自定义Native Transferable对象的多线程操作场景

在ArkTS应用开发中，有很多场景需要将ArkTS对象与Native对象进行绑定。ArkTS对象将数据写入Native对象，Native对象再将数据写入目的地。例如，将ArkTS对象中的数据写入C++数据库场景。

Native Transferable对象有两种模式：共享模式和转移模式。本示例将详细说明如何实现这两种模式。

1. Native实现各项功能。

   // napi_init.cpp
   #include <mutex>
   #include <unordered_set>
   #include "napi/native_api.h"
   #include <hilog/log.h>
   
   class CustomNativeObject {
   public:
       CustomNativeObject() {}
       ~CustomNativeObject() = default;
       static CustomNativeObject& GetInstance()
       {
           static CustomNativeObject instance;
           return instance;
       }
   
       static napi_value GetAddress(napi_env env, napi_callback_info info)
       {
           napi_value thisVar = nullptr;
           napi_get_cb_info(env, info, nullptr, nullptr, &thisVar, nullptr);
           if (thisVar == nullptr) {
               return nullptr;
           }
           void* object = nullptr;
           napi_unwrap(env, thisVar, &object);
           if (object == nullptr) {
               return nullptr;
           }
           
           uint64_t addressVal = reinterpret_cast<uint64_t>(object);
           napi_value address = nullptr;
           napi_create_bigint_uint64(env, addressVal, &address);
           return address;
       }
   
       // 获取数组大小
       static napi_value GetSetSize(napi_env env, napi_callback_info info)
       {
           napi_value thisVar = nullptr;
           napi_get_cb_info(env, info, nullptr, nullptr, &thisVar, nullptr);
           if (thisVar == nullptr) {
               return nullptr;
           }
           void* object = nullptr;
           napi_unwrap(env, thisVar, &object);
           if (object == nullptr) {
               return nullptr;
           }
           CustomNativeObject* obj = static_cast<CustomNativeObject*>(object);
           std::lock_guard<std::mutex> lock(obj->numberSetMutex_);
           uint32_t setSize = reinterpret_cast<CustomNativeObject*>(object)->numberSet_.size();
           napi_value napiSize = nullptr;
           napi_create_uint32(env, setSize, &napiSize);
           return napiSize;
       }
   
       // 往数组里插入元素
       static napi_value Store(napi_env env, napi_callback_info info)
       {
           size_t argc = 1;
           napi_value args[1] = {nullptr};
           napi_value thisVar = nullptr;
           napi_get_cb_info(env, info, &argc, args, &thisVar, nullptr);
           if (argc != 1) {
               napi_throw_error(env, nullptr, "Store args number must be one.");
               return nullptr;
           }
           napi_valuetype type = napi_undefined;
           napi_typeof(env, args[0], &type);
           if (type != napi_number) {
               napi_throw_error(env, nullptr, "Store args is not number.");
               return nullptr;
           }
           if (thisVar == nullptr) {
               return nullptr;
           }
           
           void* object = nullptr;
           napi_unwrap(env, thisVar, &object);
           if (object == nullptr) {
               return nullptr;
           }
           
           uint32_t value = 0;
           napi_get_value_uint32(env, args[0], &value);
           CustomNativeObject* obj = static_cast<CustomNativeObject*>(object);
           std::lock_guard<std::mutex> lock(obj->numberSetMutex_);
           reinterpret_cast<CustomNativeObject *>(object)->numberSet_.insert(value);
           return nullptr;
       }
   
       // 删除数组元素
       static napi_value Erase(napi_env env, napi_callback_info info)
       {
           size_t argc = 1;
           napi_value args[1] = {nullptr};
           napi_value thisVar = nullptr;
           napi_get_cb_info(env, info, &argc, args, &thisVar, nullptr);
           if (argc != 1) {
               napi_throw_error(env, nullptr, "Erase args number must be one.");
               return nullptr;
           }
           napi_valuetype type = napi_undefined;
           napi_typeof(env, args[0], &type);
           if (type != napi_number) {
               napi_throw_error(env, nullptr, "Erase args is not number.");
               return nullptr;
           }
           if (thisVar == nullptr) {
               return nullptr;
           }
           
           void* object = nullptr;
           napi_unwrap(env, thisVar, &object);
           if (object == nullptr) {
               return nullptr;
           }
           
           uint32_t value = 0;
           napi_get_value_uint32(env, args[0], &value);
           
           CustomNativeObject* obj = static_cast<CustomNativeObject*>(object);
           std::lock_guard<std::mutex> lock(obj->numberSetMutex_);
           reinterpret_cast<CustomNativeObject *>(object)->numberSet_.erase(value);
           return nullptr;
       }
   
       // 清空数组
       static napi_value Clear(napi_env env, napi_callback_info info)
       {
           napi_value thisVar = nullptr;
           napi_get_cb_info(env, info, nullptr, nullptr, &thisVar, nullptr);
           if (thisVar == nullptr) {
               return nullptr;
           }
           void* object = nullptr;
           napi_unwrap(env, thisVar, &object);
           if (object == nullptr) {
               return nullptr;
           }
           CustomNativeObject* obj = static_cast<CustomNativeObject*>(object);
           std::lock_guard<std::mutex> lock(obj->numberSetMutex_);
           reinterpret_cast<CustomNativeObject *>(object)->numberSet_.clear();
           return nullptr;
       }
       
       // 设置传输模式
       static napi_value SetTransferDetached(napi_env env, napi_callback_info info)
       {
           size_t argc = 1;
           napi_value args[1];
           napi_value thisVar;
           napi_get_cb_info(env, info, &argc, args, &thisVar, nullptr);
           if (argc != 1) {
               napi_throw_error(env, nullptr, "SetTransferDetached args number must be one.");
               return nullptr;
           }
           
           if (thisVar == nullptr) {
               return nullptr;
           }
           
           napi_valuetype type = napi_undefined;
           napi_typeof(env, args[0], &type);
           if (type != napi_boolean) {
               napi_throw_error(env, nullptr, "SetTransferDetached args is not boolean.");
               return nullptr;
           }
           
           bool isDetached;
           napi_get_value_bool(env, args[0], &isDetached);
           
           void* object = nullptr;
           napi_unwrap(env, thisVar, &object);
           if (object == nullptr) {
               return nullptr;
           }
           CustomNativeObject* obj = static_cast<CustomNativeObject*>(object);
           std::lock_guard<std::mutex> lock(obj->numberSetMutex_);
           obj->isDetached_ = isDetached;
           return nullptr;
       }
       
       bool isDetached_ = false;
   
   private:
       CustomNativeObject(const CustomNativeObject &) = delete;
       CustomNativeObject &operator=(const CustomNativeObject &) = delete;
   
       std::unordered_set<uint32_t> numberSet_{};
       std::mutex numberSetMutex_{};
   };
   
   void FinalizeCallback(napi_env env, void *data, void *hint)
   {
       return;
   }
   
   // 解绑回调，在序列化时调用，可在对象解绑时执行一些清理操作
   void* DetachCallback(napi_env env, void *value, void *hint)
   {
       if (hint == nullptr) {
           return value;
       }
       napi_value jsObject = nullptr;
       napi_get_reference_value(env, reinterpret_cast<napi_ref>(hint), &jsObject);
       void* object = nullptr;
       if (static_cast<CustomNativeObject*>(value)->isDetached_) {
           napi_remove_wrap(env, jsObject, &object);
       }
       return value;
   }
   
   // 绑定回调，在反序列化时调用
   napi_value AttachCallback(napi_env env, void* value, void* hint)
   {
       napi_value object = nullptr;
       napi_create_object(env, &object);
       napi_property_descriptor desc[] = {
           {"getAddress", nullptr, CustomNativeObject::GetAddress, nullptr, nullptr, nullptr, napi_default, nullptr},
           {"getSetSize", nullptr, CustomNativeObject::GetSetSize, nullptr, nullptr, nullptr, napi_default, nullptr},
           {"store", nullptr, CustomNativeObject::Store, nullptr, nullptr, nullptr, napi_default, nullptr},
           {"erase", nullptr, CustomNativeObject::Erase, nullptr, nullptr, nullptr, napi_default, nullptr},
           {"clear", nullptr, CustomNativeObject::Clear, nullptr, nullptr, nullptr, napi_default, nullptr}};
       napi_define_properties(env, object, sizeof(desc) / sizeof(desc[0]), desc);
       // 将JS对象object和native对象value生命周期进行绑定
       napi_wrap(env, object, value, FinalizeCallback, nullptr, nullptr);
       // JS对象携带native信息
       napi_coerce_to_native_binding_object(env, object, DetachCallback, AttachCallback, value, nullptr);
       return object;
   }
   
   EXTERN_C_START
   static napi_value Init(napi_env env, napi_value exports)
   {
       napi_property_descriptor desc[] = {
           {"getAddress", nullptr, CustomNativeObject::GetAddress, nullptr, nullptr, nullptr, napi_default, nullptr},
           {"getSetSize", nullptr, CustomNativeObject::GetSetSize, nullptr, nullptr, nullptr, napi_default, nullptr},
           {"store", nullptr, CustomNativeObject::Store, nullptr, nullptr, nullptr, napi_default, nullptr},
           {"erase", nullptr, CustomNativeObject::Erase, nullptr, nullptr, nullptr, napi_default, nullptr},
           {"clear", nullptr, CustomNativeObject::Clear, nullptr, nullptr, nullptr, napi_default, nullptr},
           {"setTransferDetached", nullptr, CustomNativeObject::SetTransferDetached,
               nullptr, nullptr, nullptr, napi_default, nullptr}};
       napi_define_properties(env, exports, sizeof(desc) / sizeof(desc[0]), desc);
       auto &object = CustomNativeObject::GetInstance();
       napi_wrap(env, exports, reinterpret_cast<void*>(&object), FinalizeCallback, nullptr, nullptr);
       napi_ref exportsRef;
       napi_create_reference(env, exports, 1, &exportsRef);
       napi_coerce_to_native_binding_object(env, exports, DetachCallback,
           AttachCallback, reinterpret_cast<void*>(&object), exportsRef);
       return exports;
   }
   EXTERN_C_END
   
   static napi_module demoModule = {
       .nm_version = 1,
       .nm_flags = 0,
       .nm_filename = nullptr,
       .nm_register_func = Init,
       .nm_modname = "entry",
       .nm_priv = ((void*)0),
       .reserved = { 0 },
   };
   
   extern "C" __attribute__((constructor)) void RegisterEntryModule(void)
   {
       napi_module_register(&demoModule);
   }

2. 在ArkTS中声明接口。

   // Index.d.ts
   export const getAddress: () => number;
   export const getSetSize: () => number;
   export const store: (a: number) => void;
   export const erase: (a: number) => void;
   export const clear: () => void;
   export const setTransferDetached: (b : boolean) => number;

3. ArkTS对象调用Native侧实现的各项功能。

   在转移模式下，跨线程传递后，原来的ArkTS对象与Native对象解绑，因此不能继续访问。示例如下：

   import testNapi from 'libentry.so';
   import { taskpool } from '@kit.ArkTS';
   
   @Concurrent
   function getAddress() {
     let address: number = testNapi.getAddress();
     console.info('taskpool:: address is ' + address);
   }
   
   @Concurrent
   function store(a:number, b:number, c:number) {
     let size:number = testNapi.getSetSize();
     console.info('set size is ' + size + ' before store');
     testNapi.store(a);
     testNapi.store(b);
     testNapi.store(c);
     size = testNapi.getSetSize();
     console.info('set size is ' + size + ' after store');
   }
   
   @Concurrent
   function erase(a:number) {
     let size:number = testNapi.getSetSize();
     console.info('set size is ' + size + ' before erase');
     testNapi.erase(a);
     size = testNapi.getSetSize();
     console.info('set size is ' + size + ' after erase');
   }
   
   @Concurrent
   function clear() {
     let size:number = testNapi.getSetSize();
     console.info('set size is ' + size + ' before clear');
     testNapi.clear();
     size = testNapi.getSetSize();
     console.info('set size is ' + size + ' after clear');
   }
   
   // 转移模式
   async function test(): Promise<void> {
     // setTransferDetached 设置为true，表示传输方式为转移模式
     testNapi.setTransferDetached(true);
     let address:number = testNapi.getAddress();
     console.info('host thread address is ' + address);
   
     let task1 = new taskpool.Task(getAddress, testNapi);
     await taskpool.execute(task1);
   
     let task2 = new taskpool.Task(store, 1, 2, 3);
     await taskpool.execute(task2);
   
     let task3 = new taskpool.Task(store, 4, 5, 6);
     await taskpool.execute(task3);
   
     // 由于已经设置了转移模式，且testNapi已跨线程传递，所以主线程无法继续访问到Native对象的值
     let size:number = testNapi.getSetSize();
     // 输出的日志为“host thread size is undefined”
     console.info('host thread size is ' + size);
   
     let task4 = new taskpool.Task(erase, 3);
     await taskpool.execute(task4);
   
     let task5 = new taskpool.Task(erase, 5);
     await taskpool.execute(task5);
   
     let task6 = new taskpool.Task(clear);
     await taskpool.execute(task6);
   }
   
   @Entry
   @Component
   struct Index {
     @State message: string = 'Hello World';
   
     build() {
       Row() {
         Column() {
           Text(this.message)
             .fontSize($r('app.float.page_text_font_size'))
             .fontWeight(FontWeight.Bold)
             .onClick(() => {
               test();
             })
         }
         .width('100%')
       }
       .height('100%')
     }
   }

   在共享模式下，跨线程传递后，原来的ArkTS对象还可以继续访问Native对象。示例如下：

   // Index.ets
   import testNapi from 'libentry.so';
   import { taskpool } from '@kit.ArkTS';
   
   @Concurrent
   function getAddress() {
     let address: number = testNapi.getAddress();
     console.info('taskpool:: address is ' + address);
   }
   
   @Concurrent
   function store(a:number, b:number, c:number) {
     let size:number = testNapi.getSetSize();
     console.info('set size is ' + size + ' before store');
     testNapi.store(a);
     testNapi.store(b);
     testNapi.store(c);
     size = testNapi.getSetSize();
     console.info('set size is ' + size + ' after store');
   }
   
   @Concurrent
   function erase(a:number) {
     let size:number = testNapi.getSetSize();
     console.info('set size is ' + size + ' before erase');
     testNapi.erase(a);
     size = testNapi.getSetSize();
     console.info('set size is ' + size + ' after erase');
   }
   
   @Concurrent
   function clear() {
     let size:number = testNapi.getSetSize();
     console.info('set size is ' + size + ' before clear');
     testNapi.clear();
     size = testNapi.getSetSize();
     console.info('set size is ' + size + ' after clear');
   }
   
   // 共享模式
   async function test(): Promise<void> {
     let address:number = testNapi.getAddress();
     console.info('host thread address is ' + address);
   
     let task1 = new taskpool.Task(getAddress, testNapi);
     await taskpool.execute(task1);
   
     let task2 = new taskpool.Task(store, 1, 2, 3);
     await taskpool.execute(task2);
   
     let task3 = new taskpool.Task(store, 4, 5, 6);
     await taskpool.execute(task3);
   
     // 由于默认的传输模式为共享模式，testNapi跨线程传递后，主线程可以继续访问Native对象的值
     let size:number = testNapi.getSetSize();
     // 输出的日志为“host thread size is 6”
     console.info('host thread size is ' + size);
   
     let task4 = new taskpool.Task(erase, 3);
     await taskpool.execute(task4);
   
     let task5 = new taskpool.Task(erase, 5);
     await taskpool.execute(task5);
   
     let task6 = new taskpool.Task(clear);
     await taskpool.execute(task6);
   }
   
   @Entry
   @Component
   struct Index {
     @State message: string = 'Hello World';
   
     build() {
       Row() {
         Column() {
           Text(this.message)
             .fontSize($r('app.float.page_text_font_size'))
             .fontWeight(FontWeight.Bold)
             .onClick(() => {
               test();
             })
         }
         .width('100%')
       }
       .height('100%')
     }
   }