32(env, resultNumber, &res);
   }
  
   // Call this API in an asynchronous thread to pass a task with the specified priority and enqueuing mode to an ArkTS thread.
   static void ExecuteWork(napi_env env, void *data) {
       CallbackData *callbackData = reinterpret_cast<CallbackData *>(data);
       // The task priority is napi_priority_idle, and the task is added to the end of the task queue.
       napi_call_threadsafe_function_with_priority(callbackData->tsfn, nullptr, napi_priority_idle, true);
       napi_call_threadsafe_function_with_priority(callbackData->tsfn, nullptr, napi_priority_low, true);
       napi_call_threadsafe_function_with_priority(callbackData->tsfn, nullptr, napi_priority_high, true);
       napi_call_threadsafe_function_with_priority(callbackData->tsfn, nullptr, napi_priority_immediate, true);
       // The task priority is napi_priority_high, and the task is added to the head of the task queue.
       napi_call_threadsafe_function_with_priority(callbackData->tsfn, nullptr, napi_priority_high, false);
   }
  
   static void WorkComplete(napi_env env, napi_status status, void *data) {
       CallbackData *callbackData = reinterpret_cast<CallbackData *>(data);
       napi_release_threadsafe_function(callbackData->tsfn, napi_tsfn_release);
       napi_delete_async_work(env, callbackData->work);
       callbackData->work = nullptr;
       callbackData->tsfn = nullptr;
   }
  
   static napi_value CallThreadSafeWithPriority(napi_env env, napi_callback_info info) {
       size_t argc = 1;
       napi_value jsCb = nullptr;
       CallbackData *callbackData = nullptr;
       napi_get_cb_info(env, info, &argc, &jsCb, nullptr, reinterpret_cast<void **>(&callbackData));
       napi_value resourceName = nullptr;
       napi_create_string_utf8(env, "Thread-safe Function Demo", NAPI_AUTO_LENGTH, &resourceName);
       napi_create_threadsafe_function(env, jsCb, nullptr, resourceName, 0, 1, callbackData, nullptr, callbackData, CallJs,
                                       &callbackData->tsfn);
       napi_create_async_work(env, nullptr, resourceName, ExecuteWork, WorkComplete, callbackData, &callbackData->work);
       napi_queue_async_work(env, callbackData->work);
       return nullptr;
   }
  
   // Register the module.
   EXTERN_C_START
   static napi_value Init(napi_env env, napi_value exports)
   {
       CallbackData *callbackData = new CallbackData();
       napi_property_descriptor desc[] = {
           { "callThreadSafeWithPriority", nullptr, CallThreadSafeWithPriority, nullptr, nullptr, nullptr, napi_default, callbackData }
       };
       napi_define_properties(env, exports, sizeof(desc) / sizeof(desc[0]), desc);
       return exports;
   }
   EXTERN_C_END
  
   static napi_module nativeModule = {
       .nm_version = 1,
       .nm_flags = 0,
       .nm_filename = nullptr,
       .nm_register_func = Init,
       .nm_modname = "entry",
       .nm_priv = nullptr,
       .reserved = { 0 },
   };
  
   extern "C" __attribute__((constructor)) void RegisterEntryModule()
   {
       napi_module_register(&nativeModule);
   }
  

• Declare the API.

  // index.d.ts
  export const callThreadSafeWithPriority: (cb: (a: number, b: number) => number) => void;
  

• Configure compile settings.

  Configure the CMakeLists.txt file as follows:

  // CMakeLists.txt
  # the minimum version of CMake.
  cmake_minimum_required(VERSION 3.4.1)
  project(myapplication)
  
  set(NATIVERENDER_ROOT_PATH ${CMAKE_CURRENT_SOURCE_DIR})
  
  if(DEFINED PACKAGE_FIND_FILE)
      include(${PACKAGE_FIND_FILE})
  endif()
  
  include_directories(${NATIVERENDER_ROOT_PATH}
                      ${NATIVERENDER_ROOT_PATH}/include)
  add_library(entry SHARED hello.cpp)
  target_link_libraries(entry PUBLIC libace_napi.z.so)
  

• ArkTS sample code

  // index.ets
  import testNapi from 'libentry.so'
  
  let callback = (a: number, b: number) : number => {
      console.info('result is ' + (a + b))
      return a + b;
  }
  testNapi.callThreadSafeWithPriority(callback);